[Effects of adaptation to work in heat of rectal temperature evolution during recovery]

Evolution of rectal temperature (Tre) during recovery in different air temperatures was studied following different patterns of heat load before and after adaptation to work in heat (10 consecutive days). Three subjects have been exposed, after a 30 min rest period (Ta=28degrees C, Pwa=14 mb) to 4 heat loads, each producing 1 degreeC increase in Tre in approximatively 30 min (Co:Ta= 50 degrees C, Pwa = 60 mb, W = O watt; C1; 50 degrees C, 42 mb, 50 W on bicycle ergometer; C2;39 degrees C, 38 mb, 100 W and C3: 28 degrees C, 31 mb, 150 W). After of these heat loads, subjects were allowed to recover during 2 h at Ta = 28, 22 or 16 degrees C (Pwa = 14 mb). Results show that: (a) the cooler was the Ta, the faster was the recovery time; (b) before adaptation occurs, the evolution of Tre depended on the preceding heat load pattern; (c) the more intense was the work load, the more the adaptation reduced time for subsequent recovery. The interaction obtained between adaptation and intensity of preceding work load is discussed. The evolutions of leg skin temperatures suggest that a decreased local heat conductance (of inferior limbs) is associated with a local increase in external heat exchange. Adaptation to work in heat would take the form of a local re-adjustment of internal and external heat exchanges.