For fitness ...... Intensity matters

 This year, exercise science expanded
and fine-tuned our understanding
of how physical activity affects our brains, joints, hearts, and even genes, beginning before birth and continuing throughout our
lifespans, which can be lengthened,
it seems, by exercise, especially if we
pick up the pace. This year’s fitness news, as a look
back through 2013’s Phys Ed columns shows, was variously enlightening, validating (if, like me,
you never bothered cooling down after a workout anyway), and practical (D.I.Y. concussion testing, anyone?). It was also occasionally
deflating, at least if you hoped that barefoot running invariably would
reduce the risk of injury, gentle exercise would quash your appetite, or training for a marathon would
automatically exempt you from being a couch potato. But the lesson that seemed to
emerge most persistently from the
fitness-related studies published
this year was that intensity matters,
especially if you wish to complete
your workout quickly. The most popular column that I wrote this
year, by a wide margin, detailed “The Scientific 7-Minute Workout,” a concept that appealed, I have no
doubt, because the time
commitment was so slight. But the
vigor required was considerable; to
gain health benefits from those
seven minutes, you needed to maintain a thumping heart rate and
spray sweat droplets around the
room. Almost halving the time spent
exercising was also effective, a later and likewise popular column
showed. In that study, out-of-shape volunteers who ran on a treadmill
for a mere four minutes three times
a week for 10 weeks raised their
maximal oxygen uptake, or
endurance capacity, by about 10
percent and significantly improved their blood sugar control and blood
pressure profiles. The results undercut a common
excuse for skipping workouts. “One
of the main reasons people give” for
not exercising is that they don’t have
time, said Arnt Erik Tjonna, a
postdoctoral fellow at the Norwegian University of Science
and Technology, who led the study. But they emphasize, too, the
potency of hard effort. The
volunteers ran at 90 percent of their
maximum aerobic capacity for those
four minutes, a level that is frankly
unpleasant. But, in four minutes, they were done. There were other hints throughout
the year that exerting yourself
vigorously may have unique payoffs,
compared with less strenuous
exercise. In a study that I wrote about a few weeks ago, for instance, people who walked briskly, at a pace
of 17 minutes per mile or less,
generally lived longer than those
men and women who strolled
during their walks, at a pace of 20
minutes per mile or slower, although the study was not designed
to determine why the intensity of
the exercise mattered. And in September, I wrote about
two studies showing that strenuous
exercise blunted volunteers’ appetites after workouts more effectively than longer sessions of
easy exercise did. The studies were
small, though, and involved only
young-ish, overweight men.
Whether the results are applicable to
other people, including those of us who are not male, requires
additional experiments. I expect to
be covering the results in 2014. Meanwhile, other studies that I
wrote about this year emphasize
how pervasive the impacts of any
amount and type of exercise can be.
One of my favorite experiments of 2013 detailed how rodents that ran on wheels for several weeks
responded far better to stressful
situations than sedentary animals,
in large part, it seems, because their
brains contained specialized cells
that dampened unnecessary anxiety. At a molecular level, the
runners’ brains were calmer than
those of their sedentary lab mates. But perhaps the most remarkable
studies of the year examined the
effect of exercise on our DNA. In
several experiments, which I wrote about in July, scientists found that exercise reshapes genes in human
cells, changing how atoms attach to
the outside of individual portions of
our DNA. As a result, I wrote, the
behavior of the gene changes. In
one of the studies, researchers found that six months of moderate
exercise profoundly remodeled
genes related to the risk for diabetes
and heart disease. But for those of
us too impatient to wait six months,
the other study found that a single session of bike riding altered genes
in volunteers’ muscle cells. The
effects showed up whether the
pedaling was easy or strenuous, but,
in line with so much of this year’s
exercise science, were more pronounced when cyclists rode
vigorously. Still, for everyone, as one of the
scientists told me, the studies are an
important and inspirational
reminder of “the robust effect
exercise can have on the human
body, even at the level of our DNA