(MayoClinic.com) Are you ready to shake up your workout? Do you wish you could burn more calories without spending more time at the gym? Consider aerobic interval training. Once the domain of elite athletes, interval training has become a powerful tool for the average exerciser, too.

It's not as complicated as you might think. Interval training is simply alternating bursts of intense activity with intervals of lighter activity.

Take walking. If you're in good shape, you might incorporate short bursts of jogging into your regular brisk walks. If you're less fit, you might alternate leisurely walking with periods of faster walking. For example, if you're walking outdoors, you could walk faster between certain mailboxes, trees or other landmarks.

Whether you're a novice exerciser or you've been exercising for years, interval training can help you jazz up your workout routine. Consider the benefits:

• You'll burn more calories. The more vigorously you exercise, the more calories you'll burn — even if you increase intensity for just a few minutes at a time.
• You'll improve your aerobic capacity. As your cardiovascular fitness improves, you'll be able to exercise longer or with more intensity. Imagine finishing your 60-minute walk in 45 minutes — or the additional calories you'll burn by keeping up the pace for the full 60 minutes.
• You'll keep boredom at bay. Turning up your intensity in short intervals can add variety to your exercise routine.
• You don't need special equipment. You can simply modify your current routine.

During intense exercise, muscles produce waste products that can contribute to muscle soreness. Too many accumulated waste products can make exercise painful and exhausting. But by alternating bursts of intense exercise with easier intervals, you'll help reduce the buildup of waste products in your muscles. The result is more comfortable exercise.

Yes — but you can take interval training to many levels. If you simply want to vary your exercise routine, you can determine the length and speed of each high-intensity interval based on how you feel that day.

After warming up, you might increase the intensity for 30 seconds and then resume your normal pace. The next burst of more intense activity may last two to three minutes. How much you pick up the pace, how often and for how long is up to you.

If you're working toward a specific fitness goal, you may want to take a more scientific approach. A personal trainer or other expert can help you time the intensity and duration of your intervals — which may include movement patterns similar to those you'll use during your sport or activity — based on your target heart rate, the ability of your heart and lungs to deliver oxygen to your muscles (peak oxygen intake), and other factors.

Interval training isn't appropriate for everyone. If you have a chronic health condition or haven't been exercising regularly, consult your doctor before trying any type of interval training. Recent studies suggest, however, that interval training can be used safely for short periods even in individuals with heart disease.

Also keep the risk of overuse injury in mind. If you rush into a strenuous workout before your body is ready, you may hurt your muscles, tendons or bones. Instead, start slowly. Try just one or two higher intensity intervals during each workout at first. If you think you're overdoing it, slow down. As your stamina improves, challenge yourself to vary the pace. You may be surprised by the results.

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