PHYSIOLOGICAL-RESPONSES TO MODERATE COLD STRESS IN MAN AND THE INFLUENCE OF PRIOR PROLONGED EXHAUSTIVE EXERCISE

A study was undertaken in man to investigate whether during moderate c old stress, the proportion of carbohydrate (CHO) oxidized is increased , and whether prior prolonged exhaustive exercise compromises thermore gulation. Eight euglycaemic men were cooled by a liquid-conditioned su it (I) after an overnight fast (Con) and (2) similar to 2 h after an e xercise protocol in which CHO availability was substantially lowered ( Post-Ex). The cooling stimulus lasted 90 min (Cooling) and was precede d by a 30 min thermo-neutral baseline phase (Base). In Con, aural temp erature (T-aural) and the rate of CHO oxidized (C(H) over dot O-ox) we re not altered from the values at Base during Cooling, whereas the fol lowing were increased: the rate of heat production ((H) over dot (prod ), similar to 1.9-fold), thigh electro-myographical activity (EMG, sim ilar to 2.5-fold), and the rate of fat oxidized (FAT(ox), similar to 1 .7-ford). In Post-Ex, T-aural did not decrease from the value at Base during Cooling, and compared with Con, EMG, CHOox and the rate of heat loss were not different, whereas (H) over dot (prod) (P less than or equal to 0.01), F(A) over dot T-ox (P less than or equal to 0.01) and mean skin temperature (P less than or equal to 0.01) were higher, and T-aural, was lower (P less than or equal to 0.05). It is concluded tha t during moderate cold stress, shivering thermogenesis is supported by an increase in the oxidation of fat, and despite an alteration in the initial thermoregulatory responses to Cooling similar to 2 h after ex haustive exercise, thermoregulation was not impaired.