Heat Acclimatization, Cooling Strategies, and Hydration during an Ultra-Trail in Warm and Humid Conditions

• Published in: Nutrients Vol. 13; no. 4; p. 1085
• Main Authors: Bouscaren, Nicolas, Faricier, Robin, Millet, Guillaume Y, Racinais, Sébastien
• Format: Journal Article
• Language: English
• Published: Switzerland MDPI AG 26.03.2021; MDPI
• Subjects: Acclimatization; Acclimatization - physiology; Adult; Ambient temperature; body temperature regulation; Climate; Cooling; dehydration; Drinking; electrolyte balance; Endurance; Environmental conditions; Female; Heat; Heat acclimatization; Heat stress; Heat Stress Disorders - prevention & control; Heat tolerance; Hot Temperature; Humans; Humidity; Hydration; Male; Marathon Running; Marathons; Middle Aged; Population studies; Races; Relative humidity; Running; Water; Women; running; ultra-endurance running; electrolyte balance; hydration; dehydration; acclimatization; hot temperature; body temperature regulation
• ISSN: 2072-6643; 2072-6643
• DOI: 10.3390/nu13041085

The aim of this study was to assess the history of exertional heat illness (EHI), heat preparation, cooling strategies, heat related symptoms, and hydration during an ultra-endurance running event in a warm and humid environment. This survey-based study was open to all people who participated in one of the three ultra-endurance races of the Grand Raid de la Réunion. Ambient temperature and relative humidity were 18.6 ± 5.7 °C (max = 29.7 °C) and 74 ± 17%, respectively. A total of 3317 runners (56% of the total eligible population) participated in the study. Overall, 78% of the runners declared a history of heat-related symptoms while training or competing, and 1.9% reported a previous diagnosis of EHI. Only 24.3% of study participants living in temperate climates declared having trained in the heat before the races, and 45.1% of all respondents reported a cooling strategy during the races. Three quarter of all participants declared a hydration strategy. The planned hydration volume was 663 ± 240 mL/h. Fifty-nine percent of the runners had enriched their food or drink with sodium during the race. The present study shows that ultra-endurance runners have a wide variability of hydration and heat preparation strategies. Understandings of heat stress repercussions in ultra-endurance running need to be improved by specific field research.