Five studies from the University of Michigan found that two-minute bursts of in-class exercise breaks increased the amount of daily exercise for elementary children without hurting math performance.

More importantly, when the practice was incorporated into classrooms across southeast Michigan, teachers found the breaks were manageable and didn't disrupt learning.

While 16 minutes doesn't sound like much, it adds up, says Rebecca Hasson, principal researcher and one of the lead authors. Kids are supposed to get an hour of exercise a day - 30 minutes of that during school. Most don't.

The Active Class Space lab studies examined the effect of activity breaks on mood, cognition, appetite and overall physical activity of 39 children. A study done in real classrooms tested the feasibility of implementing the method of "Interrupting Prolonged Sitting with Activity".

In the lab studies, kids aged 7 to 11 completed four experiments: eight hours of sitting, interrupted with two-minute low-, moderate- or high-intensity activity breaks, and eight hours of sitting interrupted with two minutes of sedentary screen time.

The researchers found that when the sitting was interrupted with high-intensity activity breaks, children maintained their usual activity levels away from the laboratory, thereby burning an additional 150 calories a day without overeating. Unlike adults, children in the study didn't compensate for the increased exercise by sitting around after school or by eating more, says Hasson.

While moods were higher immediately following the screen-time breaks compared to the activity breaks, children reported a more positive mood during both the sedentary and exercise conditions, and they subsequently rated the activity breaks as more fun.

Besides, after high-intensity activity, overweight and obese children enjoyed improved moods all day, says Hasson. This suggests children reflected upon the exercise and took more satisfaction in it.

All of the activity breaks elicited the same level of math performance. Then Hasson took the exercise breaks to real classrooms.

"We got a lot of pushback at first," says Hasson. "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."

Initially, the researchers requested that teachers do 10 three-minute breaks, but most teachers averaged between five and six breaks totaling around 15 to 18 minutes of activity.

Schools in disadvantaged districts didn't complete as many activity breaks as schools in wealthier districts. Hasson is currently working to eliminate this disparity by adding elements of game playing - point scoring, competition and reward systems - to increase the enjoyment of physical activity in the children.

"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 the school's requirements," says Hasson. "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."

In the next step, the researchers will try five four-minute activity breaks totaling 20 minutes, and gauge the impact on mood, activity levels, calorie intake and cognition.