Evaluating Changes in Skeletal Muscle Proteins Following Resistance Exercise and Single-Leg Disuse

NCT ID: NCT06350591

Last Updated: 2025-10-01

Basic Information

• Recruitment Status: COMPLETED
• Clinical Phase: NA
• Total Enrollment: 15 participants
• Study Classification: INTERVENTIONAL
• Study Start Date: 2024-04-01
• Study Completion Date: 2025-03-11

Brief Summary

Skeletal muscle plays a critical role in supporting human health. Beyond its role in providing the force to move, skeletal muscle accounts for a large proportion of metabolic rate, glucose disposal, and amino acid storage. Skeletal muscle is dynamically regulated by environmental stimuli, such as loading (i.e., resistance training]) and unloading (i.e., disuse atrophy) as well as the intake of essential amino acids (EAAs). However, the precise mechanisms that regulate skeletal muscle mass in response to various conditions (e.g., EAA supplementation, resistance training, and unloading) are not completely understood. Therefore, concerted efforts to better understand the mechanisms regulating skeletal muscle size are needed that aid in the development of therapeutic interventions to combat age, disease, and disuse related muscular atrophy.

Detailed Description

Skeletal muscle is a highly plastic tissue capable of modifying its phenotype (i.e., structural, contractile, and metabolic properties) in response to alterations in mechanical loading. Mechanistically underpinning skeletal muscle plasticity are changes in skeletal muscle protein turnover. Skeletal muscle size is dictated by changes in rates of muscle protein synthesis (MPS) and rates of muscle protein breakdown (MPB) with changes in rates of MPS being the primary determinant of human skeletal muscle mass. Both MPS and MPB are highly sensitive to contractile and nutritional cues. In response to EAA ingestion, there is a rise in rates of MPS and a mild suppression of MPB rates resulting in a positive state of protein balance. Similarly, when an individual performs a bout of resistance exercise, there is an increase in rates of MPS that is potentiated by EAA feeding; It is for this reason that when repeated bouts of resistance exercise are coupled with EAA intake over time, there is a gradual increase in skeletal muscle mass termed hypertrophy. In contrast, when an individual undergoes a reduction in levels of contractile activity (e.g., immobilization due to injury or surgery), there is a reduction in both fed and fasted rates of MPS leading to the loss of skeletal muscle mass and size termed muscle atrophy.

Although it is well known that both nutrition and contractile activity affect rates of muscle protein turnover and skeletal muscle mass, our current knowledge is limited by most studies reporting rates of MPS and MPB that are averages of thousands of proteins in the whole muscle, or subcellular protein fractions, such as myofibrillar, sarcoplasmic, and mitochondrial. Further, individual protein MPS and MPB rates might span a broad range and there may be selective changes to the turnover of individual proteins under different skeletal muscle loading scenarios. Dynamic proteomic profiling (DPP) is an emerging methodology that combines quantitative proteomic abundance measurements with individual protein MPS and MPB rates, to deliver unprecedented insight into the molecular regulation of individual protein turnover. Another major consideration is that nearly all studies in this field have been conducted in males, with limited data in females. The lack of data in females is a major knowledge gap and of major concern particularly given there is evidence that women may display different molecular responses to exercise, nutrition, and disuse compared to men.

The purpose of this investigation is to gain a better understanding of the acute and short-term effects of an EAA supplement and an acute bout of resistance exercise on rates of muscle protein turnover. Further, the investigators aim to measure the dynamic proteome during 10 days of unilateral leg immobilization, and following several bouts of resistance exercise in the contralateral leg, in young healthy women. The present investigation will characterize skeletal muscle mass, strength, protein expression, and protein synthesis rates (individual [i.e., DPP] and average). The study may inform potential future novel interventions to attenuate losses in skeletal muscle mass owing to disuse, aging, or injury.

Conditions

Healthy; Skeletal Muscle Atrophy; Skeletal Muscle Hypertrophy

Study Design

• Allocation Method: RANDOMIZED
• Intervention Model: PARALLEL
• Primary Study Purpose: BASIC_SCIENCE
• Blinding Strategy: NONE

Study Groups

Immobilization

Participants will undergo 10 days of unilateral immobilization whereby a leg will remain in 60 degrees of flexion with the use of a brace. All participants will complete this protocol.

Group Type: EXPERIMENTAL

Immobilization

Intervention Type: OTHER

single-leg immobilization

Resistance Training

Participants will undergo 4 sessions of unilateral resistance training over a 10 day period (the resistance training protocol will include 3 sets of 8-12 reps of leg press and leg extension). All participants will complete this protocol. On day 0, participants will be asked to undergo a bout of unilateral resistance exercise, and the investigators will assess the acute response to exercise + protein feeding (via EAA supplement).

Group Type: EXPERIMENTAL

Resistance training

Intervention Type: OTHER

Leg extension and leg press; 3 sets of 8-12 reps

Interventions

Immobilization

single-leg immobilization

Intervention Type: OTHER

Resistance training

Leg extension and leg press; 3 sets of 8-12 reps

Intervention Type: OTHER

Eligibility Criteria

Inclusion Criteria

• Females 18-30 years
• BMI between 18-28 kg/m2
• ≥2 days per week of structured exercise
• Generally healthy as assessed by medical and physical activity questionnaires
• Participants not currently pregnant

Exclusion Criteria

• Any muscular, neurological, respiratory, or metabolic disease including diabetes
• Any form of cancer currently or in the last 5 years
• Bleeding disorders or antiplatelet / anticoagulation therapy
• Currently taking fish oils or within the last 6 months
• Currently taking any form of steroid or within the last 3 months
• Inability to attain magnetic resonance imaging scans
• Known irregular responses to physical activity (e.g., shortness of breath, chest pain, dizziness, etc.)
• Any current illness
• Currently smoking or smoking within the last 6 months
• Currently pregnant
• Any concurrent medical, psychiatric, or orthopedic condition that, subject to investigators' discernment, would negatively affect the subject's ability to comply with the study requirements

• Minimum Eligible Age: 18 Years
• Maximum Eligible Age: 30 Years
• Eligible Sex: FEMALE
• Accepts Healthy Volunteers: Yes

Sponsors

Queen's University

OTHER

Sponsor Role: lead

Responsible Party

Dr. Chris McGlory, PhD

Assistant Professor

Responsibility Role: PRINCIPAL_INVESTIGATOR

Locations

School of Kinesiology and Health Studies

Kingston, Ontario, Canada

Countries

Canada

Other Identifiers

6038674

Identifier Type: -

Identifier Source: org_study_id