Medical complications can occur in people who run long distances.
One such complication is an abnormally low blood level of sodium, a salt that is present in body fluids. Both conditions are potentially deadly, yet little is known about these complications in runners. Since little is known about this complication, the researchers wanted to describe what they had observed in long-distance runners who accumulated water in their brains and lungs. Seven runners, cared for by the authors, who developed medical complications during marathon races between 1993 and 1999. While the authors were caring for the patients who became ill while running, they studied the patients' medical histories, physical examinations, chest x-rays, and tests for blood sodium and blood oxygen.