Working harder and smarter can make exercise more efficient, effective, and fun.
Credit: Illustration: Bee Johnson

Think you don't have time to work out? You're not alone: Half of all people give up on an exercise program after six months for lack of time. But you may not need as much time as you think: The latest research finds short workouts can add up to big fitness benefits. It's called high-intensity interval training (HIIT), which simply means alternating short bursts of intense effort with longer bouts of recovery.

Elite athletes have long used HIIT to improve speed, strength, and stamina. And now researchers are finding it works for the rest of us, too, from out-of-shape couch potatoes to women with rheumatoid arthritis and everyone in between. "It's extremely potent and time efficient," says Martin Gibala, PhD, chair of the kinesiology department at McMaster University in Ontario, Canada, and author of The One-Minute Workout. "It's an approach that can be applied to almost anyone."

Short Workout, Big Benefits

HIIT turns your body into a calorie-burning machine. Pete McCall, senior exercise scientist at the American Council on Exercise, likens it to driving a car: Stop-and-go driving in traffic burns more fuel than steady highway driving. Similarly, HIIT workouts burn more calories than exercising at a steady pace.

That can help with weight loss, of course, and HIIT is especially effective at reducing belly fat, the kind that increases your risk for metabolic syndrome, heart disease, and diabetes. Research also suggests HIIT improves blood sugar and insulin resistance as effectively as longer moderate workouts to help prevent or manage type 2 diabetes.

Gauge Your Effort

"Perceived effort" is a fine measure for this type of workout. "We like to use the 1 to 10 scale, where 10 is the absolute hardest you can work, and 1 is the amount of energy you're burning when you sit on the couch," says McCall. "So you generally want to consider 'high intensity' being at a 9 or 10. It's something you can't do for more than 30 to 45 seconds." The "talk test" is another tool: When you're working at high intensity, you can only get out a word or two, and when you're recovering, you could have a conversation with a friend.

But you don't have to push yourself to the limit to reap the benefits of intervals, says Gibala. "If your habitual exercise is walking around the block, an interval workout for you may be picking up the pace for [the space of] a few lampposts, then backing off. There's a whole spectrum of interval-type exercise. It can be scaled to almost any starting level of fitness." (If you haven't been exercising or you have a health condition, it's a smart idea to check with your doctor before starting high-intensity interval training.)

One Minute to Better Fitness

Gibala's research on healthy yet sedentary volunteers found that a 10-minute workout with 60 total seconds of intervals has benefits comparable to a traditional 50-minute moderate-intensity workout. "After a few months of training, the improvements in their cardiovascular fitness, blood sugar control, and other health markers are very similar, even though the time commitment required for the interval trainers was fivefold lower," he notes.

HIIT also boasts quick and noticeable benefits: You'll start to see improvement surprisingly fast, McCall adds. Intervals that seem hard at first will feel easier after just a few weeks, and you'll soon find your intervals get faster with less effort. Short, sweet, and effective—now there's really no excuses to skip exercise.

Speedy Strength Training

The intensity principle applies to strength training, too. Choose a weight that you can hoist for six reps, max. "Muscles won't get bigger—they just get more effective at generative force," McCalls explains.

Old-school calisthenics can also help. "It's very effective for boosting and maintaining muscle mass, and that's important as we age," says Gibala.