Today, as an
estimated 20,000 runners begin their mad dash from
Hopkinton to Boston, Dr. Wood, a cardiologist,
four-time marathoner and co-director of the
Massachusetts General Hospital Women’s
Cardiovascular Health Center, will be setting up
shop in the corner of the medical tent at the finish
line.
As soon as they’re
finished, about 25 amateur runners will stroll or
hobble over to Wood’s corner to let her take a
sample of their blood. They will also get a
non-invasive test to see how well their hearts are
working after the stress of running for about 4
hours. As they have done every year since 2003, Wood
and her MGH colleagues will then compare these
post-race test results to the pre-race exams done
two weeks earlier.
The MGH findings on
Boston marathoners – three published papers to date
and two pending - are sobering and lend support to
the idea that while moderate exercise is perhaps the
most important thing a person can do for health,
taking it to extremes, like a marathon, may not be.
Among marathon
runners, the biggest cardiac risk seems to arise in
people who train the least. People who worked up to
a marathon by running at least 45 miles a week for
at least three to four months “were golden,” said
Wood. “They didn’t get into any trouble at all. If
they trained less than 35 miles a week, they were in
big trouble.”
Translated for the
rest of us, this means that “sudden, strenuous
activity can trigger a heart attack,” said Dr.
Arthur Siegel , a 20-time marathoner and director of
internal medicine at Harvard’s McLean Hospital.
Roughly 450,000
Americans now run in marathons every year. And
325,000 do triathlons, which involves swimming,
biking and running, according to USA Triathlon, the
sport’s organizing body. Many of these are not
well-trained athletes but newcomers who race to
raise money for charities. That means, said Siegel,
that in many such events, participants “are getting
older and slower. That’s where the cardiac risk
comes in, especially for middle-aged men with
previously silent heart disease.”
The key to healthy
exercise, in other words, is moderation and
consistency, especially if you are new to a sport.
Moderate exercise is
unarguably good for you. “The greatest hazard of
exercise is not doing it,” said Dr. Harvey Simon.
Simon is an avid runner, former marathoner, MGH
internist and author of “The No Sweat Exercise
Plan,” which advocates very moderate exercise – even
as moderate as gardening and housework – instead of
extreme exertion like marathoning.
Study after study
has shown that moderate, regular exercise can indeed
reduce the risk of heart disease, diabetes, stroke,
hip fracture and some kinds of cancer.
But exercising
moderately takes patience and persistence. If you
have not been exercising regularly, you should work
up over several weeks to walking 45 minutes a day at
least five days a week, said exercise physiologist
Kerry Stewart at Johns Hopkins School of Medicine.
At first, you may
have to stop every few minutes and rest, he said.
That’s fine, just start up again. If you get chest
pains or severe shortness of breath, of course, stop
and call your doctor. Obviously, if you have heart
disease or have had a heart attack, check with your
doctor before starting or substantially increasing
your workouts.
To gauge whether
you’re working hard enough, you can take your pulse
or use a strap-on heart monitor, available at many
sports stores. If you’re healthy, the goal is to
work out at about 70 percent of your maximum heart
rate, which can be determined by a stress test in a
doctor’s office.
You can also
estimate your maximum heart rate by taking the
number 220 and subtracting your age; if you’re 60,
your maximum heart rate is 160, so your “target”
heart rate during exercise should be about 112 beats
per minute. You can also use the subjective
“perceived exertion” scale, which runs from 6 (no
effort) to 20 (your absolute max). The goal is to
have your perceived exertion be about 12 to 14. An
even simpler way is to use the “sing/talk test:”
Work hard enough that you can’t sing but can talk.
Moderation is the
key, said Simon of MGH. “I used to preach ‘No pain,
no gain,’ but now I say, “No pain, big gain,’ ” he
said. The whole “aerobics doctrine” that a person
needs a lot of strenuous exercise “inspired the few,
but discouraged the many,” he said. Even just
walking at the extremely leisurely pace of half an
hour per mile has benefits.
In other words, you
shouldn’t under-do exercise, but you shouldn’t
overdo it, either. Chronic fatigue, trouble
sleeping, muscle tiredness, nagging congestion or
sore throat, persistent aches and pains and
depression are common signs that you may be working
out too hard, said Siegel. To avoid this, try not to
increase your exercise duration or intensity by more
than 10 percent over any two-week period.
Experienced athletes
“know how delicate the balance is between training
to obtain optimal performance and overtraining to
the point where muscle function begins to
deteriorate,” said Dr. Christopher Cooper , an
exercise physiologist at UCLA. But for amateurs,
finding that balance point can be hard.
As for marathoners,
Wood and her MGH colleagues have found that running
26.2 miles can lead to clear signs of cardiac
stress. They have found that cardiac troponin, a
chemical that only shows up in blood tests when
heart muscle is damaged, rises in 60 percent of
runners, and in some, it rises so high that “if you
had just looked at these scores, these people would
have been admitted to the hospital for heart
attacks,” Wood said.
They’ve found that
another chemical, BNP (for brain natriuretic
peptide), another red flag for cardiac dysfunction,
also goes up after a marathon in 60 percent of
runners. Platelets also become activated and more
likely to form the clots that can trigger heart
attacks, according to a just-published paper by
Siegel and Alexander Kratz, director of the
hematology lab at MGH. And, as shown on
echocardiograms, the heart’s ability to relax after
each beat remains impaired for at least several
weeks in most marathoners.
Bottom line? You
don’t have to run a marathon to get into good shape.
Just put on comfortable shoes, get out and walk.
Moderately. And consistently.
Judy Foreman’s
column appears every other week. Past columns are
available on
www.myhealthsense.com .
To Latest News
To Exercise