Mens sana in corpore sano [ENG]

Among the best-known latin proverbs is the one that entitles this post. I particularly like it because it refers to two of the things that interest me most: the mind and exercise. Today’s chapter is about the influence of physical exercise on cognitive performance.

Physical exercise is a must among the recommendations to increase concentration and enhance attention. The scientific evidence supporting this claim is huge. However, one has to dig deeper to get to the root causes of how this happens; Which of the effects triggered by physical exercise are involved in cognitive enhancement? What mechanisms make it possible for them to happen? Does any type of exercise work in the same way? How much time is enough? Is the improvement general or specific to each function and type of exercise? These are some questions regarding the relationship between physical exercise and the brain.

Given that exercise stimulates the response of several body systems, the first question mentioned above is as logical as necessary. In this sense, one of the consequences of physical exercise is the increase of body temperature and sweating, but neither of them have nothing to do with memory or attention. Thus, given the wide variety of effects, I will try to cover here only a few of those directly related to cognitive processes.

The first cause of this exercise-induced cognitive stimulation is the increased oxygen supply to the brain. More oxygen means more, faster energy, thus speeding up the mechanisms behind this process to take place. With this said, I advance that the majority of results point to the hippocampus as the most sensitive brain area to physical exercise influence. Therefore, it is not surprising that the cognitive domains primarily benefited from exercising will be learning and memory. But there are more, as we shall see.

Many studies in both humans and animals have shown that exercise has a positive effect on neuronal growth. For instance, it is known that strengths memory and potentiates information processing 1,2. In addition, it has been proven that it also facilitates both acquisition and performance of spatial learning tasks 3In relation to this, it is known that whenever there is learning, there is neuroplasticity too. One of the components involved in this phenomenon is BDNF,  a neurotrophic factor involved in learning, as well as in central and peripheral energy metabolism 4. Interestingly, it has been demonstrated that both acute and continued exercise may trigger the process by which neurotrophins mediate energy metabolism and synaptic plasticity 5,6 . Therefore, stimulation BDNF-mediated neuroplasticity seems to be the main mechanism by which physical exercise exerts its positive effects on cognition.

As for the type of exercise, several studies show that aerobic work prevents tissue loss and neuronal decline in the hippocampus 7,8. Moreover, it has been shown that it may even reverse the negative effects caused by an unbalanced diet 9. Other studies suggest that this type of activity is particularly positive on those tasks (or task components) that involve an important executive control, such as action planning or behavioral inhibition 10. However, little is known about the effect of resistance training on hippocampal-dependent memory. It seems that this type of exercise does not have a particularly significant effect on BDNF levels, although it does improve cognitive abilities, especially in the elderly 11.

No pain, no brain

To explain this paradox, it has been suggested that each type of exercise produce its effects through different mechanisms 12. On one hand, the benefits of aerobic exercise would be motivated by the increase in BDNF and its TrkB receptor. On the other hand, although resistance training does not increases BDNF levels, it effectively increases insulin-like growth factor 1 (IGF-1) and its receptor. The reason why these two pathways are able to produce an improvement in cognitive performance is because both of them increase the expression of synapsin 1 and synaptophysin, one as well as the other determinant in synaptic transmission. It should be noted though that these results were obtained under a workout schedule of 1 hour per day, 3 days per week during 24 weeks.

But let’s be honest here. Nobody wants to train for 24 weeks just to test if memory has improved. The question is, is acute exercise also effective? Well, apparently it is.

There is evidence showing that when practiced occasionally, exercising can boost cognition, too. For instance, a study conducted in preadolescent concluded that following the Fitnessgram assessment program promotes cognitive performance, specially in those tasks involving executive functions 13. Similarly, other studies show that high-intensity interval training (HIIT) is able to enhance selective attention and short-term memory 14.

In summary, physical exercise, either aerobic or strength, acute or chronic produce an increase in oxygen supply to the brain and rises (1) the levels of certain factors related to neuroplasticity, (2) the production of neurotransmitters, and (3) synaptic transmission. And although not by the same mechanisms, exercising seems to positively affect different cognitive domains such as spatial learning and memory, short term memory, selective attention and executive function.