"Drink before you are thirsty" is bad advice for athletes. Over-hydration is caused by drinking too much fluid. While not as common as dehydration, over-hydration is more common than most think and can be more dangerous than dehydration. Too much water results in low blood sodium, also known as hyponatremia. According to a study by TD Noakes in the December 2005 Proceedings of the National Academy of Science, of 2,135 athletes competing in endurance events, 11 percent were heavier at the end of the event than at the start. One in in four of those had low blood sodium and half of those had symptoms of hyponatremia.
Things You'll Need
- Digital bathroom scale
- Exercise diary
Weigh yourself in the morning, before breakfast and drinking any fluids, on the day of a long training or a competition. Record the results in an exercise diary. The goal is to have a history of pre-event body weights as a basis for comparison.
Drink to satisfy thirst during the event. Don't pre-load and don't force yourself to drink beyond your thirst. Athletes drinking to satisfy thirst will typically replace 75 percent of the fluids they're losing during the event. Full replacement comes after the event is over. Performance is not usually impaired until weight loss exceeds two percent of starting weight.
Know the danger signs of low blood sodium. Be on the lookout for one or more of the following: headache, nausea, dizziness, confusion, agitation, vomiting, trouble breathing, coma and epilepsy-like seizures. Low blood sodium can lead to death.
Weigh yourself after the training or competition. The International Marathon Medical Directors Association recommends that marathon runners who experience before-to-after weight gain consider immediate medical consultation, especially if one or more hyponatremia symptoms are present. Hyponatremia is treatable if managed promptly with oral or IV saline and medical care.
Avoid the post-event over-hydration trap. Exercise can trigger a condition called the "syndrome of inappropriate antidiuretic hormone secretion," or SIADH. Urine production shuts off even if the person is over-hydrated. SIADH usually lasts only as long as one is exercising, but for some people it can persist for hours after. Believing they're dehydrated because they're not producing urine, they force themselves to drink more. Again, a simple body weight check can help prevent this mistake.