New York Times Health -
Slow Runners Come Out Ahead
By Gretchen Reynolds
The ideal amount of running for someone who wants to live a long and
healthy life is less than most of us might expect, according to a new
study, which also suggests that people can overdo strenuous exercise and
potentially shorten their lives.
There is increasing
consensus among physicians and exercise scientists that people should
exercise intensely at least sometimes. Past studies have found,
for instance, that walkers who move at a brisk pace tend to live longer
than those who stroll, even if they cover about the same distance.
Similarly, a 2012 study of cyclists in Denmark
concluded that those who regularly rode hard tended to live longer than
those who rode gently, even if the easy riders put in more hours on the
road each week.
But that result, while
intriguing, felt unsatisfyingly vague to the Danish researchers. It did
not delineate just how much intense exercise might be most protective
against premature death. It also didn’t address whether there could be a
ceiling to the benefits from vigorous exercise and, in terms of
lifespan, whether someone might work out too much.
So for the new study, which was published this month in The Journal of the American College of Cardiology,
the researchers, most of them affiliated with the University of
Copenhagen, turned to the enormous database about health habits among
Danes known as the Copenhagen City Heart Study.
In this case, instead
of focusing on cycling, the researchers decided to look at jogging,
since it is the most popular strenuous activity worldwide.
The researchers culled
data for 1,098 adult men and women of varying ages who, upon their
entry into the study in 2001, had identified themselves as joggers. They
also had provided information about how often they ran per week, at
what pace, and for how long.
The researchers also
pulled records for 3,950 age-matched volunteers who had said in 2001
that they did not engage in any type of vigorous exercise or, in fact,
any exercise at all.
All of the volunteers were generally healthy, however, without evidence at the time of disease or obesity.
Then last year, the
researchers compared the names of the volunteers in both groups against
death records. They also determined whether, based on average life
expectancies, the volunteers were living longer, or had shortened
lifespans.
As it turned out, and as expected, joggers consistently tended to live longer than people who did not exercise.
But when the researchers closely parsed the data about how much and how intensely people jogged, some surprises emerged.
The ideal amount of
jogging for prolonged life, this nuanced analysis showed, was between 1
hour and 2.4 hours each week. And the ideal pace was slow. (The
researchers did not specify exact paces in their study, using instead
the broad categories of slow, average and fast, based on the volunteers’
self-reported usual pace.)
Plodding joggers
tended to live longer than those who ran faster. In fact, the people who
jogged most often and at the fastest pace — who were, in effect,
runners rather than joggers — did not enjoy much benefit in terms of
mortality. In fact, their lifespans tended to be about the same as those
who did not exercise at all.
The results suggest
that the “optimal dose of jogging is light, and strenuous joggers and
sedentary non-joggers have similar mortality rates,” said Jacob Louis
Marott, a researcher for the Copenhagen City Heart Study and a co-author
of the study.
You can, in other words, potentially run too much.
Of course, there are
caveats. The number of hardcore runners in the study was quite small,
for one thing, consisting of barely 80 men and women. So any statistical
information about death rates among that group must be viewed
cautiously, as the scientists acknowledge.
And perhaps most
important, the researchers did not determine how and why the runners and
nonrunners had died. So it is impossible to draw any conclusions about
what deleterious effects, if any, hard and prolonged exercise might have
on our bodies. There could be scarring or other impacts on the heart
muscle after years of strenuous exercise, the Danish scientists suggest,
though that possibility remains completely speculative at the moment.
So the message of this
study remains that sweaty exercise is generally healthy and desirable –
but a little sweat goes a long ways. Even slow jogging counts as
“vigorous exercise,” Mr. Marott said and, as this study showed, can
lengthen lifespans.
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