Thermoregulation in the cold after physical training at different ambient air temperatures.

Since human thermoregulation at rest is altered by cold exposure, it was hypothesized that physical training under cold conditions would alter thermoregulation. Three groups (n = 8) of male subjects (mean age 24.3 +/- 0.9 years) were evaluated: group T (interval training at 21degreesC), group CT (interval training at 1degreesC), and group C (no training, equivalent exposure to 1degreesC). Each group was submitted, before and after 4 weeks of interval training (5 d/week), to a cold air test at rest (SCAT) (dry bulb temperature (T-db) = 1degreesC) for a 2-h period for evaluation of the thermoregulatory responses. During SCAT, after the training/acclimation period, group T exhibited a higher rectal temperature (T-re) (P < 0.05) without significant change in mean skin temperature (Tbar(sk)) whereas metabolic heat production (Mdot) was higher at the beginning of the SCAT (P < 0.05). For group CT, no thermoregulatory change was observed. Group C showed a lower T-re (P < 0.05) without significant change in either Tbar(sk) or in Mdot, suggesting the development of a hypothermic general cold adaptation. This study showed, first, that the cold thermoregulatory responses induced by an interval training differed following the climatic conditions of the training and, second, that this training performed in the cold prevented the development of a general cold adaptation.