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Effect of extracellular hyperosmolality on sweat rate during metaboreflex activation in passively heated young men.
- Source :
- American Journal of Physiology: Regulatory, Integrative & Comparative Physiology; Jan2022, Vol. 322 Issue 1, pR1-R13, 13p
- Publication Year :
- 2022
-
Abstract
- Metaboreflex activation augments sweating during mild-to-moderate hyperthermia in euhydrated (isosmotic isovolemic) individuals. Recent work indicates that extracellular hyperosmolality may augment metaboreflex-mediated elevations in sympathetic nervous activity. Our primary objective was, therefore, to test the hypothesis that extracellular hyperosmolality would exacerbate metaboreflex-mediated increases in sweat rate. On two separate occasions, 12 young men [means (SD): 25 (5) yr] received a 90-min intravenous infusion of either 0.9% saline (isosmotic condition, ISO) or 3.0% saline (hyperosmotic condition, HYP), resulting in a postinfusion serum osmolality of 290 (3) and 301 (7) mosmol/kgH<subscript>2</subscript>O, respectively. A whole body water perfusion suit was then used to increase esophageal temperature by 0.8°C above resting. Participants then performed a metaboreflex activation protocol consisting of 90-s isometric handgrip exercise (40% of their predetermined maximum voluntary contraction), followed by 150 s of brachial occlusion (trapping produced metabolites within the limb). Metaboreflex-induced sweating was quantified as the change in global sweat rate (from preisometric handgrip exercise to brachial occlusion), estimated as the surface area-weighted average of local sweat rate on the abdomen, axilla, chest, bicep, quadriceps, and calf, measured using ventilated capsules (3.8 cm²). We also explored whether this response differed between body regions. The change in global sweat rate due to metaboreflex activation was significantly greater in HYP compared with ISO (0.03 mg/min/cm² [95% confidence interval: 0.00, 0.06]; P = 0.047), but was not modulated by body region (site x condition interaction: P = 0.679). These findings indicate that extracellular hyperosmolality augments metaboreflex-induced increases in global sweat rate, with no evidence for region-specific differences. [ABSTRACT FROM AUTHOR]
- Subjects :
- REFLEXES
MUSCLE contraction
YOUNG men
ISOMETRIC exercise
Subjects
Details
- Language :
- English
- ISSN :
- 03636119
- Volume :
- 322
- Issue :
- 1
- Database :
- Complementary Index
- Journal :
- American Journal of Physiology: Regulatory, Integrative & Comparative Physiology
- Publication Type :
- Academic Journal
- Accession number :
- 154850262
- Full Text :
- https://doi.org/10.1152/ajpregu.00161.2021