It sounds too good to be true: To get fit more quickly, spend less time working out.
But high-intensity interval training, which alternates short bouts of intense exercise with active recovery periods, has been found to be as effective as longer bouts of less strenuous activity — in much less time.
High-intensity interval training, commonly called HIIT (pronounced “hit”), can fast-track your efforts to get fit, burn fat, decrease the risk of diabetes and heart disease, and build muscle. And there's no need to pedal a bike or run on a treadmill for hours.
“It takes care of the main obstacle to exercise people have, which is time,” says Gretchen Reynolds, a New York Times fitness columnist and author of “The First 20 Minutes: Surprising Science Reveals How We Can Exercise Better, Train Smarter, Live Longer” (Hudson Street Press, $25.95). “It is the most efficient way to exercise. In less than 10 minutes, you can be much healthier.”
HIIT doesn't have to be complicated, and there's no set structure. A sample workout: Run as fast as you can for one minute, then walk for two minutes, then repeat that pattern.
The catch? Those intervals of intense exercise aren't fun.
“If you think you can just reorganize your workout and have it take a quarter of the time, you're sorely mistaken,” says Alex Hutchinson, a columnist for Runner's World magazine. “You have to go really hard for that interval, not just a little harder. The effort you would have spent in an hour, you have to exert in 10 minutes.”
Thankfully, those intervals are short, and so is the workout as a whole. An article in the current issue of the American College of Sports Medicine's Health & Fitness Journal details a seven-minute workout consisting of 12 exercises using body weight, a chair and a wall.
Interval training is nothing new. Runners and endurance athletes have been relying on it for decades, but it's garnered more attention since a landmark study published in the Journal of Applied Physiology in 2005 showed six minutes of hard cycling a week led to increases in endurance nearly identical to those from an hour of daily moderate cycling.
Plus, it just makes common sense, says Hutchinson, author of “Which Comes First, Cardio or Weights? Fitness Myths, Training Truths and Other Surprising Discoveries from the Science of Exercise” (Harper, $14.99).
“Intensity is really a key part of challenging your body to make it adapt,” he says. “But if you just sprint forever, you'll get tired really quickly. If you really want to get fit, there's no better way than high-intensity intervals.”
While HIIT certainly is challenging, some research shows people are more likely to stick with that form of training, probably because the workouts are short.
“It is a popular class,” says Laura Lombard, who oversees group fitness at Life Time Fitness at the Rim, which offers HIIT classes. “They move quickly. It prevents boredom. You really get a lot of bang for your buck.”
HIIT can also produce results fast, which can motivate you to continue the workouts.
“The body does respond very well to HIIT,” Reynolds says. “I was surprised. I felt much fitter quite quickly.”
Some small studies also suggest HIIT helps the body burn fat post-workout. Some people report feeling less hungry when doing interval training than after longer, moderate workouts.
It's important to note that high-intensity does not necessarily mean high impact, says Jessica Matthews, an exercise physiologist with the American Council on Exercise.
“Jump squats aren't appropriate for everyone,” Matthews says. “Walking might be high-intensity for someone.”
Although HIIT is popular with athletes, it can benefit a wide range of people, she says. HIIT has been proven to be an effective training method for people with heart disease and congestive heart failure, although people with health problems should check with a physician before trying it.
Although the benefits of HIIT are clear, that doesn't mean longer workouts are obsolete. If you like long, leisurely walks, don't ditch them.
“You don't get the meditative effects of exercise (with HIIT),” Reynolds says. “I would not say HIIT is particularly relaxing. In my experience, you do not get the quietude, the chance to think through problems. You are primarily thinking about your workout. But I still like going for a long walk and thinking.”
Hutchinson recommends adding in other kinds of workouts instead of sticking to an all-HIIT regimen, including longer, moderate-intensity workouts.
“Variety is best,” he says. “From a health perspective, I think once a week or twice a week, include something at higher intensity. It forces your body to adapt in different ways.”