['This study investigated the isolated and combined effects of heat [temperate (22\xa0°C/30\xa0% rH) vs. hot (35\xa0°C/40\xa0% rH)] and hypoxia [sea level (FiO2 0.21) vs. moderate altitude (FiO2 0.15)] on exercise capacity and neuromuscular fatigue characteristics.', 'Eleven physically active subjects cycled to exhaustion at constant workload (66\xa0% of the power output associated with their maximal oxygen uptake in temperate conditions) in four different environmental conditions [temperate/sea level (control), hot/sea level (hot), temperate/moderate altitude (hypoxia) and hot/moderate altitude (hot\xa0+\xa0hypoxia)]. Torque and electromyography (EMG) responses following electrical stimulation of the tibial nerve (plantar-flexion; soleus) were recorded before and 5\xa0min after exercise.', 'Time to exhaustion was reduced (P\xa0<\xa00.05) in hot (-35\xa0±\xa015\xa0%) or hypoxia (-36\xa0±\xa014\xa0%) compared to control (61\xa0±\xa028\xa0min), while hot\xa0+\xa0hypoxia (-51\xa0±\xa020\xa0%) further compromised exercise capacity (P\xa0<\xa00.05). However, the effect of temperature or altitude on end-exercise core temperature (P\xa0=\xa00.089 and P\xa0=\xa00.070, respectively) and rating of perceived exertion (P\xa0>\xa00.05) did not reach significance. Maximal voluntary contraction torque, voluntary activation (twitch interpolation) and peak twitch torque decreased from pre- to post-exercise (-9\xa0±\xa01, -4\xa0±\xa01 and -6\xa0±\xa01\xa0% all trials compounded, respectively; P\xa0<\xa00.05), with no effect of the temperature or altitude. M-wave amplitude and root mean square activity were reduced (P\xa0<\xa00.05) in hot compared to temperate conditions, while normalized maximal EMG activity did not change. Altitude had no effect on any measured parameters.'] Does combining heat stress and moderate hypoxia reduce cycling time to exhaustion without modifying neuromuscular fatigue characteristics?