boosts your heart rate to 80-90% of maximum capacity, followed by a steady pace that allows your heart rate to fall back to normal—helps to more efficiently burn both carbohydrates and fat. Even after you are done, it is not uncommon for your metabolism to remain elevated for several hours-- resulting in sustained fat loss.

For weight training, this same approach can be applied by training multiple muscle groups per workout with high repetitions (12-15) and shorter rest periods (60-120 seconds). Interval training pushes the body to it's limit, so it is important to wait at least 24-48 hours in between each workout.

Interval training has been adopted by numerous athletes to boost muscular endurance, and increase performance by training the aerobic and anaerobic systems. Anaerobic means without oxygen, and during a period of intense exercise, this system uses carbohydrates stored in the muscles (glycogen) for fuel. Once the exercise is complete, the body to goes in to "oxygen debt", making the lungs and heart work harder to recover. This causes the aerobic system—or the system you use when at rest—to burn more overall calories.

According to the American College of Sports Medicine, short bursts of high intensity exercise are far more efficient in burning fat, and overall calories than longer periods of repetitive exercise. One example of this can by observed by comparing the training of sprinters to marathon runners. While marathon runners undoubtedly run longer distances, their bodies tend to hold more body fat than relatively muscular sprinters—who run shorter

distances at higher intensities. This is due to a difference in muscle tissue which burns fat and is created by forcing the body to adapt to different conditions.

But you don't need to be a world-class athlete to take advantage. Intensity can be applied to virtually any goal based on the following guidelines:

Cardio:

1) Warm up with 5-10 minutes of slow, steady walking on a treadmill or elliptical.

2) Cardio intervals should last between 30-120 seconds followed by rest periods of equal length.

3) Bring your heart rate down to around 100-120 beats per minute during the rest interval.

4) To improve, increase intensity or duration of intervals, but not both at the same time

5) Allow between 24-48 hours between each session

Strength Training:

1) Stretch out before your workout.

2) Each workout should include exercises that work the upper and lower body.

3) Pick exercises which work multiple muscle groups (such as squats, bench press, dead lifts, and pushups).

4) Choose a relatively high volume of sets (15-20) of 12-20 repetitions each.

5) Rest periods should last 90-120 seconds.

6) Workouts should last no longer than 45 minutes to an hour, and should only be done 2-3 times per week.

Chris Kelly is a NASM Certified Fitness Trainer, nutritionist, and editor of the Spotter, a webzine focusing on healthy living in major cities. For more articles and live support from members and experts, check out http://www.thespotter.net (yes, it is free).