A death from hyponatremia at both the Boston Marathon and the Marine Corps Marathon has become a hot topic for marathon directors and discussed at the 2003 Marathon Directors Conference.
Hyponatremia is low blood sodium, which can occur when endurance athletes including long distance walkers and runners lose sodium through sweat and are unable to replace it. They may further dilute their blood sodium by continuing to drink large amounts of water and losing further sodium through urination.
Setting Off the Hype Over Hyponatremia
"Advisory Statement on Guidelines for Fluid Replacement During Marathon Running" written by Tim Noakes MD, FACSM of the University of Cape Town, South Africa and David E. Martin, Ph.D. FACSM, of Georgia State University ignited changes in many marathons."Drink when thirsty" is the biggest change from standard guidelines, and drink only enough to replace lost fluids - 400-800 milliters an hour (no more than a water bottle full an hour, or about a pint, a maximum of 20 oz. per hour). Many marathon programs had been recommending drinking before you are thirsty and replacing up to 150% of lost fluids.
The USATF further recommended that the replacement fluid should be sodium-containing sports drink in preference to plain water.
Profiles of runners and walkers who became hyponatremic, published in the Oct. 23, 2003 edition of the Washington Post, showed them drinking as much as 3000 ml of water (3 quarts) before the marathon and 500 ml (a pint) or more at each water stop.
Hype or Growing Hazard?
Dr. Jack Schaff, medical director of the Honolulu Marathon Clinic, at the National Event Director's Workshop in October, 2003 declared that Dr. Noakes was wrong. He raised fears that races would restrict or remove water stops, leading to more dehydration and heat sickness. At the Honolulu Marathon the temperature and humidity is high and most participants have just flown in and are not acclimated. The Honolulu Marathon attracts many slow runners, walkers, and first-timers. Yet he does not see hyponatremia, but rather sees hundreds of cases of dehydration and heat sickness each year. Update: at the 2005 Race Director's College, Dr. Schaff and other race medical directors were in agreement with updated drinking guidelines that address the hyponatremia hazard.Drinking Guidelines 2006
Experts tend to agree that each individual has a different risk of dehydration and hyponatremia and the whole issue is not well understood. To limit their liability, marathon coaches will be modifying their guidelines to match those issued by USATF following the Noakes paper.
Other sports physicians take issue with Dr. Noakes' assertion that dehydration doesn't contribute to heat illness and cite studies that show it certainly does, especially at a level of 8% of body weight.
What Should You Do?
- Rely more on your thirst level rather than forcing yourself to drink.
- Drink a big glass of water 1-2 hours before a long walk - approximately a half-liter or pint. Have some salty food before your long walk.
- While walking, drink approximately a sports water bottle full of water an hour (500 ml or 1 pint) and after the first hour you should be drinking a sodium-replacement sports drink or eating salty foods such as salty pretzels.
- Weigh yourself immediately before and immediately after your training walks. Gaining weight during the walk is a sign of developing hyponatremia. Losing weight is a sign of dehydration.
- Note how much and what you ate and drank during the training walk, plus the temperature and how much you are sweating.
- Adjust your drinking intake, or your use of sports drink or salty foods before and during your training walks, until you are neither gaining nor losing weight during the walk.
- Pain-relievers such as ibuprofen, acetaminophen, aspirin, and naprosyn - NSAIDS - may contribute to developing hyponatremia. Discuss this with your physician if you are on them for a condition. Otherwise, avoid them before and during your long walks.
- Before your walk - increase your salt intake so you have some in reserve. Consult your physician if you are on a sodium-restricted diet.
- After your walk - eat salty foods and do not drink water to excess. Keep to the same guideline of a pint or half a liter an hour. Many people end their walk feeling good, then wash out their sodium by drinking too much afterwards. Let thirst be your guide.
