Incidence and Cause of Hyponatremia in Endurance Runners, Also to Determine if Oral Hypertonic Saline is as Efficacious as Intravenous Hypertonic Saline in the Correction of Below Normal Blood Sodium Concentrations in Runners With Hyponatremia Without Neurological Symptoms

The purpose of the study is to 1) evaluate incidence and primary cause of exercise-associated Hyponatremia (EAH) in race finishers participating in the Western States 100-mile Endurance Run, 2) determine if the ingestion of oral hypertonic saline (high salt) is as effective as intravenous administration of hypertonic saline to elevate below-normal blood salt concentrations (EAH) at the end of the Western States Endurance Run, and 3) determine if oral and intravenous hypertonic saline solutions are equally as effective at reversing mild (without altered mental status) symptoms associated with EAH.