Whether you’re new to the gym or you’ve racked up six Trifectas, chances are, you’re heard of high-intensity interval training—AKA HIIT. The original basis for HIIT workouts was Tabata, a workout created by Japanese sports doctor Izumi Tabata in 1996 that consists of eight intervals performed in four minutes. The benefits of HIIT are numerous, which is why you can now find all kinds of variations on it. But each HIIT workout, whether you’re on a treadmill, a bike, or just using bodyweight, includes fast, intense bursts of exercise followed by short, sometimes active, recovery periods. And that set-up has been proven many times over to be seriously effective at boosting your health and your fitness levels. Here’s how.
1. It burns tons of calories.
You can't hype up the benefits of HIIT without talking about its calorie-scorching capabilities. For people who want to be efficient in the gym (or don’t have a ton of time to spend there), there’s really no more effective option than HIIT: HIIT burns 25 to 30 percent more calories than resistance training, cycling, and treadmill running in the same amount of time, according to research published in the The Journal of Strength and Conditioning Research.
2. It keeps burning calories.
HIIT is famous for its afterburn effect (scientifically known as excess post-exercise oxygen consumption, or EPOC). That means that even after you finish your workout, your body keeps burning calories as it goes through all the necessary recovery mechanisms to bring itself back to normal. In addition to its initial wins on the calorie fronts, one of the major benefits of HIIT is that its afterburn effect can last up to 24 hours, according to a study out of Colorado State University (although most of the calorie burning was seen during and just after exercise). The afterburn effect is important because it revs up your metabolism—and HIIT has been shown to increase your metabolism post-exercise even more than jogging and resistance training.
3. It burns more fat.
HIIT’s effect on fat metabolism have also been linked to weight loss in the Spanish journal Revista Brasileira de Medicina do Esporte. When you perform high-intensity intervals, your body starts burning fat for energy instead of carbs, according to research published in the journal Sports Medicine Open. Just doing three HIIT workouts for 20 minutes each helped participants lose 4.4-pounds of body fat in 12 weeks, a study in the Journal of Obesity found.
4. It helps your heart.
Tabata workouts (remember, the OG form of HIIT) make your heart workout harder, which boosts your cardiovascular strength, according to a study by the American Council on Exercise. And for people who are already suffering from heart issues, HIIT may actually more than double cardio fitness improvements compared to moderate-intensity workouts, reports the British Journal of Sports Medicine.
5. It helps stabilize your blood sugar levels.
Maintaining your blood sugar (or glucose) levels is important for feeling your best—if it’s too low, you’ll experience cravings and hanger; too high, and your body will release too much insulin, which can eventually lead to things like high blood pressure, obesity, and heart disease. A review of 50 studies found that HIIT improves insulin resistance more than steady-state exercise.
6. It lowers your blood pressure.
High blood pressure is seriously bad news—it can lead to heart attacks, heart disease, and heart failure, as well as kidney disease or failure and strokes. But doing 20 minutes of HIIT workouts three times a week for eight weeks decreased blood pressure as much as continuously exercising for 30 minutes a day four times a week over the same amount of time, according to a study published in the journal The Physician and Sportsmedicine. FYI: That means you’d spend half the amount of time in the gym if you were doing HIIT workouts.
7. It increases your oxygen consumption.
Oxygen consumption is important because it’s what establishes the limits of your endurance. And the more endurance you have, the stronger you’ll feel on the race course—which is why athletes are all about the benefits of HIIT. Just 20 minutes of HIIT four days a week can improve oxygen consumption by nine percent over five weeks, which is almost as much of an increase as 40 minutes of continuous cycling four days a week, according to a study published in PLoS One—except HIIT workouts are way less time-intensive.