Study of Thermoregulatory Processes in Ultra-endurance Runners in a Hot and Humid Environment

Study Overview
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Brief Summary
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Human beings are characterized by their extraordinary ability to thermoregulate. During a physical exercise, only 20% of the energy provided by the substrates is converted into muscular mechanical work. The remaining 80% is released as heat. In temperate environments, so-called metabolic heat is dissipated by several physical phenomena (radiation, conduction, convection and evaporation). However, if the dissipation capacity (in a hot and humid environment for example) is lower than the production of metabolic heat, the body temperature increases progressively until exercise stops or heat-related pathologies develop. This pathological entity defined by the acronym EHI for Exertional Heat Illness gather a wide spectrum of clinical forms ranging from oedema or heat rash, to muscle cramps, to syncope; up to more serious forms such as heat exhaustion or heat stroke during exercise. Heatstroke during exercise is the second most common cause of death in athletes after heart disease. However, the results of the epidemiological studies and the recommendations are limited to events with effort durations or distances not exceeding those of the marathon. They therefore do not consider ultra-endurance disciplines. These disciplines, defined by durations of effort of at least 6 hours, have specific characteristics (duration of effort, intensity, steep gradients, exotic destinations, extreme environments) which means that extrapolation of the results and knowledge of the physiology of thermoregulation from classic endurance events, such as marathons, to ultra-endurance events is hazardous. There are therefore significant areas of uncertainty in understanding the thermoregulatory function, prevalence of EHI (Exertional Heat Illness) and health implications of ultra-endurance running in a hot environment. This is the context of ERUPTION-2.

Official Title
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Study of Thermoregulatory Processes in Ultra-endurance Runners in a Hot and Humid Environment

Conditions
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Intensive Sport

Intervention / Treatment
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* Other: Biological testing


Participation Criteria
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Eligibility Criteria
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Inclusion Criteria: Runners participating in  La diagonale des fous  race of the Grand Raid 2021 on Reunion Island Exclusion Criteria: Runners who do not understand French

Ages Eligible for Study
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Minimum Age: 18 Years

Sexes Eligible for Study
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All

Accepts Healthy Volunteers
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Accepts Healthy Volunteers

Study Plan
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How is the study designed?
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Design Details

Primary Purpose: Prevention
Intervention Model: Single Group Assignment
Masking: None (Open Label)


Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| Experimental: Intervention<br>Study of Thermoregulatory Processes in Ultra-endurance Runners in a Hot and Humid Environment | Other: Biological testing<br>* Blood sampling, microcapillary sampling, temperature monitoring, saliva testing, EHI questionnaire<br>|

What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Core temperature measurement | Measure of core temperature (°C) will be carried out by continuous monitoring using e-Celsius performance Bodycap technology sensors carried by the athletes through the race | during 3 days of the race | 
| Natremia measurement | Measure of natremia (blood sodium concentration) will be made by 5 measurements carried out on the eve of the start and during the race, by microcapillary blood sample using the i-STAT technology and CHEM8+ cartridges. | during 3 days of the race | 
| Hydration saliva measurement | Hydration will be measured 5 times carried out on the eve of the start and during the race using saliva sample to measure the salivary osmolarity with the MX3 testing device. | during 3 days of the race | 
| Hydration by weight measurement | Weight in kg will be measured 5 times carried out on the eve of the start and during the race | during 3 days of the race |