Leg skin temperature and thigh sweat output: possible central influence of local thermal inputs

To demonstrate whether or not the skin temperature of one lower limb can have an influence on the sweat rate of the contralateral leg, the two legs of five subjects were exposed inside leg-chambers to specific local thermal conditions while sweat rates were measured on both limbs. Three experiments (C I, II, III) of 3 h were carried out: each included two phases A and B. During A, the right leg was not ventilated, while the left leg was (C I) or was not (C II-III) ventilated. During B, the legs were either removed from the leg-chambers (C I) or ventilated inside the chambers at differently controlled levels of leg skin temperature (C II-III). At all times, sweat capsules on both legs measured the sweat rates of local areas of the thigh which were also temperature-controlled. Results showed that, at constant or slightly increased mean skin and core temperatures, the sweat output of one leg could be decreased at constant (C II) or higher local skin temperature (C III) probably due to a decrease in the temperature of the opposite leg. This finding is interpreted as a consequence of a central negative effect, originating from contralateral thermal inputs.