Research scientists debate exercise’s benefits for the human brain

The health benefits of physical activity are undeniable. Yet, a recent study based on data published over the past 30 years challenges the famous adage “a healthy mind in a healthy body” and questions the importance of exercise for both brain health and cognition.

A few days after that study was published, our team of health and neuroscience researchers released the results of our study of over a quarter million people. Our results clearly support the beneficial effects of both moderate and vigorous physical activity on cognitive functioning, fuelling an important scientific debate.

Who is right and who is wrong? Here’s what the science says.

The first study was published in March of this year.

It is a review of 24 meta-analyses that reexamines data from 11,266 healthy people using a more rigorous approach.

Although almost all of the analyses included in this review concluded that exercise had a positive effect on cognitive function, the authors argue that the analyses performed were suboptimal.

Once adjustments were made, the authors found results suggesting that the benefits of exercise are actually smaller than those estimated in the previous study, and may even be negligible.

Based on these findings, the authors argue that public health agencies such as the World Health Organization should no longer state that physical activity improves cognitive health, academic performance, and executive function, “at least until more reliable scientific evidence accumulates.”

Well, that evidence didn’t take long to arrive. The second study is a genetic study involving nearly 350,000 people, published four days later. Our results provide scientific evidence for the cognitive benefits of moderate and vigorous physical activity.

When any two humans are compared, 99.9 per cent of their genetic material is identical. DNA can be thought of as a long chain of building bricks, called nucleotides, that varies once every 1,000 bricks between these two humans. There are four types of randomly arranged bricks: thymine, adenine, guanine, and cytosine. Genetic variations can result in, for example, a cytosine brick in one place in one person’s DNA and a thymine brick in the same place in another.

The first sample in our study, consisting of 91,084 people, was used to identify genetic variations associated with differences in physical activity, as measured by wrist-worn motion sensors.

The second sample in our study, consisting of 257,854 people, was used to test whether the genetic variations associated with physical activity had a proportional effect on cognitive functioning. Since this was the case, we were able to conclude that there is a causal effect of physical activity on cognitive function.

In our study, we show that physical activity improves cognitive functioning, but more importantly, that the effect of moderate physical activity (brisk walking, cycling) is 1.5 times greater than that of vigorous physical activity (running, playing basketball). This finding highlights that we do not need to push ourselves to the point of exhaustion to get cognitive benefits from exercise.

As we are dealing with the temporal aspects of physical activity here, it is important to remember that it is never too late to start exercising.