Exercise Improves the Academic Performance of Children with ADHD

My son's daily schedule in his elementary school includes an hour-long period for recess and lunch. At the end of the day, he may not easily remember what he had for lunch, but what happened during recess is something he could recall without difficulty. In fact, he tells me that he has scored a dozen goals in soccer since the start of the academic year. He may not share with me readily what transpired during math period but I am certain that at the end of the day when I pick him up from school I will be briefed on the highlights from the day's recess. Recess makes my son's day in school. It is his favorite period. And it is the period that has helped him a lot academically.

It has become evident especially from the work pioneered by Charles Hillman at the University of Illinois that exercise heightens brain activity. The figure below shows this clearly:

Electrophysiological plots representing brain processing
capacity and mental workload (P3 amplitude) during
cognitive tasks that require executive control in children
in the experiment and control groups. Red represents
the greatest amplitude, and blue the lowest.
(Hillman et al, Pediatrics/The Atlantic)
Exercise not only improves brain processing but also academic outcomes. The specific results are:
Analysis revealed that both children with ADHD and Healthy Match-Control children exhibited enhanced performance following exercise on tests of reading comprehension (115.2 ± 2.2) and arithmetic (112.5 ± 2.7) relative to following the seated reading condition (reading comprehension: 110.1 ± 1.8, p < .001, Cohen’s d = 1.58; arithmetic: 110.0 ± 3.1, p = .03, Cohen’s d = 1.25)
How exercise exactly benefits academic performance remains an active area of research. A recent systematic review of the mechanisms by which exercise affects mental health and performance suggests three ways:

Above copied from
Lubans D, Richards J, Hillman C, et al. Physical Activity for Cognitive and Mental Health in Youth: A Systematic Review of Mechanisms. Pediatrics.2016;138(3):e20161642
It should be made clear that what is not fully known is the mechanism, but the fact that exercise improves mental performance and health is already established. Play and physical activity are very important for a growing child. This is the primary reason why homework in the elementary years is not beneficial. This is also evidently the big reason why recess is one of the most important periods in a school day.