You no longer have to avoid doing aerobic exercise in the name of preserving the muscle you’ve worked so hard to build.

On the other hand, physique or bodybuilders want to burn as much fat as possible to knock their body fat percentage down to competition or photoshoot range.

Often they feel they must take a little muscle loss in exchange for the fat burning required to get “cut.” There is a way to solve this problem: high intensity interval training.

For example, find the setting on a treadmill that you can maintain a run on for less than 30 seconds before being forced to quit from mechanical failure.

Mechanical failure is when your legs literally can’t perform a second longer, such as in your fastest sprint. This will mean a speed in excess of 10 mph on a level course.

Pay attention to the machine’s clock. If you can persist longer than 30 seconds, increase speed and/or add an incline for subsequent work intervals. Don’t hold onto the machine; this will suppress fat-burning.

You might also want to try HIIT walking, using a 15 percent incline and a high walking speed such as 4 or 4.5 mph.

Again, holding on is barred if you want maximum fat-burning. Do HIIT sessions for only 20 minutes (excluding warm-up and cool-down) to guard against muscle loss.

What about long, slow cardio?

Lengthy steady state cardio keeps you safe from fat storage and muscle burning. Long slow aerobics do not unleash the hormone cortisol, which can promote fat storage and muscle breakdown.

HIIT does unleash cortisol, but HIIT also unleashes growth hormone and testosterone, which cancel out the cortisol!

The advantage of HIIT is that it saves tremendous time: 20 minutes will burn up a lot of fat.

To avoid muscle loss and burn a lot of fat, do HIIT cardio, or if you’re not up to the grueling nature, do long, slow aerobics, such as a one-hour 4 mph jog or a light step class.

Avoid moderate cardio! Moderate is when there’s heavy panting, but you can still sustain the effort: a long duration but challenging cardio rather than “slow.”

This type of activity releases cortisol, which, again, can lead to fat storage and muscle loss.

However, moderate effort fails to unleash the opposing growth hormone and testosterone! Stick to HIIT or long duration aerobics to burn fat and save muscle.

Lorra Garrick is a former personal trainer certified through the American Council on Exercise. At Bally Total Fitness she trained women and men of all ages for fat loss, muscle building, fitness and improved health.