By Lewis Maharam, MD, FACSM
Medical director, NYRR and ING New York City Marathon
- Respect your limits. Heat and humidity increase the physical challenges of running, and health problems can occur when you push beyond what your body can handle. Do not aim for a personal best on a warm, sticky day, particularly if you are not used to such conditions.
Acclimate. It takes 10 days to two weeks for the body to acclimate to keeping cool at higher temperatures. Give your body time to adjust. If you donít have 10 days, respect the heat and donít try for your personal best: Back down and seek medical aid if you donít feel well.
- Know the signs of heat problems. If you feel faint, dizzy, disoriented, have stopped sweating, or your skin is cool and clammy, slow down or stop running. If symptoms continue, sit or lie down in the shade and seek help.
- Drink enough. Drink throughout the day, so that your urine remains plentiful and pale yellow (lemonade colored). Even mild dehydration (scant, dark-yellow urine) will make you feel sluggish and tire early during exercise, and can increase the risk of heat-related problems during exercise. Water is fine for hydration, but in the heat or exercise lasting longer than 30 minutes, sports drinks are even better because the sugar and salt they contain form an ďactive pumpĒ that transports fluid to cells more quickly than water alone. Before workouts or races lasting longer than one hour in the heat, drink 16 ounces of fluid several hours in advance, another 16 ounces in the hour before, and more just before the start if your urine isnít pale.
- Donít drink too much. Overhydrating before and during exercise can cause a dangerous condition known as hyponatremia (water intoxication). This drop in the bodyís sodium levels can cause nausea, fatigue, vomiting, weakness, and in the most severe cases, seizures, coma, and death. To avoid hyponatremia, do not overdrink, use thirst as a guide, include salty foods in your pre-run meal, and use a sports drink that contains sodium. During exercise, drink no more than a cup (4-8 ounces) of fluid every 15 to 20 minutes. Itís also recommended that you eat one salt packet (dissolved in your mouth) just before the start and again halfway events of the half-marathon distance or longer. This will help you maintain your fluid and salt electrolyte levels to prevent dehydration and cramping. (Note: Consult your physician if you are on a salt-restricted diet.)
- Skip dehydrationg drugs and supplements such as ephedra (or synthetic ephedrine), cold medicines, anti-diarrhea drugs, and caffeine. These increase the risk of heat illness by raising metabolism and causing you to lose more fluid than you can replace; they also may inhibit sweating.
- Wear synthetic fabrics. Unlike cotton, synthetics wick moisture from your skin so cooling evaporation can occur. Synthetics also decrease chafing and donít cling and cause a chill. Look for loose-fitting garments with mesh inserts under the arms, on the sides of the torso, down the arms, and on the outer thighs. Acrylic socks keep feet dry and cool.
- Protect yourself from the sun. Wear a cap or visor to shield your head, face, and eyes from the sunís burning rays. Use sunscreen on exposed skin, even on overcast days.
- Use water along the course (cups, spray stations) to cool yourself during races. If you are overheating, a cool spray will cool you down quickly and have a lasting effect as the water evaporates from your skin. Keep in mind, though, that drenched clothing will cling to skin and prevent evaporation, and wet socks can cause blisters, so use this strategy wisely.