Several recent studies how that aspirin, Indocin, Celebrex and other arthritis pain medicines may cause some cases of hyponatremia, a condition that can kill novice athletes in ultra long endurance events. These medications, often taken to relieve muscle and joint pain, cause the body to retain fluid during exercise (Medicine & Science in Sports & Exercise, May, 2005).

For many years, exercise physiologists have told athletes in endurance events to take in fluids frequently during events lasting more than an hour. However, on rare occasions, athletes have died of hyponatremia in these endurance events. Hyponatremia is caused by taking in too much fluid; it is not caused by excessive loss of salt in your sweat. The extra fluid expands blood volume and dilutes blood salt levels, which forces fluid to enter and swell the brain, causing nausea and vomiting, weakness, headache, and extreme tiredness. Since these same symptoms can be caused by dehydration alone, the only way to diagnose hyponatremia is with blood tests. As blood salt levels drop even lower, the person becomes confused, develops seizures and falls unconscious.

How can you know how much fluid you should drink? Experts do not agree because thirst is a late sign of dehydration. The American College of Sports Medicine recommends three to six cups of fluid per hour. For a person who is not exercising near his maximum, this could be too much. The person who is out of shape, exhausted, or exercising significantly below his capacity probably should take in only two to three cups per hour. Above all, do not take aspirin or any arthritis pain medicines before you compete in events taking more than an hour.