Thermoregulatory, metabolic and sympathoadrenal responses to repeated brief exposure to cold.

This study examined the metabolic, thermoregulatory and sympathoadrenal response pattern of eight male subjects to repeated bouts of brief cold stress. Water immersion (WI) was used to induce cold stress over a 60 min period on three separate occasions on three successive days. Rectal temperature (T(re)), mean skin temperature (T(sk)) and metabolic rate (VO2) were measured at 10 min intervals throughout WI and for 20 min post-immersion (PI). Blood was drawn and assayed for plasma adrenaline (ADR), noradrenaline (NDR) and cortisol at rest, at the end of immersion and PI. Acute cold stress was induced for each of the three exposures with a reduction in T(re) of approximately 0.63 degrees C (p<0.01) and approximately 1.2 degrees C (p<0.01) at the end of immersion and PI, respectively. T(sk) was reduced for all trials by approximately 6.0 degrees C (p<0.01) at the end of immersion and approximately 3.0 degrees C (p<0.01) at PI. VO2 peaked at 40-50 min of WI to 83%, 58% and 47% above rest for each consecutive trial. Plasma ADR did not show any change (p=0.34) as a consequence of cold stress between trials. Plasma NDR increased at the end of immersion (p<0.01) and remained elevated at PI (p<0.01). Plasma cortisol showed no change for any of the exposure periods. DeltaT(re) was more pronounced for the last exposure and was negatively correlated (r= -0.78, p<0.02) with plasma NDR. The results of this investigation complement previous findings of cold adaptation and suggest a possible adaptive response to repeated brief bouts of cold exposure evidenced by the changing trends in body temperature, metabolic rate and plasma NDR.