By Dr. Bruce Erik Hedendal

For decades, health educators have stressed jogging, cycling and mat-prancing jazzercise as key ingredients in a weight-loss regimen. But recent studies show that there's a better way to stay fit and energetic. Our fitness expert, Dr. Bruce Erik Hedendal, explains it all.

Think back to your days as a kid, running around, bouncing off the walls, as if driven by some inexhaustible power supply. Remember that "alive" feelingthat exhilarating rushimmediately following an all-out bike race or sprint down the block? Believe it or not, that high-intensity play may have been the best exercise you've ever had.

In fact, high-intensity (HI), short-duration exercise has been proven to be better than long periods of low-impact aerobic activity when it comes to strength and weight loss. But this is no new phenomenonhumans have been sprinting to keep fit (and alive) for thousands of years.

To fully understand this concept, you have to think like a caveman (which comes far too easily for many of us). As a caveman, your survival depends on your ability to run faster and hit harder than your dinner (as well as the beastie who's trying to make you their dinner). Short bursts of activity. Quick, all-out sprints. But not very much long-distance jogging (unless you're just trying to wear out your prey). As a caveman, you're getting a serious non-stop HI workout. It's easy to see how the human body has been biologically programmed to get the most out of HI exercise through eons of survival instinct.

So, now that our survival no longer includes outrunning man-eating tigers (unless you happen to work in Vegas), is HI exercise still the way to go? Absolutely.

For decades, scientists have known that short-duration anaerobic exercise improves athletic performance, and that the release of human growth hormone (hGH), testosterone and other bone-building, body-enhancing hormones are directly related to the intensitynot the durationof exercise. (1) When charged with these anabolic hormones, our bodies build more muscle mass, which dramatically improves weight loss, resulting in slimmer, more-toned physique. Anabolic hormones are also known to enhance skin and hair, improve sleeping habits, strengthen immune response and improve sexual performance.

Ready to throw out your NordicTrack and go full-time HI? Wait a second. While low-intensity, long-endurance aerobic exercise may not be the gold-standard fat-burner we've always thought, it's important to remember that cardiovascular activity is vital to circulatory health, preventing heart disease and increasing lung capacity, and should be incorporated as a part of your normal exercise regimen. Stop. Read that sentence again. I'm not saying that aerobic exercise is bad. On the contrary, it's very important. But it shouldn't be the primary component in your weight-loss regimen. You just have to find the best balance between low-intensity aerobic and HI anaerobic to achieve the best results.

Making it happen

Working a HI component into your regular exercise regimen is surprisingly simple. There are two elements to a HI exercise regimen: interval sprints and resistance training, and the key to both is the anaerobic characteristic of the exercise. You'll know when you're doing a HI exercise right when you can't breathe through your nose or talk easily. And because anaerobic training causes rapid muscle fatigue, your interval sprinting workouts will rarely last more than 20 minutes.

As you push yourself through your workout, anabolic hormones are released into the system, and you will feel energized and powerfulso powerful, in fact, that you may have to force yourself to resist the temptation to keep going through more and more reps. It's important that you do no more than the recommended number of repetitions per workout, and you must make sure your body gets a full two-minute rest period between each repetition.

As with any new exercise regimen, proceed incrementally. Tune in and listen to your body, it will tell you where your limits are. And remember, it has been demonstrated that you can experience strength and muscle gains of up to 200 percent with resistance training, and increases of hGH and testosterone in adults even beyond 70. (2, 3)

Sprints

There is no need to be scared by the word "sprint." Any exercise done with short bursts of extreme intensity qualifies as a sprint (remember your days as a caveman) Examples of HI sprinting include running, biking, rowing and swimming, or even squats and jumping rope. To get started, set your own baseline for a sprint, and then push yourself as hard and as fast as you can. Rest completely between repetitions and repeat the process.

Warm-up slowly by either powerwalking or jogging (best done on grass or a quality track). If you're older, work up to a real all-out sprint (90% or more of full speed) over several sessions. Progress to eight repetitions per workout over several sessions. The key to success is putting out high-intensity bursts of speed lasting 15 to 60 seconds (depending on the sport), with two minutes of recovery between intervals. For running, 60 to 100 meters is a good distance to start. If you cycle or swim, you will need to go between 30 to 45 seconds to get the required high level of intensity to get the hGH-releasing effect. Be sure to stretch after your workout and go home feeling powerful from the natural "HI."

Resistance training

Work in resistance/weight training one to three times weekly, alternating with one to three interval sprints weekly. It's best to work with a trainer to get the form right for each exercise, and to determine which exercises to include for each muscle group. Determine the weight to use for each exercise and keep a written log.

In HI weight training, muscle failure means success. It's your only way of knowing when you've reached the hGH-releasing benchmark and achieved the most anabolic stimulus possible from that exercise.

The human body is a moving, changing machine. Evolutionary heritage has trained our biology to extract the optimum benefit from different types of exercisewhether short, HI training or extended aerobic activity. High-intensity exercise offers much more than just a better body, it unlocks a more alert, peaceful mind, increased physical and mental energy, and a more-satisfying sex life. The research is in and it's conclusive. Challenge yourself to live the "HI" life, and discover the fit, sexy youno matter how old you are.

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