Moderate exercise increases postexercise thresholds for vasoconstriction and shivering

Abstract

The purpose of this study was to evaluate the effect of exercise on the subsequent postexercise thresholds for vasoconstriction and shivering. On two separate days, with six subjects (3 women), a whole body water-perfused suit slowly decreased mean skin temperature (approximately 7.0 degreesC/h) until thresholds for vasoconstriction and shivering were clearly established. Subjects were then rewarmed by increasing water temperature until both esophageal and mean skin temperatures returned to near-baseline values. Subjects either performed 15 min of cycle ergometry (65% maximal O2 consumption) followed by 30 min of recovery (Exercise) or remained seated with no exercise for 45 min (Control). Subjects were then cooled again. We mathematically compensated for changes in skin temperatures by using the established linear cutaneous contribution of skin to the control of vasoconstriction and shivering (20%). The calculated core temperature threshold (at a designated skin temperature of 30.0 degreesC) for vasoconstriction increased significantly from 36.64 +/- 0.20 to 36.89 +/- 0.22 degreesC postexercise (P < 0.01). Similarly, the shivering threshold increased from 35.73 +/- 0.13 to 36.13 +/- 0.12 degreesC postexercise (P < 0.01). In contrast, sequential measurements, without exercise, demonstrate a time-dependent decrease in both the vasoconstriction (0.10 degreesC) and shivering (0.12 degreesC) thresholds. These data indicate that exercise has a prolonged effect by increasing the postexercise thresholds for both cold thermoregulatory responses.

Thermoregulatory and Immune Responses During Cold Exposure: Effects of Repeated Cold Exposure and Acute Exercise

“…Our results contrast those reported by Kenny et al (58) who found that the threshold for vasoconstriction was elevated after exercise. They suggested that exercise would result in the retention of heat during subsequent recovery in a cold environment (58).…”

“…They suggested that exercise would result in the retention of heat during subsequent recovery in a cold environment (58). However, our subjects exercised for one hour in water while those studied by Kenny et al (58) only completed a short exercise bout (15 min) and thus our subjects may have been more fatigued.…”

“…They suggested that exercise would result in the retention of heat during subsequent recovery in a cold environment (58). However, our subjects exercised for one hour in water while those studied by Kenny et al (58) only completed a short exercise bout (15 min) and thus our subjects may have been more fatigued. In addition, Kenny et al (58) did not control for differences in initial core temperature before cold exposure, but we matched initial T CO re values before cold exposure between our trials.…”

“…However, our subjects exercised for one hour in water while those studied by Kenny et al (58) only completed a short exercise bout (15 min) and thus our subjects may have been more fatigued. In addition, Kenny et al (58) did not control for differences in initial core temperature before cold exposure, but we matched initial T CO re values before cold exposure between our trials. Finally, our volunteers were subjected to a whole body cold air exposure at a constant temperature compared to the waterperfused suit that Kenny et al (58) used.…”

“…In addition, Kenny et al (58) did not control for differences in initial core temperature before cold exposure, but we matched initial T CO re values before cold exposure between our trials. Finally, our volunteers were subjected to a whole body cold air exposure at a constant temperature compared to the waterperfused suit that Kenny et al (58) used. Thus methodological differences probably account for discrepant observations in our study and that of Kenny et al (58).…”