Trial Outcomes & Findings for Jump-In: Building Better Bones (NCT NCT00729378)

NCT ID: NCT00729378

Last Updated: 2025-10-28

Results Overview

Baseline to 24-month change in cortical bone area at the femur 4% site . Measurement made by pQCT at a distance of 4% of total femur length from the distal growth plate. Measurement units: square millimeters (mm\^2).

• Recruitment status: COMPLETED
• Study phase: NA
• Target enrollment: 509 participants
• Primary outcome timeframe: Baseline to 24-months
• Results posted on: 2025-10-28

Participant Flow

Recruitment was performed for three years (2007-2009) in a total of 16 elementary and middle schools (9 intervention and 7 control) in two Tucson, Arizona area school districts. Recruitment consisted of attending back to school days and holding recruitment assemblies before or after school.

Intervention and control schools designated prior to recruiting. Schools were selected based on size, demographics, and student flow from elementary to middle school to prevent contamination. 739 participants completed informed consent process (agreed to participate); only 509 scheduled measurement appointments and completed study measurements.

Participant milestones

Measure	Exercise Intervention Subjects in the exercise intervention arm performed activities designed to provide skeletal loading: impact activities, 3 times per week, increasing the number of jumps (up to 40) and increasing height (from 6 inches to 24 inches per repetition) over the initial 8-weeks (2 months). New activities were introduced approximately every 2-3 months in order to continually stress the skeleton over 2 years. Physical activity performed by these subjects (in addition to intervention activities) was objectively assessed by pedometer (7-day wear period) and further assessed by a validated past year physical activity questionnaire PYPAQ).	Control Subjects in the control arm did not take part in intervention exercises. Physical activity performed by these subjects was objectively assessed by pedometer (7-day wear period) and further assessed by a validated past year physical activity questionnaire PYPAQ).
Baseline STARTED	430	309
Baseline COMPLETED	292	217
Baseline NOT COMPLETED	138	92
12-months STARTED	292	217
12-months COMPLETED	192	152
12-months NOT COMPLETED	100	65
24-months STARTED	192	152
24-months COMPLETED	120	101
24-months NOT COMPLETED	72	51
36-months STARTED	120	101
36-months COMPLETED	105	95
36-months NOT COMPLETED	15	6

Reasons for withdrawal

Measure	Exercise Intervention Subjects in the exercise intervention arm performed activities designed to provide skeletal loading: impact activities, 3 times per week, increasing the number of jumps (up to 40) and increasing height (from 6 inches to 24 inches per repetition) over the initial 8-weeks (2 months). New activities were introduced approximately every 2-3 months in order to continually stress the skeleton over 2 years. Physical activity performed by these subjects (in addition to intervention activities) was objectively assessed by pedometer (7-day wear period) and further assessed by a validated past year physical activity questionnaire PYPAQ).	Control Subjects in the control arm did not take part in intervention exercises. Physical activity performed by these subjects was objectively assessed by pedometer (7-day wear period) and further assessed by a validated past year physical activity questionnaire PYPAQ).
Baseline Did not complete study measurements	72	33
Baseline Withdrawal by Subject	66	59
12-months Lost to Follow-up	100	65
24-months Lost to Follow-up	72	51
36-months Lost to Follow-up	15	6

Baseline Characteristics

Jump-In: Building Better Bones

Baseline characteristics by cohort

Measure	Exercise Intervention n=292 Participants Subjects in the exercise intervention arm performed activities designed to provide skeletal loading: impact activities, 3 times per week, increasing the number of jumps (up to 40) and increasing height (from 6 inches to 24 inches per repetition) over the initial 8-weeks (2 months). New activities were introduced approximately every 2-3 months in order to continually stress the skeleton over 2 years. Physical activity performed by these subjects (in addition to intervention activities) was objectively assessed by pedometer (7-day wear period) and further assessed by a validated past year physical activity questionnaire PYPAQ).	Control n=217 Participants Subjects in the control arm did not take part in intervention exercises. Physical activity performed by these subjects was objectively assessed by pedometer (7-day wear period) and further assessed by a validated past year physical activity questionnaire PYPAQ).	Total n=509 Participants Total of all reporting groups
Age, Continuous	10.6 years STANDARD_DEVIATION 1.1 • n=5 Participants	10.7 years STANDARD_DEVIATION 1.0 • n=7 Participants	10.7 years STANDARD_DEVIATION 1.1 • n=5 Participants
Sex: Female, Male Female	292 Participants n=5 Participants	217 Participants n=7 Participants	509 Participants n=5 Participants
Sex: Female, Male Male	0 Participants n=5 Participants	0 Participants n=7 Participants	0 Participants n=5 Participants
Ethnicity (NIH/OMB) Hispanic or Latino	67 Participants n=5 Participants	50 Participants n=7 Participants	117 Participants n=5 Participants
Ethnicity (NIH/OMB) Not Hispanic or Latino	225 Participants n=5 Participants	167 Participants n=7 Participants	392 Participants n=5 Participants
Ethnicity (NIH/OMB) Unknown or Not Reported	0 Participants n=5 Participants	0 Participants n=7 Participants	0 Participants n=5 Participants
Race (NIH/OMB) American Indian or Alaska Native	1 Participants n=5 Participants	2 Participants n=7 Participants	3 Participants n=5 Participants
Race (NIH/OMB) Asian	20 Participants n=5 Participants	11 Participants n=7 Participants	31 Participants n=5 Participants
Race (NIH/OMB) Native Hawaiian or Other Pacific Islander	2 Participants n=5 Participants	1 Participants n=7 Participants	3 Participants n=5 Participants
Race (NIH/OMB) Black or African American	11 Participants n=5 Participants	3 Participants n=7 Participants	14 Participants n=5 Participants
Race (NIH/OMB) White	254 Participants n=5 Participants	196 Participants n=7 Participants	450 Participants n=5 Participants
Race (NIH/OMB) More than one race	2 Participants n=5 Participants	0 Participants n=7 Participants	2 Participants n=5 Participants
Race (NIH/OMB) Unknown or Not Reported	2 Participants n=5 Participants	4 Participants n=7 Participants	6 Participants n=5 Participants
Region of Enrollment United States	292 Participants n=5 Participants	217 Participants n=7 Participants	509 Participants n=5 Participants

PRIMARY outcome

Timeframe: Baseline

Population: Population consists of all participants that had complete measurements at the baseline time point (N = 503; Age = 10.6 +/- 1.1 yrs; Height = 144.5 +/- 9.7 cm; Weight = 39.2 +/- 10.5 kg).

Baseline (initial) measurement of total volumetric bone density at the femur 4% site. Measurement made by peripheral quantitative computed tomography (pQCT) at a distance of 4% of total femur length from the distal growth plate. Measurement units: milligrams per cubic centimeter (mg/ccm).

Outcome measures

Measure	Exercise Intervention n=286 Participants Participants randomized to the exercise intervention group performed activities designed to provide skeletal loading: impact activities 3 times per week, increasing the number of jumps (up to 40) and increasing height (from 6 inches to 24 inches per repetition) over the initial 8-weeks (2 months). New activities were introduced approximately every 2-3 months in order to continually stress the skeleton over 2 years. Physical activity performed by these subjects (in addition to intervention activities) was objectively assessed by pedometer (7-day wear period) and further assessed by a validated past year physical activity questionnaire PYPAQ).	Control n=217 Participants Participants randomized to the control arm did not perform intervention activities. Physical activity was objectively assessed by pedometer (7-day wear period) and further assessed by a validated past year physical activity questionnaire (PYPAQ).
Baseline Total Volumetric Bone Density at the Femur 4% Site	277.25 milligrams per cubic centimeter (mg/ccm) Standard Deviation 33.83	270.79 milligrams per cubic centimeter (mg/ccm) Standard Deviation 32.97

PRIMARY outcome

Timeframe: Baseline

Population: Population consists of all participants that had complete measurements at the baseline time point (N = 503; Age = 10.6 +/- 1.1 yrs; Height = 144.5 +/- 9.7 cm; Weight = 39.2 +/- 10.5 kg).

Baseline (initial) measurement of volumetric bone density of trabecular bone at the femur 4% site . Measurement made by pQCT at a distance of 4% of total femur length from the distal growth plate. Measurement units: milligrams per cubic centimeter (mg/ccm).

Outcome measures

Measure	Exercise Intervention n=286 Participants Participants randomized to the exercise intervention group performed activities designed to provide skeletal loading: impact activities 3 times per week, increasing the number of jumps (up to 40) and increasing height (from 6 inches to 24 inches per repetition) over the initial 8-weeks (2 months). New activities were introduced approximately every 2-3 months in order to continually stress the skeleton over 2 years. Physical activity performed by these subjects (in addition to intervention activities) was objectively assessed by pedometer (7-day wear period) and further assessed by a validated past year physical activity questionnaire PYPAQ).	Control n=217 Participants Participants randomized to the control arm did not perform intervention activities. Physical activity was objectively assessed by pedometer (7-day wear period) and further assessed by a validated past year physical activity questionnaire (PYPAQ).
Baseline Volumetric Bone Density of Trabecular Bone at the Femur 4% Site	239.32 milligrams per cubic centimeter (mg/ccm) Standard Deviation 32.2	232.34 milligrams per cubic centimeter (mg/ccm) Standard Deviation 31.56

PRIMARY outcome

Timeframe: Baseline

Population: Population consists of all participants that had complete measurements at the baseline time point (N = 503; Age = 10.6 +/- 1.1 yrs; Height = 144.5 +/- 9.7 cm; Weight = 39.2 +/- 10.5 kg).

Baseline (initial) measurement of volumetric bone density of Cortical bone at the femur 4% site . Measurement made by pQCT at a distance of 4% of total femur length from the distal growth plate. Measurement units: milligrams per cubic centimeter (mg/ccm).

Outcome measures

Measure	Exercise Intervention n=286 Participants Participants randomized to the exercise intervention group performed activities designed to provide skeletal loading: impact activities 3 times per week, increasing the number of jumps (up to 40) and increasing height (from 6 inches to 24 inches per repetition) over the initial 8-weeks (2 months). New activities were introduced approximately every 2-3 months in order to continually stress the skeleton over 2 years. Physical activity performed by these subjects (in addition to intervention activities) was objectively assessed by pedometer (7-day wear period) and further assessed by a validated past year physical activity questionnaire PYPAQ).	Control n=217 Participants Participants randomized to the control arm did not perform intervention activities. Physical activity was objectively assessed by pedometer (7-day wear period) and further assessed by a validated past year physical activity questionnaire (PYPAQ).
Baseline Volumetric Bone Density of Cortical Bone at the Femur 4% Site	273.80 milligrams per cubic centimeter (mg/ccm) Standard Deviation 31.23	267.89 milligrams per cubic centimeter (mg/ccm) Standard Deviation 30.75

PRIMARY outcome

Timeframe: Baseline

Population: Population consists of all participants that had complete measurements at the baseline time point (N = 503; Age = 10.6 +/- 1.1 yrs; Height = 144.5 +/- 9.7 cm; Weight = 39.2 +/- 10.5 kg).

Baseline (initial) measurement of trabecular bone area at the femur 4% site . Measurement made by pQCT at a distance of 4% of total femur length from the distal growth plate. Measurement units: square millimeters (mm^2).

Outcome measures

Measure	Exercise Intervention n=286 Participants Participants randomized to the exercise intervention group performed activities designed to provide skeletal loading: impact activities 3 times per week, increasing the number of jumps (up to 40) and increasing height (from 6 inches to 24 inches per repetition) over the initial 8-weeks (2 months). New activities were introduced approximately every 2-3 months in order to continually stress the skeleton over 2 years. Physical activity performed by these subjects (in addition to intervention activities) was objectively assessed by pedometer (7-day wear period) and further assessed by a validated past year physical activity questionnaire PYPAQ).	Control n=217 Participants Participants randomized to the control arm did not perform intervention activities. Physical activity was objectively assessed by pedometer (7-day wear period) and further assessed by a validated past year physical activity questionnaire (PYPAQ).
Baseline Trabecular Bone Area at the Femur 4% Site	1039.55 millimeters squared (mm^2) Standard Deviation 220.17	1053.15 millimeters squared (mm^2) Standard Deviation 227.32

PRIMARY outcome

Timeframe: Baseline

Population: Population consists of all participants that had complete measurements at the baseline time point (N = 503; Age = 10.6 +/- 1.1 yrs; Height = 144.5 +/- 9.7 cm; Weight = 39.2 +/- 10.5 kg).

Baseline (initial) measurement of cortical bone area at the femur 4% site . Measurement made by pQCT at a distance of 4% of total femur length from the distal growth plate. Measurement units: square millimeters (mm^2).

Outcome measures

Measure	Exercise Intervention n=286 Participants Participants randomized to the exercise intervention group performed activities designed to provide skeletal loading: impact activities 3 times per week, increasing the number of jumps (up to 40) and increasing height (from 6 inches to 24 inches per repetition) over the initial 8-weeks (2 months). New activities were introduced approximately every 2-3 months in order to continually stress the skeleton over 2 years. Physical activity performed by these subjects (in addition to intervention activities) was objectively assessed by pedometer (7-day wear period) and further assessed by a validated past year physical activity questionnaire PYPAQ).	Control n=217 Participants Participants randomized to the control arm did not perform intervention activities. Physical activity was objectively assessed by pedometer (7-day wear period) and further assessed by a validated past year physical activity questionnaire (PYPAQ).
Baseline Cortical Bone Area at the Femur 4% Site	1335.56 millimeters squared (mm^2) Standard Deviation 274.22	1348.65 millimeters squared (mm^2) Standard Deviation 284.24

PRIMARY outcome

Timeframe: Baseline

Population: Population consists of all participants that had complete measurements at the baseline time point (N = 503; Age = 10.6 +/- 1.1 yrs; Height = 144.5 +/- 9.7 cm; Weight = 39.2 +/- 10.5 kg).

Baseline (initial) measurement of periosteal circumference at the femur 4% site . Measurement made by pQCT at a distance of 4% of total femur length from the distal growth plate. Measurement units: millimeters (mm).

Outcome measures

Measure	Exercise Intervention n=286 Participants Participants randomized to the exercise intervention group performed activities designed to provide skeletal loading: impact activities 3 times per week, increasing the number of jumps (up to 40) and increasing height (from 6 inches to 24 inches per repetition) over the initial 8-weeks (2 months). New activities were introduced approximately every 2-3 months in order to continually stress the skeleton over 2 years. Physical activity performed by these subjects (in addition to intervention activities) was objectively assessed by pedometer (7-day wear period) and further assessed by a validated past year physical activity questionnaire PYPAQ).	Control n=217 Participants Participants randomized to the control arm did not perform intervention activities. Physical activity was objectively assessed by pedometer (7-day wear period) and further assessed by a validated past year physical activity questionnaire (PYPAQ).
Baseline Periosteal Circumference at the Femur 4% Site	124.91 millimeters (mm) Standard Deviation 12.42	125.63 millimeters (mm) Standard Deviation 12.50

PRIMARY outcome

Timeframe: Baseline

Population: Population consists of all participants that had complete measurements at the baseline time point (N = 503; Age = 10.6 +/- 1.1 yrs; Height = 144.5 +/- 9.7 cm; Weight = 39.2 +/- 10.5 kg).

Baseline (initial) measurement of bone strength index (BSI) at the femur 4% site. Bone Strength Index (BSI) is a measurement of the resistance to compression forces at the epiphyses of long bones. Measurement made by pQCT at a distance of 4% of total tibia length from the distal growth plate. Measurement units: mm^4.

Outcome measures

Measure	Exercise Intervention n=286 Participants Participants randomized to the exercise intervention group performed activities designed to provide skeletal loading: impact activities 3 times per week, increasing the number of jumps (up to 40) and increasing height (from 6 inches to 24 inches per repetition) over the initial 8-weeks (2 months). New activities were introduced approximately every 2-3 months in order to continually stress the skeleton over 2 years. Physical activity performed by these subjects (in addition to intervention activities) was objectively assessed by pedometer (7-day wear period) and further assessed by a validated past year physical activity questionnaire PYPAQ).	Control n=217 Participants Participants randomized to the control arm did not perform intervention activities. Physical activity was objectively assessed by pedometer (7-day wear period) and further assessed by a validated past year physical activity questionnaire (PYPAQ).
Baseline Bone Strength Index at the Femur 4% Site	96.77 mm^4 Standard Deviation 28.00	93.52 mm^4 Standard Deviation 27.39

PRIMARY outcome

Timeframe: Baseline

Population: Population consists of all participants that had complete measurements at the baseline time point (N = 503; Age = 10.6 +/- 1.1 yrs; Height = 144.5 +/- 9.7 cm; Weight = 39.2 +/- 10.5 kg).

Baseline (initial) measurement of total volumetric bone density at the femur 20% site . Measurement made by pQCT at a distance of 20% of total femur length from the distal growth plate. Measurement units: milligrams per cubic centimeter (mg/ccm).

Outcome measures

Measure	Exercise Intervention n=286 Participants Participants randomized to the exercise intervention group performed activities designed to provide skeletal loading: impact activities 3 times per week, increasing the number of jumps (up to 40) and increasing height (from 6 inches to 24 inches per repetition) over the initial 8-weeks (2 months). New activities were introduced approximately every 2-3 months in order to continually stress the skeleton over 2 years. Physical activity performed by these subjects (in addition to intervention activities) was objectively assessed by pedometer (7-day wear period) and further assessed by a validated past year physical activity questionnaire PYPAQ).	Control n=217 Participants Participants randomized to the control arm did not perform intervention activities. Physical activity was objectively assessed by pedometer (7-day wear period) and further assessed by a validated past year physical activity questionnaire (PYPAQ).
Baseline Total Volumetric Bone Density at the Femur 20% Site	489.70 milligrams per cubic centimeter (mg/ccm) Standard Deviation 63.98	478.72 milligrams per cubic centimeter (mg/ccm) Standard Deviation 60.59

PRIMARY outcome

Timeframe: Baseline

Population: Population consists of all participants that had complete measurements at the baseline time point (N = 503; Age = 10.6 +/- 1.1 yrs; Height = 144.5 +/- 9.7 cm; Weight = 39.2 +/- 10.5 kg).

Baseline (initial) measurement of volumetric bone density of trabecular bone at the femur 20% site . Measurement made by pQCT at a distance of 20% of total femur length from the distal growth plate. Measurement units: milligrams per cubic centimeter (mg/ccm).

Outcome measures

Measure	Exercise Intervention n=286 Participants Participants randomized to the exercise intervention group performed activities designed to provide skeletal loading: impact activities 3 times per week, increasing the number of jumps (up to 40) and increasing height (from 6 inches to 24 inches per repetition) over the initial 8-weeks (2 months). New activities were introduced approximately every 2-3 months in order to continually stress the skeleton over 2 years. Physical activity performed by these subjects (in addition to intervention activities) was objectively assessed by pedometer (7-day wear period) and further assessed by a validated past year physical activity questionnaire PYPAQ).	Control n=217 Participants Participants randomized to the control arm did not perform intervention activities. Physical activity was objectively assessed by pedometer (7-day wear period) and further assessed by a validated past year physical activity questionnaire (PYPAQ).
Baseline Volumetric Bone Density of Trabecular Bone at the Femur 20% Site	163.81 milligrams per cubic centimeter (mg/ccm) Standard Deviation 39.43	153.11 milligrams per cubic centimeter (mg/ccm) Standard Deviation 36.77

PRIMARY outcome

Timeframe: Baseline

Population: Population consists of all participants that had complete measurements at the baseline time point (N = 503; Age = 10.6 +/- 1.1 yrs; Height = 144.5 +/- 9.7 cm; Weight = 39.2 +/- 10.5 kg).

Baseline (initial) measurement of volumetric bone density of Cortical bone at the femur 20% site . Measurement made by pQCT at a distance of 20% of total femur length from the distal growth plate. Measurement units: milligrams per cubic centimeter (mg/ccm).

