title: Heat stress and dehydration in adapting for performance: Good, bad, both, or neither?
abstract: Physiological systems respond acutely to stress to minimize homeostatic disturbance, and typically adapt to chronic stress to enhance tolerance to that or a related stressor. It is legitimate to ask whether dehydration is a valuable stressor in stimulating adaptationper se. While hypoxia has had long-standing interest by athletes and researchers as an ergogenic aid, heat and nutritional stressors have had little interest until the past decade. Heat and dehydration are highly interlinked in their causation and the physiological strain they induce, so their individual roles in adaptation are difficult to delineate. The effectiveness of heat acclimation as an ergogenic aid remains unclear for team sport and endurance athletes despite several recent studies on this topic. Very few studies have examined the potential ergogenic (or ergolytic) adaptations to ecologically-valid dehydration as a stressor in its own right, despite longstanding evidence of relevant fluid-regulatory adaptations from short-term hypohydration. Transient and self-limiting dehydration (e.g., as constrained by thirst), as with most forms of stress, might have a time and a place in physiological or behavioral adaptations independently or by exacerbating other stressors (esp. heat); it cannot be dismissed without the appropriate evidence. The present review did not identify such evidence. Future research should identify how the magnitude and timing of dehydration might augment or interfere with the adaptive processes in behaviorally constrained versus unconstrained humans.
authors.affiliation: School of Physical Education, Sport and Exercise Sciences, Division of Sciences, University of Otago , New Zealand.
authors.forename: Ashley Paul
authors.initials: AP
authors.lastname: Akerman
authors.affiliation: Extreme Environments Laboratory, Department of Sport & Exercise Science, University of Portsmouth , UK.
authors.forename: Michael
authors.initials: M
authors.lastname: Tipton
authors.affiliation: Department of Human Physiology, University of Oregon , Eugene, OR, USA.
authors.forename: Christopher T
authors.initials: CT
authors.lastname: Minson
authors.affiliation: School of Physical Education, Sport and Exercise Sciences, Division of Sciences, University of Otago , New Zealand.
authors.forename: James David
authors.initials: JD
authors.lastname: Cotter
keywords: acclimatization; adaptation; dehydration; ergogenic; heat; hormesis; hypohydration; performance