Take Your Fitness Level up a Notch

Do you know what your anaerobic threshold is? Do you care? You should: The higher your anaerobic threshold, the longer, harder, and faster you can exercise aerobically before your muscles cry uncle.

When you exercise, your body uses two primary energy sources: fat and carbohydrate. When you exercise at an easy level (e.g., a long, slow run), there's no rush to supply energy, so your body can take the time necessary to metabolize fats. However, during vigorous exercise (e.g., one to three miles of high-speed running), your body uses more carbohydrates because they are easier to "grab" and put to use for energy.

The anaerobic threshold (AT) is that level of intensity where carbohydrates take over as the major supplier of energy. It's also the point at which the oxygen supply to your muscles starts to dwindle. The result is a buildup of lactic acid (which is why it's also called the lactate threshold). And, as you probably know from your own experience, excess levels of lactic acid inhibit muscle contractions and cause a feeling of heaviness, fatigue, and possibly cramping. This is what some call "hitting the wall."

To improve performance, you want your AT to be as high as possible. If you gauge it by your heart rate (an excellent measure of intensity), the AT typically occurs at around 75 to 80 percent of your maximum heart rate. (To determine your maximum heart rate in beats per minute, subtract your age from 220.) If you're 30 years old, for example, your maximum heart rate would be 190 and your AT is likely to be around 143 to 152 beats per minute. (If you really want to keep track of your workout intensity and your AT, use a heart rate monitor or go to a sports medicine clinic, where they can scientifically pinpoint both your max heart rate and AT.)

To improve your AT, you should exercise at or slightly above your threshold level for a minimum of 20 minutes about three times a week in the beginning. After three to four weeks, you can go to twice a week. With the proper training, you can push your AT to 85 percent or higher. A well-trained athlete's AT can approach 94 to 95 percent of maximum.

- Declan Connolly

This article is provided by GymAmerican.com. You can view their site and similar articles at http://www.gymamerica.com/