Outcome measures

Measure	Exercise Intervention n=286 Participants Participants randomized to the exercise intervention group performed activities designed to provide skeletal loading: impact activities 3 times per week, increasing the number of jumps (up to 40) and increasing height (from 6 inches to 24 inches per repetition) over the initial 8-weeks (2 months). New activities were introduced approximately every 2-3 months in order to continually stress the skeleton over 2 years. Physical activity performed by these subjects (in addition to intervention activities) was objectively assessed by pedometer (7-day wear period) and further assessed by a validated past year physical activity questionnaire PYPAQ).	Control n=217 Participants Participants randomized to the control arm did not perform intervention activities. Physical activity was objectively assessed by pedometer (7-day wear period) and further assessed by a validated past year physical activity questionnaire (PYPAQ).
Baseline Volumetric Bone Density of Cortical Bone at the Femur 20% Site	1046.01 milligrams per cubic centimeter (mg/ccm) Standard Deviation 22.27	1045.20 milligrams per cubic centimeter (mg/ccm) Standard Deviation 23.07

PRIMARY outcome

Timeframe: Baseline

Population: Population consists of all participants that had complete measurements at the baseline time point (N = 503; Age = 10.6 +/- 1.1 yrs; Height = 144.5 +/- 9.7 cm; Weight = 39.2 +/- 10.5 kg).

Baseline (initial) measurement of periosteal circumference at the femur 20% site . Measurement made by pQCT at a distance of 20% of total femur length from the distal growth plate. Measurement units: millimeters (mm).

Outcome measures

Measure	Exercise Intervention n=286 Participants Participants randomized to the exercise intervention group performed activities designed to provide skeletal loading: impact activities 3 times per week, increasing the number of jumps (up to 40) and increasing height (from 6 inches to 24 inches per repetition) over the initial 8-weeks (2 months). New activities were introduced approximately every 2-3 months in order to continually stress the skeleton over 2 years. Physical activity performed by these subjects (in addition to intervention activities) was objectively assessed by pedometer (7-day wear period) and further assessed by a validated past year physical activity questionnaire PYPAQ).	Control n=217 Participants Participants randomized to the control arm did not perform intervention activities. Physical activity was objectively assessed by pedometer (7-day wear period) and further assessed by a validated past year physical activity questionnaire (PYPAQ).
Baseline Periosteal Circumference at the Femur 20% Site	77.43 millimeters (mm) Standard Deviation 8.56	77.78 millimeters (mm) Standard Deviation 8.66

PRIMARY outcome

Timeframe: Baseline

Population: Population consists of all participants that had complete measurements at the baseline time point (N = 503; Age = 10.6 +/- 1.1 yrs; Height = 144.5 +/- 9.7 cm; Weight = 39.2 +/- 10.5 kg).

Baseline (initial) measurement of cortical thickness at the femur 20% site . Measurement made by pQCT at a distance of 20% of total femur length from the distal growth plate. Measurement units: millimeters (mm).

Outcome measures

Measure	Exercise Intervention n=286 Participants Participants randomized to the exercise intervention group performed activities designed to provide skeletal loading: impact activities 3 times per week, increasing the number of jumps (up to 40) and increasing height (from 6 inches to 24 inches per repetition) over the initial 8-weeks (2 months). New activities were introduced approximately every 2-3 months in order to continually stress the skeleton over 2 years. Physical activity performed by these subjects (in addition to intervention activities) was objectively assessed by pedometer (7-day wear period) and further assessed by a validated past year physical activity questionnaire PYPAQ).	Control n=217 Participants Participants randomized to the control arm did not perform intervention activities. Physical activity was objectively assessed by pedometer (7-day wear period) and further assessed by a validated past year physical activity questionnaire (PYPAQ).
Baseline Cortical Thickness at the Femur 20% Site	2.52 millimeters (mm) Standard Deviation .37	2.50 millimeters (mm) Standard Deviation .35

PRIMARY outcome

Timeframe: Baseline

Population: Population consists of all participants that had complete measurements at the baseline time point (N = 503; Age = 10.6 +/- 1.1 yrs; Height = 144.5 +/- 9.7 cm; Weight = 39.2 +/- 10.5 kg).

Baseline (initial) measurement of stress-strain index at the femur 20% site. Stress-strain index (also called strength-strain index and stress-strength index in the literature) is a measure of the resistance to torsional and bending forces at diaphyseal sites of long bones. Measurement made by pQCT at a distance of 20% of total femur length from the distal growth plate. Measurement units: mm^3.

Outcome measures

Measure	Exercise Intervention n=286 Participants Participants randomized to the exercise intervention group performed activities designed to provide skeletal loading: impact activities 3 times per week, increasing the number of jumps (up to 40) and increasing height (from 6 inches to 24 inches per repetition) over the initial 8-weeks (2 months). New activities were introduced approximately every 2-3 months in order to continually stress the skeleton over 2 years. Physical activity performed by these subjects (in addition to intervention activities) was objectively assessed by pedometer (7-day wear period) and further assessed by a validated past year physical activity questionnaire PYPAQ).	Control n=217 Participants Participants randomized to the control arm did not perform intervention activities. Physical activity was objectively assessed by pedometer (7-day wear period) and further assessed by a validated past year physical activity questionnaire (PYPAQ).
Baseline Stress-Strain Index at the Femur 20% Site	1340.19 mm^3 Standard Deviation 404.78	1344.66 mm^3 Standard Deviation 399.31

PRIMARY outcome

Timeframe: Baseline

Population: Population consists of all participants that had complete measurements at the baseline time point (N = 503; Age = 10.6 +/- 1.1 yrs; Height = 144.5 +/- 9.7 cm; Weight = 39.2 +/- 10.5 kg).

Baseline (initial) measurement of volumetric bone density of trabecular bone at the tibia 4% site . Measurement made by pQCT at a distance of 4% of total tibia length from the distal growth plate. Measurement units: milligrams per cubic centimeter (mg/ccm).

Outcome measures

Measure	Exercise Intervention n=286 Participants Participants randomized to the exercise intervention group performed activities designed to provide skeletal loading: impact activities 3 times per week, increasing the number of jumps (up to 40) and increasing height (from 6 inches to 24 inches per repetition) over the initial 8-weeks (2 months). New activities were introduced approximately every 2-3 months in order to continually stress the skeleton over 2 years. Physical activity performed by these subjects (in addition to intervention activities) was objectively assessed by pedometer (7-day wear period) and further assessed by a validated past year physical activity questionnaire PYPAQ).	Control n=217 Participants Participants randomized to the control arm did not perform intervention activities. Physical activity was objectively assessed by pedometer (7-day wear period) and further assessed by a validated past year physical activity questionnaire (PYPAQ).
Baseline Volumetric Bone Density of Trabecular Bone at the Tibia 4% Site	224.03 milligrams per cubic centimeter (mg/ccm) Standard Deviation 27.58	219.74 milligrams per cubic centimeter (mg/ccm) Standard Deviation 25.56

PRIMARY outcome

Timeframe: Baseline

Population: Population consists of all participants that had complete measurements at the baseline time point (N = 503; Age = 10.6 +/- 1.1 yrs; Height = 144.5 +/- 9.7 cm; Weight = 39.2 +/- 10.5 kg).

Baseline (initial) measurement of total volumetric bone density at the tibia 4% site . Measurement made by pQCT at a distance of 4% of total tibia length from the distal growth plate. Measurement units: milligrams per cubic centimeter (mg/ccm).

Outcome measures

Measure	Exercise Intervention n=286 Participants Participants randomized to the exercise intervention group performed activities designed to provide skeletal loading: impact activities 3 times per week, increasing the number of jumps (up to 40) and increasing height (from 6 inches to 24 inches per repetition) over the initial 8-weeks (2 months). New activities were introduced approximately every 2-3 months in order to continually stress the skeleton over 2 years. Physical activity performed by these subjects (in addition to intervention activities) was objectively assessed by pedometer (7-day wear period) and further assessed by a validated past year physical activity questionnaire PYPAQ).	Control n=217 Participants Participants randomized to the control arm did not perform intervention activities. Physical activity was objectively assessed by pedometer (7-day wear period) and further assessed by a validated past year physical activity questionnaire (PYPAQ).
Baseline Total Volumetric Bone Density at the Tibia 4% Site	297.27 milligrams per cubic centimeter (mg/ccm) Standard Deviation 37.02	291.62 milligrams per cubic centimeter (mg/ccm) Standard Deviation 33.17

PRIMARY outcome

Timeframe: Baseline

Population: Population consists of all participants that had complete measurements at the baseline time point (N = 503; Age = 10.6 +/- 1.1 yrs; Height = 144.5 +/- 9.7 cm; Weight = 39.2 +/- 10.5 kg).

Baseline (initial) measurement of volumetric bone density of cortical bone at the tibia 4% site . Measurement made by pQCT at a distance of 4% of total tibia length from the distal growth plate. Measurement units: milligrams per cubic centimeter (mg/ccm).

Outcome measures

Measure	Exercise Intervention n=286 Participants Participants randomized to the exercise intervention group performed activities designed to provide skeletal loading: impact activities 3 times per week, increasing the number of jumps (up to 40) and increasing height (from 6 inches to 24 inches per repetition) over the initial 8-weeks (2 months). New activities were introduced approximately every 2-3 months in order to continually stress the skeleton over 2 years. Physical activity performed by these subjects (in addition to intervention activities) was objectively assessed by pedometer (7-day wear period) and further assessed by a validated past year physical activity questionnaire PYPAQ).	Control n=217 Participants Participants randomized to the control arm did not perform intervention activities. Physical activity was objectively assessed by pedometer (7-day wear period) and further assessed by a validated past year physical activity questionnaire (PYPAQ).
Baseline Volumetric Bone Density of Cortical Bone at the Tibia 4% Site	297.40 milligrams per cubic centimeter (mg/ccm) Standard Deviation 35.63	291.93 milligrams per cubic centimeter (mg/ccm) Standard Deviation 31.92

PRIMARY outcome

Timeframe: Baseline

Population: Population consists of all participants that had complete measurements at the baseline time point (N = 503; Age = 10.6 +/- 1.1 yrs; Height = 144.5 +/- 9.7 cm; Weight = 39.2 +/- 10.5 kg).

Baseline (initial) measurement of trabecular bone area at the tibia 4% site . Measurement made by pQCT at a distance of 4% of total tibia length from the distal growth plate. Measurement units: square millimeters (mm^2).

Outcome measures

Measure	Exercise Intervention n=286 Participants Participants randomized to the exercise intervention group performed activities designed to provide skeletal loading: impact activities 3 times per week, increasing the number of jumps (up to 40) and increasing height (from 6 inches to 24 inches per repetition) over the initial 8-weeks (2 months). New activities were introduced approximately every 2-3 months in order to continually stress the skeleton over 2 years. Physical activity performed by these subjects (in addition to intervention activities) was objectively assessed by pedometer (7-day wear period) and further assessed by a validated past year physical activity questionnaire PYPAQ).	Control n=217 Participants Participants randomized to the control arm did not perform intervention activities. Physical activity was objectively assessed by pedometer (7-day wear period) and further assessed by a validated past year physical activity questionnaire (PYPAQ).
Baseline Trabecular Bone Area at the Tibia 4% Site	467.73 millimeters squared (mm^2) Standard Deviation 100.86	475.80 millimeters squared (mm^2) Standard Deviation 108.85

PRIMARY outcome

Timeframe: Baseline

Population: Population consists of all participants that had complete measurements at the baseline time point (N = 503; Age = 10.6 +/- 1.1 yrs; Height = 144.5 +/- 9.7 cm; Weight = 39.2 +/- 10.5 kg).

Baseline (initial) measurement of cortical bone area at the tibia 4% site . Measurement made by pQCT at a distance of 4% of total tibia length from the distal growth plate. Measurement units: square millimeters (mm^2).

Outcome measures

Measure	Exercise Intervention n=286 Participants Participants randomized to the exercise intervention group performed activities designed to provide skeletal loading: impact activities 3 times per week, increasing the number of jumps (up to 40) and increasing height (from 6 inches to 24 inches per repetition) over the initial 8-weeks (2 months). New activities were introduced approximately every 2-3 months in order to continually stress the skeleton over 2 years. Physical activity performed by these subjects (in addition to intervention activities) was objectively assessed by pedometer (7-day wear period) and further assessed by a validated past year physical activity questionnaire PYPAQ).	Control n=217 Participants Participants randomized to the control arm did not perform intervention activities. Physical activity was objectively assessed by pedometer (7-day wear period) and further assessed by a validated past year physical activity questionnaire (PYPAQ).
Baseline Cortical Bone Area at the Tibia 4% Site	617.19 millimeters squared (mm^2) Standard Deviation 117.67	625.57 millimeters squared (mm^2) Standard Deviation 127.11

PRIMARY outcome

Timeframe: Baseline

Population: Population consists of all participants that had complete measurements at the baseline time point (N = 503; Age = 10.6 +/- 1.1 yrs; Height = 144.5 +/- 9.7 cm; Weight = 39.2 +/- 10.5 kg).

Baseline (initial) measurement of periosteal circumference at the tibia 4% site . Measurement made by pQCT at a distance of 4% of total tibia length from the distal growth plate. Measurement units: millimeters (mm).

Outcome measures

Measure	Exercise Intervention n=286 Participants Participants randomized to the exercise intervention group performed activities designed to provide skeletal loading: impact activities 3 times per week, increasing the number of jumps (up to 40) and increasing height (from 6 inches to 24 inches per repetition) over the initial 8-weeks (2 months). New activities were introduced approximately every 2-3 months in order to continually stress the skeleton over 2 years. Physical activity performed by these subjects (in addition to intervention activities) was objectively assessed by pedometer (7-day wear period) and further assessed by a validated past year physical activity questionnaire PYPAQ).	Control n=217 Participants Participants randomized to the control arm did not perform intervention activities. Physical activity was objectively assessed by pedometer (7-day wear period) and further assessed by a validated past year physical activity questionnaire (PYPAQ).
Baseline Periosteal Circumference at the Tibia 4% Site	85.86 millimeters (mm) Standard Deviation 8.36	86.43 millimeters (mm) Standard Deviation 8.82

PRIMARY outcome

Timeframe: Baseline

Population: Population consists of all participants that had complete measurements at the baseline time point (N = 503; Age = 10.6 +/- 1.1 yrs; Height = 144.5 +/- 9.7 cm; Weight = 39.2 +/- 10.5 kg).

Baseline (initial) measurement of bone strength index (BSI) at the tibia 4% site. Bone Strength Index (BSI) is a measurement of the resistance to compression forces at the epiphyses of long bones. Measurement made by pQCT at a distance of 4% of total tibia length from the distal growth plate. Measurement units: mm^4.

Outcome measures

Measure	Exercise Intervention n=286 Participants Participants randomized to the exercise intervention group performed activities designed to provide skeletal loading: impact activities 3 times per week, increasing the number of jumps (up to 40) and increasing height (from 6 inches to 24 inches per repetition) over the initial 8-weeks (2 months). New activities were introduced approximately every 2-3 months in order to continually stress the skeleton over 2 years. Physical activity performed by these subjects (in addition to intervention activities) was objectively assessed by pedometer (7-day wear period) and further assessed by a validated past year physical activity questionnaire PYPAQ).	Control n=217 Participants Participants randomized to the control arm did not perform intervention activities. Physical activity was objectively assessed by pedometer (7-day wear period) and further assessed by a validated past year physical activity questionnaire (PYPAQ).
Baseline Bone Strength Index at the Tibia 4% Site	52.45 mm^4 Standard Deviation 15.15	51.03 mm^4 Standard Deviation 13.63

PRIMARY outcome

Timeframe: Baseline

Population: Population consists of all participants that had complete measurements at the baseline time point (N = 503; Age = 10.6 +/- 1.1 yrs; Height = 144.5 +/- 9.7 cm; Weight = 39.2 +/- 10.5 kg).

Baseline (initial) measurement of total volumetric bone density at the tibia 50% site . Measurement made by pQCT at a distance of 50% of total tibia length from the distal growth plate. Measurement units: milligrams per cubic centimeter (mg/ccm).

Outcome measures

Measure	Exercise Intervention n=286 Participants Participants randomized to the exercise intervention group performed activities designed to provide skeletal loading: impact activities 3 times per week, increasing the number of jumps (up to 40) and increasing height (from 6 inches to 24 inches per repetition) over the initial 8-weeks (2 months). New activities were introduced approximately every 2-3 months in order to continually stress the skeleton over 2 years. Physical activity performed by these subjects (in addition to intervention activities) was objectively assessed by pedometer (7-day wear period) and further assessed by a validated past year physical activity questionnaire PYPAQ).	Control n=217 Participants Participants randomized to the control arm did not perform intervention activities. Physical activity was objectively assessed by pedometer (7-day wear period) and further assessed by a validated past year physical activity questionnaire (PYPAQ).
Baseline Total Volumetric Bone Density at the Tibia 50% Site	745.69 milligrams per cubic centimeter (mg/ccm) Standard Deviation 59.54	736.33 milligrams per cubic centimeter (mg/ccm) Standard Deviation 58.07

PRIMARY outcome

Timeframe: Baseline

Population: Population consists of all participants that had complete measurements at the baseline time point (N = 503; Age = 10.6 +/- 1.1 yrs; Height = 144.5 +/- 9.7 cm; Weight = 39.2 +/- 10.5 kg).

Baseline (initial) measurement of volumetric bone density of trabecular bone at the tibia 50% site . Measurement made by pQCT at a distance of 50% of total tibia length from the distal growth plate. Measurement units: milligrams per cubic centimeter (mg/ccm).

Outcome measures

Measure	Exercise Intervention n=286 Participants Participants randomized to the exercise intervention group performed activities designed to provide skeletal loading: impact activities 3 times per week, increasing the number of jumps (up to 40) and increasing height (from 6 inches to 24 inches per repetition) over the initial 8-weeks (2 months). New activities were introduced approximately every 2-3 months in order to continually stress the skeleton over 2 years. Physical activity performed by these subjects (in addition to intervention activities) was objectively assessed by pedometer (7-day wear period) and further assessed by a validated past year physical activity questionnaire PYPAQ).	Control n=217 Participants Participants randomized to the control arm did not perform intervention activities. Physical activity was objectively assessed by pedometer (7-day wear period) and further assessed by a validated past year physical activity questionnaire (PYPAQ).
Baseline Volumetric Bone Density of Trabecular Bone at the Tibia 50% Site	137.39 milligrams per cubic centimeter (mg/ccm) Standard Deviation 26.83	131.63 milligrams per cubic centimeter (mg/ccm) Standard Deviation 26.97

PRIMARY outcome

Timeframe: Baseline

Population: Population consists of all participants that had complete measurements at the baseline time point (N = 503; Age = 10.6 +/- 1.1 yrs; Height = 144.5 +/- 9.7 cm; Weight = 39.2 +/- 10.5 kg).

Baseline (initial) measurement of volumetric bone density of cortical bone at the tibia 50% site . Measurement made by pQCT at a distance of 50% of total tibia length from the distal growth plate. Measurement units: milligrams per cubic centimeter (mg/ccm).

Outcome measures

Measure	Exercise Intervention n=286 Participants Participants randomized to the exercise intervention group performed activities designed to provide skeletal loading: impact activities 3 times per week, increasing the number of jumps (up to 40) and increasing height (from 6 inches to 24 inches per repetition) over the initial 8-weeks (2 months). New activities were introduced approximately every 2-3 months in order to continually stress the skeleton over 2 years. Physical activity performed by these subjects (in addition to intervention activities) was objectively assessed by pedometer (7-day wear period) and further assessed by a validated past year physical activity questionnaire PYPAQ).	Control n=217 Participants Participants randomized to the control arm did not perform intervention activities. Physical activity was objectively assessed by pedometer (7-day wear period) and further assessed by a validated past year physical activity questionnaire (PYPAQ).
Baseline Volumetric Bone Density of Cortical Bone at the Tibia 50% Site	1070.32 milligrams per cubic centimeter (mg/ccm) Standard Deviation 32.88	1070.95 milligrams per cubic centimeter (mg/ccm) Standard Deviation 31.93

PRIMARY outcome

Timeframe: Baseline

Population: Population consists of all participants that had complete measurements at the baseline time point (N = 503; Age = 10.6 +/- 1.1 yrs; Height = 144.5 +/- 9.7 cm; Weight = 39.2 +/- 10.5 kg).

