High-Intensity Interval Training (HIIT) has been around the athletic world since the 1970s. Its original purpose was to help competitive athletes, both Olympic and professional, increase their performances by improving aerobic fitness, glucose metabolism, and fat-burning (fuel) ability. Now, however, it’s gaining popularity among the I-work-out-to-prevent/get-rid-of-the-tire-around-my-gut set. HIIT is perceived to be a more efficient cardio workout. Done properly, HIIT is a better fat burner, preserves muscle mass, improves physiological efficiency, and takes less time to complete an entire session than regular cardio. What’s not to love?
What HIIT Training Is and How it Works
HIIT is alternating all-out exercises, about 85+% of maximum effort, like sprinting or bicycling hard, for 15 to 60 seconds, followed by an active rest period of lower-intensity exercise, about 50% of maximum effort, like walking or bicycling easily, for about 60 to 15 seconds. As you become more fit, you lengthen the amount of time spent in high-intensity exercises and shorten the amount of time spent in active rest. You always, though, have both intensities of exercise in your HIIT workout.
HIIT is not the same as interval cardio training. Interval cardio alternates between 65% and 85% of your maximum heart rate. By contrast, HIIT demands maximum effort for the high-intensity bits. Eighty-five percent effort is a minimum number and it’s not easy to maintain. As a consequence, most regular exercisers don’t get to and maintain a high enough intensity to reap the fat-burning benefits of HIIT.
Things to Keep in Mind
OK, let’s define “high intensity.” For a proper HIIT workout, we’re talking about at least 85% of maximum effort for the high-intensity intervals. Some coaches push their athletes even harder than that. So, it’s critically important to know your body can handle that kind of intensity. Of all the exercise programs out there, HIIT is the one that begs the hardest for checking with a doctor before starting. No one wants to suffer a coronary, or stroke out doing something that is supposed to improve physical fitness, not kill them.
Recovery time between HIIT workouts is longer than conventional cardio workouts. The American Council on Exercise (ACE) and the American College of Sports Medicine (ACSM) both recommend no more than two HIIT workouts a week. Because the exercise intensity is so high, the body needs more time to recover, to prevent musculoskeletal injuries and joint problems from cropping up.
If you want to burn more fat, preserve muscle mass, increase the efficiency of your metabolism and are willing and able to work REALLY hard, HIIT may be the right kind of cardio for you.