title: Characteristics of 161-km ultramarathon finishers developing exercise-associated hyponatremia.
abstract: This study sought to identify runner characteristics or symptoms that could distinguish those finishers developing exercise-associated hyponatremia (EAH) from those not developing EAH in a 161-km ultramarathon. Of 310 finishers, 207 (67%) underwent postrace blood studies. Twelve (6%) finishers had EAH (blood sodium range 131-134 mmol/L). Experience at 161-km ultramarathons was lower (p = 0.01) and blood creatine kinase (CK) concentration was higher (p = 0.04) among those with EAH than those not developing EAH. Blood sodium and CK concentration were negatively correlated (p = 0.0015, r = -0.22). There were no group differences in age, sex, regular running experience, weekly training distance, use of sodium supplements during training, immediately postrace sodium palatability and thirst ratings, body mass change, urination frequency, nonsteroidal anti-inflammatory drugs (NSAIDs) use, and various symptoms experienced during the race. These findings indicate that a clinical suspicion and measurement of blood sodium concentration remain the only viable means for determining when an ultramarathon runner has EAH.
authors.affiliation: Department of Physical Medicine & Rehabilitation, Department of Veterans Affairs, Northern California Health Care System, Sacramento, California 95655-1200, USA. martin.hoffman@va.gov
authors.forename: Martin D
authors.initials: MD
authors.lastname: Hoffman
authors.forename: Kevin
authors.initials: K
authors.lastname: Fogard
authors.forename: James
authors.initials: J
authors.lastname: Winger
authors.forename: Tamara
authors.initials: T
authors.lastname: Hew-Butler
authors.forename: Kristin J
authors.initials: KJ
authors.lastname: Stuempfle
mesh_terms: D000328:Adult; D003402:Creatine Kinase / Q000097:blood*; D005260:Female; D006801:Humans; D007010:Hyponatremia / Q000097:blood* / Q000175:diagnosis / Q000503:physiopathology; D008297:Male; D008875:Middle Aged; D012307:Risk Factors; D012420:Running / Q000502:physiology*; D012964:Sodium / Q000097:blood* / Q000502:physiology; D018709:Statistics, Nonparametric; D011795:Surveys and Questionnaires; D013649:Taste; D013894:Thirst; D014883:Water-Electrolyte Imbalance / Q000097:blood
chemical_list: D012964:Sodium; D003402:Creatine Kinase