Hyperhydration: tolerance and cardiovascular effects during uncompensable exercise-heat stress

被引:86
作者
Latzka, WA [1 ]
Sawka, MN
Montain, SJ
Skrinar, GS
Fielding, RA
Matott, RP
Pandolf, KB
机构
[1] USA, Environm Med Res Inst, Thermal & Mt Med Div, Natick, MA 01760 USA
[2] Boston Univ, Boston, MA 02215 USA
关键词
cardiac output; core temperature; fluid replacement; glycerol; heat stress; hydration; sweating; heat tolerance; physiological tolerance;
D O I
10.1152/jappl.1998.84.6.1858
中图分类号
Q4 [生理学];
学科分类号
071003 ;
摘要
This study examined the efficacy of glycerol and water hyperhydration (1 h before exercise) on tolerance and cardiovascular strain during uncompensable exercise-heat stress. The approach was to determine whether l-h preexercise hyperhydration (29.1 ml H2O/kg lean body mass with or without 1.2 g/kg lean body mass of glycerol) provided a physiological advantage over euhydration. Eight heat-acclimated men completed three trials (control euhydration before exercise, and glycerol and water hyperhydrations) consisting of treadmill exercise-heat stress (ratio of evaporative heat loss required to maximal capacity of climate = 416). During exercise (similar to 55% maximal O-2 uptake), there was no difference between glycerol and water hyperhydration methods for increasing (P < 0.05) total body water. Glycerol hyperhydration endurance time (33.8 +/- 3.0 min) was longer (P < 0.05) than for control (29.5 +/- 3.5 min), but was not different (P > 0.05) from that of water hyperhydration (31.3 +/- 3.1 min). Hyperhydration did not alter (P > 0.05) core temperature, whole body sweating rate, cardiac output, blood pressure, total peripheral resistance, or core temperature tolerance. Exhaustion from heat strain occurred at similar core and skin temperatures and heart rates in each trial. Symptoms at exhaustion included syncope and ataxia, fatigue, dyspnea, and muscle cramps (n = 11, 10, 2, and 1 cases, respectively). We conclude that 1-h preexercise glycerol hyperhydration provides no meaningful physiological advantage over water hyperhydration and that hyperhydration per se only provides the advantage (over euhydration) of delaying hypohydration during uncompensble exercise-heat stress.
引用
收藏
页码:1858 / 1864
页数:7
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