Athletic Performance, Lower-Limb Asymmetry, Muscle Strength
Conditions
Keywords
Unilateral Resistance Training, Load-Velocity Relationship, Inter-Limb Asymmetry, Free-Weight Split Squat, Velocity-Based Training, Team-Sport Athletes
Brief summary
This randomized, parallel-group study evaluated the effects of an 8-week unilateral resistance training program with strength- and velocity-oriented loading on limb-specific load-velocity relationships and lower-limb asymmetry in male university team-sport players. Participants were randomly assigned to a strength-oriented training group, which trained at 80% of the limb-specific one-repetition maximum (1RM), or a velocity-oriented training group, which trained at 40% of the limb-specific 1RM. Both groups completed 16 supervised free-weight split-squat training sessions over 8 weeks. In each session, the non-dominant limb performed four sets of five repetitions, while the dominant limb performed three sets of five repetitions. All repetitions were performed with maximal intended concentric velocity and real-time velocity feedback. Limb-specific load-velocity relationships were assessed at baseline, Week 4, and Week 8. Lower-limb asymmetry, balance, unilateral jump performance, and basketball-specific change-of-direction performance were assessed at baseline and Week 8. The purpose was to determine whether the two training orientations produced different adaptations and whether the additional training volume assigned to the non-dominant limb influenced inter-limb asymmetry.
Detailed description
This study used a randomized, two-arm, parallel-group design. Following familiarization and baseline testing, eligible male university team-sport players were randomly allocated to either a strength-oriented training group or a velocity-oriented training group. Participants completed two supervised training sessions per week for 8 weeks, resulting in a total of 16 training sessions. The primary training exercise was the unilateral free-weight split squat. The strength-oriented group trained at 80% of the limb-specific one-repetition maximum, whereas the velocity-oriented group trained at 40% of the limb-specific one-repetition maximum. In both groups, the non-dominant limb performed four sets of five repetitions and the dominant limb performed three sets of five repetitions during each session. Repetitions were performed with maximal intended concentric velocity, with real-time velocity feedback provided to participants. Loads were adjusted when necessary to maintain the prescribed limb-specific training intensity. Assessments were conducted before the intervention and after completion of the 8-week intervention. An additional interim assessment was conducted at Week 4, after the first eight training sessions. Data from the Week 4 assessment were used for an exploratory interim analysis of limb-specific load-velocity relationships and between-limb differences in derived mean concentric velocity. The Week-8 assessment evaluated the effects of the complete intervention on unilateral strength, load-velocity characteristics, balance, unilateral jump performance, basketball-specific change-of-direction performance, and lower-limb asymmetry.
Interventions
BEHAVIORALStrength-Oriented Unilateral Resistance Training
Participants completed 16 supervised unilateral free-weight split-squat training sessions over 8 weeks, with two sessions per week and at least 48 hours between sessions. Each limb trained at 80% of its limb-specific one-repetition maximum. During each session, the non-dominant limb performed four sets of five repetitions, while the dominant limb performed three sets of five repetitions. Inter-set rest was 4 minutes. All repetitions were performed with maximal intended concentric velocity, with real-time velocity feedback. Training loads were prescribed using the individual limb-specific load-velocity relationship and adjusted when necessary to maintain the target training intensity.
BEHAVIORALVelocity-Oriented Unilateral Resistance Training
Participants completed 16 supervised unilateral free-weight split-squat training sessions over 8 weeks, with two sessions per week and at least 48 hours between sessions. Each limb trained at 40% of its limb-specific one-repetition maximum. During each session, the non-dominant limb performed four sets of five repetitions, while the dominant limb performed three sets of five repetitions. Inter-set rest was 4 minutes. All repetitions were performed with maximal intended concentric velocity, with real-time velocity feedback. Training loads were prescribed using the individual limb-specific load-velocity relationship and adjusted when necessary to maintain the target training intensity.
