Exercise for children may do far more than improve physical fitness. It may also stimulate brain growth and boost cognitive performance. How do we know?
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 pathways
• prevents brain tissue loss in older adults
(For reviews, see Cotman and Berchtold 2002 and von Pragg 2008).
What about kids?
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 children, and the results suggest that aerobic exercise can make kids more focused and less impulsive.
For instance, 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).
Fit children also showed distinctive patterns of brain activity. For example, when 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).
But as intriguing as these correlations are, they don't prove causation.What if smarter kids are more likely to seek out physical activity? That could explain the results.
So we need experimental studies, and in recent years there have been several.
Some research has been aimed at understanding the immediate effects of aerobic activity. Does a quick bout of exercise make a child feel more focused?
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). A similar experiment found that a 20 minute session of walking boosted children's performance on tests of reading, spelling, and arithmetic (Hillman et al 2009a).
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).
Then there are the interventions aimed at understanding long-term outcomes. What happens if you enroll previously sedentary children in a program of daily physical exercise? One randomized, controlled study of overweight kids 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.
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).
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.
But the experiments on rodents and children suggest that aerobic activity does indeed has a positive effect of cognitive performance. Given that physical fitness is also good for the body, it seems we have nothing to lose by encouraging kids to exercise.
Still, 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.
So it’s important to find form(s) of aerobic exercise that your child really enjoys. Structured activities—-like team sports or dance lessons—-may be fine 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 exercise for children is free, unstructured, physical play.
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Content of "The cognitive benefits of exercise for children" last modified 3/15
Image of child running on the beach by Black Imp Photography