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

Abstract

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.

Effects of Ultratrail Running on Neuromuscular Function, Muscle Damage and Hydration Status. Differences According to Training Level

“…Drinking plenty of liquids during races is recommended to avoid dehydration [ 1 ]. Different hydration strategies are used during ultratrail races to avoid dehydration [ 85 ]. The problems of dehydration regarding metabolic and neuromuscular performance were previously outlined [ 25 , 28 ].…”

Is There Evidence for the Development of Sex-Specific Guidelines for Ultramarathon Coaches and Athletes? A Systematic Review

“…There was no difference in the overall rate of exercise-related injuries across a 12-month period; however, female athletes suffered a disproportionate number of stress fractures [ 52 ]. Females were more likely to encounter medical illness during a race, with one study demonstrating four times the risk of developing an AKI during a multi-stage ultramarathon compared to males [ 53 , 54 ]. One study found that males were significantly more likely to report a history of heat-related illness and muscle cramps, and to experience heat-related symptoms during an ultramarathon [ 55 ].…”

“…Stress fractures were more common among females, compared with males ( p < 0.001) Khodaee et al (Abstract only) [ 57 ] 308 athletes who completed a 100 mile ultramarathon. Sex split not reported Race-related injuries requiring medical attention post-race Cross-sectional Low No sex differences in incidence of race-related injuries requiring medical attention Krabak et al[ 53 ] 396 athletes (20.8% females, 79.2% males) who completed a 250 km 7-day trail ultramarathon Rate of medical illness and injury Cohort study Low Females were 16% more likely to encounter medical illness when adjusted for age and race hours No difference in overall injury/illness rates, skin problems, or MSK injuries Lipman et al[ 54 ] 128 athletes (28% females and 72% males) who competed in a 250 km multi-stage ultramarathon Changes in serum creatinine, cumulative incidence and prevalence of AKI Cohort study Low Overall cumulative incidence of AKI was 41.4%. Odds ratio for females and AKI was 4.64 (95% CI 2.07–10.37, p < 0.001) Hoffman et al[ 58 ] 201 athletes who completed a 161 km ultramarathon.…”

The Effects of Sex, Age and Performance Level on Pacing in Ultra-Marathon Runners in the ‘Spartathlon’

“…Another limitation is that we had no data about the training and pre-race experience of these participants [ 53 ], such as details of nutrition and fluid intake would have been of interest [ 55 ] that are associated with energy distribution across the race. Furthermore, the influence of course elevation and environmental conditions such as weather was not considered [ 56 ]. Unfortunately, we could not consider physiological and pathophysiological aspects in this analysis [ 57 ].…”