Then, on three subsequent visits to the clinic, each volunteer simulated a six-hour workday.

During one visit, the volunteers sat for the whole time with no interruptions, except for bathroom breaks.

During another, they walked moderately for 30 minutes at the start of their experimental day, and then sat for the next five and a half hours with no additional scheduled breaks.

Finally, during a third visit, the volunteers sat for most of the six hours, but began each hour with five minutes of moderate walking, using treadmills at the clinic.

At the start and end of each session, the researchers drew blood to check levels of stress hormones. And periodically throughout each day, they asked their volunteers to numerically rate their moods, energy, fatigue and appetites.

The volunteers also repeated the computerized testing of their thinking skills at the close of each session.

The researchers then analyzed the data.

The numbers showed that on almost all measures, the subjects’ ratings of how they were feeling rose when they did not sit for six uninterrupted hours. They said that they felt much more energetic throughout the day if they had been active, whether that activity was bunched into a single longish walk at the start of the day or distributed into multiple brief breaks.

On other measures, though, the five-minute walks were more potent than the concentrated 30-minute version. When the workers rose most often, they reported greater happiness, less fatigue and considerably less craving for food than on either of the other days. Their feelings of vigor also tended to increase throughout the day, while they often had plateaued by early afternoon after walking only once in the morning.