Etiology and Recovery of Neuromuscular Fatigue after Simulated Soccer Match Play

Purpose: We profiled the etiology and recovery of neuromuscular fatigue after simulated soccer match play. Methods: Fifteen semiprofessional players completed a 90-min simulated soccer match. Before, immediately after, and at 24, 48, and 72 h, participants completed a battery of neuromuscular, physical, and perceptual tests. Perceived fatigue and muscle soreness were assessed via visual analog scales. Maximum voluntary contraction (MVC) and twitch responses to electrical (femoral nerve) and magnetic (motor cortex) stimulation during isometric knee extensor contractions and at rest were measured to assess central (voluntary activation) and peripheral (quadriceps potentiated twitch force, Qtw, pot) fatigue, and responses to single and paired magnetic stimuli were assessed to quantify corticospinal excitability and short intracortical inhibition, respectively. Countermovement jump, reactive strength index, and sprint performance were assessed to profile the recovery of physical function. Results: Simulated match play elicited decrements in MVC that remained unresolved at 72 h (P = 0.01). Central fatigue was prominent immediately postexercise (-9% reduction in voluntary activation) and remained depressed at 48 h (-2%, P = 0.03). Qtw, pot declined by 14% postexercise, remained similarly depressed at 24 h, and had not fully recovered 72 h after (-5%, P = 0.01). Corticospinal excitability was reduced at 24 h (P = 0.047) only, and no change in short intracortical inhibition was observed. Measures of jump performance and self-reported fatigue followed a similar time course recovery to neuromuscular fatigue. Conclusion: Central processes contribute significantly to the neuromuscular fatigue experienced in the days after soccer match play, but the magnitude and slower recovery of peripheral fatigue indicates that it is the resolution of muscle function that primarily explains the recovery of neuromuscular fatigue after soccer match play.