NEW YORK (Reuters Health) - The most physically fit group of third-, fourth- and fifth-graders tend to score highest on an academic test known as the Illinois Standard Achievement Test, a group of researchers from the University of Illinois at Urbana-Champaign reports.

"We found a general relationship between physical fitness and improvement on this test," study author Dr. Charles Hillman told Reuters Health.

These findings present an additional reason why it's important for students to get plenty of exercise, Hillman noted.

"It's a good thing for everyone to stay fit," he said.

Hillman added that the reasons why fitness helps kids' minds as well as bodies are unclear, but previous research has shown the same pattern in older adults. He suggested that being physically active may boost the amount of molecules that protect the brain, and prevent the loss of brain tissue. "I personally don't think there's one answer," he said in an interview.

During the study, Hillman and his colleagues tested the physical fitness of around 500 kids between the ages of 7 and 11. As part of the fitness test, students ran a series of increasingly faster sprints, did push-ups and sit-ups, completed tests of flexibility, and were weighed.

To test kids' minds, the researchers reviewed their scores on the standardized tests, and asked kids to look at a series of cartoon drawings, most of which were of dogs. The researchers would occasionally throw in a picture of a cat, after which students had to press a button as quickly as they could.

The investigators found that kids who scored highest on the tests of physical fitness -- particularly the sprinting test -- tended to also score higher on the standardized test, and press the button faster when they saw a picture of a cat.

Moreover, tests of brain activity showed that fitter kids tended to be better able to focus the attention resources of their brains on the dog/cat task.

Hillman and his team presented their findings last week during the annual meeting of the Society for Psychophysiological Research in Santa Fe, New Mexico.

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