You don't have to be a distance runner or athlete to benefit from interval training. Whatever your level of fitness, age or choice of exercise, interval training energizes, slims you down and can boost your fitness to astonishing levels. Best of all, you won't pound the pavement for hours on end or spend your life (and your bankroll) in the gym. Twenty minutes, three or four times a week, is all it takes to get in the best shape of your life.

Picture a sprinter exploding off the starting blocks, flying all out to the finish, then coasting. Imagine pushing yourself to your limit, slowing to catch your breath then hitting your max again - that's interval training. An interval is a space between things. If you're a runner, you go into an all out sprint, then slow to an easier pace to recuperate for your next sprint. If you're a walker, you speed up then slow down at intervals. No matter your sport or exercise, crank up the pace until you hit your max heart rate, hold for a short time, then ease off to a recovery interval. It's that simple.

Before you even begin, visit your family doc for a stress test. You'll have a clean bill of health and you'll have your max heart rate as an accurate guideline. Take it easy at first. Ease into your interval training with short bursts and longer recovery. Listen to your body. As you move along in the program, you'll be able to increase the intensity of your sprints while shortening your recovery intervals.

Why do intervals in the first place? When you use resistance training to build strength, you challenge your muscles with heavier weights and they respond by growing stronger. Your heart is a muscle too, probably the most important one in your body. Intervals work to strengthen your heart muscle. When you use whole body exercises like sprinting or even walking, you'll work nearly every muscle you own. Just compare the physique of a sprinter and a long distance runner and you'll see what I mean.

Traditional cardio is a steady exercise that builds efficiency and endurance so you can do more with less. Sure aerobics burns fat, but the burn stops when you stop. Intensity training takes aerobics to a whole new level because it speeds your metabolism and you'll burn fat for hours after you finish exercising.

Most important though, intensity training teaches your body (especially your heart) to meet sudden challenges. You'll have the 'juice' when you need it for peak performance. Without that extra reserve, your next spotter might be wearing a white coat or if you're lucky, a stethoscope.

Photo by: keyseeker at morguefile.com