There's no lack of evidence that children are getting fatter and weaker. And children who are obese or out of shape tend to do worse in school. But scientists are just starting to figure out just what it is in that mix that makes the difference with academics.
It looks like just being strong isn't the secret. Children and teens who did well on a hand-grip test and on a standing long jump did less well in school than peers who tested well on cardiovascular fitness and motor ability, according to a study of about 2,000 people in Spain. And motor ability mattered the most.
Cardiovascular fitness I get, but I found myself puzzled by motor ability. So I called Irene Esteban-Cornejo, a graduate student at the Autonomous University of Madrid who led the study. Um, just what is that?
"Velocity and coordination in combination," Esteban-Cornejo replied. She tested it by having people do a shuttle run test, in which they would run 10 meters, pick up a stone, turn and run back 10 meters, put the stone down. Repeat.
The shuttle run test is a good stand-in for sports like basketball or soccer that require movement, agility and coordination. And they often promote cardiovascular fitness, too. But plain old running will do just fine for both.
The researchers tested the fitness of 2,038 children and teenagers in Cadiz and Madrid, Spain, in 2011 and 2012. Their grades were compared to their fitness, body mass index, body fat and waist circumference, socioeconomic status and parents' education.
The study was published Thursday in the Journal of Pediatrics.
People who were fitter tended to do well on all three fitness measures. But the big surprise is that motor ability was most strongly linked to higher grades, followed by aerobic capacity. But muscle strength on its own wasn't associated with academics. And fitness mattered more than fatness.
"Physical activity at the school should be oriented to improve cardiovascular fitness and motor performance to improve academic performance," Esteban-Cornejo says. "You can't improve one without the other."
The increased blood flow due to aerobic fitness could be making for a happier brain, the researchers speculate. Other studies have found that motor skills relate to memory, attention and academic performance, that that work has been done mostly with small children. Maybe the fine motor skills needed for reading and writing benefit, too.
This study doesn't prove cause and effect; it may be that the better students are more motivated to exercise and try hard on the researchers' tests. Esteban-Cornejo and her colleagues are completing another phase of the experiment to explore that.
But should help parents and children make the case for more physical activity in school.
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