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Hyperhydration: tolerance and cardiovascular effects during uncompensable exercise-heat stress
- Source :
- Journal of applied physiology (Bethesda, Md. : 1985). 84(6)
- Publication Year :
- 1998
-
Abstract
- 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 1-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 (∼55% maximal O2 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.
- Subjects :
- Adult
Male
medicine.medical_specialty
Time Factors
Physiology
medicine.medical_treatment
Physical exercise
Blood Pressure
Cardiovascular control
Core temperature
Heat Stress Disorders
Body Temperature
Body Water
Heart Rate
Physiology (medical)
Internal medicine
medicine
Humans
Cardiac Output
Cardiovascular strain
Exercise Tolerance
business.industry
Hemodynamics
Heat stress
Heat tolerance
Cardiology
Physical therapy
Physical Endurance
Vascular Resistance
business
Fluid replacement
Subjects
Details
- ISSN :
- 87507587
- Volume :
- 84
- Issue :
- 6
- Database :
- OpenAIRE
- Journal :
- Journal of applied physiology (Bethesda, Md. : 1985)
- Accession number :
- edsair.doi.dedup.....49d306bf88f6114517ffeabc66f9e748