AUTHOR=Seal Adam D. , Anastasiou Costas A. , Skenderi Katerina P. , Echegaray Marcos , Yiannakouris Nikos , Tsekouras Yiannis E. , Matalas Antonia L. , Yannakoulia Mary , Pechlivani Fani , Kavouras Stavros A. 

TITLE=Incidence of Hyponatremia During a Continuous 246-km Ultramarathon Running Race

JOURNAL=Frontiers in Nutrition

VOLUME=6

YEAR=2019

URL=https://www.frontiersin.org/journals/nutrition/articles/10.3389/fnut.2019.00161

DOI=10.3389/fnut.2019.00161

ISSN=2296-861X

ABSTRACT=<p><bold>Purpose:</bold> The purpose of this observational study was to examine the incidence of exercise-associated hyponatremia (EAH) in a 246-km continuous ultra-marathon.</p><p><bold>Methods:</bold> Over 2 years, 63 male finishers of the annual Spartathlon ultra-marathon foot race from Athens to Sparta, Greece were included in the data analysis. A blood sample was drawn from an antecubital vein the day before the race as well as within 15 min post-race and analyzed for sodium concentration. During the second year of data collection, blood was also drawn at the 93-km checkpoint (<italic>n</italic> = 29). Height and weight were measured pre and post-race.</p><p><bold>Results:</bold> Mean race time of all subjects was 33 ± 3 h with a range of 23.5 and 36.0 h. Of the 63 finishers recruited, nine began the race with values indicative of mild hyponatremia. Seven runners were classified as hyponatremic at the 93-km checkpoint, three of whom had sodium levels of severe hyponatremia. After the race, 41 total finishers (65%) developed either mild (<italic>n</italic> = 27, 43%) or severe hyponatremia (<italic>n</italic> = 14, 22%). Mean change in bodyweight percentage and serum sodium from pre-race to post-race was −3.6 ± 2.7% (−2.5 ± 1.9 kg) and −6.6 ± 5.6 mmol·L<sup>−1</sup>, respectively. Pre-race serum sodium level was not a significant predictor of post-race serum sodium levels (β = 0.08, <italic>R</italic><sup>2</sup> = 0.07, <italic>P</italic> = 0.698), however, there was a significant negative association between change in bodyweight percentage and post-race serum sodium concentration (β = −0.79, <italic>R</italic><sup>2</sup> = 0.29, <italic>P</italic> = 0.011).</p><p><bold>Conclusion:</bold> The incidence of EAH of 52 and 65%, when excluding or including these individuals with pre-race hyponatremia, was the highest reported in current literature.</p>