Whether you’ve reached a plateau or haven’t worked out since gym class, interval training could be your fix. A 2007 Australian study found that women who used this method—alternating between fast- and moderate-paced exercise speeds—for 20 minutes three days a week lost five times as much weight as those who exercised at a steady, fast speed for 40 minutes three days a week. Evidence also suggests that interval training may increase good (HDL) cholesterol levels, improve cardiovascular health and jump-start metabolism. Seattle-based exercise physiologist Elizabeth Quinn, MS, gave us the 411 on this super fat-burning workout.

Explain interval training.
Interval training combines moderate-paced aerobic activity with short bursts of high-intensity or high-speed exercise.

Can you give an example?
You might walk on a treadmill at 3.5 mph for five minutes, then switch the speed to 5.5 mph for one minute. Repeat this sequence three times, and you have a routine.

How does increasing speed affect the body?
The faster intervals stress the cardiovascular system. In response, your body stimulates more muscle fibers—ones that don’t get used at the moderate level.

What are some other benefits?
Interval training makes exercising less intimidating and more efficient. It can be incorporated into any type of exercise—the elliptical machine, treadmill or stair stepper, swimming, walking—even strength training. And at any fitness level, you can do some variation.

Are there any risks? 
Interval training stresses the body. To get stronger, you need to push yourself—but don’t push too hard. If you have heart disease or joint problems, talk to your doctor first.

QUINN’S TIPS
Take precautions: Warm up thoroughly to avoid pulling a muscle. Cool down afterward to lower your heart rate. Stretch after exercising.

Start slow: Begin with one interval workout a week; work up to two—I don’t recommend more than that. Begin at 30 seconds for the fast interval. Once you get used to that, progress to a minute or more. Same with the speed: Start at a speed that is challenging but not too hard; increase over time.

Shake it up: You can mix different exercises. Alternate walking with jumping jacks or a set of push-ups, then return to walking. Have fun with it!     

PACE-YOURSELF PLAYLIST
We compiled a list of fast- and medium-paced songs tailored for interval training. Download ’em all for an upbeat workout.

Moderate:
“All Night Long”—Mary Jane Girls
“One in a Million”—Aaliyah
“Little Red Corvette” —Prince
“You’ve Got the Best of
 My Love” —The Emotions
“Teenage Love Affair” —Alicia Keys

Fast:
“1 Thing” —Amerie
“Closer” —Ne-Yo
“Work That” —Mary J. Blige
“Don’t Stop ’Til You
 Get Enough”  —Michael Jackson
“Stronger” —Kanye West