One of the most popular assessments of neuromuscular function for many athletes is the vertical countermovement jump (CMJ). It is a valuable measurement of maximal output when performed with a limited number of repetitions and sufficient rest between attempts. However, this design offers little insight into the influence of exercise-induced fatigue on neuromuscular function, which is relevant to the demands of various sports. When CMJs are performed on a dual-force plate system, limb-specific metrics and inter-limb asymmetry can be assessed, providing further insight into the link between fatigue and lower-limb function. Purpose : The purpose of this study was to implement a repetitive CMJ protocol to investigate the effect of fatigue on CMJ performance and to determine if inter-limb asymmetry increased as fatigue progressed. Methods : Forty-two male, youth hockey athletes (15.6 1.2 y) performed 30 CMJs at 4-second intervals on a dual-force plate system. Force- and power-related dependent variables were separated into bins of 5 consecutive jumps (eg, 1–5, 5–10, etc) for subsequent data and statistical analyses. Results : Compared to bin 1, relative peak power and jump height were reduced by 6.1% and 5.5% respectively, whereas braking and total jump duration increased by 5.2% and 3.7%, respectively ( P < .01). There were no changes to relative peak force, relative braking rate of force development, or any inter-limb asymmetry measure throughout the fatiguing task ( P ≥ .06). Conclusions : Thirty CMJs induced modest performance impairments and alterations to jump strategy, thereby providing insight into the influence of fatigue on neuromuscular function during repeated exercise, which exceeds possible insights when CMJs are compared before and after exercise.
Twible et al. (Thu,) studied this question.