This randomised controlled trial compared the effects of two load-matched squat training modalities on physical performance in elite youth futsal players. Seventeen players from the Antioqueña regional futsal squad in Colombia were randomly allocated to either a unilateral squat training group or a bilateral squat training group. Both groups completed a six-week velocity-based training programme, with two supervised sessions per week, while continuing their usual futsal training.

Training intensity was prescribed using mean propulsive velocity targets across three two-week blocks. The main outcomes were countermovement jump height, single-leg countermovement jump height for the right and left limbs, 10-metre sprint time, and estimated squat one-repetition maximum. Secondary descriptive data included 20-metre sprint time. The study aimed to determine whether unilateral squat training produced superior adaptations compared with bilateral squat training when training load was objectively standardised.

Elite futsal requires repeated accelerations, decelerations, changes of direction, and lower-limb power actions within a compact playing area. Because many sport-specific actions occur under unilateral support, unilateral lower-body strength training is frequently proposed as a more specific conditioning strategy than bilateral strength training. However, previous comparative studies have often failed to equate training intensity objectively across unilateral and bilateral exercises.

This parallel-group randomised controlled trial was designed to compare unilateral and bilateral squat training under velocity-based training standardisation. Eligible elite youth futsal players were allocated to one of two training groups: unilateral squat training or bilateral squat training. Randomisation was conducted using matched pairs based on estimated one-repetition maximum and a permuted-block sequence generated in Epidat 2.0. Outcome assessors were masked to group allocation. Participants and training supervisors were not masked because blinding is not feasible in exercise modality interventions.

Both groups trained twice weekly for six weeks. Each session included three sets of six repetitions. The unilateral group performed six repetitions per leg per set using the single-leg squat, while the bilateral group performed six bilateral squat repetitions per set. Training intensity was prescribed using mean propulsive velocity targets: 1.00 metres per second during weeks 1-2, 0.92 metres per second during weeks 3-4, and 0.85 metres per second during weeks 5-6. Three minutes of passive recovery were provided between sets. All participants continued their usual futsal training programme during the intervention.

Assessments were performed at baseline and within 72 hours after the final training session. Testing included 10-metre and 20-metre sprint performance using photoelectric cells, bilateral countermovement jump testing, single-leg countermovement jump testing for both limbs, and progressive squat load assessment with a linear position transducer. Estimated one-repetition maximum was calculated from the mean propulsive velocity obtained during progressive squat loading.

Inclusion Criteria:

• Competitive futsal experience of at least two years.
• Affiliation with the Antioqueña regional futsal squad.
• Technical proficiency in bilateral squat and single-leg squat execution, verified by an accredited specialist.
• No musculoskeletal injury during the three months before enrolment.
• No pharmacological, ergogenic, or supplementary intervention likely to influence physical performance.
• Exclusive participation in standard futsal training during the intervention period.
• Written informed assent from the participant and written informed consent from a parent or legal guardian when required by age.

Exclusion Criteria

• Musculoskeletal injury during the three months before enrolment.
• Inability to perform bilateral or single-leg squat exercises with acceptable technique.
• Participation in another structured lower-limb strength training programme during the study period.
• Use of pharmacological, ergogenic, or supplementary interventions likely to affect performance.
• Failure to complete baseline testing, the training intervention, or post-intervention testing.
• Withdrawal of participant assent or parental/legal guardian consent.

Individual participant data will not be publicly shared because the study involved a small cohort of elite youth athletes from an identifiable regional squad, which increases the risk of re-identification even after de-identification. Aggregated results are reported in the manuscript, and additional aggregate information may be made available upon reasonable academic request where ethically appropriate.

Outcome assessors and data collectors were masked to group allocation. Participants and training supervisors were not masked because the allocated exercise modality was visible during training.