How to Use the Heat Index When Exercising

Scientists have labeled what your body has always known: heat and humidity add up to danger. The day's highest temperature is not the best measure of the danger of heat waves—it is when the heat joins forces with humidity that the risks increase dramatically.

The heat index measures that combination—it’s like a wind chill factor for the summer. If you are trying to exercise when the heat index is high, consider these pointers and stay safe.

Difficulty: Moderately Easy

Instructions

1. When the heat index is high, your sweat evaporates more slowly and outdoor exercise becomes dangerous even for athletes in good shape.

2. If the heat index is over 90 you should use extreme caution when exercising outdoors. A heat index above 100 is considered dangerous and above 125 is extremely dangerous. (See Resources below for a link to NOAA's heat index chart.)

3. During hot and humid days, increase your water intake. Aim for 10 to 12 8-oz glasses of water a day. (If you eat plenty of fresh fruit, you can count that as a liquid.)

4. Slow down and cool off when you start to feel fatigued, begin fighting a headache, or notice a high pulse rate or shallow breathing. Overheating can cause serious, life-threatening conditions.

5. If you experience muscle cramps or fainting, take it easy and head indoors.

6. Heat exhaustion occurs when you lose fluid and salt through perspiration (or you replace them in an imbalanced way). Dizziness, weakness and an elevated body temperature (not above 102 degrees) are all symptoms. Again, rest and hydration are the best solutions. Don't take salt tablets without consulting your physician.

7. Under extreme conditions, heatstroke is a frightening risk. Heatstroke can alter the body’s thermostat causing the body temperature to rise to 105 degrees or higher. Symptoms are lethargy, confusion and unconsciousness. If you even suspect that someone might be suffering from a heatstroke, call for immediate medical aid.

Resources

• NOAA's Heat Index Chart