Most Effective Knee Joint Angle Pair for Isometric Exercise

NCT ID: NCT07207135

Last Updated: 2025-10-03

Basic Information

• Recruitment Status: COMPLETED
• Clinical Phase: NA
• Total Enrollment: 44 participants
• Study Classification: INTERVENTIONAL
• Study Start Date: 2024-03-15
• Study Completion Date: 2025-05-30

Brief Summary

This study investigated the effects of isometric exercises applied to the quadriceps and hamstring muscles at different knee joint angles on balance, joint position sense, and functional performance in healthy individuals. Thirty participants aged 20-30 years were randomized into four groups and performed an eight-week training program, three times per week. Outcome measures included the Y Balance Test, digital goniometer assessments for joint position sense, and functional performance tests (stair climb and 30-second sit-to-stand). The results aim to identify which knee joint angles are most effective for improving neuromuscular function and may guide future rehabilitation and training protocols.

Detailed Description

Isometric exercises applied to the quadriceps and hamstring muscles are widely used both in rehabilitation programs and in improving physical fitness in athletes. Isometric contractions occur when the muscle generates tension without changing its length, making them especially suitable in conditions where joint movement is limited or contraindicated. Previous studies have demonstrated the benefits of isometric training in increasing muscle strength, enhancing proprioception, and supporting functional performance. However, there is no clear consensus regarding the effects of isometric exercises performed at different knee joint angles on balance, joint position sense, and functional capacity.

The aim of this study was to investigate the effects of isometric exercises applied to the quadriceps and hamstring muscles at different knee angles (15°-90°, 30°-105°, 45°-120°, 60°-135°) on balance, joint position sense, and functional performance in healthy individuals. Participants aged 20-30 years, without knee pain, previous knee surgery, or pathologies preventing ambulation, were included. All participants were randomized into four groups. Each group performed progressive resistance exercises for the hip and ankle, combined with isometric exercises of the quadriceps and hamstring muscles at the specified knee angles.

The training program lasted eight weeks, with sessions three times per week. During each session, isometric contractions were performed against resistance for 10 seconds at the assigned knee angles, with standardized rest periods between sets. The number of repetitions was progressively increased throughout the program.

Assessments were conducted at baseline and after eight weeks. The following outcome measures were used:

Balance: Y Balance Test

Joint position sense: Digital goniometer measurements

Functional performance: Stair climb test and 30-second sit-to-stand test

The hypothesis of the study was that isometric exercises performed at different knee joint angles would result in different responses in balance, joint position sense, and functional performance. The findings are expected to provide valuable insights both for improving physical fitness in healthy populations and for guiding rehabilitation protocols in clinical populations.

Conditions

Isometric Exercise; Exercise Training; Musculoskeletal Function; Balance, Proprioception, and Functional Performance; Healthy Volunteers

Study Design

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

Study Groups

Group 1

Isometric Exercise at 15° and 90° Knee Angles

Group Type: EXPERIMENTAL

Isometric Exercise at 15° and 90° Knee Angles

Intervention Type: OTHER

Participants performed quadriceps and hamstring isometric contractions at 15° and 90° of knee flexion. Each contraction lasted 10 seconds against resistance, three times per week for eight weeks, with progressive repetitions. Hip and ankle strengthening was also included.

Group 2

Isometric Exercise at 30° and 105° Knee Angles

Group Type: EXPERIMENTAL

Isometric Exercise at 30° and 105° Knee Angles

Intervention Type: OTHER

Same protocol as Group 1, but at 30° and 105° of knee flexion.

Group 3

Isometric Exercise at 45° and 120° Knee Angles

Group Type: EXPERIMENTAL

Isometric Exercise at 45° and 120° Knee Angles

Intervention Type: OTHER

Same protocol as Group 1, but at 45° and 120° of knee flexion.

Group 4

Isometric Exercise at 60° and 135° Knee Angles

Group Type: EXPERIMENTAL

Isometric Exercise at 60° and 135° Knee Angles

Intervention Type: OTHER

Same protocol as Group 1, but at 60° and 135° of knee flexion.

Interventions

Isometric Exercise at 15° and 90° Knee Angles

Participants performed quadriceps and hamstring isometric contractions at 15° and 90° of knee flexion. Each contraction lasted 10 seconds against resistance, three times per week for eight weeks, with progressive repetitions. Hip and ankle strengthening was also included.

Intervention Type: OTHER

Isometric Exercise at 30° and 105° Knee Angles

Same protocol as Group 1, but at 30° and 105° of knee flexion.

Intervention Type: OTHER

Isometric Exercise at 45° and 120° Knee Angles

Same protocol as Group 1, but at 45° and 120° of knee flexion.

Intervention Type: OTHER

Isometric Exercise at 60° and 135° Knee Angles

Same protocol as Group 1, but at 60° and 135° of knee flexion.

Intervention Type: OTHER

Eligibility Criteria

Inclusion Criteria

• Age between 20 and 30 years
• Voluntary participation with signed informed consent
• No history of knee pain
• No history of knee surgery
• No musculoskeletal pathology preventing ambulation

Exclusion Criteria

• Presence of cardiovascular or pulmonary diseases that prevent exercise
• Inflammatory or infectious pathology of the knee joint
• Uncontrolled endocrinological disorders or significant systemic/organ insufficiency
• Neurological disorders affecting knee joint innervation

• Minimum Eligible Age: 20 Years
• Maximum Eligible Age: 30 Years
• Eligible Sex: ALL
• Accepts Healthy Volunteers: Yes

Sponsors

Firat University

OTHER

Sponsor Role: lead

Responsible Party

Muharrem Gökhan Beydağı

Assistant Professor

Responsibility Role: PRINCIPAL_INVESTIGATOR

Locations

Fırat Üniversitesi

Elâzığ, Merkez, Turkey (Türkiye)

Countries

Turkey (Türkiye)

Other Identifiers

FU_MGBeydagi_Isometric

Identifier Type: -

Identifier Source: org_study_id