Can sport make us smarter?

Until two years ago, experts agreed on the beneficial impact of sport on cognition. In particular, its impact on our executive functions, which allow us to plan, solve problems, organize tasks and adapt to new situations. A slew of studies had supposedly endorsed the immediate benefits — that clarity we get after a run or a CrossFit session — and also the long-term cumulative advantages. Although children and older people were the main winners, all age groups could apparently become smarter by being more active.

A 2020 meta-analysis led by Swiss researcher Sebastian Ludyga and published in the journal Nature laid out something almost no one disputed. Even the World Health Organization echoed this robust cause-effect relationship. With hardly any dissenting voices, the most relevant literature had ruled that sport is not only excellent for health, but that it helps us to get better grades, make better decisions, and perform better at work.

But, in 2023, something changed when Spaniard Luis Ciria, together with others, published a review in Nature of 24 meta-analyses on the subject. Their conclusions were devastating: with the evidence in hand, it could not be asserted that exercise per se had a noticeable impact on cognition. “We saw that the results were not solid, that the supposedly beneficial effect had to be taken with a grain of salt,” says Ciria.

This bombshell was followed by a response signed by 21 researchers from around the world, including Ludyga himself and the Frenchman Boris Cheval, who had examined the sport-cognition dynamic. This, in turn, gave rise to a response from Ciria and some of the experts who had participated in his study. Nature became a vehicle for airing the two opposing arguments, building a massive controversy.

The core of the debate lies in what criteria is used for selecting valid studies to draw reliable conclusions. For some, it was essential to separate the purely physical from the cognitive before proclaiming that sport also helps to fine tune our intellect. For others, the bar used in Ciria’s 2023 review was set too high.

According to Ciria, only randomized controlled trials (RCTs), “the best done,” should be used, he says. By eliminating the risk of bias as far as possible, RCTs are the most reliable way to establish causality relationships. Moreover, the 2023 review also excluded any type of cognitively demanding activity, such as team sports or martial arts. The premise is clear: if we want to observe the effect of exercise on cognition, we have to abstract it as far as possible from its mental component, lest it contaminate the result. “It is very difficult to isolate the strictly physical part,” admits Ciria, although he adds that, scientifically speaking, there is no other option.

What exercise is just exercise?

The problem, say Ludyga and Cheval, is that for Ciria and his collaborators almost no exercise seems “pure enough in its restrictive exclusion criteria,” notes Ludyga. Cheval emphasizes that the physical activities that “most improve executive functions are those that include decision making.” And Ludyga insists that “any exercise has benefits, although the most significant impact is produced by those that involve coordination.” This is more of a long-term benefit because if one wants to clear one’s mind right away, the less one activates the brain, the better. “Think about when students’ attention and concentration levels decline and they are given aerobic exercises. If these don’t require the use of cognitive functions, that’s perfect, because they’re precisely what you’re trying to restore.”

Cheval and Ludyga recognize the impossibility of separating the physical from the cognitive when shooting a basket in a basketball game or executing an accurate karate kick. Even when lifting weights or running a race, it is obvious that the brain is not in limbo, since we need it to activate motor skills. Both researchers add that there is still much to learn and that “mind/body relationships are particularly complex, as many factors come into play,” as Ludyga explains.

Is it legitimate to take into account activities that are not mechanical, and should studies that are not based on RCTs be dismissed? While these doubts are being resolved, the advocates of sport for greater intellectual performance have another ace up their sleeve. It is the neurobiological mechanisms that operate during exercise and that could partly explain the cognitive improvements that, they claim, follow regular exercise. The most promising results point to a brain-derived neurotrophic factor (BDNF), a protein that increases with the intensity of activity and has neuroprotective properties. In a 2023 review, researchers concluded that BDNF could play an important role in memory and learning processes.

Cheval says that “there are also good indications of structural — greater connectivity in certain areas of the brain — and functional — increased neurovascular activity — changes,” produced as a consequence of sustained sports practice over time. For Ciria, these are mere speculations with little supporting evidence. “Our theory is that physical exercise is cognitively beneficial, not because of the physical activity itself, but because of everything associated with it: the social and relational part, the contact with nature, the fact that you sleep and eat better, etc.,” he says.

While the debate continues, the number of studies on the subject continues to grow. Last December, Javier S. Morales, a researcher at the University of Cádiz, published a new meta-analysis in pediatrics, this time focused on children and adolescents. His conclusion goes beyond the limits of cognitive functions to embrace intelligence itself, understood in its most empirical sense: the intelligence quotient (IQ).

“Between the ages of six and 14, we saw that physical training programs improved IQ by four points on average, an increase equivalent to one school year,” says Morales, who also participated in another Sports Medicine review on the effects of sport in early childhood. In that study “substantial improvements in working memory and cognitive flexibility” were observed, he explains. Morales and Cheval advocate promoting sport at school, not so much to create healthy habits, but as a low-cost investment in more effective learning.

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