Sit too much?

The physiology of inactivity

Well, sorry, but you probably do — even if you exercise regularly five or more days a week. We sit more than any previous generation and studies show that, on average, adults spend more than nine hours a day in sedentary activities.

The first problem with sitting is that you are not using much energy to do it. Sitting makes it a lot easier to gain weight and all the health problems that come along with being overweight.

However, there might be an even more serious problem with sitting too much, relating to the “physiology of inactivity” — the effects that prolonged sitting have on your body. Although research on the health risks of sitting is preliminary, studies show that too much sitting is distinct from too little exercise.

Sit too much? Photo of an empty chair.Here’s the startling news: People who sit a lot are more likely to be at risk for heart disease, diabetes, certain cancers, and early mortality — even if they are conscientious about spending 30 to 60 minutes a day exercising!

How can that be? Recent animal studies show that prolonged sitting decreases circulation and the body starts to shut down on a metabolic level. A key enzyme, lipoprotein lipase, breaks down fats in your body. Studies indicate that the level of this enzyme is lower in rats when they are prevented from moving around normally in their cages. The sedentary animals show signs of insulin resistance and higher levels of fatty acids in their blood. The rats only produce this protective enzyme when their muscles are actively flexed, such as when standing or moving around.

You can achieve a high level of activity, such as running for 30 minutes for five days a week, but still spend most of the waking hours sitting. You are sitting driving to work. You are sitting in front of your computer. You are sitting eating your meals. You are sitting watching your favorite TV programs. You are sitting at the movies. You are sitting playing games on your smart phone. You are sitting reading. I am sitting writing this article. Thus, it is possible to be physically active, yet highly sedentary — an “active couch potato!” Studies show that regular workouts, while beneficial to your health, do not entirely counteract the negative effects of sitting.

If you are an active couch potato, or even an inactive couch potato, there are some things you can do. Stand up! I just did! It appears that interrupting long periods of sitting with frequent breaks is helpful. Set a timer to go off every 30 minutes and stand up and move. Get an exercise (therapy) ball and sit on that instead of a chair; you’ll be using your muscles to stay balanced. Watch TV while rocking in a rocking chair, flexing your calf muscles. More dramatic solutions include using a stand-up desk, walking on a treadmill while you work, or hooking an exercise bike to your TV set so it will stay on only if you are pedaling. Whatever you decide to do – stand up!

Joyce Hanna, MA, MS, Associate Director, Stanford Health Improvement Program (July, 2010)

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