Rehydration with glycerol: endocrine, cardiovascular, and thermoregulatory responses during exercise in the heat.
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.
Kavouras
Stavros A
SA
Human Performance Laboratory, Department of Kinesiology, University of Connecticut, Storrs, USA. skav@hua.gr
Armstrong
Lawrence E
LE
Maresh
Carl M
CM
Casa
Douglas J
DJ
Herrera-Soto
Jorge A
JA
Scheett
Timothy P
TP
Stoppani
James
J
Mack
Gary W
GW
Kraemer
William J
WJ
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
D006728:Hormones; D015532:Rehydration Solutions; D005990:Glycerol