The assessment of neuromuscular fatigue during 120 minutes of simulated soccer exercise

Purpose: This investigation examined the development of neuromuscular fatigue during a simulated soccer match incorporating a period of extra-time (ET), and the reliability of these responses on repeated test occasions. Methods: Ten male amateur football players completed a 120 min soccer match simulation (SMS). Before, at half-time (HT), full-time (FT) and following a period of ET, twitch responses to supramaximal femoral nerve and transcranial magnetic stimulation (TMS) were obtained from the knee-extensors to measure neuromuscular fatigue. Within seven days of the first SMS, a second 120 min SMS was performed by eight of the original ten participants to assess the reliability of the fatigue response. Results: At HT, FT and ET, reductions in maximal voluntary force (MVC; −11, −20 and −27%, respectively, P≤0.01), potentiated twitch force (−15, −23 and −23%, respectively, P<0.05), voluntary activation (FT, −15 and ET, −18%, P≤0.01) and voluntary activation measured with TMS (−11, −15 and −17%, respectively, P≤0.01) were evident. The fatigue response was robust across both trials; the change in MVC at each time point demonstrated a good level of reliability (CV range, 6–11%; ICC2,1, 0.83-0.94) whilst the responses identified with motor nerve stimulation showed a moderate level of reliability (CV range, 5–18%; ICC2,1, 0.63-0.89) and the data obtained with motor cortex stimulation showed an excellent level of reliability (CV range, 3–6%; ICC2,1, 0.90-0.98). Conclusion: Simulated soccer exercise induces a significant level of fatigue, which is consistent on repeat tests and involves both central and peripheral mechanisms.