Except that she was doing everything right. Falkenstein spent 45 minutes a day on cardio machines at her gym and another 30 or 40 minutes lifting weights. She was dieting, but her weight wouldn't budge. To cut down on gym trips, she bought an elliptical trainer. She had no idea how much time she would save.
Falkenstein's elliptical machine was programmed with workouts from the book Ready, Set, Go!, by Phil Campbell, which promised quick weight loss. Falkenstein decided to forgo her usual steady, moderate gait and try the 20-minute fast-paced workouts, which included eight 30-second intervals—full-speed efforts—followed by slower-paced breaks for recovery. (Most exercise machines offer some version of an interval workout.) She did it three days a week, along with lifting heavier weights—choosing amounts she could heft no more than 12 times. Six weeks and one dress size later, Falkenstein was beaming. "My clothes fit and my cholesterol is normal," she says. "And I feel a lot better about myself."
While most experts keep telling us we need to exercise longer if we want to lose weight—we're supposed to exercise 60 to 90 minutes a day just to maintain weight loss—a fast-growing body of research indicates that intensity, not duration, is really the missing piece in our fitness puzzle:
- Last December, Canadian researchers reported that just two weeks of interval training boosted women's ability to burn fat during exercise by 36 percent.
- Levels of human growth hormone—which assists in building muscle and eliminating fat—skyrocketed 530 percent in subjects after just 30 seconds of sprinting as fast as they could on a stationary bike, according to a British study.
- Australian fitness researchers had 18 women perform 20 minutes of interval training on a stationary bike—eight-second sprints followed by 12 seconds of recovery throughout the workout, three days a week. The women lost an average of five and a half pounds over 15 weeks without dieting, while a similar group performing 40 minutes of moderate cycling three days a week actually gained a pound of fat over the same period. Two of the heavier women who did intervals dropped 18 pounds.
What's more, short, intense workouts also get you fitter in less time. In a side-by-side comparison, researchers at McMaster University in Ontario measured fitness gains in eight interval exercisers—20- to 30-minute cycling workouts that included four to six 30-second sprints—against eight volunteers who pedaled at a lower intensity for 90 to 120 minutes. After two weeks, the interval group was every bit as fit as those who worked out three to four times as long.
One reason intervals are effective is that they target more of your muscle, says Canadian study author Martin Gibala, PhD, associate professor of kinesiology at McMaster University. The average exerciser uses a lot of slow-twitch (endurance) muscle fibers and way too few fast-twitch (speed and power) fibers. Working more fast-twitch fibers not only gives you firm, shapely muscle tone but also fast-tracks your fitness gains. "Your body thinks, 'Whoa! That was hard work,' and it responds by increasing your ability to use oxygen and burn fat," Gibala says.
Few among us can squeeze in the recommended amount of exercise—at least 30 minutes most days of the week. So here's a comparison any overscheduled woman could love: Do a 30-minute walk at a steady, moderate pace, and you'll shed 112 calories. But mix in eight 30-second speed-walking sprints, and you'll burn 165 calories. After an interval session, your metabolism can stay elevated for a full day, and you'll burn two to three times the calories you could expect from lower-intensity exercise.
You'll feel younger, as well. Fast-twitch fibers are the first to go with age, largely because neurons stop communicating with them. "Our research finds that you can increase neuron firing rates after just one week of training," says Christopher Knight, PhD, a neuromuscular researcher at the University of Delaware in Newark.
With more muscles buzzing at attention, you have more energy for life, says Melanie Buchholz, 42-year-old mother of three from Jackson, Tennessee, who started interval training five years ago. Yes, she shrank from a size 12 to a 6, but she gets more pleasure from the vigor she gained: "Friends talk about how tired they are. This workout gives me great energy. And I sleep very soundly."
Though interval workouts sound daunting, anyone can do them, says Phil Campbell, the creator of the Sprint 8 interval program. "You don't have to run full speed," he says. "You don't even need to run. You can bike, swim, elliptical train, even power walk." What's important is that during the interval, you push yourself hard enough that you can't maintain the effort longer than 30 seconds.
How It Works
Warm up for two to three minutes. Start your first 30-second interval. If you don't want to run, simply increase the incline on the treadmill 3 to 6 percent and speed up enough to feel that you're working hard. Let the 1-to-10 exertion scale (10 being all-out) be your guide. The effort should feel like an 8 (for the first few sprints) to 10 (for the final ones). After 30 seconds, recover at a casual walking pace for one and a half to two minutes, and then do it again for a total of eight intervals. Wrap up with a two- to three-minute cooldown. The workout will take 20 to 25 minutes.
- Your body needs time to adapt to the rigors of intervals. If you've been very sedentary, ease into the intensity by brisk-walking the intervals to start. For those unused to a fast pace, do just two moderate sprints the first time.
- Allow a day of rest between interval workouts to give your body time off to recover and rebuild.
- As with any exercise program, see your doctor before starting.
Because even the shortest workouts can become a bore, you'll appreciate how easy it is to vary intervals. These two suggestions are each less than 25 minutes including warm-up and cooldown. Again, base your intensity on a 1-to-10 scale, with 10 being tail-on-fire intense.
- Three minutes: Warm up at an easy (3) to moderate pace (6).
- Three minutes: Boost intensity (7).
- Two minutes: Push a little harder (8).
- One minute: Keep increasing your effort, and finish the last ten to 15 seconds as hard as you can go (10).
- Six minutes: Recover (4 to 5).
- Repeat the three-two-one interval.
- Two minutes: Cool down (4).
- Five minutes: Warm up at an easy to moderate effort (5 to 6).
- Two minutes: Increase your intensity to just shy of full-on effort (9).
- Two minutes: Recover (5 to 6).
- Repeat the on-off interval four times.
- Three minutes: Cool down (4).