Influence of Heat Stress and Acclimation on Maximal Aerobic Power,
ARMY RESEARCH INST OF ENVIRONMENTAL MEDICINE NATICK MA
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Thirteen male volunteers performed cycle ergometer maximal oxygen uptake V02 max tests in moderate 21 C, 30 rh and hot 49 C, 20 rh environments, before and after a nine-day heat acclimation program. This program resulted in significantly decreased P0.01 final heart rate 24 btmin and rectal temperature 0.4 C from the first to last day of acclimation. The V02 max was lower P0.01 in the hot environment relative to the moderate environment both before 8 and after 7 acclimation with no significant difference P0.05 shown for maximal power output PO max, watts between environments either before or after acclimation. The V02 max was higher P0.01 by 4 after acclimation in both the moderate 4 and hot 2 environments. The reduction in V02 max in the hot compared to moderate environment was not related to the difference in core temperature at V02 max between moderate and hot trials, nor was it strongly related with aerobic fitness level. These findings indicate that heat stress, per se, reduced the V02 max. Further, the reduction in V02 max due to heat was not affected by state of heat acclimation, the degree of elevation in core temperature, or level or aerobic fitness.
- Stress Physiology