Intervals are periods (usually a minute or two) of high intensity exercise alternated with periods of low intensity exercise. You may use 1 to 1 ratios (for example, one minute of high intensity followed by one minute of low intensity) or 2 to 1 ratios (such as one minute of high intensity and then 30 seconds of low intensity).

The benefits are amazing! Intervals help you burn extra calories because your muscles are working harder. Intervals also improve your ability to tolerate higher intensities, therefore increasing your cardiovascular fitness. Finally, because they work both your aerobic and anaerobic systems, intervals do a great job of helping you retain muscle while losing fat. The more muscle mass you have, the more calories you burn, and the leaner you get - in all areas of your body, including your stomach, hips, and butt.

Remember: Do not interval train every day. Make sure you do intervals on nonconsecutive days because your body needs a minimum of 48 hours rest between interval sessions to repair, replenish, and rebuild (much like resting 48 hours between weight lifting sessions). You’ll reap all of interval training’s benefits with just two to three 30-minute sessions weekly.

During the high intensity part of your interval, you should feel you’re working hard. “Hard” means: “I’m almost at the point where I can’t talk. I can do this for another minute or two, but then I need a short rest.”

During the low intensity part of your interval, you should feel that you’re working at an easy level. “Easy” means: “I’m exercising comfortably and resting from the high intensity interval. I could go at this pace for a long time.”

During the steady state part of your session (the 3- to 5-minute periods between your “hard” and “easy” intervals), you should feel you’re working somewhat hard. “Somewhat hard” means: “I can tell I’m really getting a workout, but I can still carry on a conversation.”

Here is a typical interval training routine:

5-Minute Warm-Up (such as slow walking)

3-5 Minutes of Steady State (somewhat hard exercise)

1st Set Intervals (3 repetitions of hard to easy exercise)

3-5 Minutes of Steady State (somewhat hard exercise)

2nd Set Intervals (3 repetitions of hard to easy exercise)

3-5 Minutes of Steady State (somewhat hard exercise)

3rd Set Intervals (3 repetitions of hard to easy exercise)

5-Minute Cool-Down