Baseline (initial) measurement of periosteal circumference at the tibia 50% site . Measurement made by pQCT at a distance of 50% of total tibia length from the distal growth plate. Measurement units: millimeters (mm).

Outcome measures

Measure	Exercise Intervention n=286 Participants Participants randomized to the exercise intervention group performed activities designed to provide skeletal loading: impact activities 3 times per week, increasing the number of jumps (up to 40) and increasing height (from 6 inches to 24 inches per repetition) over the initial 8-weeks (2 months). New activities were introduced approximately every 2-3 months in order to continually stress the skeleton over 2 years. Physical activity performed by these subjects (in addition to intervention activities) was objectively assessed by pedometer (7-day wear period) and further assessed by a validated past year physical activity questionnaire PYPAQ).	Control n=217 Participants Participants randomized to the control arm did not perform intervention activities. Physical activity was objectively assessed by pedometer (7-day wear period) and further assessed by a validated past year physical activity questionnaire (PYPAQ).
Baseline Periosteal Circumference at the Tibia 50% Site	61.98 millimeters (mm) Standard Deviation 5.43	62.33 millimeters (mm) Standard Deviation 5.83

PRIMARY outcome

Timeframe: Baseline

Population: Population consists of all participants that had complete measurements at the baseline time point (N = 503; Age = 10.6 +/- 1.1 yrs; Height = 144.5 +/- 9.7 cm; Weight = 39.2 +/- 10.5 kg).

Baseline (initial) measurement of cortical thickness at the tibia 50% site . Measurement made by pQCT at a distance of 50% of total tibia length from the distal growth plate. Measurement units: millimeters (mm).

Outcome measures

Measure	Exercise Intervention n=286 Participants Participants randomized to the exercise intervention group performed activities designed to provide skeletal loading: impact activities 3 times per week, increasing the number of jumps (up to 40) and increasing height (from 6 inches to 24 inches per repetition) over the initial 8-weeks (2 months). New activities were introduced approximately every 2-3 months in order to continually stress the skeleton over 2 years. Physical activity performed by these subjects (in addition to intervention activities) was objectively assessed by pedometer (7-day wear period) and further assessed by a validated past year physical activity questionnaire PYPAQ).	Control n=217 Participants Participants randomized to the control arm did not perform intervention activities. Physical activity was objectively assessed by pedometer (7-day wear period) and further assessed by a validated past year physical activity questionnaire (PYPAQ).
Baseline Cortical Thickness at the Tibia 50% Site	4.05 millimeters (mm) Standard Deviation .58	4.00 millimeters (mm) Standard Deviation .54

PRIMARY outcome

Timeframe: Baseline

Population: Population consists of all participants that had complete measurements at the baseline time point (N = 503; Age = 10.6 +/- 1.1 yrs; Height = 144.5 +/- 9.7 cm; Weight = 39.2 +/- 10.5 kg).

Baseline (initial) measurement of stress-strain index at the tibia 50% site. Stress-strain index (also called strength-strain index and stress-strength index in the literature) is a measure of the resistance to torsional and bending forces at diaphyseal sites of long bones. Measurement made by pQCT at a distance of 50% of total tibia length from the distal growth plate. Measurement units: mm^3.

Outcome measures

Measure	Exercise Intervention n=286 Participants Participants randomized to the exercise intervention group performed activities designed to provide skeletal loading: impact activities 3 times per week, increasing the number of jumps (up to 40) and increasing height (from 6 inches to 24 inches per repetition) over the initial 8-weeks (2 months). New activities were introduced approximately every 2-3 months in order to continually stress the skeleton over 2 years. Physical activity performed by these subjects (in addition to intervention activities) was objectively assessed by pedometer (7-day wear period) and further assessed by a validated past year physical activity questionnaire PYPAQ).	Control n=217 Participants Participants randomized to the control arm did not perform intervention activities. Physical activity was objectively assessed by pedometer (7-day wear period) and further assessed by a validated past year physical activity questionnaire (PYPAQ).
Baseline Stress-Strain Index at the Tibia 50% Site	1004.97 mm^3 Standard Deviation 272.40	1023.74 mm^3 Standard Deviation 297.42

PRIMARY outcome

Timeframe: Baseline

Population: Population consists of all participants that had complete measurements at the baseline time point (N = 503; Age = 10.6 +/- 1.1 yrs; Height = 144.5 +/- 9.7 cm; Weight = 39.2 +/- 10.5 kg).

Baseline (initial) measurement of total volumetric bone density at the tibia 66% site . Measurement made by pQCT at a distance of 66% of total tibia length from the distal growth plate. Measurement units: milligrams per cubic centimeter (mg/ccm).

Outcome measures

Measure	Exercise Intervention n=286 Participants Participants randomized to the exercise intervention group performed activities designed to provide skeletal loading: impact activities 3 times per week, increasing the number of jumps (up to 40) and increasing height (from 6 inches to 24 inches per repetition) over the initial 8-weeks (2 months). New activities were introduced approximately every 2-3 months in order to continually stress the skeleton over 2 years. Physical activity performed by these subjects (in addition to intervention activities) was objectively assessed by pedometer (7-day wear period) and further assessed by a validated past year physical activity questionnaire PYPAQ).	Control n=217 Participants Participants randomized to the control arm did not perform intervention activities. Physical activity was objectively assessed by pedometer (7-day wear period) and further assessed by a validated past year physical activity questionnaire (PYPAQ).
Baseline Total Volumetric Bone Density at the Tibia 66% Site	566.04 milligrams per cubic centimeter (mg/ccm) Standard Deviation 63.11	552.71 milligrams per cubic centimeter (mg/ccm) Standard Deviation 61.05

PRIMARY outcome

Timeframe: Baseline

Population: Population consists of all participants that had complete measurements at the baseline time point (N = 503; Age = 10.6 +/- 1.1 yrs; Height = 144.5 +/- 9.7 cm; Weight = 39.2 +/- 10.5 kg).

Baseline (initial) measurement of volumetric bone density of trabecular bone at the tibia 66% site . Measurement made by pQCT at a distance of 66% of total tibia length from the distal growth plate. Measurement units: milligrams per cubic centimeter (mg/ccm).

Outcome measures

Measure	Exercise Intervention n=286 Participants Participants randomized to the exercise intervention group performed activities designed to provide skeletal loading: impact activities 3 times per week, increasing the number of jumps (up to 40) and increasing height (from 6 inches to 24 inches per repetition) over the initial 8-weeks (2 months). New activities were introduced approximately every 2-3 months in order to continually stress the skeleton over 2 years. Physical activity performed by these subjects (in addition to intervention activities) was objectively assessed by pedometer (7-day wear period) and further assessed by a validated past year physical activity questionnaire PYPAQ).	Control n=217 Participants Participants randomized to the control arm did not perform intervention activities. Physical activity was objectively assessed by pedometer (7-day wear period) and further assessed by a validated past year physical activity questionnaire (PYPAQ).
Baseline Volumetric Bone Density of Trabecular Bone at the Tibia 66% Site	159.04 milligrams per cubic centimeter (mg/ccm) Standard Deviation 30.48	152.34 milligrams per cubic centimeter (mg/ccm) Standard Deviation 28.73

PRIMARY outcome

Timeframe: Baseline

Population: Population consists of all participants that had complete measurements at the baseline time point (N = 503; Age = 10.6 +/- 1.1 yrs; Height = 144.5 +/- 9.7 cm; Weight = 39.2 +/- 10.5 kg).

Baseline (initial) measurement of volumetric bone density of cortical bone at the tibia 66% site . Measurement made by pQCT at a distance of 66% of total tibia length from the distal growth plate. Measurement units: milligrams per cubic centimeter (mg/ccm).

Outcome measures

Measure	Exercise Intervention n=286 Participants Participants randomized to the exercise intervention group performed activities designed to provide skeletal loading: impact activities 3 times per week, increasing the number of jumps (up to 40) and increasing height (from 6 inches to 24 inches per repetition) over the initial 8-weeks (2 months). New activities were introduced approximately every 2-3 months in order to continually stress the skeleton over 2 years. Physical activity performed by these subjects (in addition to intervention activities) was objectively assessed by pedometer (7-day wear period) and further assessed by a validated past year physical activity questionnaire PYPAQ).	Control n=217 Participants Participants randomized to the control arm did not perform intervention activities. Physical activity was objectively assessed by pedometer (7-day wear period) and further assessed by a validated past year physical activity questionnaire (PYPAQ).
Baseline Volumetric Bone Density of Cortical Bone at the Tibia 66% Site	1029.42 milligrams per cubic centimeter (mg/ccm) Standard Deviation 32.92	1026.07 milligrams per cubic centimeter (mg/ccm) Standard Deviation 31.38

PRIMARY outcome

Timeframe: Baseline

Population: Population consists of all participants that had complete measurements at the baseline time point (N = 503; Age = 10.6 +/- 1.1 yrs; Height = 144.5 +/- 9.7 cm; Weight = 39.2 +/- 10.5 kg).

Baseline (initial) measurement of periosteal circumference at the tibia 66% site . Measurement made by pQCT at a distance of 66% of total tibia length from the distal growth plate. Measurement units: millimeters (mm).

Outcome measures

Measure	Exercise Intervention n=286 Participants Participants randomized to the exercise intervention group performed activities designed to provide skeletal loading: impact activities 3 times per week, increasing the number of jumps (up to 40) and increasing height (from 6 inches to 24 inches per repetition) over the initial 8-weeks (2 months). New activities were introduced approximately every 2-3 months in order to continually stress the skeleton over 2 years. Physical activity performed by these subjects (in addition to intervention activities) was objectively assessed by pedometer (7-day wear period) and further assessed by a validated past year physical activity questionnaire PYPAQ).	Control n=217 Participants Participants randomized to the control arm did not perform intervention activities. Physical activity was objectively assessed by pedometer (7-day wear period) and further assessed by a validated past year physical activity questionnaire (PYPAQ).
Baseline Periosteal Circumference at the Tibia 66% Site	71.55 millimeters (mm) Standard Deviation 6.53	72.34 millimeters (mm) Standard Deviation 7.25

PRIMARY outcome

Timeframe: Baseline

Population: Population consists of all participants that had complete measurements at the baseline time point (N = 503; Age = 10.6 +/- 1.1 yrs; Height = 144.5 +/- 9.7 cm; Weight = 39.2 +/- 10.5 kg).

Baseline (initial) measurement of cortical thickness at the tibia 66% site . Measurement made by pQCT at a distance of 66% of total tibia length from the distal growth plate. Measurement units: millimeters (mm).

Outcome measures

Measure	Exercise Intervention n=286 Participants Participants randomized to the exercise intervention group performed activities designed to provide skeletal loading: impact activities 3 times per week, increasing the number of jumps (up to 40) and increasing height (from 6 inches to 24 inches per repetition) over the initial 8-weeks (2 months). New activities were introduced approximately every 2-3 months in order to continually stress the skeleton over 2 years. Physical activity performed by these subjects (in addition to intervention activities) was objectively assessed by pedometer (7-day wear period) and further assessed by a validated past year physical activity questionnaire PYPAQ).	Control n=217 Participants Participants randomized to the control arm did not perform intervention activities. Physical activity was objectively assessed by pedometer (7-day wear period) and further assessed by a validated past year physical activity questionnaire (PYPAQ).
Baseline Cortical Thickness at the Tibia 66% Site	3.06 millimeters (mm) Standard Deviation .49	3.02 millimeters (mm) Standard Deviation .46

PRIMARY outcome

Timeframe: Baseline

Population: Population consists of all participants that had complete measurements at the baseline time point (N = 503; Age = 10.6 +/- 1.1 yrs; Height = 144.5 +/- 9.7 cm; Weight = 39.2 +/- 10.5 kg).

Baseline (initial) measurement of strength-strain index at the tibia 66% site. Stress-strain index (also called strength-strain index and stress-strength index in the literature) is a measure of the resistance to torsional and bending forces at diaphyseal sites of long bones. Measurement made by pQCT at a distance of 66% of total tibia length from the distal growth plate. Measurement units: mm^3.

Outcome measures

Measure	Exercise Intervention n=286 Participants Participants randomized to the exercise intervention group performed activities designed to provide skeletal loading: impact activities 3 times per week, increasing the number of jumps (up to 40) and increasing height (from 6 inches to 24 inches per repetition) over the initial 8-weeks (2 months). New activities were introduced approximately every 2-3 months in order to continually stress the skeleton over 2 years. Physical activity performed by these subjects (in addition to intervention activities) was objectively assessed by pedometer (7-day wear period) and further assessed by a validated past year physical activity questionnaire PYPAQ).	Control n=217 Participants Participants randomized to the control arm did not perform intervention activities. Physical activity was objectively assessed by pedometer (7-day wear period) and further assessed by a validated past year physical activity questionnaire (PYPAQ).
Baseline Stress-Strain Index at the Tibia 66% Site	1167.94 mm^3 Standard Deviation 331.61	1187.31 mm^3 Standard Deviation 353.09

PRIMARY outcome

Timeframe: Baseline to 12-months

Population: Population consists of all participants that had complete measurements at the baseline, 12-month and 24-month time points (N=207). At 12-months: Age=11.8 +/- 1.0 yrs; Height=153.3 +/- 9.9 cm; Weight=44.0 +/- 9.3 kg. At 24-months: Age=12.8 +/- 1.0 yrs; Height=158.8 +/- 9.1 cm; Weight=50.0 +/- 10.7 kg.

Baseline to 12-month change in total volumetric bone density at the femur 4% site . Measurement made by pQCT at a distance of 4% of total femur length from the distal growth plate. Measurement units: milligrams per cubic centimeter (mg/ccm).

Outcome measures

Measure	Exercise Intervention n=109 Participants Participants randomized to the exercise intervention group performed activities designed to provide skeletal loading: impact activities 3 times per week, increasing the number of jumps (up to 40) and increasing height (from 6 inches to 24 inches per repetition) over the initial 8-weeks (2 months). New activities were introduced approximately every 2-3 months in order to continually stress the skeleton over 2 years. Physical activity performed by these subjects (in addition to intervention activities) was objectively assessed by pedometer (7-day wear period) and further assessed by a validated past year physical activity questionnaire PYPAQ).	Control n=98 Participants Participants randomized to the control arm did not perform intervention activities. Physical activity was objectively assessed by pedometer (7-day wear period) and further assessed by a validated past year physical activity questionnaire (PYPAQ).
12-month Change in Total Volumetric Bone Density the Femur 4% Site	3.10 milligrams per cubic centimeter (mg/ccm) Standard Deviation 15.36	2.83 milligrams per cubic centimeter (mg/ccm) Standard Deviation 12.32

PRIMARY outcome

Timeframe: Baseline to 12-months

Population: Population consists of all participants that had complete measurements at the baseline, 12-month and 24-month time points (N=207). At 12-months: Age=11.8 +/- 1.0 yrs; Height=153.3 +/- 9.9 cm; Weight=44.0 +/- 9.3 kg. At 24-months: Age=12.8 +/- 1.0 yrs; Height=158.8 +/- 9.1 cm; Weight=50.0 +/- 10.7 kg.

Baseline to 12-month change in volumetric bone density of trabecular bone at the femur 4% site . Measurement made by pQCT at a distance of 4% of total femur length from the distal growth plate. Measurement units: milligrams per cubic centimeter (mg/ccm).

Outcome measures

Measure	Exercise Intervention n=109 Participants Participants randomized to the exercise intervention group performed activities designed to provide skeletal loading: impact activities 3 times per week, increasing the number of jumps (up to 40) and increasing height (from 6 inches to 24 inches per repetition) over the initial 8-weeks (2 months). New activities were introduced approximately every 2-3 months in order to continually stress the skeleton over 2 years. Physical activity performed by these subjects (in addition to intervention activities) was objectively assessed by pedometer (7-day wear period) and further assessed by a validated past year physical activity questionnaire PYPAQ).	Control n=98 Participants Participants randomized to the control arm did not perform intervention activities. Physical activity was objectively assessed by pedometer (7-day wear period) and further assessed by a validated past year physical activity questionnaire (PYPAQ).
12-month Change in Volumetric Bone Density of Trabecular Bone at the Femur 4% Site	3.37 milligrams per cubic centimeter (mg/ccm) Standard Deviation 15.23	5.89 milligrams per cubic centimeter (mg/ccm) Standard Deviation 12.94

PRIMARY outcome

Timeframe: Baseline to 12-months

Population: Population consists of all participants that had complete measurements at the baseline, 12-month and 24-month time points (N=207). At 12-months: Age=11.8 +/- 1.0 yrs; Height=153.3 +/- 9.9 cm; Weight=44.0 +/- 9.3 kg. At 24-months: Age=12.8 +/- 1.0 yrs; Height=158.8 +/- 9.1 cm; Weight=50.0 +/- 10.7 kg.

Baseline to 12-month change in volumetric bone density of cortical bone at the femur 4% site . Measurement made by pQCT at a distance of 4% of total femur length from the distal growth plate. Measurement units: milligrams per cubic centimeter (mg/ccm).

Outcome measures

Measure	Exercise Intervention n=109 Participants Participants randomized to the exercise intervention group performed activities designed to provide skeletal loading: impact activities 3 times per week, increasing the number of jumps (up to 40) and increasing height (from 6 inches to 24 inches per repetition) over the initial 8-weeks (2 months). New activities were introduced approximately every 2-3 months in order to continually stress the skeleton over 2 years. Physical activity performed by these subjects (in addition to intervention activities) was objectively assessed by pedometer (7-day wear period) and further assessed by a validated past year physical activity questionnaire PYPAQ).	Control n=98 Participants Participants randomized to the control arm did not perform intervention activities. Physical activity was objectively assessed by pedometer (7-day wear period) and further assessed by a validated past year physical activity questionnaire (PYPAQ).
12-month Change in Volumetric Bone Density of Cortical Bone at the Femur 4% Site	2.14 milligrams per cubic centimeter (mg/ccm) Standard Deviation 14.47	1.68 milligrams per cubic centimeter (mg/ccm) Standard Deviation 11.47

PRIMARY outcome

Timeframe: Baseline to 12-months

Population: Population consists of all participants that had complete measurements at the baseline, 12-month and 24-month time points (N=207). At 12-months: Age=11.8 +/- 1.0 yrs; Height=153.3 +/- 9.9 cm; Weight=44.0 +/- 9.3 kg. At 24-months: Age=12.8 +/- 1.0 yrs; Height=158.8 +/- 9.1 cm; Weight=50.0 +/- 10.7 kg.

Baseline to 12-month change in trabecular bone area at the femur 4% site . Measurement made by pQCT at a distance of 4% of total femur length from the distal growth plate. Measurement units: square millimeters (mm^2).

Outcome measures

Measure	Exercise Intervention n=109 Participants Participants randomized to the exercise intervention group performed activities designed to provide skeletal loading: impact activities 3 times per week, increasing the number of jumps (up to 40) and increasing height (from 6 inches to 24 inches per repetition) over the initial 8-weeks (2 months). New activities were introduced approximately every 2-3 months in order to continually stress the skeleton over 2 years. Physical activity performed by these subjects (in addition to intervention activities) was objectively assessed by pedometer (7-day wear period) and further assessed by a validated past year physical activity questionnaire PYPAQ).	Control n=98 Participants Participants randomized to the control arm did not perform intervention activities. Physical activity was objectively assessed by pedometer (7-day wear period) and further assessed by a validated past year physical activity questionnaire (PYPAQ).
12-month Change in Trabecular Bone Area at the Femur 4% Site	104.16 millimeters squared (mm^2) Standard Deviation 111.80	144.97 millimeters squared (mm^2) Standard Deviation 96.38

PRIMARY outcome

Timeframe: Baseline to 12-months

Population: Population consists of all participants that had complete measurements at the baseline, 12-month and 24-month time points (N=207). At 12-months: Age=11.8 +/- 1.0 yrs; Height=153.3 +/- 9.9 cm; Weight=44.0 +/- 9.3 kg. At 24-months: Age=12.8 +/- 1.0 yrs; Height=158.8 +/- 9.1 cm; Weight=50.0 +/- 10.7 kg.

