How Much Exercise is enough?

  • Regular exercise should be part of everyone’s routine.
  • But how much you exercise depends on your fitness goals.

Stephan does track in the spring, soccer in the fall, and tennis year-round. He also attends a teen fitness class three times a week where he does aerobics, circuit training, and running-not to mention swimming and the occasional touch football with friends. “Sports is my life,” he says. “I can never get enough.”

Not Adam. The 15-year-old computer whiz gets all his exercise doing finger calisthenics on a keyboard. “I hate sports,” he says. “Gym class is more than enough for me.”

Everyone knows the benefits of regular exercise. It strengthens the heart and lungs, reduces body fat, lowers the risk of many diseases, and is a great stress buster. Exercise also boosts the body’s ability to fight off colds and other illnesses. Too much, however, can have the opposite effect, leaving you more prone to infections and more susceptible to injuries and burn-out. Experts recommend at least 30 minutes of exercise three times a week to achieve better health, and between 35 and 45 minutes of vigorous exercise three to four days a week to improve fitness.

How do you know how much exercise is right for you? “It depends on your goals,” says Susan Kalish, executive director of the American Medical Athletic Association. “A couch potato can get the health benefits without ever walking into a gym just by increasing activity, such as walking to the bus or helping out in the yard. But if you want to improve sports performance, you have to do more than the bare minimum.”

1. Rest Rx

Exercising often is fine as long as you give the body a chance to recuperate. Rest helps make muscles stronger than they were before. It also replenishes your energy stores and prepares your body for the next workout. “Hard exercise won’t make you better, unless it’s complemented by a recovery period,” says Kalish. One way to let your body recuperate is to work out at half your normal intensity. Another option is to change your exercise routine. If you run three times a week, switch to swimming on your off days. If you normally bike, try an aerobic dance class. “Set a different goal for each day,” says Kalish. “Work on improving flexibility one day, jumping ability the next, and strengthening the upper body on another. By varying your activity, you’ll be less likely to overdo it.”

Kalish urges teens to keep a workout log to record the type and intensity of exercise as well as the thoughts and moods that go with it. “Negative thoughts are one of the first signs of overtraining,” she says. A log is also useful for setting goals and tracking your progress. Before adding extra workouts, talk to a coach, parent, or to a sports doctor. Or follow the 10 percent rule. If you run for 20 minutes four times a week, for example, you can safely increase to 22 minutes the next week. Doing too much too soon can result in injuries, including fractures and muscle strains.

Some girls who try to speed up weight loss by going overboard with exercise may, for example, stop their periods, weaken their bones, and increase the risk of stress fractures.

2. Beware of Burn-out

Rachel, a high school junior, works out vigorously to keep her weight under control, including doing aerobics three times a week at school. Recently she added running every afternoon, even when she’s exhausted. Sometimes she’s so worn out, she can’t make it through her regular classes.

Too many teens wait until they are burned out or hurt before easing up on their workouts. Signs of overtraining include frequent colds, chronic fatigue, and trouble sleeping. Learn to listen to your body. If your legs say it’s time to quit, don’t pay attention to the clock telling you you have 20 minutes more. Your body knows best.

The difference between a healthy exercise habit and an unhealthy one is how exercise fits into your life. When working out comes ahead of school, friends, and other responsibilities, you are doing more harm than good by exercising too much.

“Everyone’s needs are different. The key is to strike a balance between exercise and other activities,” says Kalish. If you feel guilty about missing a workout, fill the time with activities such as going to a movie, walking around the mall with friends, or doing community service. Remember, exercise is supposed to be healthy and fun. Working out in moderation will be both.

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