Effects of Inter-Set Rest Intervals on Muscle Damage After Flywheel Exercise in Untrained Men (RCT)

This randomized parallel-group clinical trial will compare the acute effects of three different inter-set rest intervals during a single lower-limb flywheel resistance exercise session in untrained men. Participants will be randomly allocated to one of three groups: 1-minute, 2-minute, or 3-minute inter-set rest interval. The primary outcome will be the change in maximal voluntary isometric contraction of the knee extensors 48 hours after exercise. Secondary outcomes will include mechanical variables during the exercise session, countermovement jump performance, knee flexor maximal voluntary isometric contraction, muscle soreness, pressure pain threshold, range of motion, ultrasound-derived muscle thickness and echo intensity, perceived exertion, perceived discomfort, perceived recovery status, creatine kinase, and lactate dehydrogenase.

Inclusion Criteria: * Age between 18 and 40 years; * Apparently healthy and clinically able to perform physical exercise; * No participation in structured resistance training during the previous 6 months; * Agreement to comply with all study visits and procedures; * Signed informed consent form. Exclusion Criteria: * History of lower-limb musculoskeletal injury or surgery that may impair performance or safety during the proposed exercise protocol; * Current pain, injury, or functional limitation in the lower limbs; * Use of ergogenic aids that may affect physical performance or muscle recovery; * Use of analgesic or anti-inflammatory medication during the study period; * Failure to attend the scheduled visits required for the primary outcome assessment.