Balance, Proprioception, and Functional Performance, Exercise Training, Healthy Volunteers, Isometric Exercise, Musculoskeletal Function
Conditions
Keywords
Isometric Exercise, Knee Joint Angles, Joint Position Sense, Balance, Functional Performance, Exercise Therapy
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 18-26 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.
Interventions
OTHERIsometric 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.
OTHERIsometric Exercise at 30° and 105° Knee Angles
Same protocol as Group 1, but at 30° and 105° of knee flexion.
OTHERIsometric Exercise at 45° and 120° Knee Angles
Same protocol as Group 1, but at 45° and 120° of knee flexion.
OTHERIsometric Exercise at 60° and 135° Knee Angles
Same protocol as Group 1, but at 60° and 135° of knee flexion.
Sponsors
Firat University
Study design
Allocation
RANDOMIZED
Intervention model
PARALLEL
Primary purpose
TREATMENT
Masking
NONE
Intervention model description
Participants were randomly assigned to one of four parallel groups. Each group performed an eight-week exercise program consisting of progressive resistance training for the hip and ankle combined with isometric quadriceps and hamstring exercises at specific knee joint angles (15°-90°, 30°-105°, 45°-120°, and 60°-135°). The intervention was delivered three times per week under the supervision of physiotherapists.
Eligibility
Sex/Gender
ALL
Age
18 Years to 30 Years
Healthy volunteers
Yes
Inclusion criteria
* Age between 18 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
Design outcomes
Primary
| Measure | Time frame | Description |
|---|---|---|
| Balance Performance | Baseline and after 8 weeks of intervention | Balance will be assessed using the Y Balance Test, which measures dynamic postural control in anterior, posteromedial, and posterolateral directions. Normalized reach distances will be recorded. |
| Joint Position Sense | Baseline and after 8 weeks of intervention | Proprioception will be evaluated using a digital goniometer at predetermined knee joint angles (15°, 30°, 45°, 60°, 90°, and 120°). Absolute angular error between target and reproduced angles will be calculated. |
| Functional Performance- Stair Climb Test | Baseline and after 8 weeks of intervention | unctional performance will be assessed using the Stair Climb Test (time to ascend and descend 9 steps) |
Secondary
| Measure | Time frame | Description |
|---|---|---|
| Functional Performance - 30-Second Sit-to-Stand Test | Baseline and after 8 weeks. | Number of repetitions completed in 30 seconds. |
Countries
Turkey (Türkiye)
Outcome results
None listed