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The Brain Benefits of Exercise

Physical activity improves mental as well as physical skills.

Evidence for the health benefits of exercise is accumulating. In the past, emphasis was given to the cardiovascular benefits of controlling body weight and reducing blood pressure. Brain benefits are also noteworthy.

Grow Neurons by Walking

The mature brain is highly malleable, or “plastic,” contrary to earlier conclusions influenced by evidence from the permanent effects of traumatic brain injuries.

This malleability was confirmed by a study of London cab drivers who learned how to navigate all the city streets without maps or GPS and who were formally tested on “the knowledge.”

Their navigational feats produced enlargement in an area of the hippocampus associated with spatial memory (1). The longer they drove a cab for, the greater the effect, so that this was not just a matter of people with exceptional spatial ability getting selected into the occupation in the first place.

Canadian neuroscientists produced some startling evidence in support of the idea that exercise stimulates cell growth (2). They found that voluntary exercise greatly increases the proliferation of stem cells in the dentate gyrus of the hippocampus, so a keen hiker benefits from having more cells.

The hippocampus plays a key role in forming new memories and is also implicated in spatial problem-solving as illustrated by the cabbies study.

Small wonder that exercise might keep us young by helping to restore our brains.

Aging and Exercise

We often forget that muscles are as much a part of brain function as sensory systems are. If senses are the stimulus, they produce the response.

With this in mind, the logic of a healthy mind in a healthy body becomes compelling. Some confirming evidence was produced in a study showing that educated people live longer than those having less schooling. One plausible interpretation of this finding is that a well-exercised brain resists senile deterioration, possibly by having a more robust circulatory system due to increased cognitive demands placed on it (3).

Recent evidence shows that physical activity does the same for the muscular system. Indeed cyclists who remained active into middle and old age (55-79 years) had no evidence of aging in their muscular system compared to healthy young adults (aged 20-36 years). Specifically, there was no loss of either muscle mass or strength, changes that used to be considered inevitable consequences of aging.

Another recent study found fairly direct evidence of a claim by Hippocrates some 24 centuries ago that exercise is a human's best medicine.

Health Benefits of Brain Stimulation through Exercise

The fact that exercise boosts stem cell production in the hippocampus means it might contribute to improved neural and cognitive function in the elderly.

A study of cyclists found that exercising regularly affects the production of immune cells known as T cells. These are produced in the thymus (located in the chest) that normally shrinks from about the age of 20 years onward so that fewer T cells are produced. Among cyclists, the thymus continued to produce as many T cells as that of young people.

How exercise produces these beneficial effects in the thymus is poorly understood. Little is even known about the role of the nervous system in regulating thymic function. The sympathetic nervous system—that is aroused by physical activity—might play a role. Whether that is correct or not, we should not forget that movement is the output side of the nervous system and that physical exercise always involves activity by the central nervous system.


We do not necessarily get frailer and sicker with old age. On the contrary, well-trained older cyclists are in a much better position to experience healthy old age than their less active counterparts.

Perhaps the most important implication of the beneficial effects of physical activity on the nervous system is that we should no longer place mental activity and physical activity into different categories.

A healthy mind and a healthy body are one and the same, as the Greeks and Romans were well aware long before the Industrial Revolution.

Indeed, exercise tunes the brain in ways that promote creativity and complex problem solving, as described in an earlier post.


1 Maguire, E. A., Gadian, D. G., Johnsrude, I. S., Good. C. D., Ashburner, J. Frackowiac, R. S., and Frith, C. D. (2000). Navigation-related structural change in the hippocampi of taxi drivers. Proceedings of the National Academy of Sciences, 97(8), 4398-4403. doi :10:1073/pnas.070039597.

2 Olson, A. K., Eadie, B. D., Ernst, C. and Christie, B. R. (2006), Environmental enrichment and voluntary exercise massively increase neurogenesis in the adult hippocampus via dissociable pathways. Hippocampus, 16: 250–260. doi:10.1002/hipo.20157

3 Molla, M. T., Madans, J. H., and Wagener, D. K. ( 2004). Differentials in adult mortality and activity limitation by years of education in the united states at the end of the 1990s. Population and Development Review. 30, 625-646.

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