Too much water can create lethal results for long-distance runners
Wow, it's hot! Too hot to run a step.
But if you do, hydration management should be a top priority.
There are many hot-button topics buzzing around our sport of running, and here's one to consider: hyponatremia, which translates to "drinking yourself to death."
Hyponatremia, or low blood sodium, results from drinking too much water - before and during lengthy bouts of exercise - instead of sports drinks containing adequate amounts of carbohydrates and electrolytes like sodium and potassium.
Water is still a essential during exercise, but too much water combined with sweating can dilute mineral levels in the bloodstream and cause dangerous metabolic imbalances.
Deaths and near-deaths from hyponatremia have been reported at U.S. marathons. The threat of hyponatremia, often masked as heat stroke, dehydration or cardiovascular incidents, has become so serious that medical technicians at megamarathons like Boston and New York are testing runners' blood during and after the race. Trying to re-hydrate a hyponatremia victim could be fatal.
At the Boston Marathon in April, which had warm temperatures, runners suffering heat-related illnesses were given on-the-spot blood tests to determine sodium levels. Another marker is weight gain or loss, so scales manned by technicians were placed along the marathon route. Before the race, runners were asked to write their starting weight on their bib numbers. A weight gain of three percent or more from too much water would be a red-flag warning. A three percent loss signals mild dehydration.
Symptoms of hyponatremia include nausea, vomiting, muscular weakness, shortness of breath, headache, lethargy, disorientation and seizures.
Low sodium levels prevent the body from maintaining a normal fluid balance, and this has a deadly effect on the brain and lungs. The organs accumulate excess fluid, the brain swells and the lungs are flooded.
Hyponatremia has sometimes been referred to as "water intoxication." Even sports drinks formulated with proper electrolyte replacements can't always compensate for it.
In 2003, partly as a result of hyponatremia research collected at major marathons, USA Track & Field revised fluid-replacement guidelines. The American College of Sports Medicine, the International Olympic Committee, the U.S. military and others are publishing similar studies.
Following are some of the revised USATF guidelines for hydration management, along with additional tips from the American Running Association and the Gatorade Exercise Physiology Lab:
Hydrating with just water is fine for runs lasting an hour or less. But runners involved in endurance feats, especially those lasting longer than four hours, should consume 100 percent of fluids lost to sweat during exercise - no more.
Be sensitive to your onset of thirst, rather than staying ahead of the need to drink.
Begin your runs well hydrated, indicated by clear urine.
Weigh yourself before you leave for your workout, and weigh yourself when you return. If you have gained weight, don't begin drinking more water until after you've urinated. Only replace the weight loss.
Women and beginners are at greater risk for hyponatremia. Both tend to take longer to finish a long-distance run and are more vigilant about stopping at each aid station whether they need to or not.
Don't over-dilute the sports drinks with water because it negates the proper electrolyte formula.
Eat pretzels or something salty during the last half of an endurance run to restore some of the lost sodium.
My own encounter with hyponatremia symptoms occurred in April, when a group of us ran the More Marathon and Half Marathon in Central Park. The New York Road Runners, the same expert crew that organizes the New York City Marathon, tended to every aspect of this race, including the medical tent.
Large self-serve aid stations, stocked with eight-ounce cups of water and sports drinks, were placed every two miles on the repeat-loop course. It was sunny, with temperatures in 70s, but it seemed even warmer.
After 28 years of running, I believe I have a handle on hydration management. But after I finished the half marathon, I felt waves of nausea. I walked into the medical tent and asked for help.
"You may have the onset of hyponatremia," said the medic as he handed me a packet of salt and a little water. "Put this under your tongue and wash it down."
I did as I was told, under protest that it was simply dehydration. I thought paranoia had struck the medial unit, but better safe than sorry.
But after another small bag of salty Cheetohs, I was feeling like new.
For information on fluid replacement and heat studies, visit the American College of Sports Medicine site at
www.acsm.org.
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