Researchers have found an association between physical fitness and the brain in 9- and 10-year-old children: Those who are more fit tend to have a bigger hippocampus and perform better on a test of memory than their less-fit peers.

The new study, carried out by the University of Illinois, used magnetic resonance imaging to measure the relative size of specific structures in the brains of 49 child subjects.

“This is the first study I know of that has used MRI measures to look at differences in brain between kids who are fit and kids who aren’t fit,” said University of Illinois psychology professor and Beckman Institute director Art Kramer, who led the study with doctoral student Laura Chaddock and kinesiology and community health professor Charles Hillman. “Beyond that, it relates those measures of brain structure to cognition.”

The study focused on the hippocampus because it is known to be important in learning and memory. Previous studies in older adults and in animals have shown that exercise can increase the size of the hippocampus. A bigger hippocampus is associated with better performance on spatial reasoning and other cognitive tasks.

The physically fit children were “much more efficient than the less-fit children at utilising oxygen,” Kramer said.

When they analyzed the MRI data, the researchers found that the physically fit children tended to have bigger hippocampal volume – about 12 per cent bigger relative to total brain size – than their out-of-shape peers.

The children who were in better physical condition also did better on tests of relational memory – the ability to remember and integrate various types of information – than their less-fit peers.