Perceptual responses during the 10 km self-paced run.

The following perceptual variables were measured under temperate (25°C) and hot (35°C) conditions: rating of perceived exertion (RPE; panel A) and thermal sensation (panel B). Data are expressed as means ± SD. # indicates a significant difference compared to the control trial at 25°C (main effect of ambient temperature), p < 0.05.</p

Timeline of the experimental trials.

Environmental heat stress impairs endurance performance by enhancing exercise-induced physiological and perceptual responses. However, the time course of these responses during self-paced running, particularly when comparing hot and temperate conditions, still needs further clarification. Moreover, monitoring fatigue induced by exercise is paramount to prescribing training and recovery adequately, but investigations on the effects of a hot environment on post-exercise neuromuscular fatigue are scarce. This study compared the time course of physiological and perceptual responses during a 10 km self-paced treadmill run (as fast as possible) between temperate (25°C) and hot (35°C) conditions. We also investigated the changes in countermovement jump (CMJ) performance following exercise in these two ambient temperatures. Thirteen recreational long-distance runners (11 men and 2 women), inhabitants of a tropical region, completed the two experimental trials in a randomized order. Compared to 25°C, participants had transiently higher body core temperature (TCORE) and consistently greater perceived exertion while running at 35°C (p p p CORE caused by environmental heat stress, post-exercise neuromuscular fatigue is similar between temperate and hot conditions. This finding suggests that the higher external load (faster speed) at 25°C compensates for the effects of more significant perceptual responses at 35°C in inducing neuromuscular fatigue.</div

S1 Data -

Environmental heat stress impairs endurance performance by enhancing exercise-induced physiological and perceptual responses. However, the time course of these responses during self-paced running, particularly when comparing hot and temperate conditions, still needs further clarification. Moreover, monitoring fatigue induced by exercise is paramount to prescribing training and recovery adequately, but investigations on the effects of a hot environment on post-exercise neuromuscular fatigue are scarce. This study compared the time course of physiological and perceptual responses during a 10 km self-paced treadmill run (as fast as possible) between temperate (25°C) and hot (35°C) conditions. We also investigated the changes in countermovement jump (CMJ) performance following exercise in these two ambient temperatures. Thirteen recreational long-distance runners (11 men and 2 women), inhabitants of a tropical region, completed the two experimental trials in a randomized order. Compared to 25°C, participants had transiently higher body core temperature (TCORE) and consistently greater perceived exertion while running at 35°C (p p p CORE caused by environmental heat stress, post-exercise neuromuscular fatigue is similar between temperate and hot conditions. This finding suggests that the higher external load (faster speed) at 25°C compensates for the effects of more significant perceptual responses at 35°C in inducing neuromuscular fatigue.</div

Lower limb neuromuscular performance before and after running.

The countermovement jump (CMJ) height was measured before, immediately after, and 1 h after the 10 km self-paced run under temperate (25°C) and hot (35°C) conditions (panel A). Data are expressed as means ± SD. + indicates a significant difference compared to before running (main effect of time point), p i.e., lines). The black and green lines indicate, respectively, greater and lower performance reductions after running at 35°C than at 25°C.</p

Endurance performance.

The time to complete the 10 km self-paced run was measured under temperate (25°C) and hot (35°C) conditions (panel A). Data are expressed as means ± SD and individual data (i.e., lines); all participants had decreased performance in the heat. Panel B shows the average speed at different distance intervals during the self-paced run in the two environmental conditions. Data are expressed as means ± SD. * indicates a significant difference compared to the control trial at 25°C, p < 0.05.</p

Physiological responses during the 10 km self-paced run.

The following physiological variables were measured under temperate (25°C) and hot (35°C) conditions: heart rate (panel A), core temperature (panel B), and heat storage rate (panel C). Data are expressed as means ± SD. * indicates a significant difference compared to the control trial at 25°C, p < 0.05.</p