Intervals training is an efficient way of improving your health

How 1-Minute Intervals Can Improve Your Health
Can brief bursts of exercise improve your health?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 gain health and fitness, a group of scientists in Canada are
turning that issue on its head and asking, how little exercise do we

The emerging and engaging answer appears to be, a lot less than most
of us think — provided we’re 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 who’d been diagnosed
with cardiovascular disease.

The researchers tested each volunteer’s 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 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.

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 don’t engage in that much moderate exercise,
if they complete any at all. Asked why, a majority of respondents, in
survey after survey, say, “I don’t 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 haven’t 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 person’s
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 person’s 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

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.

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 it’s 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. The training 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, who’s 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. “There’s 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. “It’s very potent exercise,” Dr. Gibala
said. “And then, very quickly, it’s done.”
(NY Times)