Many of us sit in front of a computer for eight hours a day, and then go home and head for the couch to surf the Web or watch television, exchanging one seat and screen for another. Even if we try to squeeze in an hour at the gym, is it enough to counteract all that motionless sitting?
A mounting body of evidence suggests not.
Increasingly, research is focusing not on how much exercise people get, but how much of their time is spent in sedentary activity, and the harm that does.