AEROBIC POWER AS A FACTOR IN WOMENS RESPONSE TO WORK IN HOT ENVIRONMENTS

Twelve young women, athletes (n = 6) and nonathletes (n = 6), walked on a treadmill at loads equivalent to .apprx. 30% .ovrhdot.VO2 max [maximal aerobic power] for two 50-min periods in 3 environments: 28.degree. C, 45% rh [relative humidity], 35.degree. C, 65% rh and 48.degree. C, 10% rh. There were no differences between groups in rectal temperature, heart rate, evaporative heat loss or mean skin temperature at 28 or 35.degree. C or during the 1st work period in the 48.degree. C environment. A significantly lower cardiac output and stroke volume observed for nonathletes by the 46th min of work at 48.degree. C may explain why no nonathletes were able to complete a 2nd h of work while 4 of 6 athletes successfully finished the period. It appears that in conditions of severe heat stress (48.degree. C) athletes were able to maintain a cardiac output sufficient to meet the metabolic requirements and the large increase in peripheral blood flow for a longer period of time than nonathletes. [Acclimatization to heat is discussed.].