This study compared the effects of velocity-based strength training and traditional strength training on physical performance and muscle adaptations in youth soccer players. Twenty-four male youth soccer players were randomly assigned to one of three training groups: velocity-based training with 10% velocity loss, velocity-based training with 20% velocity loss, or traditional resistance training performed to failure. All groups trained twice per week for six weeks using the same relative load.

Before and after the training period, participants completed assessments of sprint performance, jump performance, change of direction speed, muscle strength, and muscle thickness. The purpose of this study was to determine whether velocity-based training could provide similar or superior improvements in performance and muscle development compared with traditional training while using a lower total training volume.

This randomized, parallel-group interventional study was designed to compare the effects of velocity-based strength training (VBT) and traditional resistance training (TRT) on selected physiological and motoric outcomes in elite youth soccer players. The intervention period lasted six weeks, with training sessions conducted twice weekly under supervised conditions.

Participants were randomly allocated to one of three groups: velocity-based training with a 10% velocity loss threshold (VBT-10), velocity-based training with a 20% velocity loss threshold (VBT-20), or traditional resistance training performed to voluntary concentric failure (TRT). All groups completed the same resistance exercises (squat, deadlift, and hip thrust) using a relative load corresponding to 80% of one-repetition maximum.

In the VBT groups, repetition velocity was continuously monitored using a wearable linear velocity tracking device. Each set was terminated when the predefined velocity loss threshold was reached. In contrast, participants in the TRT group performed sets until concentric failure without velocity monitoring. Rest intervals and exercise order were standardized across groups to ensure consistency.

Outcome assessments were conducted before and after the intervention period by the same research staff using standardized protocols. Participants were instructed to refrain from additional resistance training outside the study during the intervention period. All training sessions and testing procedures were supervised, and no training-related adverse events were reported.

The primary objective of the study was to evaluate whether velocity-based strength training could elicit comparable or superior adaptations in performance and muscle-related outcomes compared with traditional resistance training, while potentially reducing overall training volume and fatigue accumulation.

Inclusion Criteria

• Male youth soccer players aged 15-17 years
• Competing in an elite youth soccer academy league
• Actively participating in organized soccer training and official competitions
• Minimum of 2 years of structured resistance training experience as part of team training
• Training regularly five days per week with official matches on weekends
• Free from musculoskeletal injury or other health problems at the time of enrollment
• Ability to correctly perform squat, deadlift, and hip thrust exercises
• Written informed consent obtained from parents or legal guardians, and assent obtained from participants

Exclusion Criteria

• History of musculoskeletal injury or surgery within the previous 6 months
• Presence of any neurological, cardiovascular, or orthopedic disorder
• Use of performance-enhancing drugs or supplements affecting neuromuscular performance
• Participation in another structured strength or conditioning research study within the previous 3 months
• Failure to attend more than 10% of the scheduled training sessions
• Inability or unwillingness to comply with the study protocol or testing procedures

Individual participant data (IPD) will not be shared publicly due to participant confidentiality considerations and institutional data protection regulations. Aggregate data will be reported in publications.