Monday, June 2, 2003

Stay behind your thirst

Reversing previous recommendations, USA Track & Field warns of dangers of overhydration

By Llee Sivitz
Enquirer contributor

"Stay ahead of your thirst." (Or drink before you're thirsty.)

If you've tried long-distance running or walking you've probably heard this advice.

But in April, just before the Boston Marathon, USA Track & Field (USATF), a governing body for running events, declared this practice not only wrong but dangerous.

For the first time since the 1970s, runners and walkers are now being told that it's best to drink when thirsty.

Sodium is lost

Suzelle Snowden, director of the Cincinnati Jeff Galloway Marathon Training Program, says she saw this change coming. "Overhydration and saturation of sodium levels (in the blood) has been in the spotlight for the last three or four years, getting more and more press."

How to calculate your sweat rate:
• 1. Make sure you are properly hydrated before the workout - your urine should be clear.
• 2. Do a warm-up run to the point where perspiration is generated, then stop. Urinate if necessary.
• 3. Weigh yourself naked on an accurate scale.
• 4. Run for one hour at an intensity similar to your targeted race.
• 5. Drink a measured amount of a beverage of your choice during the run if and when you are thirsty. It is important that you keep track of exactly how much fluid you take in during the run.
• 6. Do not urinate during the run.
• 7. Weigh yourself naked again on the same scale you used in Step 3.
• 8. You may now urinate and drink more fluids as needed. Calculate your fluid needs using the following formula from the USATF:
• A. Enter your weight from Step 3 in kilograms (divide pounds by 2.2)
• B. Enter your weight from Step 7 in kilograms
• C. Subtract B from A
• D. Convert your total in C to grams by multiplying by 1,000
• E. Enter the amount of fluid you consumed during the run in milliliters (multiply ounces by 30)
• F. Add E to D. This figure is the number of milliliters you need to consumer per hour to remain well-hydrated.

• Note: Variables such as climate and dietary changes can affect your sweat rate.
What she refers to is a potentially fatal condition called hyponatremia. According to the USATF, it most often occurs during exercise of four hours or longer and results mainly from consuming too much fluid and not replacing sodium losses.

More than 70 cases of this condition have been documented since it was first recognized in 1985, and many scientists consider it as dangerous as heat illness (heatstroke).

Severe cases may involve grand mal seizures, respiratory arrest and even death.

Snowden says it is not as rare as you might think. "I've run 12 marathons and there have been three or four that I've run in that had someone die of this disease."

To prevent hyponatremia, USATF's new hydration guidelines include consuming no more than 100 percent of the fluids lost due to sweat during exercise, and determining one's "sweat rate."

If you don't know your sweat rate, it's recommended you begin your workout well-hydrated - indicated by clear urine - and then drink when thirsty (preferably a sports drink with sodium and electrolytes).

Those who run or walk in a marathon, and take four or more hours to do so, need to be especially cautious. The USATF states that exercising at a slower pace over extended periods means you will have a lower rate of heat production and sweating. They advise not to drink more than 800 (less than a quart) per hour during such races. They warn that higher rates of fluid intake "can be fatal if sustained for four or more hours."

To replenish fluids and salts after exercise, weigh yourself right before and after your workout. For every pound lost, drink a pint of replacement fluid (with electrolytes), the USATF says.

Lawyer Mike Marrero of downtown runs about 20 miles a week and races in the Flying Pig Marathon each year. He normally stops at two-thirds of the water stops along the route and has always thought overhydrating was a good idea.

"I like hydrating," he says. "It's easy to do and it's one of the things you think you can do for yourself."

'Back of pack' grew

The prior recommendation to overhydrate came after a 1969 laboratory study that showed a correlation between dehydration during exercise and a rise in core body temperature. This led to the conclusion that dehydration was the single cause of heatstroke and a great risk to marathoners

There were very few marathons at that time and participants were exclusively elite runners in peak condition.

Beginning with the 1976 New York City Marathon, however, thousands began taking on the 26.2-mile challenge. The number of runners in "back of the pack" grew.

By comparison, most runners in 2001 took at least one hour longer to complete the marathon than those who ran it in 1978.

Snowden, whose program specializes in training runners who want to complete their first marathon, says her program's hydration guidelines have been changed to comply with the USATF advisory.

"We changed it for the Flying Pig and we are going to make those recommendation changes for the rest of our marathons and long-run training," she says.

For more information on the USATF advisory, visit

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