RMDC QUICK FACTS:

Terry Dibble holds a Masters
Degree in Exercise Science from Oakland University in Rochester, MI

Terry is a former Cross Country Coach at Oakland University.

He currently gives back to the running community as the Co-Founder, along with another Oakland Alum, Paul Rice, of the Race Management Company, R&D Race Directors.

You can e-mail Terry at:

[email protected]

SUMMER HEAT: TO RACE OR NOT TO RACE?

By Terry Dibble - R & D Race Directors

7/15/99

The July 99 issue of the Physician and Sportsmedicine (PSM) included an article "Keeping Sports Participants Safe in Hot Weather." The article focused on running in the heat. This is a review of that article.

How often has the decision been made to participate in a race under extreme heat conditions? Most runners will chose to participate because they have been training and would not want to give up the opportunity to race. This can be a very physically detrimental decision for the runner who is not prepared.

Several factors should be taken into consideration; The runner's fitness level and training, The "Wet Bulb Globe Temperature" reading for the day, is there adequate water and other fluid replacements available, is the runner acclimated to the heat, what time of day is the race, the type of clothing the runner is wearing and is the course shady or no shade and flat or hilly. These are issues which can put the runner at risk if not addressed.

From a physiological stand point, the human body is a very inefficient machine when it relates to exercise. During heavy exercise approximately 80% of a runner's energy is used for keeping the body cool. A small proportion is actually converted to muscular work. This translates to the potential for the system to overheat under heat stress conditions.

Several of the factors mentioned above can be controlled by the runner. The one primary factor, which the runner cannot control, is the temperature. According to the PSM article, the best method for measuring the environmental heat stress is the Wet Bulb Globe Temperature (WBGT) index. This index takes into account air temperature, relative humidity, and solar radiation by measuring three temperatures. These three measurements give an accurate determination of the effect of the temperature on the body.

The American College of Sportsmedicine has established guidelines for race directors for risk of heat illness. Theoretically, if the index is 73 or above then a race should be canceled or postponed. These guidelines assume warm weather clothing is being worn. If heavier clothing is worn such as football uniforms, then the index should be adjusted.

Ultimately, the runner must chose whether to race or not. The most logical decision would be to not run, but runners being runners that is usually not the case. There are a lot of races so why create a potential medical emergency when there is always tomorrow.

If the decision has been made to run, there are several precautions a runner must take to minimize the effects for environmental heat stress.

• The runner should be in excellent physical condition, the more fit a person is the better they tolerate the heat.
  
  
• Their training should be appropriate for the weather and course. It takes about 10-14 days to become acclimated to the heat. Be sure to train under the same conditions as the race.

Fluid intake becomes critical when racing in the heat. According to the PSM article, the combination of exercise and high environmental heat stress can produce dehydration. The ACSM have some suggested strategies for fluid intake. Fluid intake during prolonged exercise should attempt to match the fluid losses from sweating or more generic 150 to 300ml ( about 5-10 ounces) every 15 minutes during running.

In the past, water was the fluid of choice. Recent studies have indicated a carbohydrate drink 5 to 8% CHO-electrolyte replacement are well tolerated during exercise in heat and improve endurance. the fluid should be cooled to about 50-59m which improves taste and digestion.

The runner should also be aware of pre and post fluid intake. According to the PSM article, the current guideline prior to exercise is to intake 500mL (17oz.) of fluid 2 hours before competition. Post-race fluids should be high in sodium, plain water seems to delay rehydration.

These are recommended strategies for runners. Every runner is different in terms of his/her fluid needs. One point is clear, it is imperative to maintain adequate fluids in the body. One other point related to fluid intake, the runner should follow the same fluid intake regiment during training runs so the body can get used to the particular fluid being used for the race.

The PSM article also just proper clothing to minimize heat storage and enhance sweat evaporation. Clothes designed to maximize skin exposure are beneficial. They should be white or light colors, cotton or other breathable fabrics The runner has the responsibility to prepare properly for the race. Using common sense and good judgment are the keys to safe and fun running.