Infl uence of body temperature on the development of fatigue during prolonged exercise in the heat

Nielsen. Influence of body temperature on the development of fatigue during prolonged exercise in the heat. J. Appl. Physiol. 86(3): 1032–1039, 1999.—We investigated whether fatigue during prolonged exercise in uncompensable hot environments occurred at the same critical level of hyperther-mia when the initial value and the rate of increase in body temperature are altered. To examine the effect of initial body temperature [esophageal temperature (Tes) 5 35.9 6 0.2, 37.4 6 0.1, or 38.2 6 0.1 (SE) °C induced by 30 min of water immersion], seven cyclists (maximal O2 uptake 5 5.1 6 0.1 l/min) performed three randomly assigned bouts of cycle ergometer exercise (60 % maximal O2 uptake) in the heat (40°C) until volitional exhaustion. To determine the influence of rate of heat storage (0.10 vs. 0.05°C/min induced by a water-perfused jacket), four cyclists performed two additiona