The most effective way to sizzle off fat is with high intensity interval training (HIIT). The end of each brief interval feels as though you just outran a lion nipping at your feet.

Myth: In order for cardio to melt fat, the motion must be done continually, with no interruptions.

Fact:  Though a 24-minute HIIT running session may involve only four minutes of actual exertion (divided into eight “work intervals”) and 20 minutes of casual walking, HIIT is far superior to 60 minutes of steady-state (sustained pace) aerobics.

Myth: HIIT increases injury risk.

Fact: Because the time spent during actual exertion is literally only seconds, there is far less impact to the joints.

Myth: You must be fit to do HIIT.

Fact: Even a 300-pound smoker can do HIIT. You may be too out of shape to run, but this doesn’t mean you’re too out of shape to deliver your best, all-out effort: HIIT can be done on the elliptical trainer, stationary bike, and even in the form of walking.

HIIT is sometimes called “hormonal exercise,” because it triggers release of human growth hormone and testosterone, which accelerate fat loss.

A study in a 2002 issue of the Journal of Applied Physiology reported that high-intensity sprinting produced 96 percent more growth hormone when tested against the effects of jogging at a significantly slower pace.

HIIT involves alternating very short-duration doses of power-based, all-out efforts, with one to several minutes of casual effort (the “recovery interval”), over a 20- to 30-minute session.

Just two HIIT sessions per week will raise resting metabolic rate and dramatically increase cardiovascular fitness.

Don’t be fooled by the “fat-burning zone” diagrams on cardio equipment. Though a higher percentage of fat is burned during fixed-pace moderate aerobics, more total fat is burned via HIIT, because HIIT burns far more calories to begin with.

Plus, only HIIT results in an after-burn. “The real fat-burning zone occurs at levels exceeding 85% of max heart rate where the body becomes anaerobic,” says Jade Teta, an exercise physiologist, and strength and conditioning specialist, from Winston-Salem, NC.

“It is at this intensity where the body mobilizes hormones to create a leaner, faster, stronger physique. This hormonal effect is responsible for the increased caloric consumption induced by excess post-exercise oxygen consumption.

“While aerobic exercise is useful, it is unable to produce the same result because the intensity needed to trigger the EPOC phenomenon is never reached.”

In plain English, your body takes such a thrashing during HIIT, that it’s forced to ransack fat reserves for the energy it needs to recuperate from the HIIT session – even while you sleep!

Example: After a warm-up (which should include several sub-intense work intervals), a fit person runs eight, 30-second intervals at 12 mph on a treadmill (no holding on.)

The slow-walk recovery intervals last between two and three minutes. If only a 7 mph run wipes you out within 30 seconds, then so be it. If you’re very heavy, then perhaps your maximum speed is just 5 mph. It’s all relative.

This principle can be applied to other cardio equipment or outdoor running (your fastest sprint), or hill-stampeding. You must be depleted within about 30 seconds, such that one second longer is unthinkable. Talking is nearly impossible after each work interval.

A trained body from consistent HIIT sessions will derive about 70 percent of its daily requirement for fuel, from body fat, and 30 percent from stored sugar: a 70/30 ratio.

On the other hand, the person who adheres only to steady-state may burn at only a 50/50 ratio, or even a 30/70 ratio, during everyday living. Thus, you can clearly see the superiority that HIIT has over steady-state “fat-burning zone” aerobics.