Slow your exercise pace in hot weather


Hot summer weather can sap your strength, reduce your endurance and throw your athletic performance way off balance.

If you are a marathon runner, for example, you should expect to add 5 to 15 minutes to your time; pace yourself accordingly. A tennis player who normally can blast a serve at 100 mph might lose up to 15 mph when playing in the heat. Every athlete, when competing in the heat, eventually learns to hold back early to have something left in reserve.

This time of year, your heart must work harder. In addition to

pumping blood to supply oxygen and nourishment to your muscles, your heart must increase the amount of blood it pumps to the skin to help keep your body temperature from rising too high.

Your muscles do not work as efficiently. Exercise in hot weather increases fluid loss and pushes your body and muscle temperature up, impairing your overall performance. When the temperature of your muscles rises, the muscle fibers don't extract oxygen, produce energy or contract efficiently.

It takes more calories to exercise in the heat. The extra workload placed on your heart requires more energy. Your heart burns more calories than any other muscle in your body; since it must work harder in hot weather, your calorie requirements increase.

So, take it easy. A summer day of heat and humidity is no time to try to set records.


Q: Is walking a good fitness activity?

A: If you want to walk to become fit, you have to move fast enough to increase your heart rate at least 20 beats per minutes more than when you are resting.

There are two ways to increase your walking speed. You can take longer steps and you can move your feet at a faster rate.

lengthen your stride, swivel your hips so your feet reach out further forward with each step. Your body will twist from side to side, causing you to point your toss forward when your feet hit the ground.

To move your feet at a faster rate, you have to move your arms faster. Each time the leg is placed forward, the arm on that same side is placed backward and the arm on the other side moves forward. For every step forward there is an equal number of arm movements forward.

To move your arms faster, keep your elbows bent. The fulcrum of your arm-swing is at your shoulder. The straighter you hold your elbows, the longer it takes your arms to swing forward and back, and your legs will move more slowly. Bending your elbows shortens the swing and helps you move your arms faster, helping to propel you forward faster.

Dr. Mirkin is a practicing physician in Silver Spring specializing in sports medicine and nutrition.

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