Heat Stress Test Research Articles

Responses to dry heat of men and women with similar aerobic capacities.

Four men and four women with similar VO2max (56.33 +/- 4.05 and 54.08 +/- 4.27 ml.kg-1.min-1, respectively) exercised up to 3 h at 30% VO2max during heat stress tests (HST) before and after acclimation to dry heat [dry-bulb temperature (Tdb)/wet-bulb temperature (Twb) = 48/25 degrees C]. Rectal (Tre), tympanic sweat on the chest (msw), and total sweat rate (Msw) were recorded. There were no differences in the responses of the women between phases of the menstrual cycle. Tre, Tty, Tsk, and Tdb at the onset of sweating were similar in both sexes before and after acclimation. The nonacclimated men had significantly higher Msw and slower rise in Tre as compared to the nonacclimated women. Following acclimation these differences were no longer evident. Acclimation produced an increase in Msw in both sexes that was characterized by an increase in sweating sensitivity (delta msw/delta Tre). It was concluded that sex alone does not determine responses to heat stress. Consideration should also be given to the relative cardiovascular strain, state of acclimation, and the ambient conditions.

GROWTH HABIT AND HEAT TOLERANCE OF A COLLECTION OF POA ANNUA PLANTS IN CANADA

Forty-four Poa annua L. clones of a 115-plant collection from across Canada were found to be upright, wide-leaved types. Fifty-five clones were prostrate with narrow leaves and exhibited considerable node rooting. Twenty-six clones indicated some heat tolerance in heat stress tests.

HEAT REACTIONS OF SOME BANTU TRIBESMEN IN SOUTHERN AFRICA.

Samples of 20 Bantu each from various tribes in southern Africa have been subjected in the late summer in Johannesburg to the established “standard heat-stress test” and were compared with a sample of mixed Bantu, studied in Johannesburg in the late winter. The mean rectal temperatures of the summer group were significantly lower than the mean of the winter group. Heart rates and sweat rates were not different. Intertribal comparisons revealed no significant differences in resting values or in heat reactions. An outstanding feature was that only 3 men of the 120 unacclimatized Bantu reached a rectal temperature of 104 F, and only one collapsed (this is 3% compared to the 50% of Caucasians who did not complete the test). No distinctions can be made between these Bantu tribes in their states of acclimatization in spite of the fact that some came from temperate and others from subtropical regions. The range of climates in the tribal territories is, however, small. Expressed as basic effective temperatures, the January climates—a hot, summer month—vary from 71 to 79 F in these different region physiological reactions of Bantu tribesmen Submitted on September 17, 1963