Abstract
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°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 VO2max in the heat (Ta: 31.1°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.
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Acknowledgements
The authors wish to acknowledge the research grants from the Grant-in-Aid for the twenty-first Century COE programme a Grant-in Aid for Scientific Research (16107006), the Japan Society of the Promotion Sciences (JSPS) and the Universiti Sains Malaysia (304/PPSP/6131256) that enabled this study to be conducted.
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Saat, M., Sirisinghe, R.G., Singh, R. et al. Decay of heat acclimation during exercise in cold and exposure to cold environment. Eur J Appl Physiol 95, 313–320 (2005). https://doi.org/10.1007/s00421-005-0012-9
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DOI: https://doi.org/10.1007/s00421-005-0012-9