Exercise-Associated Hyponatremia during the Olympus Marathon Ultra-Endurance Trail Run.

Giannis Arnaoutis,Dimitra Papamichalopoulou,Costas A Anastasiou,Maria Maraki,Marcos Echegaray,Labros S Sidossis,Hyungyu Suh,Emmanouel Dimitroulis,Stavros A Kavouras,Spyridon Methenitis,Yiannis Tsekouras

doi:10.3390/nu12040997

Abstract

Research on hyponatremia during mountain marathons is scarce. The present study aimed to investigate the prevalence of exercise-associated hyponatremia during a 44-km trail running race that reached an altitude of 2780 m (Olympus Marathon). Sixty-two runners (five women) who completed the race participated in the study (age: 34.4 ± 8.6 years; height: 1.77 ± 0.06 m; and weight: 75.3 ± 10.0 kg). Anthropometric characteristics, blood, and urine samples were collected pre- and post-race. Food and fluid intake were recorded at each checkpoint. Due to race regulations, the runners could not carry any additional food and fluids besides the ones provided at specific checkpoints. Five runners (8%) exhibited asymptomatic hyponatremia (serum sodium <135 mmol∙L−1). Serum sodium in the hyponatremic runners decreased from 138.4 ± 0.9 (pre) to 131.4 ± 5.0 mmol∙L−1 (post), p < 0.05. Plasma osmolality increased only in the eunatremic runners (pre: 290 ± 3; post: 295 ± 6 mmol∙kg−1; p < 0.05). Plasma volume decreased more in the hyponatremic compared to eunatremic runners (−4.4 ± 2.0 vs. −3.2 ± 1.4%, p < 0.05). Lastly, dietary sodium intake was lower in the hyponatremic runners compared to eunatremic (789 ± 813 vs. 906 ± 672 mg; p < 0.05). The incidence of hyponatremia among the athletes was relatively low, possibly due to race conditions.

Highlights

Marathon running and ultra-endurance events have gained significant popularity during the last decades worldwide [1,2]
Of the 62 volunteer athletes who participated in the study, five (8%) experienced exercise-associated hyponatremia
We examined the prevalence of exercise-associated hyponatremia in a sample of runners participating in the Olympus Marathon

Summary

Introduction

Marathon running and ultra-endurance events have gained significant popularity during the last decades worldwide [1,2]. Exercise associated hyponatremia (EAH) is a potentially life-threatening condition that can happen in athletic endurance events lasting more than four hours. A high incidence of EAH has been documented mainly in ultra-endurance sports events and in sports of shorter duration such as marathon [6,7,8,9,10]. Nutrients 2020, 12, 997 has been observed among marathon runners, cyclists, triathlon athletes, and recreational runners, participating most commonly in endurance events [3,4]. Data from studies carried out at the London and Boston Marathons indicate that EAH occurs in 10–15% of sampled marathon finishers [6,8,11]

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