Ask kids what their favorite time of the school day is, and many may say either gym class or recess. They get to run around, play with their friends and take a break from the books. It may be a great way to release stress, but could fitness also contribute to better grades? A recent study revealed that kids who are in better shape also perform better on school aptitude tests.

Researchers in West Virgina studied 725 fifth grade students, measuring their fitness levels and their academic performance. Then, two years later, they followed up with the students as seventh graders. They divided the kids into four groups, including those that were:

  • in excellent shape in fifth grade and stayed that way in seventh grade;
  • fit in fifth grade but not in seventh grade;
  • not fit in fifth grade but were physically fit by seventh grade;
  • not physically fit in fifth grade, nor in seventh grade.

To evaluate the students' fitness, the researchers used the standardized FitnessGram, which includes a variety of tests that assess aerobic capacity, muscular strength, muscular endurance, flexibility and body composition.

The results were clearly in favor of the kids in motion. The group that was in shape in fifth grade and in seventh grade performed the best on standardized tests in reading, math, science and social studies. The next best academically were those who were not fit in fifth grade but had worked their way into shape by seventh grade.

The students that lost their fitness levels during those two years came in third place. Finally, the kids that were not fit in either grade turned in the worst test scores.

"The take-home message from this study is that we want our kids to be fit as long as possible and it will show in their academic performance," said Lesley Cottrell, associate professor of pediatrics at West Virginia University who led the work. "If we can intervene for those children who are not necessarily fit and get them to fit levels, we may also see their academic performance increase."

John Ratey, a Harvard clinical associate professor of psychiatry and author of "Spark: The Revolutionary New Science of Exercise and the Brain," agrees that more time needs to be devoted to physical activity.

"I cannot overestimate how important regular exercise is in improving the function and performance of the brain," Ratey said. "Exercise stimulates our gray matter to produce Miracle-Gro for the brain. The exercise itself doesn't make you smarter, but it puts the brain of the learners in the optimal position for them to learn.

Dan Peterson writes about sports science at Sports Are 80 Percent Mental.