Central and peripheral inputs in sweating regulation during thermal transients

Eight nude resting men were exposed to consecutive heating-cooling cycles of air and wall temperatures varying from 28 to 45 degrees C in a sawtooth pattern using one of the following slopes: +/- 3.40, +/- 2.27, +/- 1.70, +/- 1.42, or +/- 1.13 degrees C . min-1. Ambient vapor pressure and air velocity were kept constant at 20.0 mbar and 0.9 m . s-1, respectively. Continuous measurements were made of rectal, esophageal, and mean skin temperatures. Local upper limb sweating response was measured from an arm chamber under a local thermal clamp. The results point out the insufficiency of an explantation based on a simple additive function of core and skin temperatures for describing the sweating regulation. During transient thermal loads, a multiplicative interaction of mean skin and core temperatures must also be taken into account for describing the central drive for local sweating response. The interindividual differences observed in the sweating regulation mechanism seem to be linked to a nonlinearity in the response of the thermoregulatory system.