By GRETCHEN REYNOLDS
ONE lesson I’ve learned while writing about fitness is that few things impinge on an active life as much as writing about fitness — all that time spent hunched before a computer or puzzling over scientific journals, the countless hours of feckless, seated procrastination. While writing about the benefits of exercise, my muscles slackened. Fat seeped insidiously into my blood, liver and ventricles. Stupor infiltrated my brain.
We all know by now that being inactive is unhealthy. But far too many of us think that being inactive is something that happens to other people.
Studies of daily movement patterns, though, show that your typical modern exerciser, even someone who runs, subsequently sits for hours afterward, often moving less over all than on days when he or she does not work out more…