Baseline to 12-month change in cortical bone area at the femur 4% site . Measurement made by pQCT at a distance of 4% of total femur length from the distal growth plate. Measurement units: square millimeters (mm^2).

Outcome measures

Measure	Exercise Intervention n=109 Participants Participants randomized to the exercise intervention group performed activities designed to provide skeletal loading: impact activities 3 times per week, increasing the number of jumps (up to 40) and increasing height (from 6 inches to 24 inches per repetition) over the initial 8-weeks (2 months). New activities were introduced approximately every 2-3 months in order to continually stress the skeleton over 2 years. Physical activity performed by these subjects (in addition to intervention activities) was objectively assessed by pedometer (7-day wear period) and further assessed by a validated past year physical activity questionnaire PYPAQ).	Control n=98 Participants Participants randomized to the control arm did not perform intervention activities. Physical activity was objectively assessed by pedometer (7-day wear period) and further assessed by a validated past year physical activity questionnaire (PYPAQ).
12-month Change in Cortical Bone Area at the Femur 4% Site	140.00 millimeters squared (mm^2) Standard Deviation 131.17	185.50 millimeters squared (mm^2) Standard Deviation 119.42

PRIMARY outcome

Timeframe: Baseline to 12-months

Population: Population consists of all participants that had complete measurements at the baseline, 12-month and 24-month time points (N=207). At 12-months: Age=11.8 +/- 1.0 yrs; Height=153.3 +/- 9.9 cm; Weight=44.0 +/- 9.3 kg. At 24-months: Age=12.8 +/- 1.0 yrs; Height=158.8 +/- 9.1 cm; Weight=50.0 +/- 10.7 kg.

Baseline to 12-month change in periosteal circumference at the femur 4% site . Measurement made by pQCT at a distance of 4% of total femur length from the distal growth plate. Measurement units: millimeters (mm).

Outcome measures

Measure	Exercise Intervention n=109 Participants Participants randomized to the exercise intervention group performed activities designed to provide skeletal loading: impact activities 3 times per week, increasing the number of jumps (up to 40) and increasing height (from 6 inches to 24 inches per repetition) over the initial 8-weeks (2 months). New activities were introduced approximately every 2-3 months in order to continually stress the skeleton over 2 years. Physical activity performed by these subjects (in addition to intervention activities) was objectively assessed by pedometer (7-day wear period) and further assessed by a validated past year physical activity questionnaire PYPAQ).	Control n=98 Participants Participants randomized to the control arm did not perform intervention activities. Physical activity was objectively assessed by pedometer (7-day wear period) and further assessed by a validated past year physical activity questionnaire (PYPAQ).
12-month Change in Periosteal Circumference at the Femur 4% Site	6.17 millimeters (mm) Standard Deviation 5.80	8.09 millimeters (mm) Standard Deviation 4.84

PRIMARY outcome

Timeframe: Baseline to 12-months

Population: Population consists of all participants that had complete measurements at the baseline, 12-month and 24-month time points (N=207). At 12-months: Age=11.8 +/- 1.0 yrs; Height=153.3 +/- 9.9 cm; Weight=44.0 +/- 9.3 kg. At 24-months: Age=12.8 +/- 1.0 yrs; Height=158.8 +/- 9.1 cm; Weight=50.0 +/- 10.7 kg.

Baseline to 12-month change in bone strength index (BSI) at the femur 4% site. Bone Strength Index (BSI) is a measurement of the resistance to compression forces at the epiphyses of long bones. Measurement made by pQCT at a distance of 4% of total tibia length from the distal growth plate. Measurement units: mm^4.

Outcome measures

Measure	Exercise Intervention n=109 Participants Participants randomized to the exercise intervention group performed activities designed to provide skeletal loading: impact activities 3 times per week, increasing the number of jumps (up to 40) and increasing height (from 6 inches to 24 inches per repetition) over the initial 8-weeks (2 months). New activities were introduced approximately every 2-3 months in order to continually stress the skeleton over 2 years. Physical activity performed by these subjects (in addition to intervention activities) was objectively assessed by pedometer (7-day wear period) and further assessed by a validated past year physical activity questionnaire PYPAQ).	Control n=98 Participants Participants randomized to the control arm did not perform intervention activities. Physical activity was objectively assessed by pedometer (7-day wear period) and further assessed by a validated past year physical activity questionnaire (PYPAQ).
12-month Change in Bone Strength Index at the Femur 4% Site	12.84 mm^4 Standard Deviation 12.67	15.03 mm^4 Standard Deviation 14.19

PRIMARY outcome

Timeframe: Baseline to 12-months

Population: Population consists of all participants that had complete measurements at the baseline, 12-month and 24-month time points (N=207). At 12-months: Age=11.8 +/- 1.0 yrs; Height=153.3 +/- 9.9 cm; Weight=44.0 +/- 9.3 kg. At 24-months: Age=12.8 +/- 1.0 yrs; Height=158.8 +/- 9.1 cm; Weight=50.0 +/- 10.7 kg.

Baseline to 12-month change in total volumetric bone density at the femur 20% site . Measurement made by pQCT at a distance of 20% of total femur length from the distal growth plate. Measurement units: milligrams per cubic centimeter (mg/ccm).

Outcome measures

Measure	Exercise Intervention n=109 Participants Participants randomized to the exercise intervention group performed activities designed to provide skeletal loading: impact activities 3 times per week, increasing the number of jumps (up to 40) and increasing height (from 6 inches to 24 inches per repetition) over the initial 8-weeks (2 months). New activities were introduced approximately every 2-3 months in order to continually stress the skeleton over 2 years. Physical activity performed by these subjects (in addition to intervention activities) was objectively assessed by pedometer (7-day wear period) and further assessed by a validated past year physical activity questionnaire PYPAQ).	Control n=98 Participants Participants randomized to the control arm did not perform intervention activities. Physical activity was objectively assessed by pedometer (7-day wear period) and further assessed by a validated past year physical activity questionnaire (PYPAQ).
12-month Change in Total Volumetric Bone Density at the Femur 20% Site	2.40 milligrams per cubic centimeter (mg/ccm) Standard Deviation 22.38	-2.46 milligrams per cubic centimeter (mg/ccm) Standard Deviation 18.74

PRIMARY outcome

Timeframe: Baseline to 12-months

Population: Population consists of all participants that had complete measurements at the baseline, 12-month and 24-month time points (N=207). At 12-months: Age=11.8 +/- 1.0 yrs; Height=153.3 +/- 9.9 cm; Weight=44.0 +/- 9.3 kg. At 24-months: Age=12.8 +/- 1.0 yrs; Height=158.8 +/- 9.1 cm; Weight=50.0 +/- 10.7 kg.

Baseline to 12-month change in volumetric bone density of trabecular bone at the femur 20% site . Measurement made by pQCT at a distance of 20% of total femur length from the distal growth plate. Measurement units: milligrams per cubic centimeter (mg/ccm).

Outcome measures

Measure	Exercise Intervention n=109 Participants Participants randomized to the exercise intervention group performed activities designed to provide skeletal loading: impact activities 3 times per week, increasing the number of jumps (up to 40) and increasing height (from 6 inches to 24 inches per repetition) over the initial 8-weeks (2 months). New activities were introduced approximately every 2-3 months in order to continually stress the skeleton over 2 years. Physical activity performed by these subjects (in addition to intervention activities) was objectively assessed by pedometer (7-day wear period) and further assessed by a validated past year physical activity questionnaire PYPAQ).	Control n=98 Participants Participants randomized to the control arm did not perform intervention activities. Physical activity was objectively assessed by pedometer (7-day wear period) and further assessed by a validated past year physical activity questionnaire (PYPAQ).
12-month Change in Volumetric Bone Density of Trabecular Bone at the Femur 20% Site	7.12 milligrams per cubic centimeter (mg/ccm) Standard Deviation 12.98	5.77 milligrams per cubic centimeter (mg/ccm) Standard Deviation 12.38

PRIMARY outcome

Timeframe: Baseline to 12-months

Population: Population consists of all participants that had complete measurements at the baseline, 12-month and 24-month time points (N=207). At 12-months: Age=11.8 +/- 1.0 yrs; Height=153.3 +/- 9.9 cm; Weight=44.0 +/- 9.3 kg. At 24-months: Age=12.8 +/- 1.0 yrs; Height=158.8 +/- 9.1 cm; Weight=50.0 +/- 10.7 kg.

Baseline to 12-month change in volumetric bone density of cortical bone at the femur 20% site . Measurement made by pQCT at a distance of 20% of total femur length from the distal growth plate. Measurement units: milligrams per cubic centimeter (mg/ccm).

Outcome measures

Measure	Exercise Intervention n=109 Participants Participants randomized to the exercise intervention group performed activities designed to provide skeletal loading: impact activities 3 times per week, increasing the number of jumps (up to 40) and increasing height (from 6 inches to 24 inches per repetition) over the initial 8-weeks (2 months). New activities were introduced approximately every 2-3 months in order to continually stress the skeleton over 2 years. Physical activity performed by these subjects (in addition to intervention activities) was objectively assessed by pedometer (7-day wear period) and further assessed by a validated past year physical activity questionnaire PYPAQ).	Control n=98 Participants Participants randomized to the control arm did not perform intervention activities. Physical activity was objectively assessed by pedometer (7-day wear period) and further assessed by a validated past year physical activity questionnaire (PYPAQ).
12-month Change in Volumetric Bone Density of Cortical Bone at the Femur 20% Site	6.87 milligrams per cubic centimeter (mg/ccm) Standard Deviation 20.02	4.39 milligrams per cubic centimeter (mg/ccm) Standard Deviation 19.38

PRIMARY outcome

Timeframe: Baseline to 12-months

Population: Population consists of all participants that had complete measurements at the baseline, 12-month and 24-month time points (N=207). At 12-months: Age=11.8 +/- 1.0 yrs; Height=153.3 +/- 9.9 cm; Weight=44.0 +/- 9.3 kg. At 24-months: Age=12.8 +/- 1.0 yrs; Height=158.8 +/- 9.1 cm; Weight=50.0 +/- 10.7 kg.

Baseline to 12-month change in thickness of cortical bone at the femur 20% site . Measurement made by pQCT at a distance of 20% of total femur length from the distal growth plate. Measurement units millimeters (mm).

Outcome measures

Measure	Exercise Intervention n=109 Participants Participants randomized to the exercise intervention group performed activities designed to provide skeletal loading: impact activities 3 times per week, increasing the number of jumps (up to 40) and increasing height (from 6 inches to 24 inches per repetition) over the initial 8-weeks (2 months). New activities were introduced approximately every 2-3 months in order to continually stress the skeleton over 2 years. Physical activity performed by these subjects (in addition to intervention activities) was objectively assessed by pedometer (7-day wear period) and further assessed by a validated past year physical activity questionnaire PYPAQ).	Control n=98 Participants Participants randomized to the control arm did not perform intervention activities. Physical activity was objectively assessed by pedometer (7-day wear period) and further assessed by a validated past year physical activity questionnaire (PYPAQ).
12-month Change in Thickness of Cortical Bone at the Femur 20% Site	.11 millimeters (mm) Standard Deviation .17	.11 millimeters (mm) Standard Deviation .15

PRIMARY outcome

Timeframe: Baseline to 12-months

Population: Population consists of all participants that had complete measurements at the baseline, 12-month and 24-month time points (N=207). At 12-months: Age=11.8 +/- 1.0 yrs; Height=153.3 +/- 9.9 cm; Weight=44.0 +/- 9.3 kg. At 24-months: Age=12.8 +/- 1.0 yrs; Height=158.8 +/- 9.1 cm; Weight=50.0 +/- 10.7 kg.

Baseline to 12-month change in periosteal circumference at the femur 20% site . Measurement made by pQCT at a distance of 20% of total femur length from the distal growth plate. Measurement units: millimeters (mm).

Outcome measures

Measure	Exercise Intervention n=109 Participants Participants randomized to the exercise intervention group performed activities designed to provide skeletal loading: impact activities 3 times per week, increasing the number of jumps (up to 40) and increasing height (from 6 inches to 24 inches per repetition) over the initial 8-weeks (2 months). New activities were introduced approximately every 2-3 months in order to continually stress the skeleton over 2 years. Physical activity performed by these subjects (in addition to intervention activities) was objectively assessed by pedometer (7-day wear period) and further assessed by a validated past year physical activity questionnaire PYPAQ).	Control n=98 Participants Participants randomized to the control arm did not perform intervention activities. Physical activity was objectively assessed by pedometer (7-day wear period) and further assessed by a validated past year physical activity questionnaire (PYPAQ).
12-month Change in Periosteal Circumference at the Femur 20% Site	4.89 millimeters (mm) Standard Deviation 2.21	5.65 millimeters (mm) Standard Deviation 2.20

PRIMARY outcome

Timeframe: Baseline to 12-months

Population: Population consists of all participants that had complete measurements at the baseline, 12-month and 24-month time points (N=207). At 12-months: Age=11.8 +/- 1.0 yrs; Height=153.3 +/- 9.9 cm; Weight=44.0 +/- 9.3 kg. At 24-months: Age=12.8 +/- 1.0 yrs; Height=158.8 +/- 9.1 cm; Weight=50.0 +/- 10.7 kg.

Baseline to 12-month change in strength-strain index at the femur 20% site. Stress-strain index (also called strength-strain index and stress-strength index in the literature) is a measure of the resistance to torsional and bending forces at diaphyseal sites of long bones. Measurement made by pQCT at a distance of 20% of total femur length from the distal growth plate. Measurement units: mm^3.

Outcome measures

Measure	Exercise Intervention n=109 Participants Participants randomized to the exercise intervention group performed activities designed to provide skeletal loading: impact activities 3 times per week, increasing the number of jumps (up to 40) and increasing height (from 6 inches to 24 inches per repetition) over the initial 8-weeks (2 months). New activities were introduced approximately every 2-3 months in order to continually stress the skeleton over 2 years. Physical activity performed by these subjects (in addition to intervention activities) was objectively assessed by pedometer (7-day wear period) and further assessed by a validated past year physical activity questionnaire PYPAQ).	Control n=98 Participants Participants randomized to the control arm did not perform intervention activities. Physical activity was objectively assessed by pedometer (7-day wear period) and further assessed by a validated past year physical activity questionnaire (PYPAQ).
12-month Change in Stress-Strain Index at the Femur 20% Site	261.94 mm^3 Standard Deviation 137.73	297.43 mm^3 Standard Deviation 145.31

PRIMARY outcome

Timeframe: Baseline to 12-months

Population: Population consists of all participants that had complete measurements at the baseline, 12-month and 24-month time points (N=207). At 12-months: Age=11.8 +/- 1.0 yrs; Height=153.3 +/- 9.9 cm; Weight=44.0 +/- 9.3 kg. At 24-months: Age=12.8 +/- 1.0 yrs; Height=158.8 +/- 9.1 cm; Weight=50.0 +/- 10.7 kg.

Baseline to 12-month change in total volumetric bone density at the tibia 4% site . Measurement made by pQCT at a distance of 4% of total tibia length from the distal growth plate. Measurement units: milligrams per cubic centimeter (mg/ccm).

Outcome measures

Measure	Exercise Intervention n=109 Participants Participants randomized to the exercise intervention group performed activities designed to provide skeletal loading: impact activities 3 times per week, increasing the number of jumps (up to 40) and increasing height (from 6 inches to 24 inches per repetition) over the initial 8-weeks (2 months). New activities were introduced approximately every 2-3 months in order to continually stress the skeleton over 2 years. Physical activity performed by these subjects (in addition to intervention activities) was objectively assessed by pedometer (7-day wear period) and further assessed by a validated past year physical activity questionnaire PYPAQ).	Control n=98 Participants Participants randomized to the control arm did not perform intervention activities. Physical activity was objectively assessed by pedometer (7-day wear period) and further assessed by a validated past year physical activity questionnaire (PYPAQ).
12-month Change in Total Volumetric Bone Density at the Tibia 4% Site	9.87 milligrams per cubic centimeter (mg/ccm) Standard Deviation 17.29	10.34 milligrams per cubic centimeter (mg/ccm) Standard Deviation 19.34

PRIMARY outcome

Timeframe: Baseline to 12-months

Population: Population consists of all participants that had complete measurements at the baseline, 12-month and 24-month time points (N=207). At 12-months: Age=11.8 +/- 1.0 yrs; Height=153.3 +/- 9.9 cm; Weight=44.0 +/- 9.3 kg. At 24-months: Age=12.8 +/- 1.0 yrs; Height=158.8 +/- 9.1 cm; Weight=50.0 +/- 10.7 kg.

Baseline to 12-month change in volumetric bone density of trabecular bone at the tibia 4% site . Measurement made by pQCT at a distance of 4% of total tibia length from the distal growth plate. Measurement units: milligrams per cubic centimeter (mg/ccm).

Outcome measures

Measure	Exercise Intervention n=109 Participants Participants randomized to the exercise intervention group performed activities designed to provide skeletal loading: impact activities 3 times per week, increasing the number of jumps (up to 40) and increasing height (from 6 inches to 24 inches per repetition) over the initial 8-weeks (2 months). New activities were introduced approximately every 2-3 months in order to continually stress the skeleton over 2 years. Physical activity performed by these subjects (in addition to intervention activities) was objectively assessed by pedometer (7-day wear period) and further assessed by a validated past year physical activity questionnaire PYPAQ).	Control n=98 Participants Participants randomized to the control arm did not perform intervention activities. Physical activity was objectively assessed by pedometer (7-day wear period) and further assessed by a validated past year physical activity questionnaire (PYPAQ).
12-month Change in Volumetric Bone Density of Trabecular Bone at the Tibia 4% Site	2.84 milligrams per cubic centimeter (mg/ccm) Standard Deviation 10.22	2.36 milligrams per cubic centimeter (mg/ccm) Standard Deviation 9.33

PRIMARY outcome

Timeframe: Baseline to 12-months

Population: Population consists of all participants that had complete measurements at the baseline, 12-month and 24-month time points (N=207). At 12-months: Age=11.8 +/- 1.0 yrs; Height=153.3 +/- 9.9 cm; Weight=44.0 +/- 9.3 kg. At 24-months: Age=12.8 +/- 1.0 yrs; Height=158.8 +/- 9.1 cm; Weight=50.0 +/- 10.7 kg.

Baseline to 12-month change in volumetric bone density of cortical bone at the tibia 4% site . Measurement made by pQCT at a distance of 4% of total tibia length from the distal growth plate. Measurement units: milligrams per cubic centimeter (mg/ccm).

Outcome measures

Measure	Exercise Intervention n=109 Participants Participants randomized to the exercise intervention group performed activities designed to provide skeletal loading: impact activities 3 times per week, increasing the number of jumps (up to 40) and increasing height (from 6 inches to 24 inches per repetition) over the initial 8-weeks (2 months). New activities were introduced approximately every 2-3 months in order to continually stress the skeleton over 2 years. Physical activity performed by these subjects (in addition to intervention activities) was objectively assessed by pedometer (7-day wear period) and further assessed by a validated past year physical activity questionnaire PYPAQ).	Control n=98 Participants Participants randomized to the control arm did not perform intervention activities. Physical activity was objectively assessed by pedometer (7-day wear period) and further assessed by a validated past year physical activity questionnaire (PYPAQ).
12-month Change in Volumetric Bone Density of Cortical Bone at the Tibia 4% Site	9.69 milligrams per cubic centimeter (mg/ccm) Standard Deviation 16.76	10.10 milligrams per cubic centimeter (mg/ccm) Standard Deviation 18.73

PRIMARY outcome

Timeframe: Baseline to 12-months

Population: Population consists of all participants that had complete measurements at the baseline, 12-month and 24-month time points (N=207). At 12-months: Age=11.8 +/- 1.0 yrs; Height=153.3 +/- 9.9 cm; Weight=44.0 +/- 9.3 kg. At 24-months: Age=12.8 +/- 1.0 yrs; Height=158.8 +/- 9.1 cm; Weight=50.0 +/- 10.7 kg.

