How Much Water is Too Much?
While dehydration is a more common concern for exercisers, some experts think the public should be aware of the danger of drinking too much water, which can lead to a potentially fatal condition called hyponatremia. Characterized by an abnormally low blood concentration of sodium, it is most often seen at extremely high-endurance events such as ultra-marathons.
Hyponatremia is more common among women than men, and was responsible for the death of a 43-year-old woman running in the Chicago Marathon last year. Symptoms include nausea, vomiting, muscle weakness, headache and disorientation, and bloating in the face and hands.
Research suggests that drinking about two cups of fluid two hours before exercise and another six to eight ounces every 20 minutes can help optimize performance. Some exercisers may opt to measure the amount of fluid they lose by weighing themselves before and after exercise to determine the number of pounds lost through perspiration. For every pound lost, experts recommend drinking one pint of fluid during exercise. Sports drinks may also be a good choice because they help replace lost sodium and have been shown to enhance performance during prolonged exercise.
New Guidelines for Running and Hydration
It’s summer, you’re running a marathon, and you’ve known ”the rules” for years: To avoid dehydration, drink as much as you can at every aid station. Drink even if you are not thirsty because thirst is a poor indicator of how much fluid you need to replace.
Well, those rules have changed. USA Track & Field, the governing body of track and field, long-distance running and race walking, has issued new guidelines for athletes to ”consume 100 percent of fluids lost due to sweat while racing.” The USATF now recommends that athletes ”be sensitive to the onset of thirst as the signal to drink, rather than staying ahead of thirst.” Being guided by their thirst, runners prevent dehydration while also lowering the risk of hyponatremia (low sodium), a potentially dangerous condition increasingly seen as runners have erroneously been instructed to over-hydrate.