Though it has more than four letters, “sedentary” is a dirty word in the anti-obesity business. Sure, workers who have to stand up all day suffer from discomfort and physical consequences. But according to an ever-increasing number of authorities, sitting down all day is literally killing office workers and anyone else whose job involves prolonged contact with a chair.
Journalist Mary Murphy puts it this way:
The body’s metabolic engines go to sleep. The muscles stop moving all together and the heart slows. Then, the body’s calorie-burning rate plummets to about one calorie per minute — a third of what it would be if you were walking. Insulin effectiveness drops and the risk of developing Type 2 diabetes rises. Fat and cholesterol levels rise too.
Apparently, the effects of immobilization are even worse and more widespread than anyone suspected. For The New York Times, Gretchen Reynolds describes lab animal experiments in which:
[…] 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.
It has long been known that a broken leg healing in a cast becomes weak and flaccid. Injured athletes even do visualization meditations, mentally imagining that they are performing all their usual activities with intact extremities. In theory, the brain is somehow able to trick muscles into the perception of activity. Or maybe the practice keeps the communication pathways open.
At any rate, some swear that it works. But even if this method were 100% valid, it would be of little use to office workers, who not only sit immobile, but supposedly use their brains for their employers’ business, rather than imagining vigorous exercise.
After a fracture and/or surgery, even after the bone has knit, rehabilitation of a broken leg can take longer than the patient would have believed, prior to the injury. One reason is that a lot more is going on than anyone previously realized. A detailed picture comes from the University of Massachusetts, where researchers invented an experiment to simulate the effects of total non-use of a healthy leg, when compared to the corresponding limb on the other side. Reynolds describes it:
… [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.
Now, see what happened after not two months, not two weeks, but a mere two days. When the active muscles and the “sedentary” muscles were biopsied and compared, the legs that had started on the way to atrophy did not make a good showing. The genes were all messed up, being “expressed differently,” with evidence that the DNA repair mechanisms were out of order.
After only 48 hours of inactivity, the metabolism of each individual cell had slowed down, with increased oxidative stress and decreased insulin response. On a smaller scale, this is what happens to us when we sit around all day, whether laboring at a desk or driving or sitting in a subway car or watching TV.
Speaking of TV…
Reynolds also mentions another study that shows premature death resulting from the watching of seven or more hours of television out of each 24. One might think, “My daily TV watching is counteracted by all the hard work I do,” but one would be mistaken. She writes:
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.
(To be continued…)
Your responses and feedback are welcome!
Source: “Obesity expert says daily workouts can’t undo damage done from sitting all day,” NBCNews.com, 01/09/13
Source: “Don’t Just Sit There,” The New York Times, 04/28/12
Image by Joe Hoover.