THE EFFECTS OF EXERCISE AND GENDER ON HEAT TOLERANCE TIME DURING PROLONGED HEAT EXPOSURE

The U.S. Navy has recently begun to increase tlle number of female sailors stationed aboard ship and personnel staffing ratios on the majority of suface ships are to be 50% male and 50% female by tlle year 2000. There is concern fue Navy's current heat e"l'osure policy may not provide tllC appropriate guidance for female personnel because fuese heat exposure standards, commonly referred to as fue ~hysiological Heat J;xposure !,imits or PHEL curves, were developed using males. It has been established tlmt most gender differences in thermoregulation are negligible when males and females are evenly matched for factors such as age, acclimation, bodY size, maximal aerobic capacity, and relative versus absolute workload (1,2,3). However, female sailors within tlle U.S. Navy population differ in size, fitness, and body composition from male sailors. Additionally, tllOugh body size was incorporated in fue development of the PHEL curves, application of the PHEL curves is based on personnel performing shipboard tasks at an absolute work rate. We hypotllesized that gender differences in thermoregulation would not appear at low activity levels (pHEL I, PHEL 2) and/or low thenual environments, but may begin to appear at a moderate work rate and moderate to high thermal environments. We Imve preViously reported the thermoregulatory responses of males to a PHEL 3 work rate (4,5). The purpose Oftllis study was to compare thennoregulatory responses between males and females to the PHEL 3 work rate which has time-weightedmean metabolic rate of 111.7 Wom'-