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    February 15, 2012, 12:01 am

    How 1-Minute Intervals Can Improve

    s Ed: How Interval Training Can Improve Health - N... http://well.blogs.nytimes.com/2012/02/15/how-1-m

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    Your Health

    ByGRETCHEN REYNOLDS

    John P. Kelly/Getty

    ImagesCan brief bursts of exercise improve your health?

    While many of us wonder just how much exercise we really need in order to gainhealth and fitness, a group of scientists in Canada are turning that issue on its head

    and asking, how little exercise do we need?

    The emerging and engaging answer appears to be, a lot less than most of us think

    provided were willing to work a bit.

    In proof of that idea, researchers at McMaster University in Hamilton, Ontario,

    recently gathered several groups of volunteers. One consisted of sedentary but

    generally healthy middle-aged men and women. Another was composed of

    middle-aged and older patients whod been diagnosed with cardiovascular disease.

    The researchers tested each volunteers maximum heart rate and peak power output

    on a stationary bicycle. In both groups, the peaks were not, frankly, very high; all of

    the volunteers were out of shape and, in the case of the cardiac patients, unwell. But

    they gamely agreed to undertake a newly devised program of cycling intervals.

    Most of us have heard of intervals, or repeated, short, sharp bursts of strenuous

    activity, interspersed with rest periods. Almost all competitive athletes strategically

    employ a session or two of interval training every week to improve their speed and

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    endurance.

    But the Canadian researchers were not asking their volunteers to sprinkle a few

    interval sessions into exercise routines. Instead, the researchers wanted the groups to

    exercise exclusively with intervals.

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    For years, the American Heart Association and other organizations have

    recommended that people complete 30 minutes or more of continuous, moderate-

    intensity exercise, such as a brisk walk, five times a week, for overall good health.

    But millions of Americans dont engage in that much moderate exercise, if they

    complete any at all. Asked why, a majority of respondents, in survey after survey, say,

    I dont have time.

    Intervals, however, require little time. They are, by definition, short. But whether

    most people can tolerate intervals, and whether, in turn, intervals provide the same

    health and fitness benefits as longer, more moderate endurance exercise are issues

    that havent been much investigated.

    Several years ago, the McMasters scientists did test a punishing workout, known as

    high-intensity interval training, or HIIT, that involved 30 seconds of all-out effort at

    100 percent of a persons maximum heart rate. After six weeks, these lacerating HIIT

    sessions produced similar physiological changes in the leg muscles of young men as

    multiple, hour-long sessions per week of steady cycling, even though the HIIT

    workouts involved about 90 percent less exercise time.

    Recognizing, however, that few of us willingly can or will practice such straining

    all-out effort, the researchers also developed a gentler but still chronologically

    abbreviated form of HIIT. This modified routine involved one minute of strenuous

    effort, at about 90 percent of a persons maximum heart rate (which most of us can

    estimate, very roughly, by subtracting our age from 220), followed by one minute of

    easy recovery. The effort and recovery are repeated 10 times, for a total of 20

    minutes.

    Despite the small time commitment of this modified HIIT program, after several

    weeks of practicing it, both the unfit volunteers and the cardiac patients showed

    significant improvements in their health and fitness.

    The results, published in a recent review of HIIT-related research, were especially

    remarkable in the cardiac patients. They showed significant improvements in the

    functioning of their blood vessels and heart, said Maureen MacDonald, an associate

    professor of kinesiology at McMaster who is leading the ongoing experiment.

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    It might seem counterintuitive that strenuous exercise would be productive or even

    wise for cardiac patients. But so far none have experienced heart problems related to

    the workouts, Dr. MacDonald said. It appears that the heart is insulated from the

    intensity of the intervals, she said, because the effort is so brief.

    Almost as surprising, the cardiac patients have embraced the routine. Although their

    ratings of perceived exertion, or sense of the discomfort of each individual interval,

    are high and probably accurate, averaging a 7 or higher on a 10-point scale, they

    report enjoying the entire sessions more than longer, continuous moderate exercise,

    Dr. MacDonald said.

    The hard work is short, she points out, so its tolerable. Members of a separate,

    exercise control group at the rehab center, assigned to complete standard 30-minute

    moderate-intensity workout sessions, have been watching wistfully as the interval

    trainers leave the lab before them. They want to switch groups, she said.

    The scientists have noted other benefits in earlier studies. In unfit but otherwise

    healthy middle-aged adults, two weeks of modified HIIT training prompted the

    creation of far more cellular proteins involved in energy production and oxygen. Thetraining also improved the volunteers insulin sensitivity and blood sugar regulation,

    lowering their risk of developing Type 2 diabetes, according to a study published last

    fall in Medicine & Science in Sports & Exercise.

    Since then, the scientists completed a small, follow-up experiment involving people

    with full-blown Type 2 diabetes. They found that even a single bout of the 1-minute

    hard, 1-minute easy HIIT training, repeated 10 times, improved blood sugar

    regulation throughout the following day, particularly after meals.

    Of course, HIIT training is not ideal or necessary for everyone, said Martin Gibala, a

    professor of kinesiology at McMaster, whos overseen the high-intensity studies. If

    you have time for regular 30-minute or longer endurance exercise training, then by

    all means, keep it up, he said. Theres an impressive body of science showing that

    such workouts are very effective at improving health and fitness.

    But if time constraints keep you from lengthier exercise, he continues, consult your

    doctor for clearance, and then consider rapidly pedaling a stationary bicycle or

    sprinting uphill for one minute, aiming to raise your heart rate to about 90 percent of

    your maximum. Pedal or jog easily downhill for a minute and repeat nine times,

    perhaps twice a week. Its very potent exercise, Dr. Gibala said. And then, very

    quickly, its done.

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