Abstract
We tested the hypothesis that thermal behavior alleviates thermal discomfort and accelerates core temperature recovery following low intensity exercise. Methods: In a 27 ± 0 °C, 48 ± 6% relative humidity environment, 12 healthy subjects (six females) completed 60 min of exercise followed by 90 min of seated recovery on two occasions. Subjects wore a suit top perfusing 34 ± 0 °C water during exercise. In the control trial, this water continually perfused throughout recovery. In the behavior trial, the upper body was maintained thermally comfortable by pressing a button to receive cool water (3 ± 2 °C) perfusing through the top for 2 min per button press. Results: Physiological variables (core temperature, p ≥ 0.18; mean skin temperature, p = 0.99; skin wettedness, p ≥ 0.09; forearm skin blood flow, p = 0.29 and local axilla sweat rate, p = 0.99) did not differ between trials during exercise. Following exercise, mean skin temperature decreased in the behavior trial in the first 10 min (by −0.5 ± 0.7 °C, p < 0.01) and upper body skin temperature was reduced until 70 min into recovery (by 1.8 ± 1.4 °C, p < 0.05). Core temperature recovered to pre-exercise levels 17 ± 31 min faster (p = 0.02) in the behavior trial. There were no differences in skin blood flow or local sweat rate between conditions during recovery (p ≥ 0.05). Whole-body thermal discomfort was reduced (by −0.4 ± 0.5 a.u.) in the behavior trial compared to the control trial within the first 20 min of recovery (p ≤ 0.02). Thermal behavior via upper body cooling resulted in augmented cumulative heat loss within the first 30 min of recovery (Behavior: 288 ± 92 kJ; Control: 160 ± 44 kJ, p = 0.02). Conclusions: Engaging in thermal behavior that results in large reductions in mean skin temperature following exercise accelerates the recovery of core temperature and alleviates thermal discomfort by promoting heat loss.
Highlights
Autonomic thermoregulatory responses during exercise recovery have been well described [1,2,3,4,5].Even during relatively low intensity exercise, the post exercise period is characterized by paradoxically elevated core temperatures that occur as a consequence of autonomic thermoeffectors being rapidly withdrawn [1,6]
Mean skin temperature decreased from the end-exercise time point in both conditions within the first 10 min of recovery (p < 0.01), was reduced to a greater extent in the behavior trial compared to the control trial within the first 10 min and remained lower through 20 min of recovery (p ≤ 0.01)
The present study tested the hypotheses that during recovery from low intensity exercise, The cooling present astudy tested the during recovery from low intensity exercise, voluntarily large surface areahypotheses of the body that would alleviate thermal discomfort and accelerate voluntarily cooling a large surface area of the body would alleviate thermal discomfort and accelerate the recovery of core temperature
Summary
Even during relatively low intensity exercise, the post exercise period is characterized by paradoxically elevated core temperatures that occur as a consequence of autonomic thermoeffectors being rapidly withdrawn [1,6]. It follows that evaporative heat loss is attenuated, resulting in body heat storage above pre-exercise levels for up to an hour following cessation of exercise [1]. We recently identified that while autonomic heat loss effector responses are withdrawn, behavioral thermoeffector responses remain engaged following exercise [6,7] The reason for this may be due to sustained elevations in core. Public Health 2020, 17, 20; doi:10.3390/ijerph17010020 www.mdpi.com/journal/ijerph
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