Force-Velocity Alterations in Arm and Non-Arm Swing Countermovement Jumps Following Fatigue

This study aimed to investigate the acute effects of muscular fatigue on countermovement jump (CMJ) performance with (CMJAS) and without arm swing (CMJNAS), focusing on force-time parameters derived from a force platform. Eighteen recreationally active male participants (age: 21.43 ± 1.4 years; height: 188.18 ± 5.7 cm; weight: 80.5 ± 5.4 kg) completed CMJAS and CMJNAS protocols before and after a fatigue-inducing Wingate test. Kinetic and kinematic parameters were assessed pre- and post-fatigue using a force platform. Bayesian paired-samples t-tests and mixed-design repeated measures ANOVA were employed to evaluate within- and between-condition changes, with Bayes Factors (BF₁₀) and inclusion values (BFincl) reported. Bayesian analyses revealed extreme evidence for fatigue-induced reductions in jump height calculated from flight time (BF₁₀ = 219.893) and take-off velocity (BF₁₀ = 6.605) in CMJAS. In CMJNAS, post-fatigue performance demonstrated significant increases in peak concentric force (BF₁₀ = 2.491), while average eccentric force application significantly decreased in both jump types. Vertical Take-Off Velocity exhibited the highest sensitivity to fatigue with a BFincl of 6142.381. Additionally, CMJNAS showed a distinct compensatory strategy under fatigue, as evidenced by higher post-fatigue concentric force and lower decrements in velocity-related parameters compared to CMJAS. Acute muscular fatigue alters CMJ performance parameters differently depending on arm involvement. CMJNAS appears to be a more sensitive indicator of neuromuscular fatigue and may better reflect compensatory mechanisms in lower limb function. These findings support the application of CMJNAS for fatigue monitoring in athletic and rehabilitation settings.