Exercise for children:
Why keeping kids physically fit is good for the brain and helpful in the classroom

© 2008-2016 Gwen Dewar, Ph.D., all rights reserved

Understanding the cognitive benefits of exercise for children

Does your child's daily schedule encourage physical fitness? Or is your kid stuck in a rut -- perhaps even a school system -- that leaves little time for physical activity?

We often hear about exercise as a remedy for poor health and child obesity. But exercise for children is important for other reasons too.

It appears to stimulate brain growth and boost cognitive performance. It helps kids focus. It may make it easier for kids to learn and achieve.

So when adults create environments that prevent kids from being active, we aren't only undermining their health. We're also making it harder for kids to succeed in school.

But how do we know all this?

Exercise and children: Lessons from mice

At the Salk Institute, Henriette van Pragg and her colleagues compared sedentary mice with mice that ran an average of 3 miles each night on a running wheel (van Pragg et al 1999).

Compared with the couch potatoes, the aerobically-challenged mice showed dramatic brain growth.

Specifically, the hippocampus—-a brain region associated with learning and memory--was twice as large.

In addition, the brain cells of the aerobic mouse could sustain longer bouts of "long-term potentiation," the increased efficiency of communication between neurons that occurs after neurons fire.

Better learning, too

Did these changes translate into better learning? Indeed they did. Mice who exercised performed better on a spatial learning task (finding their way through a water maze).

Why does it work?

Exercise is known to improve mood. Might that explain these results? Perhaps animals learn better when they feel better.

The explanation sounds plausible and may account for some of the effect. But it seems pretty clear there is more going on.

Since the late 1990s, research has revealed that aerobic exercise

  • boosts levels of brain-derived neurotrophic factor (BDNF), a substance essential for the growth of brain cells
  • stimulates neurogenesis—the birth of new neurons
  • mobilizes the expression of genes that are believed to enhance brain plasticity—i.e., the ability of the brain to change its neural pathway, and
  • prevents brain tissue loss in older adults

(For reviews, see Cotman and Berchtold 2002 and von Pragg 2008).

What about exercise for children?

Much of what we know about the cognitive effects of exercise comes from brain research on rodents, not humans. But some studies have been conducted on kids, and the results suggest that aerobic exercise can make children more focused and less impulsive. 

When kids have been challenged with cognitive tasks that require lots of concentration and attentional control, individuals with higher aerobic fitness have performed with more accuracy, and sometimes faster reaction times, too (Moore et al 2013; Wu et al 2011; Voss et al 2011; Hillman et al 2005; Hillman et al 2009b; Raine et al 2016).

For example, school children were asked to view some images of animals and make quick judgments about them ("Is it a cat or a dog?"), physically fit kids had faster reaction times, and their brains showed evidence of more extensive processing during the task (Hillman et al 2005). Other brain research suggests that fit kids are better at filtering out task-irrelevant information (Kamijo et al 2015).

Studies also indicate that fit children tend to have greater brain volume in the hippocampus, a brain region associated with memory (Chaddock-Heyman et al 2014), and these kids show signs of enhanced long-term retention. In one study, kids memorized new places on a map equally well, regardless of their fitness levels. But when they were tested on their retention the following day, the higher fitness children performed better (Raine et al 2013).

Intriguing? Yes. But these studies report correlations only. They can't prove causation. What if more focused, quick-thinking kids are more likely to seek out physical activity? That could explain the results. We need randomized, controlled experiments (Janssen et al 2014). And in recent years, there have been several.

Mounting evidence: What experiments reveal about the cognitive benefits of exercise for children

Exercise and attention

Does a quick bout of exercise make kids more attentive?

In one recent experiment, kids who ordinarily performed poorly on attention tasks improved their accuracy when tested shortly after "moderate acute exercise" -- 20 minutes of walking on a treadmill (Drollette et al 2014).

Another experiment randomly assigned 56 school kids to one of three morning school sessions:

  • sitting all morning
  • getting a 20-minute break of physical activity after 90 minutes; and
  • getting two 20-minute physical activity bouts, one at the start and after 90min

The kids who got two bouts of morning exercise performed better on a test of attention, and this was true even after the researchers adjusted for baseline differences in attention and children's involvement in sports (Altenburg 2015).

And what about ADHD? When researchers tested the effects of short-term exercise on kids diagnosed with ADHD, they found that aerobic activity gave these kids a special boost, altering their brain activity in ways that might enhance self-discipline (Pontifex et al 2013).

