TOO MUCH HYDRATION?
(Triathletes might take heed of USATF recommendations): (contributing editor Michael Sandrock of the Daily Camera)
Runners have long been told to drink as much water as possible and to rehydrate after a long, hot run. This might not be the best policy, however. New guidelines from USA Track and Field indicate that drinking too much water can be just as dangerous as not drinking enough when running for long periods of time.
In a study reported just before this year's Boston Marathon, USATF came up with a major change in its guidelines for long-distance runners, pointing out the danger of drinking too much water. The change can be summed up like this:
Before, runners were told to "stay ahead of their thirst" by drinking water early and often. Now, we are being told it is better to "keep up with our thirst." USATF urges runners to drink 100 percent of the fluids lost while running or racing. This, according to the study, is a "significant change from the understanding most runners have that they should be drinking as much as possible and following the guideline to 'stay ahead of your thirst,' which has been held as the standard recommendation for many years."
One reason for the new guidelines is to help the burgeoning number of four-to-six-hour marathoners avoid a dangerous condition called "hyponatremia," which is becoming more common in runners who have "erroneously been instructed to overhydrate."
Hyponatremia, or "water intoxication," is a potentially fatal condition of low sodium in the blood most often found in those exercising for more than four hours. Severe cases, according to USATF, can include grand mal seizures, increased intra-cranial pressure, pulmonary edema (fluid in the lungs), respiratory arrest and even death. When exercising for a long time, runners lose sodium and other minerals in their sweat. Drinking too much water while at the same time losing sodium can result in a too-low sodium level, or hyponatremia.
The USATF guidelines also point out the dangers of two other conditions runners face: hyperthermia, or heat illness, and "postural hypotension," a condition of blood pooling in the legs that can occur when a runner comes to an immediate stop after finishing a race.
According to the USATF, shorter races "can pose more of a threat (of heat illness) due to the faster pace per mile, which causes greater heat production. An adequately hydrated runner who is running too fast or pushing herself too hard, especially in hot and humid conditions, can fall victim to hyperthermia." To avoid this, use common sense and lower your expectations when racing in the heat. And to avoid postural hypotension, runners are urged to keep walking or jogging after finishing a race. The new USATF guidelines also include:
Drink one liter of fluid for every liter lost during a race, in a one-to-one ratio. To find out how much water you will lose through sweating, check www.usatf.org for a "Self-Testing Program for Optimal Hydration."
Do not drink water constantly during a long race or run. Rather, drink when thirsty.
Drink one of the many electrolyte-laden sport drinks now available instead of water.
For texts of scientific papers on the dangers of over-hydration, check out www.usatf.org.