Marathon runners as couch potatoes

GRETCHEN REYNOLDS

Someone can train for a marathon and simultaneously qualify as a couch potato, recent research shows, raising provocative questions about how sedentary most of us really are.

The amount of time that most of us spend sitting has increased substantially in recent decades, especially as computers and deskbound activities have come to dominate the workplace. According to one telling recent study, the average American sits for at least eight hours a day.

Such prolonged sedentariness may have health consequences, additional research shows. A study of almost 2,000 older adults published in August, for instance, found that those who spent the most hours seated every day had a greater risk of high blood pressure, elevated blood sugar, a poor cholesterol profile and body-wide inflammation than those who sat the least, no matter how much either group exercised (which, generally, was not much).

So, too, a stark numerical 2012 analysis of lifestyle, health and death statistics from a large group of Australian adults concluded that every hour that someone spent watching television — a widely accepted marker of sitting time — after the age of 25 reduced his or her lifespan by almost 22 minutes. More broadly, in this analysis, watching television for six hours or more per day shaved almost five years from a typical adult's lifespan, compared with someone who did not watch TV. Lifespan was shortened even if someone met the standard medical recommendation of exercising moderately for 30 minutes or so on most days of the week.

But many highly active people, including those completing their preparations for Sunday's upcoming New York City Marathon, likely feel immune from such concerns. After all, it seems reasonable enough to assume that multiple hours spent training must lessen the number of hours spent plopped in a chair.

Until recently, however, no studies had specifically examined whether people who are extremely active are, on the whole, also truly not sedentary.