Can a glass of water be both half-full
AND half-empty at the same time? Of course, it can, right? It's just a matter of perspective. If that's the case, then is it possible to be both sedentary and physically active? Probably not at the exact same time, at least by definition, but over the course of a day, it's certainly possible. Picture me, if you will, at a desk in front of a computer either supervising senior residents or researching topics online. Either way, I'm sitting down for most of the day. Yet when I'm not at work, I make every effort to exercise daily. So am I sedentary or physically active?
Let's look at this mathematically. Out of 24 hours/d, we (should) sleep 6-8 hours; we'll choose 8 for ease of math. That means that out of a 7 day week, we sleep 56 out of 168 hours. Most sedentary white collar office workers will sit 40 hours/week. But if we achieve just the minimum amount of physical activity recommended (and remember that most Americans don't even reach this level), we've only exercised 150min/wk or less than 3 hours. That's not even 2% of the week, yet by achieving that level of exercise, we get to call ourselves physically active. Compare that to 25% of the week spent sitting down.
In a
meta-analysis published yesterday in BMJ Open, the authors analyzed 2 studies linking sitting to all-cause mortality and 3 studies linking TV viewing to all-cause mortality. The participants were all non-pregnant adults w/trials varying from 4,512 to 123,216 participants followed for 4.3-14yrs. After much number crunching, the authors concluded that
by limiting sitting time to less than 3 hours/d, we could potentially increase life expectancy by 2 years in the States. By limiting TV viewing to <2 hours/d, we could potentially increase life expectancy by 1.4 years. Granted, life expectancy is a statistical derivation and doesn't apply to individuals but you get the idea. So don't just sit there, do something! If you don't believe this study,
check out Part 6!
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