title: Rehydration with glycerol: endocrine, cardiovascular, and thermoregulatory responses during exercise in the heat.
abstract: The impact of rehydration with glycerol on cardiovascular and thermoregulatory responses during exercise in the heat was studied in eight highly trained male cyclists. Each subject completed three dehydration-rehydration experimental trials that differed only in the rehydration treatment, each separated by 7 days. Before each experimental day, subjects dehydrated to -4% of their body weight by exercise and water restriction. The experimental treatments were as follows: no fluid (NF), glycerol bolus (1 g/kg body wt) followed by water (G), and water alone (W). Rehydration (3% body weight) was given over an 80-min period. After rehydration, subjects cycled (74% peak O2 uptake) to exhaustion in a hot and wet (37 degrees C and 48% relative humidity) environment. For G, plasma volume was expanded (P < 0.05) during rehydration and remained higher than W (P < 0.05) during exercise. Exercise time to exhaustion during G (33 +/- 4 min) was longer (P < 0.05) compared with both W (27 +/- 3 min) and NF (19 +/- 3 min). Cutaneous vascular conductance was significantly elevated (P < 0.05) during G, but G provided no other thermoregulatory or cardiovascular benefits compared with W and NF. Fluid-regulating hormones (vasopressin, aldosterone, atriopeptin, and plasma renin activity) decreased during rehydration and increased during exercise (except atriopeptin), but there were no differences between G and W. These data indicated that glycerol had little or no major effect on fluid-regulating factors during rehydration or exercise, and the improved exercise capacity in G was likely due to a greater plasma volume during exercise.
authors.affiliation: Human Performance Laboratory, Department of Kinesiology, University of Connecticut, Storrs, USA. skav@hua.gr
authors.forename: Stavros A
authors.initials: SA
authors.lastname: Kavouras
authors.forename: Lawrence E
authors.initials: LE
authors.lastname: Armstrong
authors.forename: Carl M
authors.initials: CM
authors.lastname: Maresh
authors.forename: Douglas J
authors.initials: DJ
authors.lastname: Casa
authors.forename: Jorge A
authors.initials: JA
authors.lastname: Herrera-Soto
authors.forename: Timothy P
authors.initials: TP
authors.lastname: Scheett
authors.forename: James
authors.initials: J
authors.lastname: Stoppani
authors.forename: Gary W
authors.initials: GW
authors.lastname: Mack
authors.forename: William J
authors.initials: WJ
authors.lastname: Kraemer
mesh_terms: D000328:Adult; D001833:Body Temperature Regulation / Q000187:drug effects; D002320:Cardiovascular Physiological Phenomena / Q000187:drug effects; D003681:Dehydration / Q000503:physiopathology / Q000517:prevention & control; D004326:Drinking; D004703:Endocrine System / Q000187:drug effects; D015444:Exercise; D005080:Exercise Test; D005440:Fluid Therapy; D005990:Glycerol / Q000008:administration & dosage / Q000627:therapeutic use*; D006728:Hormones / Q000097:blood; D006358:Hot Temperature; D006801:Humans; D008297:Male; D010953:Plasma Volume / Q000187:drug effects; D012039:Regional Blood Flow; D015532:Rehydration Solutions / Q000008:administration & dosage / Q000627:therapeutic use*; D012867:Skin / Q000098:blood supply / Q000187:drug effects; D013997:Time Factors; D014655:Vascular Resistance; D014882:Water-Electrolyte Balance / Q000502:physiology
chemical_list: D006728:Hormones; D015532:Rehydration Solutions; D005990:Glycerol