-
5
月
22
日英语阅读<
/p>
Stand Up for
Fitness
ONE lesson I’ve
learned while writing about fitness is that few
things impinge on
an
active
life
as
much
as
writing
about
fitness
—
all
that
time
spent
hunched
before
a
computer
or
puzzling
over
scientific
journals,
the
countless
hours
of
feckless, seated procrastination. While
writing about the benefits of exercise, my
muscles
slackened.
Fat
seeped
insidiously
into
my
blood,
liver
and
ventricles.
Stupor infiltrated my brain.
We
all
know
by
now
that
being
inactive
is
unhealthy.
But
far
too
many
of
us
think that
being inactive is something that happens to other
people.
Studies
of
daily
movement
patterns,
though,
show
that
your
typical
modern
exerciser, even someone who runs,
subsequently sits for hours afterward, often
moving less over all than on days when
he or she does not work out.
The
health
consequences
are
swift,
pervasive
and
punishing.
In
a
noteworthy
recent experiment conducted by
scientists at the University of Massachusetts and
other institutions, a group of healthy
young men donned a clunky platform shoe
with
a
4-inch
heel
on
their
right
foot,
leaving
the
left
leg
to
dangle
above
the
ground.
For
two
days,
the
men
hopped
about
using
crutches
(and
presumably
gained
some
respect
for
those
people
who
regularly
toddle
about
in
platform
heels). Each man’s left leg never
touched the ground. Its muscles didn’t contract.
It was fully sedentary.
After two days,
the
scientists biopsied
muscles in both
legs and found multiple
genes
now being expressed
differently in each
man
’s two legs.
Gene
activity in
the left leg suggested that DNA repair
mechanisms had been disrupted, insulin
response was dropping, oxidative stress
was rising, and metabolic activity within
individual muscle cells was slowing
after only 48 hours of inactivity.
In
similar
experiments
with
lab
animals,
casts
have
been
placed
on
their
back
legs,
after
which
the
animals
rapidly
developed
noxious
cellular
changes
throughout
their
bodies,
and
not
merely
in
the
immobilized
muscles.
In
particular, they produced substantially
less of an enzyme that dissolves fat in the
bloodstream.
As
a
result,
in
animals
and
humans,
fat
can
accumulate
and
migrate to the heart or liver,
potentially leading to cardiac disease and
diabetes.
To see the
results of such inactivity, scientists with the
National Cancer Institute
spent
eight
years
following
almost
250,
000
American
adults.
The
participants
answered
detailed
questions
about
how
much
time
they
spent
commuting,
watching
TV,
sitting
before
a
computer
and
exercising,
as
well
as
about
their
general health. At the start of the
study, none suffered from heart disease, cancer
or diabetes.
But
after
eight
years,
many
were
ill
and
quite
a
few
had
died.
The
sick
and
deceased were also in
most cases sedentary. Those who watched TV for
seven or
more hours a day proved to
have a much higher risk of premature death than
those who sat in front of the
television less often. (Television viewing is a
widely
used measure of sedentary time.)
Exercise only slightly
lessened the health risks of sitting. People in
the study who
exercised for seven hours
or more a week but spent at least seven hours a
day in
front of the television were
more likely to die prematurely than the small
group
who worked out seven hours a week
and watched less than an hour of TV a day.
If
those
numbers
seem
abstract,
consider
a
blunt
new
Australian
study.
In
it,
researchers determined that watching an
hour of television can snip 22 minutes