Intense exercise increases the post-exercise threshold for sweating

Journal of Applied Physiology

Périard

Journeay³

et al. 2003

The hypothesis that the magnitude of the postexercise onset threshold for sweating is increased by the intensity of exercise was tested in eight subjects. Esophageal temperature was monitored as an index of core temperature while sweat rate was measured by using a ventilated capsule placed on the upper back. Subjects remained seated resting for 15 min (no exercise) or performed 15 min of treadmill running at either 55, 70, or 85% of peak oxygen consumption (V O2 peak) followed by a 20-min seated recovery. Subjects then donned a liquid-conditioned suit used to regulate mean skin temperature. The suit was first perfused with 20°C water to control and stabilize skin and core temperature before whole body heating. Subsequently, the skin was heated (ϳ4.0°C/h) until sweating occurred. Exercise resulted in an increase in the onset threshold for sweating of 0.11 Ϯ 0.02, 0.23 Ϯ 0.01, and 0.33 Ϯ 0.02°C above that measured for the no-exercise resting values (P Ͻ 0.05) for the 55, 70, and 85% of V O2 peak exercise conditions, respectively. We did note that there was a greater postexercise hypotension as a function of exercise intensity as measured at the end of the 20-min exercise recovery. Thus it is plausible that the increase in postexercise threshold may be related to postexercise hypotension. It is concluded that the sweating response during upright recovery is significantly modified by exercise intensity and may likely be influenced by the nonthermal baroreceptor reflex adjustments postexercise. sudomotor activity; baroreceptor reflexes; heat loss; thermoregulation RECENT STUDIES INDICATE THAT exercise induces a residual effect on thermal control, resulting in an increase in the postexercise esophageal temperature at which sweating occurs (11,13). Although the mechanism(s) for thermoregulatory control of sweating before and during exercise has been evaluated, there remains a lack of information on its nature and role during postexercise temperature regulation. Various studies have shown that the sweating response during exercise not only involves changes in thermal factors, such as core and skin temperatures (4, 23, 24), but also nonthermal factors, including central command, baroreceptors, mechanoreceptors, and metaboreceptors (15,24,30). This is in contrast to passive heating at rest, in which the primary stimuli for sweating is thought to be a factor of thermal origin (25).More recently, it has been shown that the postexercise sweating response is to some degree influenced by nonthermal baroreflex control (10). Specifically, the modification of postexercise venous pooling by lower body positive pressure results in a lowering of the resting postexercise elevation in the onset threshold for sweating. However, the mechanism of control is still unknown. Dynamic exercise is known to result in postexercise hypotension in the upright position (3,6,7,14,18,26,27). During postexercise hypotension, mean arterial pressure (MAP) is reduced subsequent to both neural and vascular activity (6-8). This postexercise hypotension is ...

Section: Discussionmentioning

confidence: 99%

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confidence: 99%

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confidence: 99%

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Effect of exercise intensity on the postexercise sweating threshold

Journal of Applied Physiology

Périard

Journeay³

et al. 2003

“…It has been shown that acute reductions in central venous pressure delay or decrease the rise in skin blood flow (SkBF) that occurs during heat stress (Mack et al 1988;Morimoto 1990). Thus, a reasonable postulate for the post-exercise increase in Th vd (Kenny et al 2000a) is that SkBF control following exercise is subject to significant modifications by non-thermoregulatory baroreceptor reflexes. Manipulating post-exercise venous pooling by means of head-down tilt and lowerbody positive pressure was shown to result in a decrease of the resting post-exercise elevation in Th vd (Jackson et al 2000;Kenny et al 2000b).…”

Section: Introductionmentioning

confidence: 98%

“…In more recent studies, the effects of exercise on the post-exercise threshold of warm (i.e., cutaneous vasodilation and sweating) thermoregulatory responses have been evaluated. These studies have indicated that exercise induces a residual effect on thermal control by increasing (@0.3°C) the post-exercise rest threshold for warm thermal responses (Kenny et al 2000a).…”

Section: Introductionmentioning

confidence: 99%

The effect of exercise intensity on the post-exercise esophageal temperature response

Niedre

2002

Eur J Appl Physiol

On 2 separate days, nine volunteers aged 23.8 (2.0) years performed 15-min bouts of treadmill running in a temperature-controlled chamber at 29 degrees C at a power output that elicited either 70% (moderate) or 93% (intense) of maximum oxygen consumption. Exercise was followed by a 45-min recovery period. End-exercise esophageal temperature (Tes) was elevated by 0.97 degrees C and 2.17 degrees C above baseline for the moderate and intense exercise trials, respectively. Post-exercise Tes achieved a sustained elevated value of 0.38 degrees C and 0.79 degrees C within 15 min of exercise cessation. Systolic blood pressure (SBP) for both exercise trials became hypotensive for the full recovery period, with the magnitude of the reduction being greater for the intense exercise (P < 0.05). Diastolic blood pressure (DBP) was unaffected by exercise intensity and values were lower than baseline between 15 min and 30 min post-exercise (P < 0.05). Mean arterial pressure (MAP) was reduced from baseline for both exercise trials, with intense exercise showing a greater decrement (P < 0.05). It was shown that the increase in the post-exercise hypotensive response, induced by exercise of increasing intensity, was paralleled by an increase in the magnitude of the post-exercise elevation in Tes (i.e., a difference of 0.41 degrees C between conditions).

Evidence of a greater onset threshold for sweating in females following intense exercise

Jay

2007

Eur J Appl Physiol

We evaluated the hypothesis that females would show a greater postexercise hypotension and concurrently a greater increase in the onset threshold for sweating. Fourteen subjects (7 males and 7 females) of similar age, body composition, and fitness status participated in the study. Esophageal temperature was monitored as an index of core temperature while sweat rate was measured by using a ventilated capsule placed on the upper back. Subjects cycled at either 60% (moderate) or 80% (intense) of peak oxygen consumption (VO2speak) followed by 20-min recovery. Subjects then donned a liquid-conditioned suit used to regulate mean skin temperature. The skin was then heated (approximately 4.3 degrees C.h(-1)) until sweating occurred. Esophageal temperatures were similar to baseline before the start of whole body warming for all conditions. The postexercise threshold values for sweating following moderate and intense exercise were an esophageal temperature increase of 0.10+/-0.02 and 0.22+/-0.04 degrees C, respectively for males, and 0.15+/-0.03 and 0.34+/-0.01 degrees C, respectively for females. All were elevated above baseline resting (P<0.05) and a significant sex-related difference was observed for sweating threshold values following intense exercise (P<0.05). This was paralleled by a greater decrease in mean arterial pressure in females at the end of the 20-min recovery (P<0.05). In conclusion, females demonstrate a greater postexercise onset threshold for sweating, which is paralleled by a greater postexercise hypotensive response following intense exercise.