This study examined the effects of hyperhydration on thermoregulatory responses during compensable exercise-heat stress. The general approach was to determine whether 1-h preexercise hyperhydration [29. 1 ml/kg lean body mass; with or without glycerol (1.2 g/kg lean body mass)] would improve sweating responses and reduce core temperature during exercise. During these experiments, the evaporative heat loss required (Ereq = 293 W/m2) to maintain steady-state core temperature was less than the maximal capacity (Emax = 462 W/m2) of the climate for evaporative heat loss (Ereq/Emax = 63%). Eight heat-acclimated men completed five trials: euhydration, glycerol hyperhydration, and water hyperhydration both with and without rehydration (replace sweat loss during exercise). During exercise in the heat (35 degrees C, 45% relative humidity), there was no difference between hyperhydration methods for increasing total body water (approximately 1.5 liters). Compared with euhydration, hyperhydration did not alter core temperature, skin temperature, whole body sweating rate, local sweating rate, sweating threshold temperature, sweating sensitivity, or heart rate responses. Similarly, no difference was found between water and glycerol hyperhydration for these physiological responses. These data demonstrate that hyperhydration provides no thermoregulatory advantage over the maintenance of euhydration during compensable exercise-heat stress.
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http://dx.doi.org/10.1152/jappl.1997.83.3.860 | DOI Listing |
Prev Med
February 2024
Department of Sport and Wellbeing, Leeds Trinity University, Leeds, United Kingdom.
Objective: Drowning is a leading cause of death. The World Health Organization (WHO) and United Nations (UN) emphasise the need for population-level data-driven approaches to examine risk factors to improve water safety policies. Weather conditions, have the potential to influence drowning risk behaviours as people are more likely to spend time around water and/or undertake risky activities in aquatic spaces as a behavioural thermoregulatory response (e.
View Article and Find Full Text PDFSports Med
November 2023
School of Exercise and Nutrition Sciences, Centre for Sport Research, Deakin University, 221 Burwood Highway, Burwood, VIC, 3125, Australia.
Background: Fluid loss during prolonged exercise in hot conditions poses thermoregulatory and cardiovascular challenges for athletes that can lead to impaired performance. Pre-exercise hyperhydration using nutritional aids is a strategy that may prevent or delay the adverse effects of dehydration and attenuate the impact of heat stress on exercise performance.
Objectives: The aim of this systematic review was to examine the current literature to determine the effect of pre-exercise hyperhydration on performance, key physiological responses and gastrointestinal symptoms.
Eur J Appl Physiol
December 2022
Laboratory for Exercise and Environmental Physiology, Faculty of Education, Niigata University, 8050, Igarashi-Ninocho, Nishiku, Niigata, Japan.
Purpose: Isomaltulose is a low glycemic and insulinaemic carbohydrate increasingly used as an alternative sweetener in commercial beverages. While isomaltulose beverages can improve hydration status compared to sucrose-based beverages, it remains unclear if ingestion of an isomaltulose beverage prior to exercise in the heat may improve plasma volume (PV) and thermoregulatory responses.
Methods: Twelve endurance-trained men consumed a 1L carbohydrate beverage containing either 6.
Auton Neurosci
November 2021
Department of Nutrition, Dietetics and Food, Monash University, Notting Hill, Victoria, Australia. Electronic address:
Exertional heat stress presents a different acute challenge to salt balance compared to at rest. Sodium (Na) and chloride (Cl) losses during exercise are overwhelmingly driven by eccrine sweat glands (the "leader"), with minimal urinary excretion. Total salt losses are therefore largely influenced by thermoregulatory need, although adaptations from prior heat exposure or altered dietary intake influences sweat gland ion reabsorption, and therefore sweat Na ([Na]) and Cl concentrations.
View Article and Find Full Text PDFIt is the position of Sports Dietitians Australia (SDA) that exercise in hot and/or humid environments, or with significant clothing and/or equipment that prevents body heat loss (i.e., exertional heat stress), provides significant challenges to an athlete's nutritional status, health, and performance.
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