Sponsors
South China Normal University
Study design
Allocation
RANDOMIZED
Intervention model
PARALLEL
Primary purpose
BASIC_SCIENCE
Masking
NONE
Intervention model description
Participants were randomly assigned to one of two parallel groups: a strength-oriented unilateral training group or a velocity-oriented unilateral training group. Each participant received only the intervention assigned to that group throughout the 8-week training period.
Eligibility
Sex/Gender
MALE
Age
18 Years to No maximum
Healthy volunteers
Yes
Inclusion criteria
Functional Movement Screen inline lunge score of at least 2 and ability to correctly perform the barbell split squat. At least one year of resistance-training experience. No sports-related injury within the previous 3 months that could affect participation in the study procedures. Willing and able to provide written informed consent
Exclusion criteria
Current or planned use during the study of medications that could affect the study outcomes. Current musculoskeletal injury or medical condition that could prevent completion of the training program or study assessments.
Design outcomes
Primary
| Measure | Time frame | Description |
|---|---|---|
| Mean Change From Baseline in Single-Leg Countermovement Jump Height Inter-Limb Asymmetry at Week 8 | Baseline and post-intervention at Week 8 | Single-leg countermovement jump height was measured separately for the dominant and non-dominant limbs using a force-platform system. Inter-limb asymmetry was calculated as 2 × the absolute difference between the dominant- and non-dominant-limb values divided by the sum of the two limb values, multiplied by 100. The outcome is expressed as a percentage, with higher values indicating greater inter-limb asymmetry. The mean change from baseline to Week 8 was compared between the two training groups. |
Secondary
| Measure | Time frame | Description |
|---|---|---|
| Mean Change From Baseline in Y-Balance Test Composite Score Inter-Limb Difference at Week 8 | Baseline and post-intervention at Week 8 | Anterior, posteromedial, and posterolateral reach distances were measured separately for the dominant and non-dominant limbs using the Y-Balance Test. The composite score for each limb was calculated as the sum of the three reach distances divided by three times the limb length, multiplied by 100. The inter-limb difference was calculated as the absolute difference between the dominant- and non-dominant-limb composite scores and expressed in percentage points. Higher values indicate a larger inter-limb difference. The mean change from baseline to Week 8 was compared between the two training groups. |
| Mean Change From Baseline in Limb-Specific Mean Concentric Velocity at Prespecified Relative Loads at Week | Baseline and interim assessment at Week 4 | Individual limb-specific load-velocity relationships were established during the unilateral free-weight split-squat one-repetition maximum test using linear regression. Mean concentric velocity was derived separately for the dominant and non-dominant limbs at 30%, 45%, 60%, 75%, and 90% of the directly measured limb-specific one-repetition maximum. Velocity was expressed in meters per second. Higher values indicate faster concentric movement at the same relative load. Mean changes from baseline to the Week 4 interim assessment were evaluated by training group and limb. |
| Mean Change From Baseline in Basketball Dribbling T-Test Directional Asymmetry at Week 8 | Baseline and post-intervention at Week 8 | Directional change-of-direction performance was assessed using left-side-dominant and right-side-dominant versions of the basketball dribbling T-test. Participants completed two maximal trials in each direction, and the fastest completion time for each direction was recorded in seconds. Directional asymmetry was calculated as the absolute difference between the left- and right-side completion times divided by the faster completion time, multiplied by 100. Higher percentage values indicate greater directional asymmetry. The mean change from baseline to Week 8 was compared between the two training groups. |
| Mean Change From Baseline in Absolute Inter-Limb Difference in Unilateral Split-Squat One-Repetition Maximum at Week 8 | Baseline and post-intervention at Week 8 | Unilateral split-squat one-repetition maximum was measured separately for the dominant and non-dominant limbs using a progressive loading protocol. The absolute inter-limb difference was calculated as the absolute difference between the dominant- and non-dominant-limb one-repetition maximum values and expressed in kilograms. Higher values indicate greater inter-limb strength asymmetry. The mean change from baseline to Week 8 was compared between the two training groups. |
Countries
China
Outcome results
None listed