The effect of fatigue on interlimb communication

Performing repeated motor tasks during a volleyball, basketball, or soccer game can lead to muscular fatigue, inducing a decrease in the capacity of a muscle to generate force, changes in motor coordination, and an alteration in motor performance. These changes have been attributed to an elevated risk of musculoskeletal injury. Little is known about if and how fatigue affects the coordination between the two legs during a long lasting game, and whether this could be one of the causes behind the increased occurrence of injuries towards the end of a game. The aim of the present study was to investigate the possible effect of muscular fatigue on interlimb communication. Eight amateur male soccer players took part to two recording sessions in which they either performed a 90-minute simulated soccer match (SAFT90) or rested (control session). Interlimb communication was investigated by quantifying short latency crossed responses (SLCR) observed in muscles of the contralateral (dominant) leg following nerve stimulation of the ipsilateral (non-dominant) leg. SLCR and maximal voluntary contraction (MVC) of the ankle plantarflexors in the dominant leg were measured before and after the SAFT90 and control session. MVC was quantified while the participants performed a plantarflexion on a force platform, with the ankle and knee joints fastened at 90[[unable to display character: &#8304;]]. SLCR were elicited by electrical stimulation of the ipsilateral tibial nerve while the participants walked on a treadmill. The stimulation (intensity 85% Mmax) was delivered at 80% of the participant’s walking cycle. SLCR in the contralateral gastrocnemius lateralis were quantified as the ratio between the root mean square (RMS) value of the averaged EMG in a time window between 65 and 95ms after the stimulation, and the RMS in the same time window of the control EMG (average of gait cycles with no stimulation). One participant did not show any decrease in MVC after the SAFT90 and was therefore excluded from further analysis. The MVC significantly decreased (P < .05) from 1633 ± 151 N to 1263 ± 292 N in the SAFT90 session, but not in the control session (1354 ± 391N before and 1352 ± 404 N after). No significant changes were observed in the SLCR amplitudes. However, a bigger decrease (18% decrease, from 206 ± 107 to 183 ± 85%) was observed after the SAFT90 compared to the control session (14% decrease, from 171 ± 55% to 146 ± 34%). These preliminary results show that fatigue induces a reduction, although not significant, of the SLCR. Further testing is needed to confirm this hypothesis. Such information may be relevant for preventing musculoskeletal injuries caused by fatigue.