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 need?
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.
Related
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 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.
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.”
No comments:
Post a Comment