Several recent studies add to the evidence that physical fitness boosts cognitive processing in children.
Physically fit kids have better white matter
A brain imaging study involving 24 9- and 10-year-olds has found that physical fitness was associated with significant differences in the integrity of several white-matter tracts in the brain: the corpus callosum, the superior longitudinal fasciculus, and the superior corona radiata. All of these are involved in learning and memory. The differences are associated with faster and more efficient nerve activity.
The findings build on previous research linking higher levels of aerobic fitness with greater volumes of gray matter (i.e., more neurons) in regions important for memory and learning, and suggest that better communication along the white-matter tracts might be another mechanism explaining why aerobic fitness is associated with improved cognition.
Factors such as socio-economic status, the timing of puberty, IQ, or a diagnosis of ADHD or other learning disabilities, were taken into account in the analysis.
Physical fitness linked to better reading skills in children
A study looking at brain activity during reading has found that physically fit children have faster and more robust brain responses during reading than their less-fit peers. These differences correspond with better language skills.
Brainwave patterns called "event-related potentials" (ERPs) vary by person, stimulus and task. A brainwave component called N400 is stronger when a sentence doesn't make sense compared to a meaningful sentence, for example. The component P600 is associated with grammatical rules.
The study found that children who were more fit (as measured by oxygen uptake during exercise) had higher amplitude N400 and P600 waves than their less-fit peers when reading normal or nonsensical sentences. The N400 also had shorter latency in children who were more fit, suggesting that they processed the same information more quickly. These differences corresponded to better reading performance and language comprehension.
Such findings suggest that higher fitness may be associated with a richer network of words and their meanings, and a greater ability to detect and/or repair syntactic errors.
Large study links physical fitness to school grades
A large Spanish study involving 2,038 young people (6-18; average age 10) has found that physical fitness was associated with better academic performance.
Fitness was measured in terms of cardiorespiratory capacity, motor ability and muscle strength. Cardiorespiratory capacity and motor ability were independently associated with all measures of academic performance (math grade, language grade, average of math and language grades, and overall grade point average), even after adjusting for fitness and fatness. Muscle strength was not associated with academic performance independent of cardiorespiratory capacity and motor ability.
Aerobic fitness boosts learning in school children
A study involving 48 9- and 10-year-olds has found that those with higher levels of physical fitness performed significantly better at a memorization task. The task involved memorizing names and locations on a fictitious map, either by study only or by being tested on the material as they studied. They were then tested a day later, under conditions of free recall and cued recall. Half the children were in the top 30% of their age group on a test measuring aerobic fitness, while the other half scored in the lowest 30%.
While there was no difference between the high-fitness and low-fitness groups at the initial learning session, and no difference on the delayed test when learning had involved study plus testing, the high-fitness group scored considerably better than the low-fitness group when learning involved study only (an average of 43% correct vs 25.8%).
This suggests that the benefits of fitness are greatest when initial learning is most challenging (as discussed at length by me in my book on practice, and in other articles, retrieval practice as a part of study improves learning significantly).
Childhood obesity linked to poorer cognitive control
A study involving 74 preadolescent children, of whom half were obese and half at a healthy weight, has found that the obese children were considerably slower at a task in which they were shown three fish facing either left or right and had to press a button based on the direction of the middle fish.
The healthy-weight children also improved their performance more after making an error, and their brain activity showed a larger response when they made an error. This difference was even greater in more demanding situations (the flanking fish could either point in the same direction or in the opposite direction). This suggests that childhood obesity is associated with poorer action monitoring, a vital aspect of cognitive control.
There are two particularly interesting findings from this collection of studies:
- the idea that physical fitness helps cognition through multiple effects, such as increasing gray matter volume, improving white matter integrity, and strengthening brainwave patterns
- the idea that the effects of fitness may not be revealed in less-demanding situations.
 . Aerobic fitness is associated with greater white matter integrity in children. Frontiers in Human Neuroscience [Internet]. 2014 ;8. Available from: http://journal.frontiersin.org/Journal/10.3389/fnhum.2014.00584/abstract
 . The association between aerobic fitness and language processing in children: Implications for academic achievement. Brain and Cognition [Internet]. 2014 ;87:140 - 152. Available from: http://www.sciencedirect.com/science/article/pii/S0278262614000608
 . Independent and Combined Influence of the Components of Physical Fitness on Academic Performance in Youth. The Journal of Pediatrics [Internet]. 2014 ;165(2):306 - 312.e2. Available from: http://www.jpeds.com/article/S0022347614004028/abstract
 . The Influence of Childhood Aerobic Fitness on Learning and Memory. PLoS ONE [Internet]. 2013 ;8(9). Available from: http://dx.doi.org/10.1371/journal.pone.0072666
 . The Negative Association of Childhood Obesity to Cognitive Control of Action Monitoring. Cerebral Cortex [Internet]. 2012 . Available from: http://cercor.oxfordjournals.org/content/early/2012/11/09/cercor.bhs349