Even after years in the spotlight, high-intensity interval training (HIIT) hasn't lost its luster. This fast-paced training method continues to dominate the fitness scene—and for good reason: When it comes to weight-loss, there's no better exercise option than HIIT. So, if you can't get the scale to budge in your favor, consider jumping on the HIIT bandwagon.
In general, HIIT is characterized by structured work/rest periods, where you alternate bursts of all-out activity performed at 90 to 100 percent of your maximum heart rate with a period of recovery to bring your heart rate back down. The intensity of HIIT sessions can also be measured using the rated perceived exertion (RPE) scale, or how hard you feel like your body is working. On a zero-to-10 physical exertion scale, where zero is the equivalent of sitting on the couch and 10 is an all-out sprint, HIIT calls for bursts of activity performed at a nine or a 10.
Chances are, you're familiar with one of the most widely-publicized forms of HIIT known as the Tabata protocol. Named after Japanese researcher Dr. Izumi Tabata, the author of a groundbreaking study on the benefits of HIIT, the Tabata protocol is famous for its ability to induce physical exhaustion and improve both aerobic and anaerobic capacity with a mere four minutes of actual work. With this method, you complete eight 20-second bouts of intense exercise (think: sprints, burpees or dumbbell thrusters), taking only 10 seconds of rest between bouts.
Read more: How to Do HIIT Treadmill Workouts
The Weight-Loss Magic of HIIT
In the original 1996 Tabata study, researchers set out to discover if high-intensity exercise could improve both aerobic and anaerobic capacity. (It can.) Since then, other researchers have stepped on the scene to see if HIIT also offered weight-loss benefits. (It does.)
For example, researchers from the University of New South Wales discovered that women who performed three HIIT sessions per week, alternating eight-second sprints with 12 seconds of recovery for 20 minutes each session, lost as much as 7.3 pounds by the end of 15 weeks. Meanwhile, women who performed 40 minutes of steady-state exercise three times per week actually gained as much as 2.7 pounds over the same period of time.
A more recent study in Journal of Diabetes Research found that 12 weeks of moderate-intensity and high-intensity aerobic training were equally effective in reducing abdominal fat in young women, leading researchers to suggest that, thanks to its time efficiency, HIIT is a superior method for weight-loss.
So, why is HIIT such an effective strategy for weight-loss? There are a few reasons:
First, intense exercise demands more energy, as your body has to produce higher levels of adenosine triphosphate (ATP) to fuel your muscles during your exercise session. And even once you've called it quits, your body will continue burning calories like crazy. This is known as excess post-exercise oxygen consumption (EPOC), or the afterburn effect.
A good way to think of EPOC is to compare your body to a car engine: An engine will stay warm for a time after you shut off the ignition. Similarly, your body stay warm – and burning calories – as your systems work to cool you down post-workout. And since HIIT often incorporates high-impact strength exercises, it tends to break down muscle tissue, which then has to be rebuilt. As a result, you burn even more calories during the recovery process.
How to Incorporate HIIT Into Your Routine
HIIT comes in a variety of flavors, which means there are countless ways to do it. So long as you're continuously shifting between periods of high-intensity and low-intensity, you're doing some version of HIIT. This could mean walking on a treadmill at a challenging pace and incline for 60 seconds, and then bringing the intensity back down to recover for 60 seconds. Or, you could cycle through four different strength exercises — such as, jump squats, pushups, bent-over rows and straight-legged sit-ups. Perform as many repetitions as possible in 30 seconds, pause for a 30-second rest, and then move on to the next exercise in the series.
During HIIT sessions, aim to work at 90 to 100 percent of your maximum heart rate. To find your maximum heart rate, subtract your age from 220, then multiply that number by 0.17. Or, use the RPE scale to gauge your intensity, shooting for a nine or a 10.
Just keep in mind: In the case of HIIT, more is not better. Because it's such an intense mode of exercise, you'll want to limit sessions to two or three times per week to reduce your risk injury and burnout.
Read more: HIIT Exercises at Home
Don't Forget Moderate-Intensity Cardio
And while HIIT is superior for weight-loss, don't think you have license to cut moderate-intensity activities from your weekly routine.
Moderate-intensity exercise plays a critical role in maintaining a healthy lifestyle. Running, for example, provides a host of good-for-you benefits, including quality sleep and a healthy heart. In fact, runners have a 45 percent lower risk of dying from heart disease than non-runners, according to one long-term study in Journal of the American College of Cardiology.
To keep your ticker strong, the American Heart Association recommends performing a minimum of 30 minutes of moderate-intensity cardio five days per week. Great options include walking, swimming, biking or jogging. So, in addition to your HIIT sessions, make sure you're including a hearty dose of good old-fashioned cardio in your weekly routine.