Rehydration with Fluid of Varying Tonicities: Effects on Fluid Regulatory Hormones and Exercise Performance in the Heat
Abstract
Rehydration with fluid of varying tonicities: effects on fluid regulatory hormones and exercise performance in the heat. J Appl Physiol 102: 1899 1905, 2007. First published February 22, 2007; doi:10.1152/japplphysiol.00920.2006. This study examined the effects of rehydration (Rehy) with fluids of varying tonicities and routes of administration after exercise-induced hypohydration on exercise performance, fluid regulatory hormone responses, and cardiovascular and thermoregulatory strain during subsequent exercise in the heat. On four occasions, eight men performed an exercise-dehydration protocol of ~ 185 min (33 C) to establish a 4% reduction in body weight. Following dehydration, 2% of the fluid lost was replaced during the first 45 min of a 100-min rest period by one of three random Rehy treatments (0.9% saline intravenous; 0.45% saline intravenous; 0.45% saline oral) or no Rehy (no fluid) treatment. Subjects then stood for 20 min at 36 C and then walked at 50% maximal oxygen consumption for 90 min. Subsequent to dehydration, plasma Na , osmolality, aldosterone, and arginine vasopressin concentrations were elevated (P < 0.05) in each trial, accompanied by a - 4% hemoconcentration. Following Rehy, there were no differences (P > 0.05) in fluid volume restored, post-rehydration (Post-Rehy) body weight, or urine volume. Percent change in plasma volume was 5% above pre-Rehy values, and plasma Na , osmolality, and fluid regulatory hormones were lower compared with no fluid. During exercise, skin and core temperatures, heart rate, and exercise time were not different (P 0.05) among the Rehy treatments.
Document Details
- Document Type
- Technical Report
- Publication Date
- Feb 22, 2007
- Accession Number
- ADA481454
Entities
People
- C. M. Maresh
- D. Riebe
- J. W. Castellani
- L. E. Armstrong
- M. E. Echegaray
- R. W. Kenefick
Organizations
- United States Army Research Institute of Environmental Medicine