Baseline to 12-month change in trabecular bone area at the tibia 4% site . Measurement made by pQCT at a distance of 4% of total tibia length from the distal growth plate. Measurement units: square millimeters (mm^2).

Outcome measures

Measure	Exercise Intervention n=109 Participants Participants randomized to the exercise intervention group performed activities designed to provide skeletal loading: impact activities 3 times per week, increasing the number of jumps (up to 40) and increasing height (from 6 inches to 24 inches per repetition) over the initial 8-weeks (2 months). New activities were introduced approximately every 2-3 months in order to continually stress the skeleton over 2 years. Physical activity performed by these subjects (in addition to intervention activities) was objectively assessed by pedometer (7-day wear period) and further assessed by a validated past year physical activity questionnaire PYPAQ).	Control n=98 Participants Participants randomized to the control arm did not perform intervention activities. Physical activity was objectively assessed by pedometer (7-day wear period) and further assessed by a validated past year physical activity questionnaire (PYPAQ).
12-month Change in Trabecular Bone Area at the Tibia 4% Site	29.87 millimeters squared (mm^2) Standard Deviation 52.91	24.65 millimeters squared (mm^2) Standard Deviation 50.00

PRIMARY outcome

Timeframe: Baseline to 12-months

Population: Population consists of all participants that had complete measurements at the baseline, 12-month and 24-month time points (N=207). At 12-months: Age=11.8 +/- 1.0 yrs; Height=153.3 +/- 9.9 cm; Weight=44.0 +/- 9.3 kg. At 24-months: Age=12.8 +/- 1.0 yrs; Height=158.8 +/- 9.1 cm; Weight=50.0 +/- 10.7 kg.

Baseline to 12-month change in cortical bone area at the tibia 4% site . Measurement made by pQCT at a distance of 4% of total tibia length from the distal growth plate. Measurement units: square millimeters (mm^2).

Outcome measures

Measure	Exercise Intervention n=109 Participants Participants randomized to the exercise intervention group performed activities designed to provide skeletal loading: impact activities 3 times per week, increasing the number of jumps (up to 40) and increasing height (from 6 inches to 24 inches per repetition) over the initial 8-weeks (2 months). New activities were introduced approximately every 2-3 months in order to continually stress the skeleton over 2 years. Physical activity performed by these subjects (in addition to intervention activities) was objectively assessed by pedometer (7-day wear period) and further assessed by a validated past year physical activity questionnaire PYPAQ).	Control n=98 Participants Participants randomized to the control arm did not perform intervention activities. Physical activity was objectively assessed by pedometer (7-day wear period) and further assessed by a validated past year physical activity questionnaire (PYPAQ).
12-month Change in Cortical Bone Area at the Tibia 4% Site	44.85 millimeters squared (mm^2) Standard Deviation 54.14	39.53 millimeters squared (mm^2) Standard Deviation 49.12

PRIMARY outcome

Timeframe: Baseline to 12-months

Population: Population consists of all participants that had complete measurements at the baseline, 12-month and 24-month time points (N=207). At 12-months: Age=11.8 +/- 1.0 yrs; Height=153.3 +/- 9.9 cm; Weight=44.0 +/- 9.3 kg. At 24-months: Age=12.8 +/- 1.0 yrs; Height=158.8 +/- 9.1 cm; Weight=50.0 +/- 10.7 kg.

Baseline to 12-month change in periosteal circumference at the tibia 4% site . Measurement made by pQCT at a distance of 4% of total tibia length from the distal growth plate. Measurement units: millimeters (mm).

Outcome measures

Measure	Exercise Intervention n=109 Participants Participants randomized to the exercise intervention group performed activities designed to provide skeletal loading: impact activities 3 times per week, increasing the number of jumps (up to 40) and increasing height (from 6 inches to 24 inches per repetition) over the initial 8-weeks (2 months). New activities were introduced approximately every 2-3 months in order to continually stress the skeleton over 2 years. Physical activity performed by these subjects (in addition to intervention activities) was objectively assessed by pedometer (7-day wear period) and further assessed by a validated past year physical activity questionnaire PYPAQ).	Control n=98 Participants Participants randomized to the control arm did not perform intervention activities. Physical activity was objectively assessed by pedometer (7-day wear period) and further assessed by a validated past year physical activity questionnaire (PYPAQ).
12-month Change in Periosteal Circumference at the Tibia 4% Site	3.17 millimeters (mm) Standard Deviation 3.70	2.77 millimeters (mm) Standard Deviation 3.44

PRIMARY outcome

Timeframe: Baseline to 12-months

Population: Population consists of all participants that had complete measurements at the baseline, 12-month and 24-month time points (N=207). At 12-months: Age=11.8 +/- 1.0 yrs; Height=153.3 +/- 9.9 cm; Weight=44.0 +/- 9.3 kg. At 24-months: Age=12.8 +/- 1.0 yrs; Height=158.8 +/- 9.1 cm; Weight=50.0 +/- 10.7 kg.

Baseline to 12-month change in bone strength index (BSI) at the tibia 4% site. Bone Strength Index (BSI) is a measurement of the resistance to compression forces at the epiphyses of long bones. Measurement made by pQCT at a distance of 4% of total tibia length from the distal growth plate. Measurement units: mm^4.

Outcome measures

Measure	Exercise Intervention n=109 Participants Participants randomized to the exercise intervention group performed activities designed to provide skeletal loading: impact activities 3 times per week, increasing the number of jumps (up to 40) and increasing height (from 6 inches to 24 inches per repetition) over the initial 8-weeks (2 months). New activities were introduced approximately every 2-3 months in order to continually stress the skeleton over 2 years. Physical activity performed by these subjects (in addition to intervention activities) was objectively assessed by pedometer (7-day wear period) and further assessed by a validated past year physical activity questionnaire PYPAQ).	Control n=98 Participants Participants randomized to the control arm did not perform intervention activities. Physical activity was objectively assessed by pedometer (7-day wear period) and further assessed by a validated past year physical activity questionnaire (PYPAQ).
12-month Change in Bone Strength Index at the Tibia 4% Site	7.84 mm^4 Standard Deviation 5.39	7.46 mm^4 Standard Deviation 5.53

PRIMARY outcome

Timeframe: Baseline to 12-months

Population: Population consists of all participants that had complete measurements at the baseline, 12-month and 24-month time points (N=207). At 12-months: Age=11.8 +/- 1.0 yrs; Height=153.3 +/- 9.9 cm; Weight=44.0 +/- 9.3 kg. At 24-months: Age=12.8 +/- 1.0 yrs; Height=158.8 +/- 9.1 cm; Weight=50.0 +/- 10.7 kg.

Baseline to 12-month change in total volumetric bone density at the tibia 50% site . Measurement made by pQCT at a distance of 50% of total tibia length from the distal growth plate. Measurement units: milligrams per cubic centimeter (mg/ccm).

Outcome measures

Measure	Exercise Intervention n=109 Participants Participants randomized to the exercise intervention group performed activities designed to provide skeletal loading: impact activities 3 times per week, increasing the number of jumps (up to 40) and increasing height (from 6 inches to 24 inches per repetition) over the initial 8-weeks (2 months). New activities were introduced approximately every 2-3 months in order to continually stress the skeleton over 2 years. Physical activity performed by these subjects (in addition to intervention activities) was objectively assessed by pedometer (7-day wear period) and further assessed by a validated past year physical activity questionnaire PYPAQ).	Control n=98 Participants Participants randomized to the control arm did not perform intervention activities. Physical activity was objectively assessed by pedometer (7-day wear period) and further assessed by a validated past year physical activity questionnaire (PYPAQ).
12-month Change in Total Volumetric Bone Density at the Tibia 50% Site	17.98 milligrams per cubic centimeter (mg/ccm) Standard Deviation 22.27	17.76 milligrams per cubic centimeter (mg/ccm) Standard Deviation 22.02

PRIMARY outcome

Timeframe: Baseline to 12-months

Population: Population consists of all participants that had complete measurements at the baseline, 12-month and 24-month time points (N=207). At 12-months: Age=11.8 +/- 1.0 yrs; Height=153.3 +/- 9.9 cm; Weight=44.0 +/- 9.3 kg. At 24-months: Age=12.8 +/- 1.0 yrs; Height=158.8 +/- 9.1 cm; Weight=50.0 +/- 10.7 kg.

Baseline to 12-month change in volumetric bone density of trabecular bone at the tibia 50% site . Measurement made by pQCT at a distance of 50% of total tibia length from the distal growth plate. Measurement units: milligrams per cubic centimeter (mg/ccm).

Outcome measures

Measure	Exercise Intervention n=109 Participants Participants randomized to the exercise intervention group performed activities designed to provide skeletal loading: impact activities 3 times per week, increasing the number of jumps (up to 40) and increasing height (from 6 inches to 24 inches per repetition) over the initial 8-weeks (2 months). New activities were introduced approximately every 2-3 months in order to continually stress the skeleton over 2 years. Physical activity performed by these subjects (in addition to intervention activities) was objectively assessed by pedometer (7-day wear period) and further assessed by a validated past year physical activity questionnaire PYPAQ).	Control n=98 Participants Participants randomized to the control arm did not perform intervention activities. Physical activity was objectively assessed by pedometer (7-day wear period) and further assessed by a validated past year physical activity questionnaire (PYPAQ).
12-month Change in Volumetric Bone Density of Trabecular Bone at the Tibia 50% Site	-2.74 milligrams per cubic centimeter (mg/ccm) Standard Deviation 13.55	-3.16 milligrams per cubic centimeter (mg/ccm) Standard Deviation 15.63

PRIMARY outcome

Timeframe: Baseline to 12-months

Population: Population consists of all participants that had complete measurements at the baseline, 12-month and 24-month time points (N=207). At 12-months: Age=11.8 +/- 1.0 yrs; Height=153.3 +/- 9.9 cm; Weight=44.0 +/- 9.3 kg. At 24-months: Age=12.8 +/- 1.0 yrs; Height=158.8 +/- 9.1 cm; Weight=50.0 +/- 10.7 kg.

Baseline to 12-month change in volumetric bone density of cortical bone at the tibia 50% site . Measurement made by pQCT at a distance of 50% of total tibia length from the distal growth plate. Measurement units: milligrams per cubic centimeter (mg/ccm).

Outcome measures

Measure	Exercise Intervention n=109 Participants Participants randomized to the exercise intervention group performed activities designed to provide skeletal loading: impact activities 3 times per week, increasing the number of jumps (up to 40) and increasing height (from 6 inches to 24 inches per repetition) over the initial 8-weeks (2 months). New activities were introduced approximately every 2-3 months in order to continually stress the skeleton over 2 years. Physical activity performed by these subjects (in addition to intervention activities) was objectively assessed by pedometer (7-day wear period) and further assessed by a validated past year physical activity questionnaire PYPAQ).	Control n=98 Participants Participants randomized to the control arm did not perform intervention activities. Physical activity was objectively assessed by pedometer (7-day wear period) and further assessed by a validated past year physical activity questionnaire (PYPAQ).
12-month Change in Volumetric Bone Density of Cortical Bone at the Tibia 50% Site	14.34 milligrams per cubic centimeter (mg/ccm) Standard Deviation 22.23	11.16 milligrams per cubic centimeter (mg/ccm) Standard Deviation 18.91

PRIMARY outcome

Timeframe: Baseline to 12-months

Population: Population consists of all participants that had complete measurements at the baseline, 12-month and 24-month time points (N=207). At 12-months: Age=11.8 +/- 1.0 yrs; Height=153.3 +/- 9.9 cm; Weight=44.0 +/- 9.3 kg. At 24-months: Age=12.8 +/- 1.0 yrs; Height=158.8 +/- 9.1 cm; Weight=50.0 +/- 10.7 kg.

Baseline to 12-month change in periosteal circumference at the tibia 50% site . Measurement made by pQCT at a distance of 50% of total tibia length from the distal growth plate. Measurement units: millimeters (mm).

Outcome measures

Measure	Exercise Intervention n=109 Participants Participants randomized to the exercise intervention group performed activities designed to provide skeletal loading: impact activities 3 times per week, increasing the number of jumps (up to 40) and increasing height (from 6 inches to 24 inches per repetition) over the initial 8-weeks (2 months). New activities were introduced approximately every 2-3 months in order to continually stress the skeleton over 2 years. Physical activity performed by these subjects (in addition to intervention activities) was objectively assessed by pedometer (7-day wear period) and further assessed by a validated past year physical activity questionnaire PYPAQ).	Control n=98 Participants Participants randomized to the control arm did not perform intervention activities. Physical activity was objectively assessed by pedometer (7-day wear period) and further assessed by a validated past year physical activity questionnaire (PYPAQ).
12-month Change in Periosteal Circumference at the Tibia 50% Site	2.98 millimeters (mm) Standard Deviation 1.33	3.11 millimeters (mm) Standard Deviation 1.09

PRIMARY outcome

Timeframe: Baseline to 12-months

Population: Population consists of all participants that had complete measurements at the baseline, 12-month and 24-month time points (N=207). At 12-months: Age=11.8 +/- 1.0 yrs; Height=153.3 +/- 9.9 cm; Weight=44.0 +/- 9.3 kg. At 24-months: Age=12.8 +/- 1.0 yrs; Height=158.8 +/- 9.1 cm; Weight=50.0 +/- 10.7 kg.

Baseline to 12-month change in cortical thickness at the tibia 50% site . Measurement made by pQCT at a distance of 50% of total tibia length from the distal growth plate. Measurement units: millimeters (mm).

Outcome measures

Measure	Exercise Intervention n=109 Participants Participants randomized to the exercise intervention group performed activities designed to provide skeletal loading: impact activities 3 times per week, increasing the number of jumps (up to 40) and increasing height (from 6 inches to 24 inches per repetition) over the initial 8-weeks (2 months). New activities were introduced approximately every 2-3 months in order to continually stress the skeleton over 2 years. Physical activity performed by these subjects (in addition to intervention activities) was objectively assessed by pedometer (7-day wear period) and further assessed by a validated past year physical activity questionnaire PYPAQ).	Control n=98 Participants Participants randomized to the control arm did not perform intervention activities. Physical activity was objectively assessed by pedometer (7-day wear period) and further assessed by a validated past year physical activity questionnaire (PYPAQ).
12-month Change in Cortical Thickness at the Tibia 50% Site	.29 millimeters (mm) Standard Deviation .20	.31 millimeters (mm) Standard Deviation .20

PRIMARY outcome

Timeframe: Baseline to 12-months

Population: Population consists of all participants that had complete measurements at the baseline, 12-month and 24-month time points (N=207). At 12-months: Age=11.8 +/- 1.0 yrs; Height=153.3 +/- 9.9 cm; Weight=44.0 +/- 9.3 kg. At 24-months: Age=12.8 +/- 1.0 yrs; Height=158.8 +/- 9.1 cm; Weight=50.0 +/- 10.7 kg.

Baseline to 12-month change in strength-strain index at the tibia 50% site. Stress-strain index (also called strength-strain index and stress-strength index in the literature) is a measure of the resistance to torsional and bending forces at diaphyseal sites of long bones. Measurement made by pQCT at a distance of 50% of total tibia length from the distal growth plate. Measurement units: mm^3.

Outcome measures

Measure	Exercise Intervention n=109 Participants Participants randomized to the exercise intervention group performed activities designed to provide skeletal loading: impact activities 3 times per week, increasing the number of jumps (up to 40) and increasing height (from 6 inches to 24 inches per repetition) over the initial 8-weeks (2 months). New activities were introduced approximately every 2-3 months in order to continually stress the skeleton over 2 years. Physical activity performed by these subjects (in addition to intervention activities) was objectively assessed by pedometer (7-day wear period) and further assessed by a validated past year physical activity questionnaire PYPAQ).	Control n=98 Participants Participants randomized to the control arm did not perform intervention activities. Physical activity was objectively assessed by pedometer (7-day wear period) and further assessed by a validated past year physical activity questionnaire (PYPAQ).
12-month Change in Stress-Strain Index at the Tibia 50% Site	171.82 mm^3 Standard Deviation 68.00	185.36 mm^3 Standard Deviation 79.04

PRIMARY outcome

Timeframe: Baseline to 12-months

Population: Population consists of all participants that had complete measurements at the baseline, 12-month and 24-month time points (N=207). At 12-months: Age=11.8 +/- 1.0 yrs; Height=153.3 +/- 9.9 cm; Weight=44.0 +/- 9.3 kg. At 24-months: Age=12.8 +/- 1.0 yrs; Height=158.8 +/- 9.1 cm; Weight=50.0 +/- 10.7 kg.

Baseline to 12-month change in total volumetric bone density at the tibia 66% site . Measurement made by pQCT at a distance of 66% of total tibia length from the distal growth plate. Measurement units: milligrams per cubic centimeter (mg/ccm).

Outcome measures

Measure	Exercise Intervention n=109 Participants Participants randomized to the exercise intervention group performed activities designed to provide skeletal loading: impact activities 3 times per week, increasing the number of jumps (up to 40) and increasing height (from 6 inches to 24 inches per repetition) over the initial 8-weeks (2 months). New activities were introduced approximately every 2-3 months in order to continually stress the skeleton over 2 years. Physical activity performed by these subjects (in addition to intervention activities) was objectively assessed by pedometer (7-day wear period) and further assessed by a validated past year physical activity questionnaire PYPAQ).	Control n=98 Participants Participants randomized to the control arm did not perform intervention activities. Physical activity was objectively assessed by pedometer (7-day wear period) and further assessed by a validated past year physical activity questionnaire (PYPAQ).
12-month Change in Total Volumetric Bone Density at the Tibia 66% Site	7.00 milligrams per cubic centimeter (mg/ccm) Standard Deviation 32.41	9.58 milligrams per cubic centimeter (mg/ccm) Standard Deviation 29.98

PRIMARY outcome

Timeframe: Baseline to 12-months

Population: Population consists of all participants that had complete measurements at the baseline, 12-month and 24-month time points (N=207). At 12-months: Age=11.8 +/- 1.0 yrs; Height=153.3 +/- 9.9 cm; Weight=44.0 +/- 9.3 kg. At 24-months: Age=12.8 +/- 1.0 yrs; Height=158.8 +/- 9.1 cm; Weight=50.0 +/- 10.7 kg.

Baseline to 12-month change in volumetric bone density of trabecular bone at the tibia 66% site . Measurement made by pQCT at a distance of 66% of total tibia length from the distal growth plate.Measurement units: milligrams per cubic centimeter (mg/ccm).

Outcome measures

Measure	Exercise Intervention n=109 Participants Participants randomized to the exercise intervention group performed activities designed to provide skeletal loading: impact activities 3 times per week, increasing the number of jumps (up to 40) and increasing height (from 6 inches to 24 inches per repetition) over the initial 8-weeks (2 months). New activities were introduced approximately every 2-3 months in order to continually stress the skeleton over 2 years. Physical activity performed by these subjects (in addition to intervention activities) was objectively assessed by pedometer (7-day wear period) and further assessed by a validated past year physical activity questionnaire PYPAQ).	Control n=98 Participants Participants randomized to the control arm did not perform intervention activities. Physical activity was objectively assessed by pedometer (7-day wear period) and further assessed by a validated past year physical activity questionnaire (PYPAQ).
12-month Change in Volumetric Bone Density of Trabecular Bone at the Tibia 66% Site	3.40 milligrams per cubic centimeter (mg/ccm) Standard Deviation 13.49	2.08 milligrams per cubic centimeter (mg/ccm) Standard Deviation 14.64

PRIMARY outcome

Timeframe: Baseline to 12-months

Population: Population consists of all participants that had complete measurements at the baseline, 12-month and 24-month time points (N=207). At 12-months: Age=11.8 +/- 1.0 yrs; Height=153.3 +/- 9.9 cm; Weight=44.0 +/- 9.3 kg. At 24-months: Age=12.8 +/- 1.0 yrs; Height=158.8 +/- 9.1 cm; Weight=50.0 +/- 10.7 kg.

