Influence of heat stress and acclimation on maximal aerobic power

Summary Thirteen male volunteers performed cycle ergometer maximal oxygen uptake (tests) in moderate (21 C, 30% rh) and hot (49 C, 20% rh) environments, before and after a 9-day heat acclimation program. This program resulted in significantly decreased (P<0.01) final heart rate (24 bt·min^–1) and rectal temperature (0.4 C) from the first to last day of acclimation. The was lower (P<0.01) in the hot environment relative to the moderate environment both before (8%) and after (7%) acclimation with no significant difference (P>0.05) shown for maximal power output (PO max, watts) between environments either before or after acclimation. The was higher (P<0.01) by 4% after acclimation in both environments. Also, PO max was higher (P<0.05) after acclimation in both the moderate (4%) and hot (2%) environments. The reduction in in the hot compared to moderate environment was not related to the difference in core temperature at between moderate and hot trials, nor was it strongly related with aerobic fitness level. These findings indicate that heat stress, per se, reduced the . Further, the reduction in due to heat was not affect be state of heat acclimation, the degree of elevation in core temperature, or level of aerobic fitness.