Soccer matches are normally played over 90 minutes, however it is common for players to encounter a period of extra-time (ET; 30 min) during knockout competitions such as the FIFA World Cup. Despite the importance of ET in terms of deciding the match outcome, there is a paucity of data investigating responses to ET. Notably, no investigation has attempted to profile the neuromuscular fatigue response. Thus, the precise mechanisms of neuromuscular fatigue during prolonged soccer-specific exercise are unknown.
PURPOSE: To evaluate the mechanisms and time-course of neuromuscular fatigue throughout simulated soccer performance lasting 120 minutes.
METHODS: Ten male amateur soccer players (V[Combining Dot Above]02max 56 ± 2 mL·kg-1·min-1) completed a soccer-specific protocol that required both intermittent exercise and skill performance, during which the development of fatigue was examined. Pre-exercise, at half-time (HT), full-time (FT) and following a period of extra-time (ET), maximal voluntary force (MVC) and twitch responses to supramaximal femoral nerve and transcranial magnetic stimulation (TMS) were obtained from the knee-extensors to assess peripheral and central fatigue, respectively. At each time point, measures of physical performance (20 m sprint time, countermovement jump height), perceived exertion (RPE) and core body temperature (Tcore) were also measured.
RESULTS: Upon completion of the protocol participants had covered an approximate distance of 14.4 km involving 30 dribbles and 30 sprints, comparable with a match requiring ET. At HT, FT and following ET reductions in MVC (–11, –20 and –27%, respectively, P≤0.001), potentiated twitch force (–14, –21 and –19%, respectively, P≤0.031), voluntary activation (–8, –16 and –20%, respectively, P ≤ 0.010) and voluntary activation measured with TMS (–12, –16 and –19%, respectively, P≤0.001) were evident compared to pre-exercise. Furthermore, all physical performance measures declined while RPE and Tcore increased (P≤0.010).
CONCLUSION: Soccer-specific exercise induces significant central and peripheral fatigue and the additional fatigue induced by a period of ET is of central in origin. Further research is warranted to investigate temporal neuromuscular recovery from soccer-specific performance, especially in periods of fixture congestion.