Characteristics of the control of human thermoregulatory behavior.

The aim of this study was to characterize several of the thermal input(s) that influence thermo-behavior in humans. Eight male subjects completed two trials in which they were free to initiate an exit from a hot chamber (45 degrees C) to a cold chamber (10 degrees C; H-->C) or from a cold chamber to a hot chamber (C-->H). Upon initiating an exit from the chamber, mean skin temperature (T(Sk)), rectal temperature (T(Rectal)), subjective thermal comfort, and time in the climate chambers prior to exit were recorded. Thermo-behavior was defined as the initiation of exit. All variables were similar (P> or =0.05) between the two trials. T(Sk) and thermal comfort at H-->C were significantly (P</=0.05) higher (34.0+/-1.1 degrees C, and 7.3+/-0.6, respectively) than at C-->H (29.4+/-0.9 degrees C, and 3.0+/-0.6, respectively). No significant differences (P> or =0.05) were found between H-->C and C-->H for T(Rectal) (H-->C: 37.0+/-0.2 degrees C vs. C-->H: 37.0+/-0.2 degrees C) or time prior to exit (H-->C: 3.9+/-2.3 min vs. C-->H: 3.9+/-1.7 min). The frequency distributions and the probability of the initiation of exit curves at H-->C and C-->H for both T(Sk) and thermal comfort were significantly negatively skewed (P< or =0.05) and normally distributed, respectively (P>/=0.05). Skin temperature appears to be an important thermal input mediating thermo-behavioral responses. This behavioral response appears to be more precise when exposed to hot temperatures compared to cold temperatures.