Exercise Now, Sit in Front of the TV Later


After working out, many of us, consciously or not, find other opportunities to move less, undermining our best intentions to stay fit.

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If we spend an hour working out, that’s one hour less during our day that we can potentially spend being sedentary.

But we may, consciously or not, find other opportunities during the day to move less, undermining our best intentions and the potential health benefits of the exercise, according to an interesting new study of how people use their time, minute by minute, on days when they exercise and when they do not. Time management is always tricky, involving constant trade-offs, not all of which are voluntary or even conscious.

If we shop for groceries, for example, we may not have enough time later to visit the gym. Or if we binge-watch sitcoms, those accumulated hours of sitting cannot be devoted to any other activity.

But while many past epidemiological studies and experiments have looked at how we apportion our days — how many hours we spend, on average, sleeping, sitting, working, eating, exercising and so on — few have closely examined how we balance one activity against another and the extent to which some activities elbow others aside.

Those details matter, because if, for instance, we hope to use exercise to increase how many calories we burn during the day, we need to avoid becoming less active over all on exercise days.

In other words, on days when we exercise, we need to avoid sitting more or skipping physical activities we might normally do, like taking the stairs or cleaning the house, during non-exercise hours.

But do we?

To find out, researchers from the National Cancer Institute turned to an existing and elaborate database of information about more than 1,000 healthy, middle-aged and older men and women.

The data had been collected over several years in conjunction with the AARP. (The current study, which will be published in September in the American Journal of Preventive Medicine, was funded by the National Cancer Institute.)

When the participants joined the study, they completed a variety of health tests and questionnaires, including a bogglingly detailed look at their lives on the previous day.