Exercise-induced dehydration does not alter time trial or neuromuscular performance

This study examined the effect of exercise-induced dehydration by ~4% body mass loss on 5-km cycling time trial (TT) performance and neuromuscular drive, independent of hyperthermia. 7 active males were dehydrated on 2 occasions, separated by 7 d. Participants remained dehydrated (DEH, -3.8±0.5%) or were rehydrated (REH, 0.2±0.6%) over 2 h before completing the TT at 18-25 °C, 20-30% relative humidity. Neuromuscular function was determined before dehydration and immediately prior the TT. The TT started at the same core temperature (DEH, 37.3±0.3°C; REH, 37.0±0.2 °C (P>0.05). Neither TT performance (DEH, 7.31±1.5 min; REH, 7.10±1.3 min (P>0.05)) or % voluntary activation were affected by dehydration (DEH, 88.7±6.4%; REH, 90.6±6.1% (P>0.05)). Quadriceps peak torque was significantly elevated in both trials prior to the TT (P<0.05), while a 19% increase in the rate of potentiated peak twitch torque development (P<0.05) was observed in the DEH trial only. All other neuromuscular measures were similar between trials. Short duration TT performance and neuromuscular function are not reduced by dehydration, independent of hyperthermia.