Baseline to 12-month change in volumetric bone density of cortical bone at the tibia 66% site . Measurement made by pQCT at a distance of 66% of total tibia length from the distal growth plate. Measurement units: milligrams per cubic centimeter (mg/ccm).

Outcome measures

Measure	Exercise Intervention n=109 Participants Participants randomized to the exercise intervention group performed activities designed to provide skeletal loading: impact activities 3 times per week, increasing the number of jumps (up to 40) and increasing height (from 6 inches to 24 inches per repetition) over the initial 8-weeks (2 months). New activities were introduced approximately every 2-3 months in order to continually stress the skeleton over 2 years. Physical activity performed by these subjects (in addition to intervention activities) was objectively assessed by pedometer (7-day wear period) and further assessed by a validated past year physical activity questionnaire PYPAQ).	Control n=9 Participants Participants randomized to the control arm did not perform intervention activities. Physical activity was objectively assessed by pedometer (7-day wear period) and further assessed by a validated past year physical activity questionnaire (PYPAQ).
12-month Change in Volumetric Bone Density of Cortical Bone at the Tibia 66% Site	11.63 milligrams per cubic centimeter (mg/ccm) Standard Deviation 24.00	12.69 milligrams per cubic centimeter (mg/ccm) Standard Deviation 21.32

PRIMARY outcome

Timeframe: Baseline to 12-months

Population: Population consists of all participants that had complete measurements at the baseline, 12-month and 24-month time points (N=207). At 12-months: Age=11.8 +/- 1.0 yrs; Height=153.3 +/- 9.9 cm; Weight=44.0 +/- 9.3 kg. At 24-months: Age=12.8 +/- 1.0 yrs; Height=158.8 +/- 9.1 cm; Weight=50.0 +/- 10.7 kg.

Baseline to 12-month change in periosteal circumference at the tibia 66% site . Measurement made by pQCT at a distance of 66% of total tibia length from the distal growth plate. Measurement units: millimeters (mm).

Outcome measures

Measure	Exercise Intervention n=109 Participants Participants randomized to the exercise intervention group performed activities designed to provide skeletal loading: impact activities 3 times per week, increasing the number of jumps (up to 40) and increasing height (from 6 inches to 24 inches per repetition) over the initial 8-weeks (2 months). New activities were introduced approximately every 2-3 months in order to continually stress the skeleton over 2 years. Physical activity performed by these subjects (in addition to intervention activities) was objectively assessed by pedometer (7-day wear period) and further assessed by a validated past year physical activity questionnaire PYPAQ).	Control n=98 Participants Participants randomized to the control arm did not perform intervention activities. Physical activity was objectively assessed by pedometer (7-day wear period) and further assessed by a validated past year physical activity questionnaire (PYPAQ).
12-month Change in Periosteal Circumference at the Tibia 66% Site	3.69 millimeters (mm) Standard Deviation 2.35	3.79 millimeters (mm) Standard Deviation 2.06

PRIMARY outcome

Timeframe: Baseline to 12-months

Population: Population consists of all participants that had complete measurements at the baseline, 12-month and 24-month time points (N=207). At 12-months: Age=11.8 +/- 1.0 yrs; Height=153.3 +/- 9.9 cm; Weight=44.0 +/- 9.3 kg. At 24-months: Age=12.8 +/- 1.0 yrs; Height=158.8 +/- 9.1 cm; Weight=50.0 +/- 10.7 kg.

Baseline to 12-month change in cortical thickness at the tibia 66% site . Measurement made by pQCT at a distance of 66% of total tibia length from the distal growth plate. Measurement units: millimeters (mm).

Outcome measures

Measure	Exercise Intervention n=109 Participants Participants randomized to the exercise intervention group performed activities designed to provide skeletal loading: impact activities 3 times per week, increasing the number of jumps (up to 40) and increasing height (from 6 inches to 24 inches per repetition) over the initial 8-weeks (2 months). New activities were introduced approximately every 2-3 months in order to continually stress the skeleton over 2 years. Physical activity performed by these subjects (in addition to intervention activities) was objectively assessed by pedometer (7-day wear period) and further assessed by a validated past year physical activity questionnaire PYPAQ).	Control n=98 Participants Participants randomized to the control arm did not perform intervention activities. Physical activity was objectively assessed by pedometer (7-day wear period) and further assessed by a validated past year physical activity questionnaire (PYPAQ).
12-month Change in Cortical Thickness at the Tibia 66% Site	.17 millimeters (mm) Standard Deviation .21	.18 millimeters (mm) Standard Deviation .22

PRIMARY outcome

Timeframe: Baseline to 12-months

Population: Population consists of all participants that had complete measurements at the baseline, 12-month and 24-month time points (N=207). At 12-months: Age=11.8 +/- 1.0 yrs; Height=153.3 +/- 9.9 cm; Weight=44.0 +/- 9.3 kg. At 24-months: Age=12.8 +/- 1.0 yrs; Height=158.8 +/- 9.1 cm; Weight=50.0 +/- 10.7 kg.

Baseline to 12-month change in strength-strain index at the tibia 66% site. Stress-strain index (also called strength-strain index and stress-strength index in the literature) is a measure of the resistance to torsional and bending forces at diaphyseal sites of long bones. Measurement made by pQCT at a distance of 66% of total tibia length from the distal growth plate. Measurement units: mm^3.

Outcome measures

Measure	Exercise Intervention n=109 Participants Participants randomized to the exercise intervention group performed activities designed to provide skeletal loading: impact activities 3 times per week, increasing the number of jumps (up to 40) and increasing height (from 6 inches to 24 inches per repetition) over the initial 8-weeks (2 months). New activities were introduced approximately every 2-3 months in order to continually stress the skeleton over 2 years. Physical activity performed by these subjects (in addition to intervention activities) was objectively assessed by pedometer (7-day wear period) and further assessed by a validated past year physical activity questionnaire PYPAQ).	Control n=98 Participants Participants randomized to the control arm did not perform intervention activities. Physical activity was objectively assessed by pedometer (7-day wear period) and further assessed by a validated past year physical activity questionnaire (PYPAQ).
12-month Change in Stress-Strain Index at the Tibia 66% Site	214.93 mm^3 Standard Deviation 96.58	228.46 mm^3 Standard Deviation 103.48

PRIMARY outcome

Timeframe: Baseline to 24-months

Population: Population consists of all participants that had complete measurements at the baseline, 12-month and 24-month time points (N=207). At 12-months: Age=11.8 +/- 1.0 yrs; Height=153.3 +/- 9.9 cm; Weight=44.0 +/- 9.3 kg. At 24-months: Age=12.8 +/- 1.0 yrs; Height=158.8 +/- 9.1 cm; Weight=50.0 +/- 10.7 kg.

Baseline to 24-month change in total volumetric bone density at the femur 4% site . Measurement made by pQCT at a distance of 4% of total femur length from the distal growth plate. Measurement units mg/ccm.

Outcome measures

Measure	Exercise Intervention n=109 Participants Participants randomized to the exercise intervention group performed activities designed to provide skeletal loading: impact activities 3 times per week, increasing the number of jumps (up to 40) and increasing height (from 6 inches to 24 inches per repetition) over the initial 8-weeks (2 months). New activities were introduced approximately every 2-3 months in order to continually stress the skeleton over 2 years. Physical activity performed by these subjects (in addition to intervention activities) was objectively assessed by pedometer (7-day wear period) and further assessed by a validated past year physical activity questionnaire PYPAQ).	Control n=98 Participants Participants randomized to the control arm did not perform intervention activities. Physical activity was objectively assessed by pedometer (7-day wear period) and further assessed by a validated past year physical activity questionnaire (PYPAQ).
24-month in Change in Total Volumetric Bone Density the Femur 4% Site	13.70 milligrams per cubic centimeter (mg/ccm) Standard Deviation 22.89	13.47 milligrams per cubic centimeter (mg/ccm) Standard Deviation 19.09

PRIMARY outcome

Timeframe: Baseline to 24-months

Population: Population consists of all participants that had complete measurements at the baseline, 12-month and 24-month time points (N=207). At 12-months: Age=11.8 +/- 1.0 yrs; Height=153.3 +/- 9.9 cm; Weight=44.0 +/- 9.3 kg. At 24-months: Age=12.8 +/- 1.0 yrs; Height=158.8 +/- 9.1 cm; Weight=50.0 +/- 10.7 kg.

Baseline to 24-month change in volumetric bone density of trabecular bone at the femur 4% site . Measurement made by pQCT at a distance of 4% of total femur length from the distal growth plate. Measurement units: milligrams per cubic centimeter (mg/ccm).

Outcome measures

Measure	Exercise Intervention n=109 Participants Participants randomized to the exercise intervention group performed activities designed to provide skeletal loading: impact activities 3 times per week, increasing the number of jumps (up to 40) and increasing height (from 6 inches to 24 inches per repetition) over the initial 8-weeks (2 months). New activities were introduced approximately every 2-3 months in order to continually stress the skeleton over 2 years. Physical activity performed by these subjects (in addition to intervention activities) was objectively assessed by pedometer (7-day wear period) and further assessed by a validated past year physical activity questionnaire PYPAQ).	Control n=98 Participants Participants randomized to the control arm did not perform intervention activities. Physical activity was objectively assessed by pedometer (7-day wear period) and further assessed by a validated past year physical activity questionnaire (PYPAQ).
24-month in Change in Volumetric Bone Density of Trabecular Bone at the Femur 4% Site	8.03 milligrams per cubic centimeter (mg/ccm) Standard Deviation 19.34	8.23 milligrams per cubic centimeter (mg/ccm) Standard Deviation 16.35

PRIMARY outcome

Timeframe: Baseline to 24-months

Population: Population consists of all participants that had complete measurements at the baseline, 12-month and 24-month time points (N=207). At 12-months: Age=11.8 +/- 1.0 yrs; Height=153.3 +/- 9.9 cm; Weight=44.0 +/- 9.3 kg. At 24-months: Age=12.8 +/- 1.0 yrs; Height=158.8 +/- 9.1 cm; Weight=50.0 +/- 10.7 kg.

Baseline to 24-month change in volumetric bone density of cortical bone at the femur 4% site . Measurement made by pQCT at a distance of 4% of total femur length from the distal growth plate. Measurement units: milligrams per cubic centimeter (mg/ccm).

Outcome measures

Measure	Exercise Intervention n=109 Participants Participants randomized to the exercise intervention group performed activities designed to provide skeletal loading: impact activities 3 times per week, increasing the number of jumps (up to 40) and increasing height (from 6 inches to 24 inches per repetition) over the initial 8-weeks (2 months). New activities were introduced approximately every 2-3 months in order to continually stress the skeleton over 2 years. Physical activity performed by these subjects (in addition to intervention activities) was objectively assessed by pedometer (7-day wear period) and further assessed by a validated past year physical activity questionnaire PYPAQ).	Control n=98 Participants Participants randomized to the control arm did not perform intervention activities. Physical activity was objectively assessed by pedometer (7-day wear period) and further assessed by a validated past year physical activity questionnaire (PYPAQ).
24-month in Change in Volumetric Bone Density of Cortical Bone at the Femur 4% Site	10.67 milligrams per cubic centimeter (mg/ccm) Standard Deviation 21.83	10.78 milligrams per cubic centimeter (mg/ccm) Standard Deviation 17.95

PRIMARY outcome

Timeframe: Baseline to 24-months

Population: Population consists of all participants that had complete measurements at the baseline, 12-month and 24-month time points (N=207). At 12-months: Age=11.8 +/- 1.0 yrs; Height=153.3 +/- 9.9 cm; Weight=44.0 +/- 9.3 kg. At 24-months: Age=12.8 +/- 1.0 yrs; Height=158.8 +/- 9.1 cm; Weight=50.0 +/- 10.7 kg.

Baseline to 24-month change in trabecular bone area at the femur 4% site . Measurement made by pQCT at a distance of 4% of total femur length from the distal growth plate. Measurement units: square millimeters (mm^2).

Outcome measures

Measure	Exercise Intervention n=109 Participants Participants randomized to the exercise intervention group performed activities designed to provide skeletal loading: impact activities 3 times per week, increasing the number of jumps (up to 40) and increasing height (from 6 inches to 24 inches per repetition) over the initial 8-weeks (2 months). New activities were introduced approximately every 2-3 months in order to continually stress the skeleton over 2 years. Physical activity performed by these subjects (in addition to intervention activities) was objectively assessed by pedometer (7-day wear period) and further assessed by a validated past year physical activity questionnaire PYPAQ).	Control n=98 Participants Participants randomized to the control arm did not perform intervention activities. Physical activity was objectively assessed by pedometer (7-day wear period) and further assessed by a validated past year physical activity questionnaire (PYPAQ).
24-month Change in Trabecular Bone Area at the Femur 4% Site	160.89 millimeters squared (mm^2) Standard Deviation 158.53	178.04 millimeters squared (mm^2) Standard Deviation 146.00

PRIMARY outcome

Timeframe: Baseline to 24-months

Population: Population consists of all participants that had complete measurements at the baseline, 12-month and 24-month time points (N=207). At 12-months: Age=11.8 +/- 1.0 yrs; Height=153.3 +/- 9.9 cm; Weight=44.0 +/- 9.3 kg. At 24-months: Age=12.8 +/- 1.0 yrs; Height=158.8 +/- 9.1 cm; Weight=50.0 +/- 10.7 kg.

Baseline to 24-month change in cortical bone area at the femur 4% site . Measurement made by pQCT at a distance of 4% of total femur length from the distal growth plate. Measurement units: square millimeters (mm^2).

Outcome measures

Measure	Exercise Intervention n=109 Participants Participants randomized to the exercise intervention group performed activities designed to provide skeletal loading: impact activities 3 times per week, increasing the number of jumps (up to 40) and increasing height (from 6 inches to 24 inches per repetition) over the initial 8-weeks (2 months). New activities were introduced approximately every 2-3 months in order to continually stress the skeleton over 2 years. Physical activity performed by these subjects (in addition to intervention activities) was objectively assessed by pedometer (7-day wear period) and further assessed by a validated past year physical activity questionnaire PYPAQ).	Control n=98 Participants Participants randomized to the control arm did not perform intervention activities. Physical activity was objectively assessed by pedometer (7-day wear period) and further assessed by a validated past year physical activity questionnaire (PYPAQ).
24-month Change in Cortical Bone Area at the Femur 4% Site	237.12 millimeters squared (mm^2) Standard Deviation 178.61	255.67 millimeters squared (mm^2) Standard Deviation 165.23

PRIMARY outcome

Timeframe: Baseline to 24-months

Population: Population consists of all participants that had complete measurements at the baseline, 12-month and 24-month time points (N=207). At 12-months: Age=11.8 +/- 1.0 yrs; Height=153.3 +/- 9.9 cm; Weight=44.0 +/- 9.3 kg. At 24-months: Age=12.8 +/- 1.0 yrs; Height=158.8 +/- 9.1 cm; Weight=50.0 +/- 10.7 kg.

Baseline to 24-month change in periosteal circumference at the femur 4% site . Measurement made by pQCT at a distance of 4% of total femur length from the distal growth plate. Measurement units: millimeters (mm).

Outcome measures

Measure	Exercise Intervention n=109 Participants Participants randomized to the exercise intervention group performed activities designed to provide skeletal loading: impact activities 3 times per week, increasing the number of jumps (up to 40) and increasing height (from 6 inches to 24 inches per repetition) over the initial 8-weeks (2 months). New activities were introduced approximately every 2-3 months in order to continually stress the skeleton over 2 years. Physical activity performed by these subjects (in addition to intervention activities) was objectively assessed by pedometer (7-day wear period) and further assessed by a validated past year physical activity questionnaire PYPAQ).	Control n=98 Participants Participants randomized to the control arm did not perform intervention activities. Physical activity was objectively assessed by pedometer (7-day wear period) and further assessed by a validated past year physical activity questionnaire (PYPAQ).
24-month Change in Periosteal Circumference at the Femur 4% Site	10.08 millimeters (mm) Standard Deviation 7.73	10.72 millimeters (mm) Standard Deviation 6.88

PRIMARY outcome

Timeframe: Baseline to 24-months

Population: Population consists of all participants that had complete measurements at the baseline, 12-month and 24-month time points (N=207). At 12-months: Age=11.8 +/- 1.0 yrs; Height=153.3 +/- 9.9 cm; Weight=44.0 +/- 9.3 kg. At 24-months: Age=12.8 +/- 1.0 yrs; Height=158.8 +/- 9.1 cm; Weight=50.0 +/- 10.7 kg.

Baseline to 24-month change in bone strength index (BSI) at the femur 4% site. Bone Strength Index (BSI) is a measurement of the resistance to compression forces at the epiphyses of long bones. Measurement made by pQCT at a distance of 4% of total tibia length from the distal growth plate. Measurement units: mm^4.

Outcome measures

Measure	Exercise Intervention n=109 Participants Participants randomized to the exercise intervention group performed activities designed to provide skeletal loading: impact activities 3 times per week, increasing the number of jumps (up to 40) and increasing height (from 6 inches to 24 inches per repetition) over the initial 8-weeks (2 months). New activities were introduced approximately every 2-3 months in order to continually stress the skeleton over 2 years. Physical activity performed by these subjects (in addition to intervention activities) was objectively assessed by pedometer (7-day wear period) and further assessed by a validated past year physical activity questionnaire PYPAQ).	Control n=98 Participants Participants randomized to the control arm did not perform intervention activities. Physical activity was objectively assessed by pedometer (7-day wear period) and further assessed by a validated past year physical activity questionnaire (PYPAQ).
24-month Change in Bone Strength Index at the Femur 4% Site	28.08 mm^4 Standard Deviation 17.51	27.81 mm^4 Standard Deviation 17.76

PRIMARY outcome

Timeframe: Baseline to 24-months

Population: Population consists of all participants that had complete measurements at the baseline, 12-month and 24-month time points (N=207). At 12-months: Age=11.8 +/- 1.0 yrs; Height=153.3 +/- 9.9 cm; Weight=44.0 +/- 9.3 kg. At 24-months: Age=12.8 +/- 1.0 yrs; Height=158.8 +/- 9.1 cm; Weight=50.0 +/- 10.7 kg.

Baseline to 24-month change in total volumetric bone density at the femur 20% site . Measurement made by pQCT at a distance of 20% of total femur length from the distal growth plate. Measurement units: milligrams per cubic centimeter (mg/ccm).

Outcome measures

Measure	Exercise Intervention n=109 Participants Participants randomized to the exercise intervention group performed activities designed to provide skeletal loading: impact activities 3 times per week, increasing the number of jumps (up to 40) and increasing height (from 6 inches to 24 inches per repetition) over the initial 8-weeks (2 months). New activities were introduced approximately every 2-3 months in order to continually stress the skeleton over 2 years. Physical activity performed by these subjects (in addition to intervention activities) was objectively assessed by pedometer (7-day wear period) and further assessed by a validated past year physical activity questionnaire PYPAQ).	Control n=98 Participants Participants randomized to the control arm did not perform intervention activities. Physical activity was objectively assessed by pedometer (7-day wear period) and further assessed by a validated past year physical activity questionnaire (PYPAQ).
24-month Change in Total Volumetric Bone Density at the Femur 20% Site	14.88 milligrams per cubic centimeter (mg/ccm) Standard Deviation 31.73	15.36 milligrams per cubic centimeter (mg/ccm) Standard Deviation 28.47

PRIMARY outcome

Timeframe: Baseline to 24-months

Population: Population consists of all participants that had complete measurements at the baseline, 12-month and 24-month time points (N=207). At 12-months: Age=11.8 +/- 1.0 yrs; Height=153.3 +/- 9.9 cm; Weight=44.0 +/- 9.3 kg. At 24-months: Age=12.8 +/- 1.0 yrs; Height=158.8 +/- 9.1 cm; Weight=50.0 +/- 10.7 kg.

