ATLANTA, Georgia (CNN) — The familiar saying that exercise is good for the body and mind may be especially true for children. Kids who are physically fit actually have differences in their brain structures that might allow them to do better in math, according to a new study.

Researchers put a small group of children ages 9 and 10 to the test both mentally, with standardized math and reading exams, and physically, testing their endurance on a treadmill. They also scanned their brains using MRI and found that the children who could run for longer periods of time on the treadmill had thinner sections of gray matter in the front of their brains, which actually signifies more brain maturation, than those with lower stamina. These children also ran laps around their less fit peers in the math test.

"It's part of a natural process that the brain goes through a period of thinning during adolescence (as) brain connections that are deemed not necessary are thinned out. (Fit) kids may be further along in this maturation process," said Charles H. Hillman, professor of kinesiology and community health at the University of Illinois Urbana-Champaign. Hillman is one of the authors of the study, which was published in August in the online journal PLOS ONE.

This part of the brain, also called the frontal cortex, could be especially key for academic performance because it is involved in working memory, which helps us figure out math problems, for example, and cognitive flexibility, or the ability to tune out distractions, Hillman said.

Earlier studies have linked physical fitness with changes in other regions of the brain, such as a larger hippocampus. A combination of areas in the brain, and connections between them, are probably important for scholarly tasks, Hillman said. And development of these areas may be either spurred or stagnated depending on exercise.

Although the current study only detected a link between fitness and math ability, other studies that Hillman and his colleagues have done suggest that reading comprehension and other areas of academic performance may also be affected by these changes in brain structure. "I don't think it's selective to math," Hillman said.

Physical activity at school

Despite the large body of research suggesting that physical activity pays off in the classroom, many schools have cut back their physical education classes and recess time, according to a 2013 report by the Institute of Medicine, a private nonprofit scientific organization.

"The vast majority of schools were not serving kids in terms of their physical activity needs," said Hillman, who was a member of the committee that wrote the Institute of Medicine report.

The report recommended that all children should be able to get an hour of moderate or vigorous activity every day in school, through physical education classes and recess. Achieving this goal will require participation from teachers and administration, as well as the use of school buildings and outdoor space, the report stated.

There are currently no federal requirements for the amount of physical activity that students receive every day, although there are government incentives for schools that promote exercise. Some states are also trying to tackle the problem, Hillman said. Texas, for example, requires that children in prekindergarten through elementary school get at least a half-hour of physical activity a day.

Copyright 2015 Cable News Network. Turner Broadcasting System, Inc. All Rights Reserved.

Related topics