Medical problems of marathon runners.

Several organ systems can be affected by marathon running. Acute musculoskeletal injuries are common, but running does not result in increased rates of musculoskeletal disability. Gastrointestinal complaints are also common among runners; some of these complaints are explained by the decreased mesenteric blood flow during exercise. Although cardiac events are rare, they can be devastating. Symptomatic hyponatremia is another serious but mostly preventable problem.