USA Track & Field (USATF) on Saturday unveiled new fluid-replacement guidelines for long-distance runners, as well as a major new initiative to educate the distance-running public about how to properly hydrate.

For athletes in general and especially for those completing a marathon in more than four hours, USATF recommends consuming 100 percent of fluids lost due to sweat while racing. This marks 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.

Simply put, runners should 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.

Announced by USATF in advance of the 2003 Boston Marathon, the new guidelines mark a significant shift in standard recommendations for fluid replacement. They reflect changes in scientific thinking as well as changes in the average finishing times of marathon fields.

"The 'new running boom' has seen more mid-pack and back-of-the-pack runners taking up marathoning," USATF CEO Craig Masback said. "The United States now has 30 million adult runners, a growth that has been tremendous for the sport and the overall health of Americans. As the national governing body for long distance running, we consider it vital that we play a key role in educating athletes of all levels, from the four-hour-plus marathoner to our Olympians."

Replacing Fluids and Sodium
A potentially fatal condition, hyponatremia most often occurs in exercise lasting four hours or longer and results primarily from consuming excessive fluids and is exacerbated by not replacing sodium losses. Severe cases of may involve grand mal seizures, increased intracranial pressure, pulmonary edema (fluid in the lungs), respiratory arrest, and even death.

In USATF's new hydration guidelines, long-distance runners are instructed to consume 1 liter of fluid for every liter lost during a race, equaling a 1:1 ratio. Runners can determine their rate of sweat loss weeks before a race by using the USATF Self- Testing Program for Optimal Hydration, as described on www.usatf.org.

Following this self-determined hydration strategy minimizes risks associated with both dehydration and over-hydration.

Athletes who have not yet had the opportunity to perform self- testing should begin their races well-hydrated--indicated by clear urine--and then drink when thirsty during their races, rather than drinking constantly as some have recommended. A sports drink with sodium and other electrolytes is preferred.

Runners lose not only water, but significant amounts of sodium and other minerals while sweating during the course of a marathon. Recommendations of 150 percent fluid replacement or more could result in runners consuming large quantities of water during their races, causing a drop in overall sodium levels and, potentially, hyponatremia.

While proper hydration is critical for all runners competing in long distance races, those who are on the course for an extended period of time have a greater risk of dehydration or of overhydration, which increases the risk of hyponatremia. This risk demands that runners know how much their bodies need in racing conditions.

Many scientists now view hyponatremia as just as much of a threat to runners as heat illness and dehydration, and major papers distributed by the International Association of Athletics Federations (IAAF) and USATF have described these potential problems and how to avoid them. (These papers are available on www.usatf.org.)

Education
USATF is issuing a call to action to energize its organizational infrastructure in a public-education push on the topic of fluid replacement and hyponatremia. USATF's fifty-six Associations and 2,500 local clubs--which serve all 50 states and 80,000 USA Track & Field members--will be a starting point for distributing the recommendations on a grassroots level.

While many runners may choose to conduct their own self-testing, USATF will work with clubs and Associations to set up clinics at which runners will do the one-hour runs under supervision to help them best determine their hydration needs.

Other Medical Issues
As runners have learned the importance of hydration during long distance events, dehydration has become a less prevalent condition. Medical crews at marathon finish lines now are dealing more with hyperthermia (heat illness), postural hypotension (pooling of blood in the legs), hyponatremia, and the normal injuries that are common among marathon runners such as blisters and muscle injuries. Hyperthermia can occur regardless of hydration levels or the distance of a race. In fact, shorter races can pose more of a threat 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. It is therefore important that athletes adjust their pace to take into consideration race conditions, slowing their pace as heat and humidity rises, regardless of how much they may be drinking.

"Postural hypotension" is experienced when a runner suddenly stops, most commonly at the finish line. With blood pooling in the legs, there is inadequate blood supply to the rest of the body and the runner feels faint and can fall down. This had been thought of as demonstrating dehydration, so the response from medical teams was to rehydrate these runners. Now, medical personnel can identify this problem correctly and treat it specifically. Treatment requires raising the runner's feet above the head for 3-4 minutes for full recovery. Runners can avoid postural hypotension by keeping the legs moving, even with light walking or moderate knee flexing when they otherwise would stand still at or immediately after the finish or at other locations along the race course.

For More Information
USATF's new guidelines, along with supporting documentation, are explained in two scientific advisories on the topic.

"Proper Hydration for Distance Running - Identifying Individual Fluid Needs," by Douglas Casa, Ph.D., ATC, FACSM, of the University of Connecticut, is issued by USA Track & Field.

"IMMDA-AIMS Advisory statement on guidelines for fluid replacement during marathon running," was written by Tim Noakes MBChB, MD, FACSM of the University of Cape Town, South Africa; and David E. Martin, Ph.D. FACSM, of Georgia State University. It was published in IAAF New Studies in Athletics, March 2002, pp. 15-24.

These two papers, including an explanation of the self-test, are now posted on the USATF Web site, www.usatf.org.

For more information about hyponatremia, read an article by Michele Burr, PhD, called My Experience with Hyponatremia at the Vermont 100 Miler.