Athletic Performance, Resistance Training, Soccer
Conditions
Keywords
Resistance training, Jump performance, Sprint, Maximal voluntary isometric contraction
Brief summary
This randomized controlled trial investigates the effects of unilateral and bilateral isometric strength training integrated into an 8-week complex training program on neuromuscular performance in elite youth soccer players. Forty-one male players competing at the national level will be randomly assigned to one of three groups: unilateral isometric training (UNI), bilateral isometric training (BI), or a control group performing the same training program without additional isometric exercises. All participants will complete a structured complex strength training program once per week for eight weeks during the competitive season. Neuromuscular performance will be assessed before and after the intervention using countermovement jump height, broad jump distance, maximal isometric squat peak force and 30-m sprint time. The aim of the study is to determine whether the mode of isometric training (unilateral vs bilateral) influences adaptations in strength, power and sprint performance in youth soccer players. An additional objective of the study is to determine whether the type of isometric training intervention influences inter-limb asymmetries in neuromuscular performance. Selected tests will therefore be performed both bilaterally and unilaterally to assess potential differences between dominant and non-dominant limbs.
Detailed description
This study is a randomized, parallel-group intervention designed to examine the effects of unilateral and bilateral isometric strength training integrated into an 8-week complex strength training program on neuromuscular performance in elite youth soccer players. Participants will be recruited from youth teams competing at the national level and randomly assigned to one of three groups: unilateral isometric training (UNI), bilateral isometric training (BI), or a control group (CRL). All groups will perform the same structured complex strength training program once per week for eight weeks during the competitive season. The UNI and BI groups will perform additional isometric exercises at the beginning of each session, whereas the control group will complete the same training program without the isometric component. The isometric protocol will include three multi-joint exercises: isometric plantar flexion, isometric squat, and isometric hip extension performed against an immovable barbell in a power rack. In the BI group exercises will be performed bilaterally, whereas in the UNI group each limb will be trained separately. The complex training program will consist of paired resistance and ballistic exercises including squats, jumps, bench press, medicine ball throws, rows, and Romanian deadlifts. Training intensity and volume will progress across two phases during the eight-week intervention. Neuromuscular performance will be assessed before and after the intervention using countermovement jump height measured with a force plate system, standing broad jump distance, maximal isometric squat peak force measured during an isometric squat test and 30-meter sprint time measured with electronic timing gates. In addition, selected performance tests (countermovement jump, standing broad jump, and isometric squat test) will be performed both bilaterally and unilaterally in order to assess potential inter-limb asymmetries. Participants will first perform the tests bilaterally, followed by unilateral trials with the dominant limb and then the non-dominant limb. Sprint performance will be assessed only bilaterally. The primary objective of the study is to evaluate the effects of unilateral versus bilateral isometric strength training on changes in jump performance, sprint performance and maximal isometric strength. A secondary objective of the study is to assess whether the type of training intervention influences inter-limb asymmetry in neuromuscular performance.
Interventions
BEHAVIORALUnilateral Isometric Training
Isometric strength exercises performed unilaterally including plantar flexion, squat, and hip extension against an immovable barbell.
BEHAVIORALBilateral Isometric Training
Isometric strength exercises performed bilaterally including plantar flexion, squat, and hip extension against an immovable barbell.
BEHAVIORALComplex Strength Training
A structured complex training program consisting of paired resistance and ballistic exercises performed once per week for eight weeks.
Sponsors
The Jerzy Kukuczka Academy of Physical Education in Katowice
Study design
Allocation
RANDOMIZED
Intervention model
PARALLEL
Primary purpose
BASIC_SCIENCE
Masking
NONE
Intervention model description
Participants will be randomly assigned to one of three parallel groups: unilateral isometric training, bilateral isometric training or a control group performing the same complex training program without additional isometric exercises.
Eligibility
Sex/Gender
MALE
Age
14 Years to 19 Years
Healthy volunteers
Yes
Inclusion criteria
* Male youth soccer players competing at the national level. * Age between 15 and 19 years. * Minimum of one year of resistance training experience. * Regular participation in organized soccer training and strength training.
Exclusion criteria
* Current neuromuscular or musculoskeletal injury or disorder. * Injury occurring during the intervention period preventing participation in training or testing. * Failure to complete the prescribed training program or attend at least 80% of training sessions. * Participation in additional resistance training programs outside the study protocol during the intervention period.
Design outcomes
Primary
| Measure | Time frame | Description |
|---|---|---|
| Countermovement Jump Height | Baseline (Week 0) and Week 9 | Change in countermovement jump (CMJ) height measured using a dual force plate system. Jump height will be calculated using the impulse-momentum method and expressed in centimeters (cm). |
| 30-Meter Sprint Time | Baseline (Week 0) and Week 9 | Change in linear sprint performance measured during a 30-meter sprint test using electronic timing gates. Sprint time will be recorded in seconds (s) using electronic timing gates positioned at positioned at 0 m, 5 m, and 30 m. |
| Maximal Isometric Squat Peak Force | Baseline (Week 0) and Week 9 | Change in maximal isometric squat peak force measured during an isometric squat test performed on a dual force plate system. Peak force will be expressed in Newtons (N). |
Secondary
| Measure | Time frame | Description |
|---|---|---|
| Reactive Strength Index Modified (RSI-mod) | Baseline (Week 0) and Week 9 | Change in reactive strength index modified (RSI-mod) obtained during the countermovement jump test and calculated as jump height divided by contraction time. |
| Standing Broad Jump Distance | Baseline (Week 0) and Week 9 | Change in horizontal jump performance measured using the standing broad jump test. Jump distance will be recorded in centimeters (cm). |
| Inter-Limb Asymmetry Index | Baseline (Week 0) and Week 9 | Inter-limb asymmetry calculated for unilateral performance tests including countermovement jump, standing broad jump, and isometric squat peak force. The asymmetry index (AI) will be calculated using the formula: (DL - NDL) / ((DL + NDL) / 2) × 100, where DL represents the dominant limb and NDL represents the non-dominant limb. |
Countries
Poland
Outcome results
None listed