How Different Velocity-Loss Thresholds Impact Acute Neuromuscular Fatigue in Flywheel Resistance Training

Flywheel resistance-training technology has been shown to be effective in improving sport performance and reducing the risk of injuries. This study aimed to evaluate the effects of different velocity-loss thresholds and moments of inertia on immediate postexercise neuromuscular fatigue during the flywheel half-squat exercise. The study followed a crossover design. Twenty physically healthy participants (15 men and 6 women) participated in the study. They completed 9 workout conditions combining 3 training intensities (inertia: 0.050, 0.100, and 0.150 kg·m2) and 3 velocity-loss thresholds (5%, 10%, and 15%) during the flywheel half-squat exercise. Conditions were administered in random order. Neuromuscular performance tests, including peak isometric force and maximum rate of force development measured by the isometric squat test, as well as the countermovement jump, were performed before and immediately after each exercise condition. In addition, a countermovement jump was performed 5 minutes postexercise. Peak isometric force significantly dropped by about 15.58% (16.70%) (P < .001, ηp2=.672). However, maximum rate of force development was similarly affected by time but also by the velocity-loss threshold (5% ≈ 10% < 15%, P = .011, ηp2=.117). Countermovement-jump performance varied significantly with time, inertia, and velocity loss (P = .015, ηp2=.062), showing a greater impact with higher speed loss (15%) compared with lower (5% and 10%). Speed losses above 10%, especially up to 0.150 kg·m2, caused significant loss of neuromuscular performance, particularly in actions requiring high-velocity force. Coaches and practitioners can use velocity-based training to individualize the training volume and adjust a desired postexercise acute fatigue.