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Department of Physiology, Kyoto Prefectural University of Medicine, Kamigyo-ku, Kyoto 602-0841, Japan
To elucidate the role of increased plasma
osmolality (Posmol), which occurs during exercise in the
regulation of cutaneous vasodilation (CVD) during exercise, we
determined the relationship between the change in esophageal
temperature (
Tes) required to elicit CVD (
Tes threshold for
CVD) and Posmol during light and moderate exercise (30 and
55% of peak oxygen consumption, respectively) and passive body
heating. Then we compared the relationship with the data obtained in
our previous study [A. Takamata, K. Nagashima, H. Nose, and T. Morimoto. Am. J. Physiol. 273 (Regulatory Integrative Comp. Physiol.
42): R197-R204, 1997], in which we determined the relationships during passive body heating following isotonic (0.9% NaCl) or hypertonic (2 or 3% NaCl) saline infusions in the same subjects. Posmol values at 5 min after the onset of
exercise were 287.5 ± 0.9 mosmol/kgH2O during light exercise
and 293.0 ± 1.2 mosmol/kgH2O
during moderate exercise. Posmol just before passive body
heating was 289.9 ± 1.4 mosmol/kgH2O. The
Tes threshold for CVD was 0.09 ± 0.05°C during light exercise, 0.31 ± 0.09°C during
moderate exercise, and 0.10 ± 0.05°C during passive body heating. The relationship between the
Tes threshold for CVD and Posmol was shown to be on the same regression line both
during exercise and during passive body heating with or without
infusions [A. Takamata, K. Nagashima, H. Nose, and T. Morimoto.
Am. J. Physiol. 273 (Regulatory Integrative Comp. Physiol.
42): R197-R204, 1997]. Our data suggest that the elevated
body core temperature threshold for CVD during exercise could be the
result of increased Posmol induced by exercise and is not
due to reduced plasma volume or the intensity of the exercise itself.
body temperature threshold; thermoregulation; exercise intensity
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