Baseline to 24-month change in volumetric bone density of trabecular bone at the femur 20% site . Measurement made by pQCT at a distance of 20% of total femur length from the distal growth plate. Measurement units: milligrams per cubic centimeter (mg/ccm).

Outcome measures

Measure	Exercise Intervention n=109 Participants Participants randomized to the exercise intervention group performed activities designed to provide skeletal loading: impact activities 3 times per week, increasing the number of jumps (up to 40) and increasing height (from 6 inches to 24 inches per repetition) over the initial 8-weeks (2 months). New activities were introduced approximately every 2-3 months in order to continually stress the skeleton over 2 years. Physical activity performed by these subjects (in addition to intervention activities) was objectively assessed by pedometer (7-day wear period) and further assessed by a validated past year physical activity questionnaire PYPAQ).	Control n=98 Participants Participants randomized to the control arm did not perform intervention activities. Physical activity was objectively assessed by pedometer (7-day wear period) and further assessed by a validated past year physical activity questionnaire (PYPAQ).
24-month Change in Volumetric Bone Density of Trabecular Bone at the Femur 20% Site	11.83 milligrams per cubic centimeter (mg/ccm) Standard Deviation 17.20	9.04 milligrams per cubic centimeter (mg/ccm) Standard Deviation 13.87

PRIMARY outcome

Timeframe: Baseline to 24-months

Population: Population consists of all participants that had complete measurements at the baseline, 12-month and 24-month time points (N=207). At 12-months: Age=11.8 +/- 1.0 yrs; Height=153.3 +/- 9.9 cm; Weight=44.0 +/- 9.3 kg. At 24-months: Age=12.8 +/- 1.0 yrs; Height=158.8 +/- 9.1 cm; Weight=50.0 +/- 10.7 kg.

Baseline to 24-month change in volumetric bone density of cortical bone at the femur 20% site . Measurement made by pQCT at a distance of 20% of total femur length from the distal growth plate. Measurement units: milligrams per cubic centimeter (mg/ccm).

Outcome measures

Measure	Exercise Intervention n=109 Participants Participants randomized to the exercise intervention group performed activities designed to provide skeletal loading: impact activities 3 times per week, increasing the number of jumps (up to 40) and increasing height (from 6 inches to 24 inches per repetition) over the initial 8-weeks (2 months). New activities were introduced approximately every 2-3 months in order to continually stress the skeleton over 2 years. Physical activity performed by these subjects (in addition to intervention activities) was objectively assessed by pedometer (7-day wear period) and further assessed by a validated past year physical activity questionnaire PYPAQ).	Control n=98 Participants Participants randomized to the control arm did not perform intervention activities. Physical activity was objectively assessed by pedometer (7-day wear period) and further assessed by a validated past year physical activity questionnaire (PYPAQ).
24-month Change in Volumetric Bone Density of Cortical Bone at the Femur 20% Site	21.56 milligrams per cubic centimeter (mg/ccm) Standard Deviation 29.46	22.26 milligrams per cubic centimeter (mg/ccm) Standard Deviation 29.62

PRIMARY outcome

Timeframe: Baseline to 24-months

Population: Population consists of all participants that had complete measurements at the baseline, 12-month and 24-month time points (N=207). At 12-months: Age=11.8 +/- 1.0 yrs; Height=153.3 +/- 9.9 cm; Weight=44.0 +/- 9.3 kg. At 24-months: Age=12.8 +/- 1.0 yrs; Height=158.8 +/- 9.1 cm; Weight=50.0 +/- 10.7 kg.

Baseline to 24-month change in thickness of cortical bone at the femur 20% site . Measurement made by pQCT at a distance of 20% of total femur length from the distal growth plate. Measurement units: millimeters (mm).

Outcome measures

Measure	Exercise Intervention n=109 Participants Participants randomized to the exercise intervention group performed activities designed to provide skeletal loading: impact activities 3 times per week, increasing the number of jumps (up to 40) and increasing height (from 6 inches to 24 inches per repetition) over the initial 8-weeks (2 months). New activities were introduced approximately every 2-3 months in order to continually stress the skeleton over 2 years. Physical activity performed by these subjects (in addition to intervention activities) was objectively assessed by pedometer (7-day wear period) and further assessed by a validated past year physical activity questionnaire PYPAQ).	Control n=98 Participants Participants randomized to the control arm did not perform intervention activities. Physical activity was objectively assessed by pedometer (7-day wear period) and further assessed by a validated past year physical activity questionnaire (PYPAQ).
24-month Change in Thickness of Cortical Bone at the Femur 20% Site	.27 millimeters (mm) Standard Deviation .22	.31 millimeters (mm) Standard Deviation .21

PRIMARY outcome

Timeframe: Baseline to 24-months

Population: Population consists of all participants that had complete measurements at the baseline, 12-month and 24-month time points (N=207). At 12-months: Age=11.8 +/- 1.0 yrs; Height=153.3 +/- 9.9 cm; Weight=44.0 +/- 9.3 kg. At 24-months: Age=12.8 +/- 1.0 yrs; Height=158.8 +/- 9.1 cm; Weight=50.0 +/- 10.7 kg.

Baseline to 24-month change in periosteal circumference at the femur 20% site . Measurement made by pQCT at a distance of 20% of total femur length from the distal growth plate. Measurement units: millimeters (mm).

Outcome measures

Measure	Exercise Intervention n=109 Participants Participants randomized to the exercise intervention group performed activities designed to provide skeletal loading: impact activities 3 times per week, increasing the number of jumps (up to 40) and increasing height (from 6 inches to 24 inches per repetition) over the initial 8-weeks (2 months). New activities were introduced approximately every 2-3 months in order to continually stress the skeleton over 2 years. Physical activity performed by these subjects (in addition to intervention activities) was objectively assessed by pedometer (7-day wear period) and further assessed by a validated past year physical activity questionnaire PYPAQ).	Control n=98 Participants Participants randomized to the control arm did not perform intervention activities. Physical activity was objectively assessed by pedometer (7-day wear period) and further assessed by a validated past year physical activity questionnaire (PYPAQ).
24-month Change in Periosteal Circumference at the Femur 20% Site	8.25 millimeters (mm) Standard Deviation 3.38	9.29 millimeters (mm) Standard Deviation 3.08

PRIMARY outcome

Timeframe: Baseline to 24-months

Population: Population consists of all participants that had complete measurements at the baseline, 12-month and 24-month time points (N=207). At 12-months: Age=11.8 +/- 1.0 yrs; Height=153.3 +/- 9.9 cm; Weight=44.0 +/- 9.3 kg. At 24-months: Age=12.8 +/- 1.0 yrs; Height=158.8 +/- 9.1 cm; Weight=50.0 +/- 10.7 kg.

Baseline to 24-month change in strength-strain index at the femur 20% site. Stress-strain index (also called strength-strain index and stress-strength index in the literature) is a measure of the resistance to torsional and bending forces at diaphyseal sites of long bones. Measurement made by pQCT at a distance of 20% of total femur length from the distal growth plate. Measurement units: mm^3.

Outcome measures

Measure	Exercise Intervention n=109 Participants Participants randomized to the exercise intervention group performed activities designed to provide skeletal loading: impact activities 3 times per week, increasing the number of jumps (up to 40) and increasing height (from 6 inches to 24 inches per repetition) over the initial 8-weeks (2 months). New activities were introduced approximately every 2-3 months in order to continually stress the skeleton over 2 years. Physical activity performed by these subjects (in addition to intervention activities) was objectively assessed by pedometer (7-day wear period) and further assessed by a validated past year physical activity questionnaire PYPAQ).	Control n=98 Participants Participants randomized to the control arm did not perform intervention activities. Physical activity was objectively assessed by pedometer (7-day wear period) and further assessed by a validated past year physical activity questionnaire (PYPAQ).
24-month Change in Stress-Strain Index at the Femur 20% Site	504.12 mm^3 Standard Deviation 202.34	582.69 mm^3 Standard Deviation 202.42

PRIMARY outcome

Timeframe: Baseline to 24-months

Population: Population consists of all participants that had complete measurements at the baseline, 12-month and 24-month time points (N=207). At 12-months: Age=11.8 +/- 1.0 yrs; Height=153.3 +/- 9.9 cm; Weight=44.0 +/- 9.3 kg. At 24-months: Age=12.8 +/- 1.0 yrs; Height=158.8 +/- 9.1 cm; Weight=50.0 +/- 10.7 kg.

Baseline to 24-month change in total volumetric bone density at the tibia 4% site . Measurement made by pQCT at a distance of 4% of total tibia length from the distal growth plate. Measurement units: milligrams per cubic centimeter (mg/ccm).

Outcome measures

Measure	Exercise Intervention n=109 Participants Participants randomized to the exercise intervention group performed activities designed to provide skeletal loading: impact activities 3 times per week, increasing the number of jumps (up to 40) and increasing height (from 6 inches to 24 inches per repetition) over the initial 8-weeks (2 months). New activities were introduced approximately every 2-3 months in order to continually stress the skeleton over 2 years. Physical activity performed by these subjects (in addition to intervention activities) was objectively assessed by pedometer (7-day wear period) and further assessed by a validated past year physical activity questionnaire PYPAQ).	Control n=98 Participants Participants randomized to the control arm did not perform intervention activities. Physical activity was objectively assessed by pedometer (7-day wear period) and further assessed by a validated past year physical activity questionnaire (PYPAQ).
24-month Change in Total Volumetric Bone Density at the Tibia 4% Site	28.22 milligrams per cubic centimeter (mg/ccm) Standard Deviation 30.58	26.76 milligrams per cubic centimeter (mg/ccm) Standard Deviation 29.35

PRIMARY outcome

Timeframe: Baseline to 24-months

Population: Population consists of all participants that had complete measurements at the baseline, 12-month and 24-month time points (N=207). At 12-months: Age=11.8 +/- 1.0 yrs; Height=153.3 +/- 9.9 cm; Weight=44.0 +/- 9.3 kg. At 24-months: Age=12.8 +/- 1.0 yrs; Height=158.8 +/- 9.1 cm; Weight=50.0 +/- 10.7 kg.

Baseline to 24-month change in volumetric bone density of trabecular bone at the tibia 4% site . Measurement made by pQCT at a distance of 4% of total tibia length from the distal growth plate. Measurement units: milligrams per cubic centimeter (mg/ccm).

Outcome measures

Measure	Exercise Intervention n=109 Participants Participants randomized to the exercise intervention group performed activities designed to provide skeletal loading: impact activities 3 times per week, increasing the number of jumps (up to 40) and increasing height (from 6 inches to 24 inches per repetition) over the initial 8-weeks (2 months). New activities were introduced approximately every 2-3 months in order to continually stress the skeleton over 2 years. Physical activity performed by these subjects (in addition to intervention activities) was objectively assessed by pedometer (7-day wear period) and further assessed by a validated past year physical activity questionnaire PYPAQ).	Control n=98 Participants Participants randomized to the control arm did not perform intervention activities. Physical activity was objectively assessed by pedometer (7-day wear period) and further assessed by a validated past year physical activity questionnaire (PYPAQ).
24-month Change in Volumetric Bone Density of Trabecular Bone at the Tibia 4% Site	7.37 milligrams per cubic centimeter (mg/ccm) Standard Deviation 13.97	7.23 milligrams per cubic centimeter (mg/ccm) Standard Deviation 17.18

PRIMARY outcome

Timeframe: Baseline to 24-months

Population: Population consists of all participants that had complete measurements at the baseline, 12-month and 24-month time points (N=207). At 12-months: Age=11.8 +/- 1.0 yrs; Height=153.3 +/- 9.9 cm; Weight=44.0 +/- 9.3 kg. At 24-months: Age=12.8 +/- 1.0 yrs; Height=158.8 +/- 9.1 cm; Weight=50.0 +/- 10.7 kg.

Baseline to 24-month change in volumetric bone density of cortical bone at the tibia 4% site . Measurement made by pQCT at a distance of 4% of total tibia length from the distal growth plate. Measurement units: milligrams per cubic centimeter (mg/ccm).

Outcome measures

Measure	Exercise Intervention n=109 Participants Participants randomized to the exercise intervention group performed activities designed to provide skeletal loading: impact activities 3 times per week, increasing the number of jumps (up to 40) and increasing height (from 6 inches to 24 inches per repetition) over the initial 8-weeks (2 months). New activities were introduced approximately every 2-3 months in order to continually stress the skeleton over 2 years. Physical activity performed by these subjects (in addition to intervention activities) was objectively assessed by pedometer (7-day wear period) and further assessed by a validated past year physical activity questionnaire PYPAQ).	Control n=98 Participants Participants randomized to the control arm did not perform intervention activities. Physical activity was objectively assessed by pedometer (7-day wear period) and further assessed by a validated past year physical activity questionnaire (PYPAQ).
24-month Change in Volumetric Bone Density of Cortical Bone at the Tibia 4% Site	27.29 milligrams per cubic centimeter (mg/ccm) Standard Deviation 29.54	25.94 milligrams per cubic centimeter (mg/ccm) Standard Deviation 28.46

PRIMARY outcome

Timeframe: Baseline to 24-months

Population: Population consists of all participants that had complete measurements at the baseline, 12-month and 24-month time points (N=207). At 12-months: Age=11.8 +/- 1.0 yrs; Height=153.3 +/- 9.9 cm; Weight=44.0 +/- 9.3 kg. At 24-months: Age=12.8 +/- 1.0 yrs; Height=158.8 +/- 9.1 cm; Weight=50.0 +/- 10.7 kg.

Baseline to 24-month change in trabecular bone area at the tibia 4% site . Measurement made by pQCT at a distance of 4% of total tibia length from the distal growth plate. Measurement units: square millimeters (mm^2).

Outcome measures

Measure	Exercise Intervention n=109 Participants Participants randomized to the exercise intervention group performed activities designed to provide skeletal loading: impact activities 3 times per week, increasing the number of jumps (up to 40) and increasing height (from 6 inches to 24 inches per repetition) over the initial 8-weeks (2 months). New activities were introduced approximately every 2-3 months in order to continually stress the skeleton over 2 years. Physical activity performed by these subjects (in addition to intervention activities) was objectively assessed by pedometer (7-day wear period) and further assessed by a validated past year physical activity questionnaire PYPAQ).	Control n=98 Participants Participants randomized to the control arm did not perform intervention activities. Physical activity was objectively assessed by pedometer (7-day wear period) and further assessed by a validated past year physical activity questionnaire (PYPAQ).
24-month Change in Trabecular Bone Area at the Tibia 4% Site	34.81 millimeters squared (mm^2) Standard Deviation 70.70	35.83 millimeters squared (mm^2) Standard Deviation 75.98

PRIMARY outcome

Timeframe: Baseline to 24-months

Population: Population consists of all participants that had complete measurements at the baseline, 12-month and 24-month time points (N=207). At 12-months: Age=11.8 +/- 1.0 yrs; Height=153.3 +/- 9.9 cm; Weight=44.0 +/- 9.3 kg. At 24-months: Age=12.8 +/- 1.0 yrs; Height=158.8 +/- 9.1 cm; Weight=50.0 +/- 10.7 kg.

Baseline to 24-month change in cortical bone area at the tibia 4% site . Measurement made by pQCT at a distance of 4% of total tibia length from the distal growth plate. Measurement units: square millimeters (mm^2).

Outcome measures

Measure	Exercise Intervention n=109 Participants Participants randomized to the exercise intervention group performed activities designed to provide skeletal loading: impact activities 3 times per week, increasing the number of jumps (up to 40) and increasing height (from 6 inches to 24 inches per repetition) over the initial 8-weeks (2 months). New activities were introduced approximately every 2-3 months in order to continually stress the skeleton over 2 years. Physical activity performed by these subjects (in addition to intervention activities) was objectively assessed by pedometer (7-day wear period) and further assessed by a validated past year physical activity questionnaire PYPAQ).	Control n=98 Participants Participants randomized to the control arm did not perform intervention activities. Physical activity was objectively assessed by pedometer (7-day wear period) and further assessed by a validated past year physical activity questionnaire (PYPAQ).
24-month Change in Cortical Bone Area at the Tibia 4% Site	65.50 millimeters squared (mm^2) Standard Deviation 69.84	66.42 millimeters squared (mm^2) Standard Deviation 73.94

PRIMARY outcome

Timeframe: Baseline to 24-months

Population: Population consists of all participants that had complete measurements at the baseline, 12-month and 24-month time points (N=207). At 12-months: Age=11.8 +/- 1.0 yrs; Height=153.3 +/- 9.9 cm; Weight=44.0 +/- 9.3 kg. At 24-months: Age=12.8 +/- 1.0 yrs; Height=158.8 +/- 9.1 cm; Weight=50.0 +/- 10.7 kg.

Baseline to 24-month change in periosteal circumference at the tibia 4% site . Measurement made by pQCT at a distance of 4% of total tibia length from the distal growth plate. Measurement units: millimeters (mm).

Outcome measures

Measure	Exercise Intervention n=109 Participants Participants randomized to the exercise intervention group performed activities designed to provide skeletal loading: impact activities 3 times per week, increasing the number of jumps (up to 40) and increasing height (from 6 inches to 24 inches per repetition) over the initial 8-weeks (2 months). New activities were introduced approximately every 2-3 months in order to continually stress the skeleton over 2 years. Physical activity performed by these subjects (in addition to intervention activities) was objectively assessed by pedometer (7-day wear period) and further assessed by a validated past year physical activity questionnaire PYPAQ).	Control n=98 Participants Participants randomized to the control arm did not perform intervention activities. Physical activity was objectively assessed by pedometer (7-day wear period) and further assessed by a validated past year physical activity questionnaire (PYPAQ).
24-month Change in Periosteal Circumference at the Tibia 4% Site	4.64 millimeters (mm) Standard Deviation 4.82	4.65 millimeters (mm) Standard Deviation 5.15

PRIMARY outcome

Timeframe: Baseline to 24-months

Population: Population consists of all participants that had complete measurements at the baseline, 12-month and 24-month time points (N=207). At 12-months: Age=11.8 +/- 1.0 yrs; Height=153.3 +/- 9.9 cm; Weight=44.0 +/- 9.3 kg. At 24-months: Age=12.8 +/- 1.0 yrs; Height=158.8 +/- 9.1 cm; Weight=50.0 +/- 10.7 kg.

Baseline to 24-month change in bone strength index (BSI) at the tibia 4% site. Bone Strength Index (BSI) is a measurement of the resistance to compression forces at the epiphyses of long bones. Measurement made by pQCT at a distance of 4% of total tibia length from the distal growth plate. Measurement units: mm^4.

Outcome measures

Measure	Exercise Intervention n=109 Participants Participants randomized to the exercise intervention group performed activities designed to provide skeletal loading: impact activities 3 times per week, increasing the number of jumps (up to 40) and increasing height (from 6 inches to 24 inches per repetition) over the initial 8-weeks (2 months). New activities were introduced approximately every 2-3 months in order to continually stress the skeleton over 2 years. Physical activity performed by these subjects (in addition to intervention activities) was objectively assessed by pedometer (7-day wear period) and further assessed by a validated past year physical activity questionnaire PYPAQ).	Control n=98 Participants Participants randomized to the control arm did not perform intervention activities. Physical activity was objectively assessed by pedometer (7-day wear period) and further assessed by a validated past year physical activity questionnaire (PYPAQ).
24-month Change in Bone Strength Index at the Tibia 4% Site	17.28 mm^4 Standard Deviation 9.35	16.86 mm^4 Standard Deviation 10.14

PRIMARY outcome

Timeframe: Baseline to 24-months

Population: Population consists of all participants that had complete measurements at the baseline, 12-month and 24-month time points (N=207). At 12-months: Age=11.8 +/- 1.0 yrs; Height=153.3 +/- 9.9 cm; Weight=44.0 +/- 9.3 kg. At 24-months: Age=12.8 +/- 1.0 yrs; Height=158.8 +/- 9.1 cm; Weight=50.0 +/- 10.7 kg.

