Medical and physiological considerations in triathlons

Am J Sports Med. Mar-Apr 1987;15(2):164-7. doi: 10.1177/036354658701500212.


Triathlons (races involving consecutive swimming, bicycling, and running) have become commonplace in the United States. These races may involve from 30 minutes to 36 hours of continuous exercise, usually in warm or hot environments. Little has been published regarding the medical and physiological aspects of these events. This paper represents the first large study to date on the subject, including both an analysis of medical complications at six triathlons as well as a prospective electrolyte study conducted at two of these races. Medical records were kept and examined for all athletes requiring treatment during a typical United States Triathlon Series (USTS) race in 1986 (1,000 starters; finish times, 2 to 4 hours), a typical Ironman Qualifier (IQ) race in 1986 (622 starters; finish times, 4 to 8 hours), and the 1982 through 1985 Hawaii Ironman World Championships (4,583 starters; finish times, 9 to 17 hours). At the USTS race, fewer than 2% (17/1,000) of the starters required aid, at the IQ, approximately 10% (61/622) of the starters were treated, and at the Ironman, an average of 17% (794/4,583) received medical attention. The most common diagnoses at the USTS and IQ were dehydration and heat exhaustion. At the Ironman, dehydration and heat problems were complicated by hyponatremia. Because hyponatremia has been reported as a complication of ultraendurance events, a prospective study was performed on 36 athletes during a USTS race and 64 athletes at the 1984 Ironman race. Prerace and postrace blood samples showed that no athletes were hyponatremic following the shorter USTS race, but 27% (17/64) of the athletes studied were hyponatremic following the Ironman race.(ABSTRACT TRUNCATED AT 250 WORDS)

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Athletic Injuries / epidemiology*
  • Bicycling*
  • Dehydration / epidemiology
  • Humans
  • Physical Endurance*
  • Potassium / blood
  • Running*
  • Sodium / blood
  • Sports*
  • Swimming*
  • United States


  • Sodium
  • Potassium