What was unexpected was that many of the men who sat long hours and developed heart problems also exercised. Quite a few of them said they did so regularly and led active lifestyles. The men worked out, then sat in cars and in front of televisions for hours, and their risk of heart disease soared, despite the exercise. Their workouts did not counteract the ill effects of sitting.
Your muscles, unused for hours at a time, change in subtle fashion, and as a result, your risk for heart disease, diabetes and other diseases can rise.
Regular workout sessions do not appear to fully undo the effects of prolonged sitting.
This is very important. It should also be obvious. If you take any organism out of its natural setting and make it live in ways it is not used to, all kinds of health problems emerge. The human body is meant for constant, low-level activity, with occasional periods of high activity. Sitting still is completely unnatural, and unhealthy.
And yet we train children from kindergarten to do just that. At the age when they should be playing, running around, and learning social and technical skills by watching what their elders do, we put them in a big box and make them sit still for hours on end while someone talks to them and makes them do strange things with symbols. Anyone who follows the healthy biological instinct to get up and move around, or at least fidget in the seat to make the muscles move, is punished, made to feel shame, and in extreme cases, dosed up with addictive mind-altering chemicals.
As a result of this training, most people are socialized to ignore their biological instincts and feel comfortable sitting still for long periods of time. Thankfully, I managed to avoid internalizing this social norm. When working at a computer, I am constantly moving around. I shift to different sitting positions, lean back and forward in the chair a lot, and occasionally stand up. Every so often I will get up and start walking around. I will take any excuse to move around.
However, for people who have lost these instincts or must work in a more public area, the problem of unhealthy sitting is a hard one to fight. Most of us have jobs that require us to be sitting for long periods of time, and the social norms from elementary school are still strong. People will look at your funny if you fidget while you work, and may think that you are not a good worker.
But there are things you can do. When the head of our dojo worked a desk job with some other guys, he got them all in the habit of doing ten push-ups every hour on the hour, no matter what they were doing. It was good exercise, and would have helped with the muscular inactivity problem.
And you have a lot more control over your free time. You may have to sit at a desk all day, but when you get home you do not have to sit in front of the television. Television may be mostly harmless for people who have physically demanding jobs, are moving around all day, and need to relax, but it is a disaster for people with desk jobs. If you have been sitting all day, then when you get home you need to do something, anything, that makes you move around. Don't just set up a time to exercise. Make movement part of your life. For example, you could prepare meals that require a half hour of chopping up and mixing ingredients, and think of that time as a kind of fun exercise. Clean up the house more often, and think of that too as useful exercise.
If nothing else, just get up and walk around a nice place. The evidence shows that constant amounts of low-level activity is as important as an exercise routine, and it is probably easier and more fun once you get in the habit of doing it.