HIIT is a training protocol that involves periods of maximum effort followed by active rest. For example, you could sprint as fast as you can for 60 seconds, followed by walking for 60 seconds, then repeat. Such a workout could be completed in 30 minutes or less.
Advocates of HIIT, such as the good people at Simply Shredded, argue that HIIT, as opposed to steady state cardio, is a better way to burn calories and reduce body fat. They highlight some of the research that has led them to this conclusion:
"One of the earliest studies, done by researchers at Laval University (Ste-Foy, Quebec, Canada), kept it basic, using two groups in a months-long experiment. One group followed a 15-week program using HIIT while the other performed only steady-state cardio for 20 weeks. Proponents of steady-state training were pleased to hear that those subjects burned 15,000 calories more than their HIIT counterparts. Those who followed the HIIT program, however, lost significantly more body fat. A 2001 study from East Tennessee State University (Johnson City) demonstrated similar findings with subjects who followed an eight-week HIIT program. Again, HIIT proved to be the better fat-burner–subjects dropped 2% body fat over the course of the experiment. Meanwhile, those who plodded through the eight weeks on a steady-state program lost no body fat."
Another advantage of HIIT, according to Jerry Yuhara, CPT, PES of Breakthrough Personal Training in Palo Alto, CA is that there is more of an anabolic, or building, effect on cells. With HIIT, there is a bigger increase in testosterone and growth hormone than in steady state cardio. These anabolic hormones promote fat loss and muscle gain, which results in the leaner look we are seeking when we do cardio.
Below is an example of a HIIT routine, created by Simply Shredded. If you are a beginner, you can modify the time, doing 30 seconds for each sprint. Try this at least 3x a week and "fine tune your fat fighting machine.
Warmup 2-3 min.
Walk 1 min.
Sprint 1 min.
Repeat walk/sprint cycle 12 times.
Cool-down 2-3 min.
TOTAL: 28-30 minutes
Despite this and other research showing the benefits of HIIT over steady state cardio, everyone is not sold on it as a superior method of fat loss. Belgium trainer Mehdi Hadim, (pictured left) "The New Muscles from Brussels", points out that in 30 minutes of HIIT, he burns 324 calories vs. 481 calories during 45 minutes of steady state cardio.
Since weight loss is a simple mathematical formula--burn more calories, lose more weight--steady state cardio proves superior in this aspect. While there is no disputing this simple fact, there is a bigger picture to consider.
Sustained aerobic activity leads to an increase in the hormone cortisol, a catabolic agent that can wreak havoc on your body. Excessive cortisol breaks down muscle tissue and slows down your metabolism as a result of this muscle loss. Your weight loss comes at a steep price.
This destructive nature of steady state cardio is why weight training is superior to cardiovascular training for fat loss. This is despite the fact that you burn more calories in one hour of cardiovascular training than you do in one hour of weight training.
Losing fat and building lean muscle tissue are about altering your body composition via strength training and HIIT. Are there exceptions? Of course there are. However, in general, HIIT is the way to go to get the leaner body you want and deserve.
What are you waiting for?