A new study suggests that engaging in low
intensity activities such as standing may not be enough to offset the
health hazards of sitting for long periods of time. On the bright side,
adding two minutes of walking each hour to your routine just might do
the trick. These findings were published in the Clinical Journal of the American Society of Nephrology (CJASN).
Numerous studies have shown that sitting for extended periods of time
each day leads to increased risk for early death, as well as heart
disease, diabetes and other health conditions. Considering that 80
percent of Americans fall short of completing the recommended amount of
exercise, 2.5 hours of moderate activity each week, it seems unrealistic
to expect that people will replace sitting with even more exercise.
With this in mind, scientists at the University of Utah School of
Medicine investigated the health benefits of a more achievable goal,
trading sitting for lighter activities for short periods of time. They
used observational data from National Health and Nutrition Examination
Survey (NHANES) to examine whether longer durations of low intensity
activities (e.g. standing), and light intensity activities (e.g. casual
walking, light gardening, cleaning) extends the life span of people who
are sedentary for more than half of their waking hours.
They found that there is no benefit to decreasing sitting by two
minutes each hour, and adding a corresponding two minutes more of low
intensity activities. However, a "trade-off" of sitting for light
intensity activities for two minutes each hour was associated with a 33
percent lower risk of dying.
"It was fascinating to see the results because the current national
focus is on moderate or vigorous activity. To see that light activity
had an association with lower mortality is intriguing," says lead author
Srinivasan Beddhu, M.D., professor of internal medicine.
Beddhu explains that while it's obvious that it takes energy to
exercise, strolling and other light activities use energy, too. Even
short walks add up to a lot when repeated many times over the course of a
week. Assuming 16 awake hours each day, two minutes of strolling each
hour expends 400 kcal each week. That number approaches the 600 kcal it
takes to accomplish the recommended weekly goal of moderate exercise. It
is also substantially larger than the 50 kcal needed to complete low
intensity activities for two minutes each awake hour over the course of
one week.
"Based on these results we would recommend adding two minutes of
walking each hour in combination with normal activities, which should
include 2.5 hours of moderate exercise each week," says Beddhu. Moderate
exercise strengthens the heart, muscles, and bones, and confers health
benefits that low and light intensity activities can't.
The study examined 3,243 NHANES participants who wore accelerometers
that objectively measured the intensities of their activities.
Participants were followed for three years after the data were
collected; there were 137 deaths during this period.
"Exercise is great, but the reality is that the practical amount of
vigorous exercise that can be achieved is limited. Our study suggests
that even small changes can have a big impact," says senior author Tom
Greene, Ph.D., director of the Study Design and Biostatistics Center at
the Center for Clinical and Translational Science.
Beddhu adds that large, randomized, interventional trials will be
needed to definitively answer whether exchanging sitting for light
activities leads to better health.
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