As a child, I lived in a town on the outskirts of Tokyo where there were also many woods and empty lots. Computer games and TV did not exist at the time (although there were street television sets), so after school we played in the nearby woods until dusk, building secret houses and playing kick-the-can.

When I came home after dark, my mother would often say something like, "Don't play outside so late—come home and study" or "Use your brain instead your body or you won't do well in school."

Later, when I entered junior high school, volleyball had just become popular because the performance of the women's team in the Tokyo Olympics, so I joined the volleyball club. Seeing me come home sweaty and soiled day after day, my mother was worried that I was neglecting my studies.

I'm sure that many other parents, not only my mother, would rather see their children study if they have the free time to engage in physical play.

Recently, however, there is much research data that these parents might find hard to believe. As the title above indicates, recent research shows that "exercise makes you smarter."

In an experiment in Canada in 1996, Dr. Roy J. Shephard had 546 first graders in elementary school participate in physical activity that raised their heart rate to 157-178 beats per minute and compared their cognitive skills with those of a control group over a period of six years (Shephard, 1996). The cognitive tests (Goodenough test, WISC) conducted after the experiment indicated significantly higher scores by children who had participated in the additional exercise.

In a study in United States in 2009, Joseph E. Donnelly had 117 children from 6 to 9 years of age take part in relatively strenuous physical exercise for at least 45 minutes a week for three years (Donnelly, 2009). Three years later, the children scored significantly higher on cognitive tests than the control group.

In recent years, there has been a shift from such experiential studies to research that shows improved brain functioning by measuring brain waves. One study tested the frontal lobe function of nine-year olds (Drolette, 2014), divided the children into high performing and low performing groups, and then had them each perform twenty minutes of treadmill walking. After exercise, when brain wave activity was recorded, the low-performing group showed an increase in brain wave response.

Drolette's research proved the brain function improved immediately after exercise, and Hillman et al. showed that with long-term physical activity, improved brain function continued for an extended period of time (Hillman, 2104). Of the 221 children from 7 to 9 years of age who participated in the study, half were assigned to a group that took part in aerobic exercise after school for 9 months (treadmill running, games requiring physical exercise, etc.), and together with the other half or control group, brain function was measured based on cognitive tests and brain waves during the tests. Nine months later, the same tests were conducted again on the group that undertook aerobic exercise and the control group. The results clearly indicated a significant correlation between the rate of participation in aerobic exercise for 9 months and the results of the cognitive tests and improvement in brain function based on brain wave measurement.

The study proved that aerobic exercise not only temporarily improved executive functions immediately after exercise, but if continued, the improvement in executive functioning is sustained.

Although these experiments have not yet clearly clarified the mechanisms involved, they do show that physical activity raises cognitive indices and executive functioning of the brain.

These findings contradict the "common sense" view that exercise builds muscle, but will not make you smart and that the only way to improve intelligence is to sit quietly and study. To the mothers and fathers who read this blog, I want to say there is no need to worry if your children spend a lot of time playing outside.
That's because exercise does make you smart.

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Donnelly JE et al. Physical activity across the curriculum (PAAC): a randomized controlled trail to promote physical activity and diminish overweight and obesity in elementary school children. Prev Med 49:336-341, 2009.
Drollette ES et al. Acute exercise facilitates brain function and cognition in children who need it most: An ERP study of individual differences in inhibitory control capacity. Dev Cog Neurosci. 7:53-64, 2014.
Hillman CH et al. Effects of the FITKids randomized controlled trail on executive control and brain function. 134: e1063-1071, 2014.
Shephard RJ. Habitual physical activity and academic performance. Nutr Rev. 54: 32-36, 1996.