title: Cardiovascular adaptations supporting human exercise-heat acclimation.
abstract: This review examines the cardiovascular adaptations along with total body water and plasma volume adjustments that occur in parallel with improved heat loss responses during exercise-heat acclimation. The cardiovascular system is well recognized as an important contributor to exercise-heat acclimation that acts to minimize physiological strain, reduce the risk of serious heat illness and better sustain exercise capacity. The upright posture adopted by humans during most physical activities and the large skin surface area contribute to the circulatory and blood pressure regulation challenge of simultaneously supporting skeletal muscle blood flow and dissipating heat via increased skin blood flow and sweat secretion during exercise-heat stress. Although it was traditionally held that cardiac output increased during exercise-heat stress to primarily support elevated skin blood flow requirements, recent evidence suggests that temperature-sensitive mechanisms may also mediate an elevation in skeletal muscle blood flow. The cardiovascular adaptations supporting this challenge include an increase in total body water, plasma volume expansion, better sustainment and/or elevation of stroke volume, reduction in heart rate, improvement in ventricular filling and myocardial efficiency, and enhanced skin blood flow and sweating responses. The magnitude of these adaptations is variable and dependent on several factors such as exercise intensity, duration of exposure, frequency and total number of exposures, as well as the environmental conditions (i.e. dry or humid heat) in which acclimation occurs.
authors.affiliation: Athlete Health and Performance Research Centre, Aspetar Orthopaedic and Sports Medicine Hospital, Doha, Qatar. Electronic address: julien.periard@aspetar.com.
authors.forename: Julien D
authors.initials: JD
authors.lastname: Périard
authors.affiliation: Athlete Health and Performance Research Centre, Aspetar Orthopaedic and Sports Medicine Hospital, Doha, Qatar; Department of Life Sciences, Centre for Sports Medicine and Human Performance, Division of Sport, Health and Exercise Sciences, Brunel University London, Uxbridge, UK.
authors.forename: Gavin J S
authors.initials: GJS
authors.lastname: Travers
authors.affiliation: Athlete Health and Performance Research Centre, Aspetar Orthopaedic and Sports Medicine Hospital, Doha, Qatar.
authors.forename: Sébastien
authors.initials: S
authors.lastname: Racinais
authors.affiliation: School of Applied Physiology, Georgia Institute of Technology, Atlanta, GA, United States.
authors.forename: Michael N
authors.initials: MN
authors.lastname: Sawka
mesh_terms: D000064:Acclimatization / Q000502:physiology*; D000222:Adaptation, Physiological / Q000502:physiology*; D000818:Animals; D015444:Exercise / Q000502:physiology*; D018882:Heat Stress Disorders / Q000503:physiopathology*; D006358:Hot Temperature; D006801:Humans; D013546:Sweating / Q000502:physiology*
keywords: Blood pressure regulation; Cardiac output; Exercise performance; Fluid balance; Heat acclimatization; Stroke volume; Thermoregulation