Just How Short Can Your Workout Be?
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You've probably heard you need to exercise for 30 minutes a day to be healthy, but if you make your workouts more intense, you may be able to get away with spending much less time working up a sweat.

The "30 minutes a day" rule comes from the current U.S. government exercise guidelines, which recommend that people engage in 150 minutes of moderate-intensity aerobic activity per week. (This works out to about 30 minutes a day, five days a week.) But the key word here is "moderate" exercise. If your workouts involve vigorous exercise, they can be shorter, experts say.

"You can get more bang for your buck with vigorous exercise," said Dr. Edward Laskowski, co-director of Mayo Clinic Sports Medicine in Rochester, Minnesota.

Specifically, new research suggests that a type of workout known as interval training may allow people to get fit in much less time than is required with traditional endurance exercise. Interval training involves the following steps: warm up for a few minutes, go "all out" for about 30 seconds, recover at a slow pace for a few minutes and then repeat this cycle several times before cooling down.

A recent study found that a 10-minute interval training workout, which involved just 1 minute of total sprinting time, was just as good as a 50-minute endurance workout done at a moderate pace in terms of getting people fit. Men in the study who did the interval-training workout showed similar improvement in aerobic fitness, metabolism and muscle function as men who did the endurance workout.

"This is good news for a lot of people," Laskowski said. "We can really get a good training effect in a shorter period of time" with interval training, he said. Laskowski recommended that people warm up for about 3 minutes, do about three to four interval cycles, and then cool down. This would take about 17 minutes if a person did four 30-second intervals of intense exercise, with 3 minutes of rest in between each, and a 3-minute warm-up and cooldown. [How to Start an Exercise Routine and Stick to It]

Although studies are finding that interval training may offer similar fitness benefits as endurance workouts, researchers still need to conduct more studies on the long-term effects of interval training, Laskowski noted.

But studies have found that interval training can be tolerated by lots of different groups, including people who are obese or have heart disease, Laskowski said. Some studies have even found that people enjoy interval training more than traditional endurance training.

"People seem to like high-intensity interval training because it is efficient and effective also," Laskowski said.

Still, it's a good idea to see your doctor before you start interval training. Some types of exercise may not be good to perform at high intensities, Laskowski said. For example, running may not be good for people with knee arthritis, because this activity is hard on the joints. But people with knee arthritis may still be able to do interval training on a bike or in the pool without damaging their joints, Laskowski said.

Follow Rachael Rettner @RachaelRettner. Follow Live Science @livescience, Facebook & Google+. Original article on Live Science.