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David Yon, July 2, 2018 (rev Jul 3)

I feel this slight vibration on my left wrist and I looked down to see my watch telling me to “Move!” I have never asked my watch to do this task, that is tell me when I have stayed in the same position (sitting) for too long.  I don’t even know how long I have to sit before it barks at me. But it does so anyway with complete confidence that it is right.  I swear, some mornings I have just settled into my desk, exhausted after a track workout and weight lifting session (stop laughing), when it says “Move!”  Just how much exercise do I have to do?

While this is not a new subject, there seems to be a fast-growing body of evidence telling us that not only do we need to be active and exercise, but also that we should not remain sedentary for long periods of time.    It is not that all the advice and recommendations about living a healthy life, with a focus on being active and fit is not still good advice.  But it may not be the full story.

More and more evidence is being gathered that supports the conclusion that no matter how much you exercise, if you follow it up by going home and sitting on your butt for too many consecutive hours, you might as well have smoked a cigarette or worse.  At best, you can hope the two behaviors cancel each other out. A group of researchers published an article in 2012 titled Too much Sitting: The Population-Health Science of Sedentary BehaviorAfter an extensive review of the literature on the topic, the authors concluded: “Even when adults meet physical activity guidelines, sitting for prolonged periods can compromise metabolic health. TV time and objective-measurement studies show deleterious associations and breaking up sedentary time is beneficial. Sitting time, TV time, and time sitting in automobiles increase premature mortality risk.”  Stated another way, the authors propose that “Put simply, the perspective that we propose is that too much sitting is distinct from too little exercise.” They conclude by saying further studies are necessary, especially to understand what impact breaking up sedentary behavior has on in mitigating any negative health results.

In 2016 the American Heart Association published a Science Advisory called Sedentary Behavior and Cardiovascular Morbidity and Mortality. In a news release describing the Advisory, the AHA said: “Being sedentary is not just a lack of exercise, it is a potentially independent risk factor for heart disease and stroke.” The release went on to quote Deborah Rohm Young, Ph.D. and director of behavioral research at Kaiser Permanente Southern California in Pasadena:

Regardless of how much physical activity someone gets, prolonged sedentary time could negatively impact the health of your heart and blood vessels.

It is of course not an easy thing to define and measure “sedentary.”  And if those problems cannot be solved with certainty, there must be some reservation about giving results full credibility at this stage.  However, there is substantial support for the proposition that regardless of how much physical activity a person engages in, sedentary behavior still produces an increased risk of developing diabetes, cardiovascular disease, impaired insulin sensitivity (linked to diabetes) and an overall higher risk of death from any cause, including cancer.

The authors of the AHA article defined sedentary behaviors to include sitting, reclining, or laying down while awake as well as reading, watching television or working on the computer. These “inactive activities” usually mean energy expenditure is less than or equal to 1.5 metabolic equivalents, or METs. Light housework or slow, leisurely walking uses about 2.5 METs; while moderate to vigorous physical activity usually requires at least 3.0 METs. While there is general support for the conclusion that “less sitting and more activity” is beneficial, I was unable to find clear evidence that defined the appropriate intensity or frequency at which sedentary behavior should be interrupted.  I would certainly start with at least once an hour and at least light to moderate (walking) exercise.
There are some studies that suggest regular exercise does offset the impact of sitting, but the majority show the amount of sedentary time, especially sitting, is an independent risk factor for cardiovascular disease and more. There is unanimous agreement that more study is needed on the effects of sitting and other sedentary behaviors on any beneficial impacts of physical activities on health. Acknowledging all of that, Dr. Edward Laskowski writing for the Mayo Clinic states…  “it seems clear that less sitting and more moving overall contribute to better health.” He recommends taking a break from sitting at least once every 30 minutes.

I am not sure how it knew, but somehow my watch recognized, that despite a lengthy and intense morning of exercise, I had been sitting in front of the computer without moving for so long that I was significantly increasing my risk of heart disease and many other bad outcomes. Who knows, maybe that explains why I had to have that stent put in a couple years ago. I certainly have had no shortage of physical exercise, but I spend a lot of time at the computer.  Maybe, if my watch back in my early days was a smart as it is now, I would not have had that problem.  So, I am thinking that time has extended well beyond my need to get up, stretch and walk around!

Neville Owen, Genevieve N. Healy, Charles E. Matthews, and David W. Dunstan and corresponding author, Neville Owen.