The exercisers’ weekly program consisted of unsupervised walking or jogging, with the aim of working out for at least 20 minutes a day and ideally for 40 minutes or more. Once a week they also visited the university for several hours of instruction and a group workout.

Meanwhile, the mindfulness group was learning to meditate, following a standard mindfulness instruction program that focuses on attending to the present moment and checking in on how your body feels. The people in this group practiced body scans and mindful walking, in addition to the usual quiet, seated meditations. Like those in the exercise group, they attended a weekly session on campus, but most of their meditations were completed at home.

Both of these programs lasted for two months, which, in this study, took people through September and October and into the early days of November.

Then, with winter on the horizon, the volunteers, including those in the control group, wore an activity monitor for another week. None of them knew that the study’s aim was to track their activities; they thought it was looking at colds.

But the two programs did seem to have had an influence, according to data from the monitors. Most noticeably, the men and the women in the control group were much less active now, in the late fall, than they had been in the summer, averaging almost 18 fewer minutes a day of walking and otherwise moving about.

But the men and women in the other two groups had not become quite so inactive, although they were no longer being asked to exercise or meditate. They were moving a bit less than they had been in the summertime, but only by about six minutes a day.

These results surprised the researchers, says Jacob Meyer, an assistant professor of kinesiology at Iowa State, who conducted the study with Bruce Barrett and other colleagues. They had expected the exercise program to get people familiar with and interested in the idea of moving, he says. “But we did not expect the mindfulness training to have the effect that it had,” he says.