There was Jazzercise in the ’70s, step aerobics in the ’80s, and Tae Bo in the ’90s… and we tried them all. But exercise fads come and go, and every few years we discover the next big thing that promises to help us burn fat and lose weight.
In recent years, though, a trend with some real staying power emerged: interval training, the varying the intensity of a workout or a walk, switching from short, fast-paced bursts of activity to slow, measured periods of rest.
Why are high-intensity bursts so effective? It’s in our biological nature, says osteopathic physician Joseph Tieri, DO, author of Staying Young with Interval Training ($10.39, Amazon). “When you start a 40-minute jog, the body thinks you’re beginning a 1,000-mile trek to find food. When it isn’t sure where its next meal is coming from, the last thing it wants to do is increase your metabolism,” he says. “But short, high-intensity bursts send a whole different set of signals. They say that you were taking a walk, but suddenly, you are being chased by coyotes and you have to run, so your body will ramp up your metabolism to help you go faster. It’s all about survival.”
Even better: Intervals are especially beneficial for women born before 1975. “As we get older, the energy factories in cells, called mitochondria, become less numerous and don’t function as well as they used to,” says Dr. Tieri. “Studies show that during interval training, mitochondria begin to work more efficiently and their numbers increase by 70 percent.”
Short bursts of exercise also target visceral fat, the dangerous midsection fat that accumulates around the organs. “Visceral fat affects blood sugar, blood pressure, and cholesterol,” says weight-management specialist Caroline Cederquist, MD. “It is the fat you want to lose.”
Indeed, a new study from France found that while both intervals and moderate-intensity exercise helped postmenopausal women slim, only intervals shrunk waist circumference and visceral fat stores. Unlike the exercise trends of decades past, women have no problem sticking with intervals. “The number-one objection people have to exercise is ‘I don’t have time,’” says Dr. Tieri. “But an interval workout only takes 10 minutes. You can get a better overall workout in a fifth of the time.”
The proof: A study at the University of Aberdeen in the U.K. found that subjects who completed five 30-second high-intensity bursts, each followed by four minutes of rest, burned three times more fat than subjects who walked at a steady pace for 30 minutes.
A speedier metabolism and increased fat loss are just some of the benefits women experience. Intervals can improve cholesterol levels, increase energy, bolster brain health, and more, says Dr. Tieri. In fact, a study at McMaster University in Canada found that completing 20-second intervals improved blood-sugar levels by 53 percent, increased cardiovascular fitness by 19 percent and raised calorie burning by 48 percent — improvements equal to or better than those experienced by subjects who exercised at a moderate pace for 50 minutes.
“Interval walking maximizes your results in a minimal amount of time — and you don’t need to be in shape to do it. For someone who is just starting out, the intervals will be less intense than for someone who has exercised more,” explains Cederquist.
To get the benefits, Tieri., recommends starting with 3 minutes of walking to warm up, then increasing your pace as much as you can for 15 to 30 seconds, followed by 2 to 3 minutes of gentle walking. Repeat the burst for 15 to 30 seconds, then walk for another 3 minutes for a total of about 10 minutes. “Studies have shown that 30 seconds of high intensity is plenty of time to get the benefits,” he says. For the best results, he suggests doing this 10-minute workout just twice a week. Or, if you prefer a longer workout, you can get similar benefits by incorporating three 30-second, high-intensity bursts into a longer walk, leaving more time for recovery between bursts.
The key, according to Cederquist, is to figure out your personal “high intensity” — that’s when the metabolism-boosting benefits go into effect. How to tell if you’ve reached that level: “You want to increase your walking speed to the point that you feel your heart rate increase and it is perceived as ‘hard’ to do for 30 seconds,” she says. For a 50-year-old woman, heart rate should climb to between 136 and 153 beats per minute. “A good rule of thumb is that you should need the whole rest period to feel recovered back to baseline. If you recover in 10 seconds, you probably didn’t push hard enough,” she adds.
One caveat: If you’re new to interval training, it is best to progress cautiously and listen to your body in order to avoid injury — and be sure to check with your healthcare provider if you have any concerns. But once you are comfortable, the benefits you can expect are vast and varied: In addition to rapid weight loss, women FIRST spoke to reported perks like stronger bones, better sleep and freedom from stress and chronic pain.
Not sure how to measure your intervals? There’s no need to invest in a stopwatch! Read on for the strategies you can use indoors or outdoors that will make your high-intensity bursts feel even easier:
- Rely on landmarks. Things in your neighborhood, such as mailboxes, driveways, trees or street signs, can be a fantastic replacement for a stopwatch when you’re tracking your intervals, says Dr. Tieri. Try strolling gently past a few mailboxes or driveways, then picking up your pace until you reach the next one, before slowing down again. Or if there is a track at your local public school, Tieri suggests walking the straightaways and pushing your pace as you go around the curves. According to a study published in the journal Motivation and Emotion, focusing on a physical stopping point in the distance can make it appear closer, encouraging exercisers to move more quickly and reducing feelings of exertion.
- Crank up the tunes. “Create an upbeat playlist filled with fast-paced songs that make you want to move,” suggests Dr. Cederquist. Then use one chorus out of each song as your high-intensity burst. Why that’s smart: Research shows that you subconsciously push your walking pace to meet the beat of the music without noticing the extra exertion when you’re listening to songs with a high tempo. What’s more, if you’re using songs you like, your walk will feel more enjoyable, and the time will go by faster. The proof: A recent review of 139 studies published in the journal Psychological Bulletin found that listening to music not only boosted subjects’ moods, it also increased blood flow and improved their overall physical performance. Two songs to try on your next walk: “Help Me, Rhonda” by The Beach Boys and “Shake It Off” by Taylor Swift.
- Switch up your intervals. If you find it difficult to pick up your pace or are walking inside and don’t have much room, you can substitute a different movement for your high-intensity burst instead, says Dr. Tieri. Simple aerobic moves like jumping rope (with a real or imaginary rope), ski jumps (jumping from side to side) or marching with high knees will turbocharge your metabolism, while low-impact moves like boxing-style uppercuts, squats or lunges will increase your heart rate and promote the growth of calorie-burning lean muscle mass. Not only will this make your walk more interesting mentally, but it will also engage different muscle groups for speedier full-body toning.
- Do a burst at a commercial break. Walking indoors on rainy or too-hot days can sap your motivation — that’s why Dr. Tieri recommends using your TV as a distraction. “Most TV commercials are about 30 seconds long, so you can use these to measure your intervals,” he suggests. To do: Try walking in place while you’re watching your favorite sitcom, then choose one commercial to speed up to a brisk march or complete another high-intensity movement.
This story originally appeared in our print magazine.
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