HIIT should burn fat, not muscle! The treadmill is a favorite for HIIT workouts.

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 may mean a speed in excess of 10 mph. Some machines go up to 15 mph.

If your machine only goes up to 10 mph, you may need to add a slight incline (depending on your cardio condition) to achieve the level at which you become depleted within 30 seconds or less.

Pay attention to the machine’s clock. If you can persist longer than 30 seconds, increase speed and/or raise incline for subsequent work intervals.

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

DO NOT HOLD ONTO THE TREADMILL.

Some treadmills take a while to get up to the desired setting. So if your recovery intervals are done at a zero incline, your intensity intervals should not begin right after you plug in the 15 percent.

They should begin only when the machine has raised all the way to the 15 percent angle.

Also, when plugging in a high speed, make sure the tread belt has reached that speed before you begin counting seconds on your sprint.

The 30-seconds-or-less concept can be applied to the elliptical, stationary bike and other cardio equipment.

Find the setting that smokes you out within this time frame. You should not be able to talk after an intensity interval. You should be gasping for air.

Don’t just go for 30 seconds because that’s the protocol. That 30 seconds (or less) should be the longest your body can last.

As 30 seconds approaches, you should practically feel like you’re going to fall off the machine. Keep your hands off the elliptical during the work interval.

The hands-off rule also applies to the revolving staircase. I’ve seen people “trotting” the steps at a fast setting—but while clinging to the rails. This is cheating and worthless for stripping off fat.

Pretend the steps are outdoor bleacher steps and keep those hands off the machine! Outdoor HIIT sessions can be done on an track, a street, up bleachers, or up hiking trail hills.

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.