EFFECT OF RATE OF CHANGE IN SKIN TEMPERATURE ON LOCAL SWEATING RATE

To evaluate the relative contributions of positive and negative variations of mean skin temperature [±dT(sk)/dt] on thermoregulatory responses, male resting nude subjects were exposed to rapid or slow alterations in air and wall temperatures [28-45°C; P(a) = 20.0 mbar]. Rates of heating-cooling cycles were equal to dT(a)/dt = ±3.40, 1.13, 0.57, 0.38, or 0.19°C/min. Continuous measurements were made of rectal, oral, ear, and mean skin temperatures and of arm sweating (dew-point hygrometer method). During all exposures the local arm skin temperature was kept constant [T(sl) = 39°C]. The results showed that peripheral inputs are a major factor in thermoregulatory processes. Cutaneous receptors produce a positive and a negative rate component within the central thermal integrator. A higher rate threshold was observed for the positive rate component than for the negative one.