Effect of Sodium Supplements and Climate on Dysnatremia During Ultramarathon Running

Abstract

Objective: Analyze the effect of sodium supplementation, hydration, and climate on dysnatremia in ultramarathon runners. Design: Prospective observational study. Setting: The 2017 80 km (50 mile) stage of the 250 km (150 mile) 6-stage RacingThePlanet ultramarathon in 2017 Chilean, Patagonian, and 2018 Namibian, Mongolian, and Chilean deserts. Participants: All race entrants who could understand English were invited to participate, with 266 runners enrolled, mean age of 43 years (± 9), 61 (36%) females, average weight 74 kg (± 12.5), and average race time 14.5 (± 4.1) hours. Post-race sodium collected on 174 (74%) and 164 (62%) participants with both the blood sample and post-race questionnaire. Intervention: Weight change and finish line serum sodium levels were gathered. Main outcome measures: Incidence of exercise-associated hyponatremia (EAH; <135 mmol·L−1) and hypernatremia (>145 mmol·L−1) by sodium ingestion and climate. Results: Eleven (6.3%) runners developed EAH, and 30 (17.2%) developed hypernatremia. Those with EAH were 14 kg heavier at baseline, had significantly less training distances, and averaged 5 to 6 hours longer to cover 50 miles (80 km) than the other participants. Neither rate nor total ingested supplemental sodium was correlated with dysnatremia, without significant differences in drinking behaviors or type of supplement compared with normonatremic runners. Hypernatremic runners were more often dehydrated [8 (28%), −4.7 kg (± 9.8)] than EAH [4 (14%), −1.1 kg (± 3.8)] (P < 0.01), and EAH runners were more frequently overhydrated (6, 67%) than hypernatremia (1, 11%) (P < 0.01). In the 98 (56%) runners from hot races, there was EAH OR = 3.5 [95% confidence interval (CI), 0.9-25.9] and hypernatremia OR = 8.8 (95% CI, 2.9-39.5) compared with cold races. Conclusions: This was the first study to show that hot race climates are an independent risk factor for EAH and hypernatremia. Sodium supplementation did not prevent EAH nor cause hypernatremia. Longer training distances, lower body mass, and avoidance of overhydration were shown to be the most important factors to prevent EAH and avoidance of dehydration to prevent hypernatremia.

Prospective Observational Study of Weight-based Assessment of Sodium Supplements on Ultramarathon Performance (WASSUP)

“…As heat stress is known to increase thirst, sweating, and compensatory hydration requirements [30], ambient temperature could presumably impact sodium intake and subsequently effect performance. The average daytime temperature was 92.8°F (33.8°C) for the hot races and 57.7°F (14.2°C) for the cold races [7], so race temperature both in absolute (average daytime temperature) and categorical (hot or cold) were included as a control variable in our analysis. To determine a potential difference in average temperature for sodium consumption groups, a Welch two-sample t test was used.…”

“…This study was an analyses of data used to study the effect climate on dysnatremia during a prospective observational study during an 80 km (50 mi) 5th stage of a 6-stage 250 km (155 mi) ultramarathon in Chile and Patagonia (2017), and Namibia, Mongolia, and Chile (2018) [7]. All participants were offered the same amount of water for any given day [approximately 1.5 L per 10-12 km (6-7.5 mi)], had to carry all their own gear and at least 2000 kcal/day (verified during registration), and did not receive any food beyond what they carried.…”

“…Hydration status was based upon body weight changes with > 0% body weight change as overhydration, < 0 to − 3% body weight change as euhydration, and < − 3% body weight change as dehydration [30]. The hot or cold climate category for each race was derived using methods fully described previously [7].…”

“…The majority of endurance athletes believe that electrolyte supplementation is necessary to prevent muscle-cramping, nausea, and hyponatremia [3]. However, most studies fail to demonstrate associations between sodium intake and muscle cramps [4], or that supplements are protective against hyponatremia [2,3,[5][6][7]. Since fluid consumption during exercise contributes more to hyponatremia than lack of sodium supplementation [8], the potential ergogenic benefits may be eclipsed by the risks of overhydration with sodium solution during endurance events [6,9].…”

Trinken beim Sport: individuell und zielorientiert

“…Dieses als "Overdrinking" bezeichnete Phänomen ist die Hauptursache für eine kritische Natrium-Blutkonzentration von weniger als 135 mmol Na/Liter Blut während der Aktivität [4][5] [6]. Seit 1985 wurden weltweit 14 Todesfälle durch eine sportbedingte Hyponatriämie (EAH = Exercise-associated Hyponatremia) dokumentiert [7].…”