Heat acclimation, physical fitness, and responses to exercise in temperate and hot environments.

SHVARTZ, E., Y. SHAPIRO, A. MAGAZANIK, A. MEROZ, H. BIRNFELD, A. MECHTINGER, AND S. SHIBOLET. Heatacclimation, physical fitness, and responses to exercise in temperate and hot environments. J. Appl. Physiol.: Respirat. Environ. Exercise Physiol. 43(4): 678-683, 1977. -Three groups of men with different ire, max (60.1, 47.7, and 35.6 ml*kg+min+) were administered two submaximal tests at 23”C, at 41 and 82 W, before and after 8 days of heat acclimation (3-h work at 41 W at 39.4”C dry bulb, 30.3OC wet bulb). A control group with ire, max of 45.3 ml l kg-’ . min-l was tested at 23°C and in heat before and after 6 days of exercise at 23°C. Trained subjects with the highest Vo, max showed the best responses, and the lowest ire 2 max group showed the worst responses at 23°C and in heat (differences in heart rates and rectal temperatures but not in sweat rates and oxygen consumption responses). Heat acclimation resulted in substantial improvements in responses at 23°C and in heat of the acclimation groups, with very minor changes shown by the control group. Changes at 23°C were characterized by decreases in heart rate, rectal temperature (0.3-0.5”C), oxygen consumption, and sweat rate (2530%), and increases of 13% and 23% in 00, max in the groups with average and low 00, max, respectively. VO 2 max correlated r = -0.62 and -0.65 with rectal temperatures at 23°C and in heat, respectively. It was shown that exercise rectal temperature at 23°C was mainly a function of heat acclimatization, as well as voZ max and surface area/ mass ratio, that heat acclimation presented an effective method of physical training, and that vo, max was partially related to heat tolerance.