Baseline to 24-month change in total volumetric bone density at the tibia 50% site . Measurement made by pQCT at a distance of 50% of total tibia length from the distal growth plate. Measurement units: milligrams per cubic centimeter (mg/ccm).

Outcome measures

Measure	Exercise Intervention n=109 Participants Participants randomized to the exercise intervention group performed activities designed to provide skeletal loading: impact activities 3 times per week, increasing the number of jumps (up to 40) and increasing height (from 6 inches to 24 inches per repetition) over the initial 8-weeks (2 months). New activities were introduced approximately every 2-3 months in order to continually stress the skeleton over 2 years. Physical activity performed by these subjects (in addition to intervention activities) was objectively assessed by pedometer (7-day wear period) and further assessed by a validated past year physical activity questionnaire PYPAQ).	Control n=98 Participants Participants randomized to the control arm did not perform intervention activities. Physical activity was objectively assessed by pedometer (7-day wear period) and further assessed by a validated past year physical activity questionnaire (PYPAQ).
24-month Change in Total Volumetric Bone Density at the Tibia 50% Site	37.26 milligrams per cubic centimeter (mg/ccm) Standard Deviation 29.74	39.83 milligrams per cubic centimeter (mg/ccm) Standard Deviation 32.94

PRIMARY outcome

Timeframe: Baseline to 24-months

Population: Population consists of all participants that had complete measurements at the baseline, 12-month and 24-month time points (N=207). At 12-months: Age=11.8 +/- 1.0 yrs; Height=153.3 +/- 9.9 cm; Weight=44.0 +/- 9.3 kg. At 24-months: Age=12.8 +/- 1.0 yrs; Height=158.8 +/- 9.1 cm; Weight=50.0 +/- 10.7 kg.

Baseline to 24-month change in volumetric bone density of trabecular bone at the tibia 50% site . Measurement made by pQCT at a distance of 50% of total tibia length from the distal growth plate. Measurement units: milligrams per cubic centimeter (mg/ccm).

Outcome measures

Measure	Exercise Intervention n=109 Participants Participants randomized to the exercise intervention group performed activities designed to provide skeletal loading: impact activities 3 times per week, increasing the number of jumps (up to 40) and increasing height (from 6 inches to 24 inches per repetition) over the initial 8-weeks (2 months). New activities were introduced approximately every 2-3 months in order to continually stress the skeleton over 2 years. Physical activity performed by these subjects (in addition to intervention activities) was objectively assessed by pedometer (7-day wear period) and further assessed by a validated past year physical activity questionnaire PYPAQ).	Control n=98 Participants Participants randomized to the control arm did not perform intervention activities. Physical activity was objectively assessed by pedometer (7-day wear period) and further assessed by a validated past year physical activity questionnaire (PYPAQ).
24-month Change in Volumetric Bone Density of Trabecular Bone at the Tibia 50% Site	-3.51 milligrams per cubic centimeter (mg/ccm) Standard Deviation 15.84	-4.00 milligrams per cubic centimeter (mg/ccm) Standard Deviation 14.16

PRIMARY outcome

Timeframe: Baseline to 24-months

Population: Population consists of all participants that had complete measurements at the baseline, 12-month and 24-month time points (N=207). At 12-months: Age=11.8 +/- 1.0 yrs; Height=153.3 +/- 9.9 cm; Weight=44.0 +/- 9.3 kg. At 24-months: Age=12.8 +/- 1.0 yrs; Height=158.8 +/- 9.1 cm; Weight=50.0 +/- 10.7 kg.

Baseline to 24-month change in volumetric bone density of cortical bone at the tibia 50% site . Measurement made by pQCT at a distance of 50% of total tibia length from the distal growth plate. Measurement units: milligrams per cubic centimeter (mg/ccm).

Outcome measures

Measure	Exercise Intervention n=109 Participants Participants randomized to the exercise intervention group performed activities designed to provide skeletal loading: impact activities 3 times per week, increasing the number of jumps (up to 40) and increasing height (from 6 inches to 24 inches per repetition) over the initial 8-weeks (2 months). New activities were introduced approximately every 2-3 months in order to continually stress the skeleton over 2 years. Physical activity performed by these subjects (in addition to intervention activities) was objectively assessed by pedometer (7-day wear period) and further assessed by a validated past year physical activity questionnaire PYPAQ).	Control n=98 Participants Participants randomized to the control arm did not perform intervention activities. Physical activity was objectively assessed by pedometer (7-day wear period) and further assessed by a validated past year physical activity questionnaire (PYPAQ).
24-month Change in Volumetric Bone Density of Cortical Bone at the Tibia 50% Site	33.70 milligrams per cubic centimeter (mg/ccm) Standard Deviation 27.35	31.06 milligrams per cubic centimeter (mg/ccm) Standard Deviation 26.75

PRIMARY outcome

Timeframe: Baseline to 24-months

Population: Population consists of all participants that had complete measurements at the baseline, 12-month and 24-month time points (N=207). At 12-months: Age=11.8 +/- 1.0 yrs; Height=153.3 +/- 9.9 cm; Weight=44.0 +/- 9.3 kg. At 24-months: Age=12.8 +/- 1.0 yrs; Height=158.8 +/- 9.1 cm; Weight=50.0 +/- 10.7 kg.

Baseline to 24-month measurement of periosteal circumference at the tibia 50% site . Measurement made by pQCT at a distance of 50% of total tibia length from the distal growth plate. Measurement units: millimeters (mm).

Outcome measures

Measure	Exercise Intervention n=109 Participants Participants randomized to the exercise intervention group performed activities designed to provide skeletal loading: impact activities 3 times per week, increasing the number of jumps (up to 40) and increasing height (from 6 inches to 24 inches per repetition) over the initial 8-weeks (2 months). New activities were introduced approximately every 2-3 months in order to continually stress the skeleton over 2 years. Physical activity performed by these subjects (in addition to intervention activities) was objectively assessed by pedometer (7-day wear period) and further assessed by a validated past year physical activity questionnaire PYPAQ).	Control n=98 Participants Participants randomized to the control arm did not perform intervention activities. Physical activity was objectively assessed by pedometer (7-day wear period) and further assessed by a validated past year physical activity questionnaire (PYPAQ).
24-month Change in Periosteal Circumference at the Tibia 50% Site	5.26 millimeters (mm) Standard Deviation 2.12	5.27 millimeters (mm) Standard Deviation 1.63

PRIMARY outcome

Timeframe: Baseline to 24-months

Population: Population consists of all participants that had complete measurements at the baseline, 12-month and 24-month time points (N=207). At 12-months: Age=11.8 +/- 1.0 yrs; Height=153.3 +/- 9.9 cm; Weight=44.0 +/- 9.3 kg. At 24-months: Age=12.8 +/- 1.0 yrs; Height=158.8 +/- 9.1 cm; Weight=50.0 +/- 10.7 kg.

Baseline to 24-month change in cortical thickness at the tibia 50% site . Measurement made by pQCT at a distance of 50% of total tibia length from the distal growth plate. Measurement units: millimeters (mm).

Outcome measures

Measure	Exercise Intervention n=109 Participants Participants randomized to the exercise intervention group performed activities designed to provide skeletal loading: impact activities 3 times per week, increasing the number of jumps (up to 40) and increasing height (from 6 inches to 24 inches per repetition) over the initial 8-weeks (2 months). New activities were introduced approximately every 2-3 months in order to continually stress the skeleton over 2 years. Physical activity performed by these subjects (in addition to intervention activities) was objectively assessed by pedometer (7-day wear period) and further assessed by a validated past year physical activity questionnaire PYPAQ).	Control n=98 Participants Participants randomized to the control arm did not perform intervention activities. Physical activity was objectively assessed by pedometer (7-day wear period) and further assessed by a validated past year physical activity questionnaire (PYPAQ).
24-month Change in Cortical Thickness at the Tibia 50% Site	.51 millimeters (mm) Standard Deviation .28	.53 millimeters (mm) Standard Deviation .28

PRIMARY outcome

Timeframe: Baseline to 24-months

Population: Population consists of all participants that had complete measurements at the baseline, 12-month and 24-month time points (N=207). At 12-months: Age=11.8 +/- 1.0 yrs; Height=153.3 +/- 9.9 cm; Weight=44.0 +/- 9.3 kg. At 24-months: Age=12.8 +/- 1.0 yrs; Height=158.8 +/- 9.1 cm; Weight=50.0 +/- 10.7 kg.

Baseline to 24-month change in strength-strain index at the tibia 50% site. Stress-strain index (also called strength-strain index and stress-strength index in the literature) is a measure of the resistance to torsional and bending forces at diaphyseal sites of long bones. Measurement made by pQCT at a distance of 50% of total tibia length from the distal growth plate. Measurement units: mm^3.

Outcome measures

Measure	Exercise Intervention n=109 Participants Participants randomized to the exercise intervention group performed activities designed to provide skeletal loading: impact activities 3 times per week, increasing the number of jumps (up to 40) and increasing height (from 6 inches to 24 inches per repetition) over the initial 8-weeks (2 months). New activities were introduced approximately every 2-3 months in order to continually stress the skeleton over 2 years. Physical activity performed by these subjects (in addition to intervention activities) was objectively assessed by pedometer (7-day wear period) and further assessed by a validated past year physical activity questionnaire PYPAQ).	Control n=98 Participants Participants randomized to the control arm did not perform intervention activities. Physical activity was objectively assessed by pedometer (7-day wear period) and further assessed by a validated past year physical activity questionnaire (PYPAQ).
24-month Change in Stress-Strain Index at the Tibia 50% Site	322.78 mm^3 Standard Deviation 114.10	336.49 mm^3 Standard Deviation 112.47

PRIMARY outcome

Timeframe: Baseline to 24-months

Population: Population consists of all participants that had complete measurements at the baseline, 12-month and 24-month time points (N=207). At 12-months: Age=11.8 +/- 1.0 yrs; Height=153.3 +/- 9.9 cm; Weight=44.0 +/- 9.3 kg. At 24-months: Age=12.8 +/- 1.0 yrs; Height=158.8 +/- 9.1 cm; Weight=50.0 +/- 10.7 kg.

Baseline to 24-month change in total volumetric bone density at the tibia 66% site . Measurement made by pQCT at a distance of 66% of total tibia length from the distal growth plate. Measurement units: milligrams per cubic centimeter (mg/ccm).

Outcome measures

Measure	Exercise Intervention n=109 Participants Participants randomized to the exercise intervention group performed activities designed to provide skeletal loading: impact activities 3 times per week, increasing the number of jumps (up to 40) and increasing height (from 6 inches to 24 inches per repetition) over the initial 8-weeks (2 months). New activities were introduced approximately every 2-3 months in order to continually stress the skeleton over 2 years. Physical activity performed by these subjects (in addition to intervention activities) was objectively assessed by pedometer (7-day wear period) and further assessed by a validated past year physical activity questionnaire PYPAQ).	Control n=98 Participants Participants randomized to the control arm did not perform intervention activities. Physical activity was objectively assessed by pedometer (7-day wear period) and further assessed by a validated past year physical activity questionnaire (PYPAQ).
24-month Change in Total Volumetric Bone Density at the Tibia 66% Site	17.83 milligrams per cubic centimeter (mg/ccm) Standard Deviation 38.18	19.26 milligrams per cubic centimeter (mg/ccm) Standard Deviation 41.46

PRIMARY outcome

Timeframe: Baseline to 24-months

Population: Population consists of all participants that had complete measurements at the baseline, 12-month and 24-month time points (N=207). At 12-months: Age=11.8 +/- 1.0 yrs; Height=153.3 +/- 9.9 cm; Weight=44.0 +/- 9.3 kg. At 24-months: Age=12.8 +/- 1.0 yrs; Height=158.8 +/- 9.1 cm; Weight=50.0 +/- 10.7 kg.

Baseline to 24-month change in volumetric bone density of trabecular bone at the tibia 66% site . Measurement made by pQCT at a distance of 66% of total tibia length from the distal growth plate. Measurement units: milligrams per cubic centimeter (mg/ccm).

Outcome measures

Measure	Exercise Intervention n=109 Participants Participants randomized to the exercise intervention group performed activities designed to provide skeletal loading: impact activities 3 times per week, increasing the number of jumps (up to 40) and increasing height (from 6 inches to 24 inches per repetition) over the initial 8-weeks (2 months). New activities were introduced approximately every 2-3 months in order to continually stress the skeleton over 2 years. Physical activity performed by these subjects (in addition to intervention activities) was objectively assessed by pedometer (7-day wear period) and further assessed by a validated past year physical activity questionnaire PYPAQ).	Control n=98 Participants Participants randomized to the control arm did not perform intervention activities. Physical activity was objectively assessed by pedometer (7-day wear period) and further assessed by a validated past year physical activity questionnaire (PYPAQ).
24-month Change in Volumetric Bone Density of Trabecular Bone at the Tibia 66% Site	4.48 milligrams per cubic centimeter (mg/ccm) Standard Deviation 14.20	1.69 milligrams per cubic centimeter (mg/ccm) Standard Deviation 16.02

PRIMARY outcome

Timeframe: Baseline to 24-months

Population: Population consists of all participants that had complete measurements at the baseline, 12-month and 24-month time points (N=207). At 12-months: Age=11.8 +/- 1.0 yrs; Height=153.3 +/- 9.9 cm; Weight=44.0 +/- 9.3 kg. At 24-months: Age=12.8 +/- 1.0 yrs; Height=158.8 +/- 9.1 cm; Weight=50.0 +/- 10.7 kg.

Baseline to 24-month change in volumetric bone density of cortical bone at the tibia 66% site . Measurement made by pQCT at a distance of 66% of total tibia length from the distal growth plate. Measurement units: milligrams per cubic centimeter (mg/ccm).

Outcome measures

Measure	Exercise Intervention n=109 Participants Participants randomized to the exercise intervention group performed activities designed to provide skeletal loading: impact activities 3 times per week, increasing the number of jumps (up to 40) and increasing height (from 6 inches to 24 inches per repetition) over the initial 8-weeks (2 months). New activities were introduced approximately every 2-3 months in order to continually stress the skeleton over 2 years. Physical activity performed by these subjects (in addition to intervention activities) was objectively assessed by pedometer (7-day wear period) and further assessed by a validated past year physical activity questionnaire PYPAQ).	Control n=98 Participants Participants randomized to the control arm did not perform intervention activities. Physical activity was objectively assessed by pedometer (7-day wear period) and further assessed by a validated past year physical activity questionnaire (PYPAQ).
24-month Change in Volumetric Bone Density of Cortical Bone at the Tibia 66% Site	28.96 milligrams per cubic centimeter (mg/ccm) Standard Deviation 28.71	31.06 milligrams per cubic centimeter (mg/ccm) Standard Deviation 28.49

PRIMARY outcome

Timeframe: Baseline to 24-months

Population: Population consists of all participants that had complete measurements at the baseline, 12-month and 24-month time points (N=207). At 12-months: Age=11.8 +/- 1.0 yrs; Height=153.3 +/- 9.9 cm; Weight=44.0 +/- 9.3 kg. At 24-months: Age=12.8 +/- 1.0 yrs; Height=158.8 +/- 9.1 cm; Weight=50.0 +/- 10.7 kg.

Baseline to 24-month change in periosteal circumference at the tibia 66% site . Measurement made by pQCT at a distance of 66% of total tibia length from the distal growth plate. Measurement units: millimeters (mm).

Outcome measures

Measure	Exercise Intervention n=109 Participants Participants randomized to the exercise intervention group performed activities designed to provide skeletal loading: impact activities 3 times per week, increasing the number of jumps (up to 40) and increasing height (from 6 inches to 24 inches per repetition) over the initial 8-weeks (2 months). New activities were introduced approximately every 2-3 months in order to continually stress the skeleton over 2 years. Physical activity performed by these subjects (in addition to intervention activities) was objectively assessed by pedometer (7-day wear period) and further assessed by a validated past year physical activity questionnaire PYPAQ).	Control n=98 Participants Participants randomized to the control arm did not perform intervention activities. Physical activity was objectively assessed by pedometer (7-day wear period) and further assessed by a validated past year physical activity questionnaire (PYPAQ).
24-month Change in Periosteal Circumference at the Tibia 66% Site	6.75 millimeters (mm) Standard Deviation 3.07	6.82 millimeters (mm) Standard Deviation 3.06

PRIMARY outcome

Timeframe: Baseline to 24-months

Population: Population consists of all participants that had complete measurements at the baseline, 12-month and 24-month time points (N=207). At 12-months: Age=11.8 +/- 1.0 yrs; Height=153.3 +/- 9.9 cm; Weight=44.0 +/- 9.3 kg. At 24-months: Age=12.8 +/- 1.0 yrs; Height=158.8 +/- 9.1 cm; Weight=50.0 +/- 10.7 kg.

Baseline to 24-month change in cortical thickness at the tibia 66% site . Measurement made by pQCT at a distance of 66% of total tibia length from the distal growth plate. Measurement units: millimeters (mm).

Outcome measures

Measure	Exercise Intervention n=109 Participants Participants randomized to the exercise intervention group performed activities designed to provide skeletal loading: impact activities 3 times per week, increasing the number of jumps (up to 40) and increasing height (from 6 inches to 24 inches per repetition) over the initial 8-weeks (2 months). New activities were introduced approximately every 2-3 months in order to continually stress the skeleton over 2 years. Physical activity performed by these subjects (in addition to intervention activities) was objectively assessed by pedometer (7-day wear period) and further assessed by a validated past year physical activity questionnaire PYPAQ).	Control n=98 Participants Participants randomized to the control arm did not perform intervention activities. Physical activity was objectively assessed by pedometer (7-day wear period) and further assessed by a validated past year physical activity questionnaire (PYPAQ).
24-month Change in Cortical Thickness at the Tibia 66% Site	.32 millimeters (mm) Standard Deviation .27	.32 millimeters (mm) Standard Deviation .31

PRIMARY outcome

Timeframe: Baseline to 24-months

Population: Population consists of all participants that had complete measurements at the baseline, 12-month and 24-month time points (N=207). At 12-months: Age=11.8 +/- 1.0 yrs; Height=153.3 +/- 9.9 cm; Weight=44.0 +/- 9.3 kg. At 24-months: Age=12.8 +/- 1.0 yrs; Height=158.8 +/- 9.1 cm; Weight=50.0 +/- 10.7 kg.

Baseline to 24-month change in strength-strain index at the tibia 66% site. Stress-strain index (also called strength-strain index and stress-strength index in the literature) is a measure of the resistance to torsional and bending forces at diaphyseal sites of long bones. Measurement made by pQCT at a distance of 66% of total tibia length from the distal growth plate. Measurement units: mm^3.

Outcome measures

Measure	Exercise Intervention n=109 Participants Participants randomized to the exercise intervention group performed activities designed to provide skeletal loading: impact activities 3 times per week, increasing the number of jumps (up to 40) and increasing height (from 6 inches to 24 inches per repetition) over the initial 8-weeks (2 months). New activities were introduced approximately every 2-3 months in order to continually stress the skeleton over 2 years. Physical activity performed by these subjects (in addition to intervention activities) was objectively assessed by pedometer (7-day wear period) and further assessed by a validated past year physical activity questionnaire PYPAQ).	Control n=98 Participants Participants randomized to the control arm did not perform intervention activities. Physical activity was objectively assessed by pedometer (7-day wear period) and further assessed by a validated past year physical activity questionnaire (PYPAQ).
24-month Change in Stress-Strain Index at the Tibia 66% Site	421.49 mm^3 Standard Deviation 172.67	435.13 mm^3 Standard Deviation 164.78

Adverse Events

Exercise Intervention Arm

Serious events: 0 serious events

Other events: 0 other events

Deaths: 0 deaths

Control Arm

Serious events: 0 serious events

Other events: 0 other events

Deaths: 0 deaths

Serious adverse events

Adverse event data not reported

Other adverse events

Adverse event data not reported

Additional Information

Dr. Scott Going, Ph.D.

University of Arizona

Phone: 520-626-3432

Email: going@u.arizona.edu

Results disclosure agreements

• Principal investigator is a sponsor employee
• Publication restrictions are in place