Low prevalence of exercise-associated hyponatremia in male 100 km ultra-marathon runners in Switzerland It considers that hyponatremia occurs more frequently in long burdens than shorter stress such as a marathon. In a long-term study, we studied the prevalence of the stress-associated hyponatremia at 100 km in Biel, the study can be found under https://pubmed.ncbi.nlm.nih.gov/21082192/