Why exercise is just as good for brains as bodies

The link between cognitive health and a good workout has been traced back two million years to when our primitive ancestors came down from the trees.

It meant their relatively sedentary ape-like existence turned into a more robust hunter-gatherer lifestyle.

Complex foraging tasks were simultaneously physically and mentally demanding explaining how physical activity and the brain came to be so connected.

The finding could lead to new ways of tackling age related neurological conditions, including dementia.

Prof Gene Alexander, a psychologist who studies brain ageing and Alzheimer’s disease, said: “Our evolutionary history suggests we are, fundamentally, cognitively engaged endurance athletes, and if we don’t remain active we are going to have this loss of capacity in response to that. So there really may be a mismatch between our relatively sedentary lifestyles of today and how we evolved.”

Anthropologist Professor David Raichlen, of the University of Arizona, added: “We think our physiology evolved to respond to those increases in physical activity levels, and those physiological adaptations go from your bones and your muscles, apparently all the way to your brain.

“It is very odd to think moving your body should affect your brain in this way - that exercise should have some beneficial impact on brain structure and function - but if you start thinking about it from an evolutionary perspective, you can start to piece together why that system would adaptively respond to exercise challenges and stresses.”

Mounting research shows exercise is as good for our brains as our bodies, but the mechanism has mystified experts. The study published in Trends in Neurosciences could help explain findings reported by the same team last year suggesting runners’ brains are more connected than those of non-runners.

It could also lead to fresh therapies to combat cognitive decline in the elderly when physical activity tends to fall away.

Co author Prof Alexander, said: “What we are proposing is, if you are not sufficiently engaged in this kind of cognitively challenging aerobic activity, then this may be responsible for what we often see as healthy brain ageing, where people start to show some diminished cognitive abilities.

“So the natural ageing process might really be part of a reduced capacity in response to not being engaged enough.”

Reduced capacity refers to what can happen in organ systems throughout the body when they are deprived of exercise. Prof Raichlen, an avid runner and expert on running, said: “Our organ systems adapt to the stresses they undergo.

“For example, if you engage in exercise, your cardiovascular system has to adapt to expand capacity, be it through enlarging your heart or increasing your vasculature, and that takes energy.

“So if you are not challenging it in that way - if you are not engaging in aerobic exercise - to save energy, your body simply reduces that capacity.”

In the case of the brain, if it is not being stressed enough it may begin to waste away. This may be especially concerning, considering how much more sedentary humans’ lifestyles have become.

Prof Alexander said:

The researchers say future studies should look at how different levels and types of exercise, or physical activity paired specifically with cognitive tasks, affect the brain. For example, exercising in a novel environment that poses a new mental challenge, may prove to be especially beneficial.

Prof Raichlen said: “Most of the research in this area puts people in a cognitively impoverished environment. They put people in a lab and have them run on a treadmill or exercise bike, and you don’t really have to do as much, so it’s possible we’re missing something by not increasing novelty.”

The team hopes their work will help advance research on exercise and the brain.

Added Prof Alexander: “This evolutionary neuroscience perspective is something that has been generally lacking in the field. And we think this might be helpful to advance research and help develop some new specific hypotheses and ways to identify more universally effective interventions that could be helpful to everyone.”

Studies have found doing moderate exercise several times a week is the best way for over 50s to keep the mind sharp.

Thinking and memory skills were most improved when people exercised the heart and muscles on a regular basis.

This remained true in those who already showed signs of cognitive decline. Experts say taking up exercise at any age is worthwhile for the mind and body.

The theory is exercise boosts blood flow to the brain, helping the formation of new neurons.