Commander's Fit Tip: Burn, baby, burn

ARNOLD AIR FORCE BASE, Tenn. -- We get this question all the time: "What's the right workout intensity to lose weight?"

Like just about every other question about the human body, the answer is "It depends!" But what it depends on may not be what you think.

Much of the advice on workout intensity and weight loss focuses on the metabolic processes that occur during a workout. But what about after the workout? What about sustainability? What about injury risk? All these factors must weigh into the decision of just how hard to work out, assuming of course, that pure weight loss is your goal. My guess is, that's rarely the case.

Most of the workout equipment at the gym will display your heart rate while you exercise, and many include illustrations that recommend a target heart rate based on your "goal." It's common to see a "aerobic zone" or "fat burn zone" label on these machines.

These charts will lead you to believe that if weight loss is your goal, you should keep your exercise intensity on the lower end of the scale, working on the science that the intensity of your workout will influence what "fuel" your body will choose to burn during the workout.

The science is sound, and it's pretty clear that intense workouts will inhibit the enzymatic reactions that are precursors to burning fat. But that's only part of the "fat burning" equation. Low-intensity workouts are much more sustainable, easier to tolerate, and generally result in fewer aches, pains, and injuries. All these factors make a low-intensity workout an attractive option. But there are trade-offs.

Perhaps the biggest drawback is time. Low-intensity workouts burn calories more slowly, and this reduced rate can make weight loss seem like a glacial process.

Think of it this way. It takes nearly the same amount of work (and calories) to walk a mile and jog a mile. As the speed increases, the burn rate will go up some, but at the lower end, a mile is about 100 calories. Walking that mile will take over 20 minutes, while a jog might take only 10 or 12. Since you need to burn 3,500 calories to lose a pound it will take much longer if you try to "walk it off." Plus, one of the greatest benefits of a vigorous workout is that you will steadily increase the "burn rate" your body needs when you are not working out. And you spend much more time NOT working out, so increasing that resting burn rate is a big factor in weight loss success.

But most importantly, pure weight loss is likely not your goal. Your goals probably include increased aerobic fitness, increased strength, or if you are struggling with your PT test, improving that score is probably part of the picture. If so, you'll be disappointed with your results if you limit your routines to the low end of the scales. So what's the answer?

Diversify, of course! One of the most successful routines is the "hard day, light day" regimen, and the low intensity, "fat burning" workout is a good option for the "light day" events. That doesn't imply that "hard day" has to be a totally exhaustive routine. On the contrary, you just need to challenge yourself enough to induce an adaptation.

For most, all you need to do is get just beyond where you can talk. If you crank it up to where you can just-get-one-word-out-at-a-time without gasping, you should be close.

No matter what your goal, it's unlikely a single regimen will work. Keep mixing it up, and give "light day, hard day" a try.