When you exercise strenuously in even moderate heat (above 60 degrees Fahrenheit; above 55 degrees F for beginning runners), you raise your core body temperature. This triggers a release of blood into the capillaries of your skin to cool you down, which then reduces the blood supply available to your exercising muscles. This basically means that you will have less blood and oxygen delivered to the power source that moves you forward--and less blood to move out the waste products from these work sites. As the waste builds up in the muscle, you will slow down.
So the bad news is that in warm weather, you are going to feel worse and run slower. The worse news is that working too hard on a hot day could result in a very serious condition called heat disease.
The good news is that you can adapt to these conditions as you learn how to handle the heat. You can keep cool by running during the best time of day and wearing clothing appropriate for the heat. But it's always better to back off or stop running at the first sign of a problem. The following are proven ways of avoiding heat adversity.
Running Workouts During Summer Heat1. Run before the sun gets above the horizon. Get up early during the warm months to avoid most of the dramatic stress from the sun and to enjoy the coolest time of day. Without having to deal with the sun, most runners can gradually adapt to heat. At the very least, your runs will be more enjoyable than later in the day.
If you must run when the sun is up, pick a shady course. Shade provides a significant relief in areas of low humidity and some relief in humid environments.
3. Run during the evening and night. In areas of low humidity, it's usually cool later in the day. When it's humid, the coolest time of the day is just before dawn.
4. Have an indoor facility available. With treadmills, you can exercise in air conditioning. If a treadmill bores you, alternate segments of five to 10 minutes--one segment outdoor, and the next indoor.
5. Don't wear a hat! You lose most of your body heat through the top of your head. Covering the head will cause a quicker internal buildup of heat.