A Daily news digest by Jasper van Santen

Sitting Down is Bad for You! – NYTimes.com

In News on April 29, 2012 at 09:56

Stand Up for Fitness – Reynolds

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.

 

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