Athletic Performance, Isometric Strength Training, Post Activation Potentiation, Volleyball
Conditions
Keywords
Post-Activation Performance Enhancement, Maximal voluntary isometric contraction, Jump performance, Resistance training
Brief summary
This randomized crossover trial investigates the acute effects of bilateral and unilateral isometric conditioning activity on bilateral and unilateral jump performance in highly trained male volleyball players. Fourteen athletes will complete three experimental conditions in randomized order: bilateral isometric squat conditioning activity (BI), unilateral isometric squat conditioning activity (UNI), and a control condition consisting of low-intensity treadmill walking (CTRL). In both isometric conditions, participants will perform three sets of three maximal 3-second contractions, with 3-minute recovery intervals between sets. Jump performance will be assessed before each experimental condition and at 4, 8, and 12 minutes afterward using bilateral countermovement jumps and single-leg jumps performed separately with each lower limb. The primary aim of the study is to determine whether the mode of isometric conditioning activity, unilateral versus bilateral, influences the magnitude and time course of acute changes in jump performance. An additional objective is to assess whether the effects of the conditioning activity differ between bilateral and unilateral jumping tasks.
Detailed description
This study is a randomized, counterbalanced crossover trial designed to examine the acute effects of unilateral and bilateral isometric conditioning activity on jump performance in highly trained male volleyball players. Fourteen participants will complete three experimental conditions on separate occasions in randomized order: bilateral isometric conditioning activity (BI), unilateral isometric conditioning activity (UNI), and a control condition (CTRL). Because each participant will complete all three conditions, every athlete will serve as his own control. Each experimental session will begin with a standardized warm-up consisting of 5 minutes of cycling followed by bodyweight squats, walking lunges, thoracic spine rotations, and submaximal countermovement jumps. Baseline jump performance will then be assessed using two bilateral countermovement jumps and two single-leg jumps performed separately with each lower limb. The single-leg jump will involve take-off from one limb and landing on both limbs. In the BI condition, participants will perform three sets of three maximal 3-second bilateral isometric squat contractions against an immovable resistance, with 3-minute recovery intervals between sets. In the UNI condition, participants will perform three sets of three maximal 3-second unilateral isometric squat contractions with each lower limb. The limbs will be alternated to reduce systematic differences in recovery time between sides. In the CTRL condition, participants will complete 9 minutes of low-intensity treadmill walking at 6 km/h. Following each experimental condition, bilateral countermovement jump and single-leg jump performance will be reassessed at 4, 8, and 12 minutes. All jumps will be performed on force platforms. The primary outcome will be bilateral countermovement jump height. Secondary outcomes will include single-leg jump height and selected force-time variables derived from the bilateral and unilateral jump tests. The primary objective of the study is to compare the acute effects of unilateral and bilateral isometric conditioning activity on bilateral countermovement jump performance. A secondary objective is to determine whether the type of conditioning activity produces task-specific effects on unilateral jump performance and whether the time course of post-activation performance enhancement differs between the BI and UNI conditions.
Interventions
BEHAVIORALBilateral Isometric Conditioning Activity
Three sets of three maximal 3-second bilateral isometric squat contractions performed against an immovable resistance, with 3-minute recovery intervals between sets. Participants will be instructed to push as hard and as fast as possible during each contraction.
BEHAVIORALUnilateral Isometric Conditioning Activity
Three sets of three maximal 3-second unilateral isometric squat contractions performed with each lower limb against an immovable resistance. The lower limbs will be alternated, and 3-minute recovery intervals will be provided between sets. Participants will be instructed to push as hard and as fast as possible during each contraction.
BEHAVIORALLow-Intensity Treadmill Walking
All participants will complete all three experimental conditions in a randomized and counterbalanced order, with a standardized recovery interval between sessions. Each participant will therefore serve as his own control.
