title: Priming of the sweat glands explains reflex sweating in the heat.
abstract: The purpose of this study was to determine whether reflex sweating during isometric handgrip exercise (IHG) in the heat was due to a priming effect in the sweat glands or an increase in skin temperature. Ten male subjects completed four trials where they performed IHG for three minutes at 40% of their maximal voluntary contraction (MVC). The four trials included: (1) a control trial in thermoneutral conditions (23±1°C), (2) after sitting in hyperthermic conditions (35±1°C) for 30 min, (3) a local heating trial after having their non-exercising arm wrapped in a heat pad that maintained forearm skin temperature at ~35°C for 30 min, 4) and after pilocarpine iontophoresis to a 5 cm(2) area of the forearm. The sweating rate (SR), as measured by resistance hygrometry, was not significantly different (P>0.05) from baseline during IHG in either the control or local heating trial, but was significantly increased (P<0.05) from baseline during the hyperthermic and pilocarpine trials. Baseline SR values of the hyperthermic and pilocarpine trials (~0.25mg/cm(2)/min) were significantly greater than the control and local heating trials (~0.05 mg/cm(2)/min). These results suggest that reflex sweating in the heat during IHG is primarily due to a priming effect in the sweat glands and not because of an increase in skin temperature.
authors.affiliation: Department of Biology, School of Exercise and Nutritional Sciences, San Diego State University, San Diego, CA 92120-7251, USA.
authors.forename: Steven
authors.initials: S
authors.lastname: Avila
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Buono
mesh_terms: D000328:Adult; D015444:Exercise / Q000502:physiology*; D018737:Hand Strength; D006358:Hot Temperature; D006801:Humans; D008297:Male; D008875:Middle Aged; D012018:Reflex / Q000502:physiology*; D012881:Skin Temperature; D013545:Sweat Glands / Q000502:physiology*; D013546:Sweating / Q000502:physiology*; D055815:Young Adult