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: A key study
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?
Admittedly, most of what we know about exercise comes from research on rodents, not humans. Ethical considerations prevent us from running the van Pragg experiments on kids.
But some studies have been conducted on kids, and the results suggest that aerobic exercise can make kids more focused and less impulsive.
First, there are the correlations.
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 2009).
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).
Second, research suggests you can improve cognitive outcomes by increasing the physical activity levels of previously sedentary children.
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.
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).
Finally, there is the indirect evidence, the outcomes at primary schools where administrators cut back on academic instruction in order to make more time for physical play. If playful exercise no effect on cognition, you might expect that kids' academic performance would have suffered. But instead, kids either maintained or improved their academic performance (Trudeau and Shephard 2008).
A safe bet...but make it fun
Correlations don’t tell us about causation. It’s possible, for instance, that smarter kids are more likely to seek out physical activity. That could explain the results of the stimulus discrimination study.
Moreover, 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 rodent experiments are compelling, and recent experiments on kids suggest that exercise 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 9/14