Exercise can boost your memory and thinking skills, says neurologist Scott McGuinness in a press release from Harvard Medical School, where he works. David Jacobs, a professor of epidemiology and community health at the University of Minnesota, agrees: “For generally healthy people, regular exercise can boost brain function over a lifetime—not just after exercise,” he wrote in an article. Scientific American. The list of researchers and health advocates who take the cognitive benefits of physical exercise for granted, and several studies seem to support this widely held belief.
But a few days ago, Dr. Daniel Sanabria Lucena (Bordeaux, France, 46 years old), professor at the University of Granada and researcher at the Center for Mind, Brain and Behavior, published a review in the journal The nature of human behavior Which calls this belief into question. Sanabria’s team analyzed 109 studies, involving more than 11,000 participants, and found that exercise had a positive effect on cognitive ability. The team discovered various problems with the studies’ methodologies, leading them to conclude that there was no different evidence to support the claim that physical activity has a positive effect on brain performance.
“Our knowledge of this topic is not advanced enough to make strong recommendations like the ones that are being made,” Saravia explained in a video interview, adding that his team is “not the first to say this.” Adele Diamond, a professor of neuroscience at the University of British Columbia in Vancouver, published research findings arguing that “aerobic exercise and resistance training were among the least effective ways to improve executive function,” which includes working memory and the ability to make plans and decisions. “We don’t talk about mental health,” explains El Sanabria. “This is a different matter.”
a question. Studies like yours show how difficult it can be to make specific recommendations for many aspects of human health. Do you think people can learn to live with this uncertainty?
Answer. First of all, I think there is a need for more science education in general, starting with school, so that people understand how science works. It is important to know that researchers have our own biases, interests, and biases. For some, science has become a kind of religion, a source of absolute certainty, but in reality it does not work that way. People want to know what they should do to take care of their well-being, including their mental health. We want simple answers. But in most cases, giving health advice is complex, and as we’ve seen with the pandemic, we have very little tolerance for uncertainty.
In the classes I taught, I remember talking about two contradictory theories about a phenomenon, and someone asking me, “So, what am I supposed to believe?” I told them that science is not about faith, it is about generating theories and accumulating evidence, which may be more or less solid and decisive in favor of one hypothesis or another.
s. So, as your students might say, what are we supposed to believe about exercise?
a. In this particular case, and based on what we know, what I would say is that if exercise makes you feel good, do it. Because there is very strong evidence pointing to its physical health benefits.
s. How do all these studies lead us to believe that exercise has a positive effect on cognition?
a. In the past two decades, there has been a growing interest in the topic, and research on the benefits of physical exercise beyond just physical health. Studies have attempted to find a link between the level of physical activity of a particular group — in some cases with thousands of participants — and their level of cardiovascular fitness, and their cognitive performance. These studies show associations, but correlation is not the same as causation. That’s why we have intervention studies, where you randomly assign people to the experimental group, who do physical exercise, and other people to the control group, who don’t do exercise, or who perform an activity that, you think, isn’t. It will have an effect on cognitive performance. The evidence from these types of studies is what is generally used to show that physical exercise improves cognition. We analyzed 109 such studies, those focusing on healthy populations, and our conclusion is that the evidence for exercise’s putative cognitive benefits is far from conclusive. In fact, we believe that intervention studies may not actually be the best tool for examining the potential effects of regular exercise on cognitive and brain functions, and that it would be best to look for evidence from longitudinal studies. If we get definitive evidence that these effects exist, then the question becomes why, but that’s a topic for another interview. Then there is the fact that, sometimes, results are not published when the desired effect has not been achieved.
s. So, are there results and studies that, because they are more in line with what is desirable, are more researched and more published?
a. One typical example is bilingualism, which are the cognitive benefits of being bilingual. Between 2000 and 2010, we saw a spike in articles reporting on how people who spoke more than one language had better cognitive performance than people who spoke only one language. I have even seen examples of bilingual schools selling bilingualism as a tool to improve the cognitive ability of their students. But research has emerged showing that there is publication bias [the tendency for positive results to be published more than null ones], particularly by organizations that have been particularly prolific in this field. Moreover, studies on the subject of bilingualism and cognitive performance have also begun to appear in recent years, with rather large samples and null results.
In the case of physical exercise, we have conducted many studies that at first glance may show unexpected results. One is about the effect of mental fatigue on physical performance. Some literature suggests that when you do a mentally demanding task just before you do physical exercise, you will perform worse physically than if you did something less demanding before. In sports science, this is a given. But we tried to replicate a classic study along these lines, and got null results, and that’s when we started to question the reliability of the evidence. We looked at the literature and noticed that the studies used very low sample sizes. We conducted a meta-analysis and found that, in fact, there was a tendency to use very small sample groups, which increases the likelihood of finding false positives, poor quality studies, and publication bias.
Another line of research that we’ve been working on is looking at the effects of low-intensity direct current electrical stimulation of the brain to improve physical and athletic performance. There is even a company that sold a device that stimulates the brain to improve physical performance. We ran a pilot study, trying to replicate previous results, and again we found blank results. We performed a meta-analysis, and again found studies with very low sample sizes, publication bias, and inconsistent literature.
However, the results of our research that I discuss here do not mean that these effects do not exist, because the absence of evidence of an effect is not evidence of the absence of an effect. What they indicate is that with the studies available so far, nothing can be concluded about these phenomena. More and better research is needed.
s. Does the method of choosing who participates in the study affect the results?
a. It can have a huge impact, yes. For example, imagine you put out an invitation to participate saying you’re looking at older adults for a study that you want to look at the effects of exercise on cognitive performance and the brain in preventing cognitive decline. Who will participate? Most likely they will be people who have an interest and expect exercise to have an impact on their minds. And this group, in many studies, has been compared to the so-called “waiting list” group, who go about their normal lives, doing nothing. In medicine, nobody buys this approach. You should always have a placebo group, because you know expectations about the effect of the drug will really have an effect. Also, in our recent review study on the effects of exercise on cognitive performance, we found that in several studies, people in the experimental group, who receive physical training, tend to start from a lower point in their cognitive performance than people in the experimental group. The control group, who do not receive physical intervention. Thus, the experimental group has more room for improvement than the control group. The fact that in many studies this difference between groups is usually in favor of the experimental group could be another indicator of publication bias.
s. Do interpretations of psychological outcomes focus too much on effects on the brain and not enough on context?
a. One of the risks with this issue of measuring the effects of something—and this applies to exercise, alertness, or anything else—is that some very relevant factors, contextual factors, are often overlooked. The best predictor of academic performance and subsequent career success is not cognitive ability, it is the sociocultural context. It is about whether your parents have money. Certain ways of interpreting results can send subtle messages, which focus on individual responsibility. If you are fat, it is your own fault, and it has nothing to do with being surrounded by junk food; If you don’t exercise and get sick, it’s because you lack willpower… I think this kind of message is dangerous.
s.This may be true, but limiting the availability of junk food is not inconsistent with telling people that their health rests partly in their hands, choosing to go for a run or trying to buy less processed foods.
a.I totally agree, they are not incompatible. And I don’t want that to be the message of our work. I recommend people to exercise, of course. But, above all, if you are thinking of enrolling your son or daughter to play sports or play chess, do it because you think they would like it, not to look for some beneficial effect on their mind, because the effects, if any, are small, and the scientific evidence, At least so far, it’s not conclusive at all in this regard. And I think it’s important to stress, again, that not all responsibility for physical and mental health should rest with the individual.
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