These studies address immediate, short-term responses to exercise, and lend support the idea that school recess periods -- breaks for play and physical activity -- can enhance attention in the classroom. But there are also studies that address long-term benefits of exercise for children.

For instance, what happens if you enroll previously sedentary kids in a program of daily physical exercise? One randomized, controlled study of overweight children found that 40 minutes a day of aerobic exercise improved executive function, that aspect of intelligence that helps us pay attention, plan, and resist distractions (Davis et al 2007).

Another experiment replicated these results, and found that 13 weeks of aerobic exercise was also linked with improved math skills and increased activity in the bilateral prefrontal cortex, a brain region associated with executive function (Davis et al 2011).

Similarly, when Keita Kamijo and colleagues randomly assigned 20 youngsters (aged 7-9 years) to an after-school exercise program, kids who got 70 minutes of moderate to vigorous physical activity each day showed improvements solving tasks that taxed executive control and working memory (Kamijo et al 2012). Kids in a control group did not.

And a recent randomized study of more than 220 school children found that kids assigned to engage in 60 minutes of daily, after-school aerobic activities performed better on tests of focus and cognitive flexibility--the ability to switch between tasks while maintaining speed and accuracy (Hillman et al 2014).

So we've got evidence that exercise can improve a child's ability to focus. But does that translate into better academic performance? There is reason to think so.

Physical exercise and academic achievement

Studies suggest that physical exercise yields short- and long-term benefits on achievement in the classroom.

For instance, one experiment found that a 20 minute session of walking boosted children's subsequent performance on tests of reading, spelling, and arithmetic (Hillman et al 2009a). Another study found that kids who exercised 10-20 minutes prior to a math test outperformed kids in sedentary control group (Howie et al 2015).

And the long-term? As noted above, one randomized study found that kids showed improved mathematics skills after a 13-week exercise program (Davis et al 2011), and other research indicates similar benefits.

In an experiment performed by Daniel Ardoy and colleagues on 67 adolescents, some kids were assigned to get 4 sessions each week of high intensity PE. After four months, these kids performed better than other kids on tests of cognitive ability and earned higher grades at school (Ardoy et al 2014). Adolescents assigned to less intense PE workouts showed no showed no cognitive improvements over kids in the control group (Ardoy et al 2014).

More recently, kids who were assigned a daily schedule with more physical activity breaks outperformed their control-group peers in mathematics and reading (Tomporowski 2016).

Exercise for children:

A safe bet...but make it fun

Can we assume that exercise will help every child perform better in school? Perhaps not. In some studies of aerobic exercise, the reported effects have been small or non-existent. As Caitlin Lees and Jessica Hopkins (2013) argue, we need more rigorous research to better understand what's going on. We need to learn more about the details -- including how the effects vary by intensity, frequency, and type of exercise being performed.

But the results aren't "mixed" in the sense that we don't know if exercise is good or bad for the brain. Clearly, it's good for the brain. Nor are the results "mixed" in the sense that we don't know if exercise during the school day helps or hurts academics.

When researchers conducted a meta-analysis of 59 studies published over the previous 60 years, they found that physical activity has a decidedly positive effect on children's achievement and cognitive outcomes (Fedewa and Ahn 2011).

There is no evidence that it's detrimental, which is striking if you consider that time spent by children in recess and physical education class is time diverted from academic study.

When schools have allocated more time for physical activity, they tend to see cognitive improvements. The worst case scenario is that kids become more fit and healthy, while their academic achievement levels remain the same (Keely and Fox 2009).

So school policies aimed cutting recess or PE -- in order to make more time for academics -- are misguided. We've got nothing to lose by encouraging kids to exercise, and much to gain. But there’s a catch: Exercise should be fun.

The mouse experiments are based on voluntary wheel-running. When rodents are forced to exercise, they don’t always reap the benefits.

Thus, it's important to find fun forms of aerobic exercise for children. Structured activities--like team sports or dance lessons--are good options. But so are nature walks, tree-climbing, roller-skating, and playing hide-and-seek.

In fact, play--like exercise--is good for the brain. Perhaps the most effective forms of exercise for children combine both high levels of physical activity and elements of play.

References: Cognitive benefits of exercise for children

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Content of "The cognitive benefits of exercise for children" last modified 3/15

Image credits for "Exercise for children":

Title image of kids running by Jackson Elizabeth, US Fish and Wildlife

Image of child running on the beach by Black Imp Photography

Imagine of boys playing with ball by cahilus / wikimedia commons

Image of girls on swing by Hartcreations/istock