Sponsors
The Jerzy Kukuczka Academy of Physical Education in Katowice
Study design
Allocation
RANDOMIZED
Intervention model
CROSSOVER
Primary purpose
BASIC_SCIENCE
Masking
NONE
Intervention model description
Participants will complete all three experimental conditions in a randomized and counterbalanced order. The conditions will include bilateral isometric conditioning activity, unilateral isometric conditioning activity, and a control condition. Experimental sessions will be separated by a standardized washout period to minimize carryover effects.
Eligibility
Sex/Gender
MALE
Healthy volunteers
Yes
Inclusion criteria
* minimum of 7 years of systematic volleyball training, * at least 3 resistance training sessions per week during the preceding 5 years, * no musculoskeletal injury requiring training cessation longer than 4 weeks within 6 months prior to enrollment, * absence of tattoos over the rectus femoris muscle that could interfere with thermographic assessment.
Exclusion criteria
* less than 7 years of systematic volleyball training, * less than 3 resistance training sessions per week during the previous 5 years, * any musculoskeletal injury within the 6 months prior to enrollment that required cessation of training for longer than 4 weeks, * current musculoskeletal pain or injury that could affect jumping performance or participation in maximal isometric exercise, * tattoos, scars, or skin conditions over the rectus femoris muscle that could interfere with thermographic measurements, * use of medications or substances that may affect neuromuscular performance or muscle function, * failure to comply with study procedures or testing requirements.
Design outcomes
Primary
| Measure | Time frame | Description |
|---|---|---|
| Changes in Bilateral Countermovement Jump Height | Baseline and 4, 8, and 12 minutes after each experimental condition | Bilateral countermovement jump height will be assessed using dual force platforms operating at a sampling frequency of 1000 Hz. Jump height will be calculated from center-of-mass take-off velocity using the impulse-momentum method and expressed in centimeters. Participants will perform two valid trials at each time point, and the mean value will be used for analysis. Changes from the condition-specific baseline will be compared between the bilateral isometric, unilateral isometric, and control conditions. |
| Changes in Single-Leg Jump Height | Baseline and 4, 8, and 12 minutes after each experimental condition | Single-leg jump height will be assessed separately for the right and left lower limbs using force platforms. Each jump will be performed with take-off from one limb and landing on both limbs. Jump height will be calculated from center-of-mass take-off velocity using the impulse-momentum method and expressed in centimeters. Two valid trials will be performed with each limb at each time point, and the mean value for each limb will be used for analysis. |
Secondary
| Measure | Time frame | Description |
|---|---|---|
| Changes in Bilateral Countermovement Jump Modified Reactive Strength Index | Baseline and 4, 8, and 12 minutes after each experimental condition | The modified reactive strength index during the bilateral countermovement jump will be calculated as jump height in meters divided by time to take-off in seconds and expressed in meters per second. Participants will perform two valid trials at each time point, and the mean value will be used for analysis. |
| Changes in Inter-Limb Concentric Impulse Asymmetry During the Bilateral Countermovement Jump | Baseline and 4, 8, and 12 minutes after each experimental condition | Concentric impulse will be calculated separately for the right and left lower limbs from force-time data recorded using dual force platforms. Inter-limb asymmetry will be expressed as a percentage and calculated using the following formula: absolute difference between limbs divided by the higher limb value, multiplied by 100. A value of 0% represents perfect symmetry, while higher values indicate greater inter-limb asymmetry. The mean of two valid trials will be used for analysis. |
| Changes in Inter-Limb Single-Leg Jump Height Asymmetry | Baseline and 4, 8, and 12 minutes after each experimental condition | Inter-limb asymmetry in single-leg jump height will be calculated from the mean jump height obtained separately for the right and left lower limbs. Asymmetry will be expressed as a percentage and calculated as the absolute difference between limbs divided by the higher limb value, multiplied by 100. A value of 0% represents perfect symmetry, while higher values indicate greater inter-limb asymmetry. |
Countries
Poland
Outcome results
None listed