High-Intensity Interval Training, or HIIT, is increasingly popular among fitness enthusiasts, and for good reason. HIIT workouts can burn a significant amount of calories, in a relatively short amount of time. Some sources promise as much as a 500+ calorie burn per 30-minute session. But how does HIIT work? And how do those calories melt away so quickly? Read on for more information about this high-intensity, high-energy, highly fun form of results-producing exercise.
HIIT is a variation of interval training that involves short bursts of rigorous cardio, followed by intermittent rest periods. You can incorporate any type of cardio into a HIIT workout, and easily adapt it to your endurance and strength level.
As you can probably tell from the name, HIIT workouts are challenging. But people love them because although they’re difficult, they help burn calories in a short amount of time. Many recent studies have determined that HIIT workouts are one of the most efficient ways to burn calories fast, even more so than steady-state cardio like running.
HIIT workouts also don’t take very long but provide a huge calorie-burning pay-off. Personal trainer Pete McCall tells Health Magazine that longer is not always better, especially when it comes to HIIT workouts — aim for a duration of 15 to 30 minutes, otherwise, you’ll overwork yourself.
If you’re still not convinced, you will be when we tell you that you continue burning calories for about 3 to 16 hours after HIIT, due to a phenomenon called excess post-exercise oxygen consumption (EPOC). The more intense the workout, the greater your body’s oxygen debt is — as a result, you’re consuming oxygen at an elevated rate, which means you’re still expending energy and burning calories. HIIT’s effects on the EPOC stage are greater than that of running or cycling at a steady pace because the intensity of a HIIT workout raises your metabolic rate.
In addition to consuming oxygen, your body uses energy replenishing its depleted resources (e.g. ATP, glycogen, lactate), reoxygenating the blood, returning to a normal temperature, and returning to a regular heart and breathing rate.
The differing effects of steady-state cardio versus HIIT are primarily a result of how the body uses oxygen during those exercises. Traditional cardio (e.g. running, cycling) is aerobic (literally “with oxygen”), meaning your body can provide enough oxygen to sustain your exercise. Anaerobic (“without oxygen”) exercise, on the other hand, is so intense that it uses up all of your body’s oxygen, leading to the production of lactate (via Healthline). With a greater oxygen debt from an anaerobic workout like HIIT comes a more intense EPOC state, and more calories burned. This is not to say that aerobic exercise is bad — anaerobic exercise tires you out faster, so it’s beneficial to incorporate some aerobic exercise into your fitness routine on alternate days to balance it out.
If you’re a busy person and don’t have time for an extended gym session, or are simply trying to spice up your fitness routine, look no further than high-intensity interval training to burn calories efficiently.
The exact number of calories burned depends on the individual, the intensity and length of the workout, and other factors. This calorie calculator can help you determine the exact amount of calories you’ll burn from a HIIT workout, except it’s only based on your weight and the length of the workout. It also doesn’t account for the calories burned during the EPOC period. There are other factors that make it difficult to make an exact determination, especially the intensity of your workout and your experience level.
That said, many experts agree that HIIT workouts are more efficient (in terms of calories per minute) at burning calories than other types of workouts. In fact, a 2015 study from the Journal of Strength and Conditioning Research found that HIIT workouts burned up to 25 to 30 percent more calories than a steady-state workout like running.
Harvard Medical School published a guide to the average amount of calories burned in a period of 30 minutes, based on activity performed. Here are some highlights that demonstrate the efficacy of HIIT versus steady-state exercise:
Cycling for 30 minutes at a steady pace, based on Harvard’s guide:
Versus a 30 minute HIIT cycling session:
*Calories burned from a HIIT workout calculated using the 25 to 30 percent increase, as determined by the 2015 study.
If HIIT seems like it could be your thing, and you’re looking to burn calories fast, try this simple, 30-minute workout you can do anywhere, no equipment needed:
Repeat this set of 6 exercises 4 times, allowing for a 60 second rest period after each circuit is completed.
Jog in place for 45 seconds with your arms at the small of your back, trying to kick your butt with your heels
Rest for 15 seconds.
Begin standing with your feet shoulder-width apart, core engaged. Using your arms for balance, launch yourself to lightly land with your left foot behind and to the right of your right foot, like a lunge. Repeat this on either side for 45 seconds.
Rest for 15 seconds.
Alternate between sides, bring your leg behind you until both knees are at 90 degrees. Return to standing and switch sides. Do this for 45 seconds.
Rest for 15 seconds.
With your hands clasped under your shoulders and toes extended, hold your body in a rigid plank position for 45 seconds. See other types of core exercises.
Rest for 15 seconds.
Start sitting on the floor with your toes off the ground. With your hands clasped, bring your hands to the right and left sides of your body, as if you’re holding a ball.
Rest for 60 seconds, then repeat this circuit.
HIIT workouts can consist of very few exercises, such as the one listed above, at high intensity for a short period of time. Thanks to HIIT’s increasing popularity, it’s simple to look it up online and find hundreds of different workouts. Don’t be fooled, however — HIIT is very challenging (hence: “high-intensity”), and won’t be easy your first time. But if you power through a difficult HIIT workout, you can sit on the couch later knowing that you’re still burning calories.
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