Hydration of the athlete
Our actions & our advice

Proper hydration
is essential
to avoid
swelling of the
brain and death

La mort subite du sportif, Ultra sports science, ultra-endurance, fondation

It is essential to understand the connection between fluid and salt. Mainstream messages are often a source of errors.

Hydration is a gentle balance between water and body salt. Not respecting this balance and especially during long efforts can be the cause of a rare but deadly situation.

Education for proper hydration is important to prevent this serious illness.
The incidence of exercise associated hyponatremia is 18% in triathlons, 28% in marathons, 50% in long cycling events and 30% -50% in 161 km (100 Miles) trails.
Specific care is therefore necessary.

We finance medical studies
dedicated to this problem in sport
to better prevent & act.

Our medical research

1. Hydration and trail running

Study: Evaluation of the impact of a “thirst” hydration protocol on the run rate of runners of the Ultra Trail du Mont-Blanc 2015.
Sporting universe: Trail-Running
Who: Center Hospitalier Universitaire de Nîmes France with Dr Olivier Mares and Dr Jean luc LE MASLE-LASTIOLAS
Partners: Ultra-Trail du Mont-Blanc
Donor company: Dokever, CHU of Nîmes, EPOC Société ALERE
Study carried out in 2015 and completed.

Thèse hydratation sportif (FR)

Résumé thèse hydratation (FR)

Abstract (EN)

2. Hydration and Cycling

Study: Ultra-endurance cycling performance: Examining the impact of drinking to thirst vs. programmed fluid intake
Sporting world: cycling
Who: Université de Sherbrooke, Research laboratory on performance, hydration and thermoregulation Canada with Mr Goulet eric
Partners: not defined
Donor companies: USS
Study in progress, started in 2017

Drinking cycling performance (EN)

Etude hydratation cyclisme (FR)

Abstract hydratation cycling (EN)

3. The impact of sodium absorption

Study: The impact of sodium ingestion during exercise on plasma sodium concentration, plasma volume and sodium balance during and 24 hours post exercise in ultra-endurance athletes
Who: McCubbin et al.
Study completed / 2018-2023.
Summary: Sweat sodium losses during ultraendurance exercise can be large in hot environments, but whether this sodium needs to be replaced is contentious.

Previous studies with exercise durations of more than 4 hours have not provided sodium replacement according to each individual’s losses, and required participants to completely replace their fluid losses, which is not a recommended or commonly practiced strategy. There have also been case reports during ultraendurance exercise of athletes taking sodium supplements which caused excessive thirst and overconsumption of water, paradoxically leading to the development of exercise-associated hyponatraemia (low blood sodium concentration). This study investigated the effect of personalized and complete sweat sodium replacement provided in capsules, compared to no sodium replacement, on thirst and the amount of fluid consumed (ad libitum) during 5 hours of running in a hot environment in 9 ultraendurance runners (7 male, 2 female). In addition, blood sodium concentration, heart rate, body temperature, thermal comfort and perception of effort were compared between trials. Following exercise, the amount of fluid consumed and lost through urine was measured, as well as the amount of sodium lost in urine.

The study found no difference in thirst rating or ad libitum fluid intake during the 5-hour run, whether sodium was replaced or not. There was also no difference in fluid or sodium losses from the body, and no differences in heart rate, body temperature or perceived effort. Blood sodium concentration increased in both trials but increased more when replacing sodium. In the 24 hours after exercise, ad libitum fluid intake was greater when sodium had been replaced during exercise. When a large sodium deficit occurred during exercise due to no replacement, urine sodium losses were reduced by about two thirds in the following 24 hours. This was not enough to make up for the large deficit during exercise, however.

We conclude that replacing 100% of sweat sodium losses (compared to no replacement) in capsules does not cause increased thirst or fluid intake during 5 hours running in the heat, but it also failed to provide any benefits for heart rate, body temperature or perceived effort. Sodium supplementation was not required to prevent a fall in blood sodium concentration when fluid was consumed ad libitum, and the kidneys can at least partially compensate for a large sodium deficit by conserving sodium in the hours after exercise, suggesting that 100% sodium replacement during or post-exercise is not required to maintain sodium balance even for multi-stage events.

Full article DOI (EN)

4. Review and practical guide to recognition of EAH, treatment and prevention

Title : Exercise associated hyponatremaia (EAH)
Project: Finished
Sports universe: all endurance sports
Topic: Hydration
Who / University: Volker Scheer
Conclusion: EAH is a serious medical condition with confirmed deaths. Main factor is overconsumption of hypotonic fluids. EAH can generally be prevented by proper hydration, which is achieved through drinking to thirst.
Donor company: Ultra Sports Science Foundation

Hyponatremia review (EN)

Hyponatremia review (ES)

Éducation / Nos conseils

Athletes and coaches:

Be aware of the condition-drink to thirst. Avoid anti-inflammatory medications as they can exacerbate EAH.

Our Tips & Recommendations (EN)

Ultra-Health Guidline (EN)

Organizers and healthcare professionals:

Prompt recognition and treatment of EAH with oral hypertonic saline beverages for mild EAH cases or intravenous infusion of hypertonic saline in moderate to severe cases of EAH and EAHE can be life-saving.

Educate medical staff about EAH. Consider planning of fluid stations.