Low prevalence of exercise-associated hyponatremia in male 100 km ultra-marathon runners in Switzerland

Abstract

We investigated the prevalence of exercise-associated hyponatremia (EAH) in 145 male ultra-marathoners at the '100-km ultra-run' in Biel, Switzerland. Changes in body mass, urinary specific gravity, haemoglobin, haematocrit, plasma [Na(+)], and plasma volume were determined. Seven runners (4.8%) developed asymptomatic EAH. Body mass, haematocrit and haemoglobin decreased, plasma [Na(+)] remained unchanged and plasma volume increased. Δ body mass correlated with both post race plasma [Na(+)] and Δ plasma [Na(+)]. Δ plasma volume was associated with post race plasma [Na(+)]. The athletes consumed 0.65 (0.30) L/h; fluid intake correlated significantly and negatively (r = -0.50, p < 0.0001) to race time. Fluid intake was neither associated with post race plasma [Na(+)] nor with Δ plasma [Na(+)], but was related to Δ body mass. To conclude, the prevalence of EAH was low at ~5% in these male 100 km ultra-marathoners. EAH was asymptomatic and would not have been detected without the measurement of plasma [Na(+)].

No case of exercise-associated hyponatraemia in top male ultra-endurance cyclists: the ‘Swiss Cycling Marathon’

“…In male 24-h ultra-marathoners (Knechtle et al 2010a) and in male ultra-endurance mountain bikers (Knechtle et al 2011c), no case of EAH was found. For ultra-marathoners in a 100-km ultra-marathon, the prevalence of EAH was low at *5% (Knechtle et al 2011b). These results are far below the reported prevalence rates of EAH in other studies in other countries as cited in ''Introduction''.…”

“…In marathoners, the prevalence of EAH amounts up to about 22% depending upon the number of investigated athletes, their gender and fitness level Chorley et al 2007;Hew et al 2003;Kipps et al 2011;Mettler et al 2008). In ultra-marathoners, the prevalence of EAH varied between 0 and 44% (Knechtle et al 2010a(Knechtle et al , 2011bReid and King 2007;Stuempfle et al 2002Stuempfle et al , 2003. For Ironman triathletes, the prevalence of EAH was described in 1.8-28% of the athletes (Speedy et al 1997(Speedy et al , 1999(Speedy et al , 2001aWharam et al 2006).…”

“…We assume that drinking behaviour among both ultraendurance athletes (Knechtle et al 2010a(Knechtle et al , 2011b and marathoners ) is different in Switzerland compared to other countries. Drinking policies during exercise have changed substantially throughout history.…”

“…The prevalence of EAH has been extensively investigated in endurance athletes such as marathoners Chorley et al 2007;Hew et al 2003;Kipps et al 2011;Mettler et al 2008), ultra-marathoners (Knechtle et al 2010a(Knechtle et al , 2011bLee et al 2011;Reid and King 2007;Stuempfle et al 2002Stuempfle et al , 2003 and Ironman triathletes Sharwood et al 2002;Speedy et al 2001a). In marathoners, the prevalence of EAH amounts up to about 22% depending upon the number of investigated athletes, their gender and fitness level Chorley et al 2007;Hew et al 2003;Kipps et al 2011;Mettler et al 2008).…”

Ultramarathon Running: Medical Issues

“…Exercise-associated hyponatremia is a rather frequently found electrolyte disorder in ultramarathoners [11,[61][62][63] where high ambient temperatures might be of high importance [11,64]. In a 5-stage 225 km multi-stage ultra-marathon where athletes competed at temperatures of up to 40 °C, the prevalence of exercise-associated hyponatremia amounted to 42% [11].…”