Not getting enough exercise and sitting too much are health concerns for older adults, but they are not the same thing — and understanding the difference is important.
The news recently has been full of reports citing evidence of the evils of sitting too long and the benefits of standing up more at the office and at home. But how should you interpret all this new information? Will getting up on your feet really make a difference to your health?
A new field of research has emerged to study what's become known as "sedentary behavior." It proposes that remaining sedentary for long periods of time potentially has metabolic effects that are distinct from the results of not exercising enough. The implication of this hypothesis is significant — if true, a person could spend all day sitting at a computer (or in front of a television or behind the wheel of a car), then head out for a vigorous workout in the evening and still have problems controlling his or her weight and health indicators, like cholesterol.
Sedentary behavior theory could go a long way toward explaining the nation's obesity epidemic in light of our increase in sitting time over the last 30 years.
Here at the Stanford Center on Longevity, we convened a conference, co-sponsored by the Steelcase Corporation, that brought together some of the world's leading experts in sedentary behavior to examine the evidence. It was chaired by William Haskell of Stanford, a noted expert in exercise physiology, and Neville Owen of the University of Queensland in Australia, one of the field's pioneers. The goal: to determine if there's sufficient justification to issue recommendations on how much sitting is too much.
In the end, the group found significant evidence that sitting all the time is not good for you. But — and this is important — most of the data was not causal, but correlational. This means we can look at the behavior of a group of people and draw conclusions based on their actions and the results, but we can't know with absolute certainty how all of the variables in their lives interact.
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Let's take as an example one of the earliest, and most entertaining, studies on sedentary behavior: In the 1950s, Professor Jeremy Morris of the London Hospital Medical College looked at the 2,270 employees at the London Transit Authority and compared the trouser waistband sizes of bus drivers, who sat all day, with those of conductors, who mainly worked on their feet. In a result that was probably more surprising to 1950s sensibilities than it would be now, drivers were found to be mostly heavier than conductors. But while this was a significant study, it didn't tell us exactly how long drivers would need to stand; whether they needed to walk more; or even if heavier people just tended to become drivers instead of conductors.
We do have some direct data about sedentary behavior, but it comes mostly from studies of rats. Marc Hamilton of the Pennington Research Center at Louisiana State University investigated what happened when the hind limbs of rats were held motionless for a period of time. He found that this inactivity caused up to a 75 percent drop in the animals' ability to remove fat from the blood.
Rats are not humans, of course, so Hamilton warned that we should be careful drawing direct conclusions from his work. What's needed is a long-term study of humans, but that will take time. After all, most of the health effects of sedentary behavior take years to manifest themselves.
So what are we left with? A high level of confidence that too much sitting is not good for us, but not enough solid data to be able to publish the health guidelines everyone wants to see — a document that says something like this: "Standing for five minutes each hour is strongly recommended."
Here at Stanford we have partnered with Blue Shield to undertake a pilot study of sitting in the workplace. We hope it will eventually lead to the kind of large, long-term study that will help us answer these questions definitively. Other research centers are also working on this issue, at places like UCLA, the Mayo Clinic and the Baker IDI Heart and Diabetes Institute in Melbourne, Australia.
While we scientists try to tease apart this complicated puzzle, there is some advice that individuals can follow right now, based on data interpreted with a little common sense:
- When working on the computer, watching television or playing video games, make an effort to get up and move around a couple of times (or more!) every hour.
- If possible, take your phone calls at work standing up, or try to arrange an office setup that allows for movement.
- On long drives, stop for a few minutes periodically to stretch your legs.
We don't yet know exactly how much movement is needed to break the effects of a sedentary lifestyle, but clearly you're better off on your feet. Stand, for sure. Move a little. Walk. Most important, don't interpret all of this attention and research on sitting as a free pass to avoid exercise.
Standing more often may help you avoid the negative effects of sedentary behavior. But the positive effects of cardio and resistance training, for both the body and mind, are well understood by science — simply standing up is no substitute for actual exercise. You need to avoid sitting too much and exercise more to get the most positive health benefits.