Decay of heat acclimation during exercise in cold and exposure to cold environment.
Sixteen male students exercised for 14 days (1 h/day) in the heat for heat acclimation (HA). During deacclimation (DA) one group exercised in the cold (EXG, n=8) for 60 min/day (morning) and was exposed to the cold for another hour (afternoon) for 14 days. The other group was exposed to the cold (EPG, n=8) for 1 h each in the morning and afternoon (Ta: 18.0 degrees C, RH: 58%) over the same period. All returned to exercise in the heat for reacclimation (RA) for 10 days. Subjects were tested on days 1, 16, 21, 32, 36 and 44 on a bicycle ergometer for 60 min at 60% of VO(2max) in the heat (Ta: 31.1 degrees C, RH: 70%). Rectal temperature (T (re)) and heart rate (HR) at 40 min of exercise were used to determine the decay/gain of HA, which was calculated using the formula described by Pandolf et al. (Ergonomics, 20:399-408, 1977). After HA (day 16) T (re) and HR decreased significantly. During DA, EXG showed decay in T (re) of 24 and 35% and HR of 29 and 35% on days 21 and 32, respectively. For EPG the corresponding decay was of 2 and 9% for T (re) and 17 and 17% for HR. After 10 days of RA, EXG showed gains of 11% in T (re) and 12% in HR, while EPG showed gains of 47% in T (re) and 38% in HR. In conclusion, EXG had greater decay during DA and lower gains in RA compared to EPG. However, the differences between groups were significant only for T (re) after 4 days of DA.
Saat
M
M
Department of Physiology, School of Medical Sciences, Universiti Sains Malaysia, 16150 KB, Kelantan, Malaysia. matsaat@kb.usm.my
Sirisinghe
R G
RG
Singh
R
R
Tochihara
Y
Y
D000064:Acclimatization; D000293:Adolescent; D000328:Adult; D001833:Body Temperature Regulation / Q000502:physiology*; D003080:Cold Temperature; D003681:Dehydration; D015444:Exercise / Q000502:physiology*; D006358:Hot Temperature; D006801:Humans; D043322:Lactase / Q000097:blood*; D008297:Male; D005082:Physical Exertion; D012107:Research Design
D043322:Lactase