Thermoregulation during cold exposure: effects of prior exercise

Thermoregulation during cold exposure: effects of prior exercise. J. Appl. Physiol. 87(1). 247-252, 1999.-This study examined whether acute exercise w ould imp; the body's capability to maintain thermal balance during a subseq uent cold exposure. Ten men rested for 2 h during a standardized cold-air t est (4.6 degrees C) after two treatments: 1) 60 min of cycle exercise (Ex) at 55% peak O-2 uptake and 2) par;sive heating (Heat). Ex was performed dur ing a 35 degrees C water immersion (WI), and Heat was conducted during a 38 .2 degrees C WI. The duration of Heat was individually adjusted (mean = 53 min) so that rectal temperature was similar at the end of WI in both Ex (38 .2 degrees C) and Heat (38.1 degrees C). During the cold-air test after Ex, relative to Heat 1) rectal temperature was lower (P < 0.05) from minutes 4 0-120, 2) mean weighted heat flow was higher (P < 0.05), 3) insulation was lower (P ( 0.05), and 4) metabolic heat production was not different. These results suggest that prior physical exercise mag predispose a person to gr eater heat loss and to experience a larger decline in core temperature when subsequently exposed to cold air. The combination of exercise intensity an d duration studied in these experiments did not fatigue the shivering respo nse to cold exposure.