This clinical trial investigates neuromuscular fatigue and recovery responses following a standardized soccer-specific fatigue protocol in trained young male soccer players. The study compares the sensitivity of different neuromuscular performance assessments, including the countermovement jump (CMJ), isometric mid-thigh pull (IMTP), and isometric hamstring 90-90 (IH90-90) tests, for detecting fatigue and recovery over time.

The main questions the study aims to answer are:

• Which neuromuscular assessment is most sensitive for detecting fatigue following soccer-specific activity?
• How do force production characteristics change immediately after exercise and during recovery?
• Do single-joint and multi-joint isometric assessments demonstrate different recovery patterns?

Participants complete a standardized soccer simulation fatigue protocol and perform neuromuscular performance tests before exercise, immediately after exercise, and 24 and 48 hours following the protocol.

The findings may help improve fatigue monitoring strategies during congested training and match schedules in soccer players and support approaches aimed at reducing injury risk.

Neuromuscular fatigue monitoring is widely used in soccer to evaluate recovery status, optimize training load, and reduce injury risk during congested training and match schedules. However, different neuromuscular assessments may reflect distinct aspects of fatigue and recovery, and the time-dependent sensitivity of commonly used force-based assessments remains unclear.

The purpose of this randomized crossover trial is to compare the time-course sensitivity of the countermovement jump (CMJ), isometric mid-thigh pull (IMTP), and isometric hamstring 90-90 (IH90-90) tests for detecting neuromuscular fatigue following a standardized soccer-specific fatigue protocol (T-SAFT90) in trained young male soccer players.

Eighteen trained male soccer players participate in the study. Neuromuscular performance is assessed before exercise, immediately after exercise, and at 24 and 48 hours following the fatigue protocol. The study evaluates changes in peak force and rapid force production characteristics obtained from single-joint and multi-joint isometric assessments, together with CMJ performance variables.

Participants complete the T-SAFT90 protocol designed to simulate the physiological and mechanical demands of competitive soccer activity. Following the protocol, participants perform a series of neuromuscular performance assessments across multiple recovery time points.

The study aims to determine which assessments are most sensitive for detecting acute and residual fatigue and whether single-joint and multi-joint force assessments demonstrate different recovery profiles. The findings may contribute to improved fatigue-monitoring strategies in soccer and assist practitioners in managing recovery and injury risk during periods of high training and match density.

Inclusion Criteria:

• Male soccer players aged 18-22 years Minimum of 3 years of active licensed soccer experience Minimum of 2 years of resistance training experience Classified as trained/development-level athletes Free from current musculoskeletal injury at the time of participation

Exclusion Criteria:

History of lower-extremity injury resulting in absence from training for longer than 1 month within the previous 3 months Use of caffeine, alcohol, or nutritional supplements during the study period Participation in heavy physical activity outside the experimental protocol during the study period Failure to maintain regular training routines during the study period

Only trained male soccer players were eligible to participate in the study.

Individual participant data may be shared upon reasonable request to the corresponding author, in accordance with institutional policies and participant confidentiality requirements.

Due to the nature of the exercise protocol, no masking procedures were applied.