Ideally, children are supposed to get an hour of exercise a day. It's good for their muscles, their weight and their brains. School budgets have forced reductions in recess time and physical education programs, so elementary schools have been scrambling to find ways to fit the half-hour of physical activity required by the government into each day. Teachers, however, tend to be unimpressed with this idea. They have too much to cover in a day as it is.

That attitude may change, however. Researchers at the University of Michigan have found that briefly interrupting class time with bouts of exercise improved kids' attention and got them burning more calories each day. In a series of experiments with grade school children in Southern Michigan, they found that a number of short bursts of exercise — just two minutes each — not only didn't disrupt learning, it also improved kids' attention and moods.

One teacher did an activity break in the middle of a math exam. She realized the benefit of getting them up and moving.

“What we're showing is that we can give kids an additional 16 minutes of health-enhancing physical activity,” said Rebecca Hasson, one of the lead authors and an associate professor of kinesiology and nutritional sciences, in a statement. “Many kids don't have PE every day but they might have recess, and if they get 10 more minutes of activity there, it would meet that school requirement,” Hasson said. “This doesn't replace PE, it's a supplement. We're trying to create a culture of health throughout the entire school day, not just in the gym.”

Children, ages 7 to 11, took part in the experiments, first in the lab and later in the classroom. In one situation they spent eight hours sitting, punctuated by two-minute breaks for low-, moderate- or high-intensity activity. In another condition, the eight hours of sitting was interrupted with two minutes of sedentary screen time.

When the kids had intense exercise breaks, they ended up burning an added 150 calories a day, and their food intake did not increase. And though their moods were higher immediately after the two minutes of screen time, they rated the activity breaks as more fun. Overweight and obese kids in particular reported their improved mood from the short bouts of exercise lasted all day, suggesting they gained satisfaction from having exercised.

When the exercise breaks were taken to real classrooms, teachers found they could do them. “We got a lot of pushback at first. The fear was that teachers would be overloaded,” Hasson said. “Teachers get a lot of stuff thrown at them. Our experience was that teachers were all very positive about exercise. They know it's good for the kids. They were open to the idea but they needed more information on how to do it safely.”

Members of the University of Michigan's College of Architecture and Urban Planning and School of Education helped design classrooms to accommodate exercise and to safely get kids exercising and then back to classwork quickly. “Teachers were worried it would make kids more rowdy, but 99 percent of kids were back on task within 30 seconds of doing activity breaks. We even had one teacher who did an activity break in the middle of a math exam — she realized the benefit of getting them up and moving.”

The researchers had requested that teachers do 10 three-minute breaks, but most teachers averaged between five and six breaks adding up to about 15-18 minutes of activity. There was also some economic disparity — schools located in disadvantaged districts weren't able to complete as many activity breaks as schools in wealthier districts. Going forward, the researchers hope to study exercise intervals of differing lengths to see what seems to work best.

The study is published in PLoS One.