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Running for your Life

McIninch/iStock

McIninch/iStock

By Aaron Kandola

Exercise can improve the way the brain functions, even in cases of brain trauma. Here’s why.

Improving the way in which our brain functions is not only important to healthy individuals but also to those with a brain injury or a neurological disorder that impairs their capacity to function as they hope. For this reason, neuroscientists are constantly looking for novel techniques to improve the way our brains works.

One of the most exciting new ideas within the field of neuroscience may raise a few eyebrows, not because it’s particularly novel or obscure but because it almost seems too obvious.

Leading a physically active lifestyle has always been recognised as vital to good physical health. While the benefits of exercise in preventing illnesses like cardiovascular or metabolic diseases are well-established, it appears to be just as important for maintaining brain health.

What’s the Deal with Exercise?

The idea that physical exercise has mental benefits is not new. Almost 100 years ago, professional athletes were observed to have a quicker reaction time on cognitive tasks compared with individuals who were less physically active.

However, it was not until the 1970s that the relationship between regular exercise and faster reaction times on cognitive tasks were confirmed using rigorous, systematic experiments. Subsequent research in the 1990s found that exercise was associated with all sorts of cognitive enhancements, such as reasoning, working memory and attention.

It’s now well-established that exercise can enhance our mental abilities in a variety of ways. Individuals who regularly exercise have better perceptual skills, attention, processing speed, executive functioning, memory capacity, verbal and mathematical abilities, and attain a higher level of academic achievement and IQ score than those who do not exercise regularly.

Research into this topic has exploded in the past two decades, leading some to wonder exactly what it is about exercise that drives such powerful mental enhancements. Instead of only relying on cognitive tasks, neuroscientists have begun to delve further into the inner workings of the brain when it is exposed to exercise.

Research reveals that exercise can stimulate many remarkable changes in the brain’s structure (see box) that are likely to underlie these improvements in cognition.

What Does Exercise Do to Our Brain?

A more connected brain

Engaging in lots of physical exercise increases the density of white matter across the brain by encouraging more axons to grow and a thicker coating of myelin around the axons. A thicker myelin coat minimises the rate at which signals can escape as they travel along the axon. Greater numbers of axons provide additional routes through which a signal can travel, increasing the efficiency of communication within the brain.

Exercise is like adding more lanes (axons) with better quality roads (myelin) to a highway (white matter), allowing more traffic (electrical signals) to cross efficiently between each city (grey matter regions). Having denser white matter increases the efficiency of information transfer between grey matter regions.

A more powerful brain

The volumes of several grey matter regions also increases with more exercise. As we age, most brain regions shrink in size, including the hippocampus, which is critical to memory processing. As more and more neurons within the hippocampus die, causing it to shrink, the area eventually loses its ability to function as it did before, resulting in a poorer memory.

Elderly people who are more physically active have larger hippocampi and score better on memory tasks. Reassuringly, elderly people who are relatively inactive show a growth in the size of their hippocampus and an improved performance on memory tasks after increasing their exercise levels.

It is worth mentioning that increasing the volume of a grey matter does not necessarily improve the way it functions. However, in the case of ageing, the shrinking hippocampus is actually causing the decline in memory performance. By boosting the size of the hippocampus, exercise can effectively counteract this age-related deterioration and preserve memory function.

A more efficient brain

A number of underlying mechanisms that support the growth of white and grey matter are also influenced by exercise. Like the rest of the body, healthy blood flow is necessary to deliver vital nutrients throughout the brain for it to function optimally. By stimulating the creation of new blood vessels – a process known as angiogenesis – exercise encourages greater blood circulation within the brain, which promotes healthy functioning.

Synapses are essential for brain regions to communicate with one another. Each neuron may be connected with up to 10,000 other neurons through as many as 1000 trillion synapses. Such a vast number of connections are necessary to allow information to flow freely in all directions throughout the brain.

Exercise increases the rate at which new axons and dendrites are formed – a process known as synaptogenesis. A greater number of synapses increases the interconnectedness between neurons within the grey matter regions of our brain. Exercise thereby increases the efficiency through which information is transferred around the brain.

Neurogenesis is the generation of entirely new neurons in the brain – a process that until very recently was thought impossible in a mature human brain. Neurogenesis only occurs in two areas of the developed human brain, yet plays a critically important role.

One area in which neurogenesis does occur is the hippocampus. These newly created neurons are integral to the way in which we form memories. For example, neurogenesis is necessary for the formation of spatial memories – it is important for tasks such as navigating your way home from the shops. Regular exercise increases the rate of neurogenesis, contributing to the efficiency with which the brain forms new memories.

What Does This All Mean?

Exercise improves the way in which our brain functions by developing the integrity of its structure and by stimulating a range of important processes. The collective impact of these changes is evident in some remarkable improvements in cognitive performance. From revising for an exam or learning a language to driving a car, a regular exercise regime will ensure that you are using your brain to its optimal capacity.

Recently, neuroscientists have begun examining the use of exercise in treating a variety of mental and neurological diseases. Studies have shown that a physically active lifestyle is associated with a lower risk of developing a degenerative disorder, such as dementia, and mood disorders such as depression or social anxiety disorder. In fact, exercise is even beneficial for patients who are already suffering with a neurological disorder, brain injury or mental illness.

The use of using exercise to promote brain health is a recent innovation, so there are limited studies that directly address the matter. However, the initial signs are extremely positive and the idea is attracting a growing amount of attention.

Could Exercise Restore Brain Damage?

Helping to fight dementia

Alzheimer’s disease is the most common form of dementia that increasingly degrades an individual’s memory, thinking and behaviour. It causes a severe degradation of the hippocampus, causing the debilitating memory impairments associated with the disease.

By increasing the volume and connectivity of the hippocampus as well as stimulating important processes like angiogenesis, synapto­genesis and neurogenesis, it is possible that exercise may counteract some of the damage incurred by Alzheimer’s disease.

Exercise is also associated with a reduction in beta-amyloid and tau proteins throughout the brain. These are thought to cause the onset and progression of Alzheimer’s disease.

Individuals with Alzheimer’s disease who report a higher level of physical activity have a slower progression of cognitive decline and a larger hippocampal volume than those who are relatively physically inactive. Moreover, individuals with Alzheimer’s disease who are put on a regular exercise regime experience a reduction in their cognitive decline.

The idea of exercise being used medicinally is not exclusive to Alzheimer’s disease, but may also be applied to reduce the risk of and potentially treat a wide range of disorders from Parkinson’s disease to depression.

It is unlikely that exercise alone is sufficient to stave off the harms associated with these disorders. However, clinicians may soon be recommending exercise to slow down the progression of the disease, perhaps in conjunction with other forms of medication.

A place in rehabilitation

Exercise may also be implicated in the rehabilitation of people who have experienced some form of brain injury to help combat the profound effect it has on cognition and brain health.

Heavy cannabis use – generally considered to be daily use for at least a year – can cause lasting memory and learning deficits as well as deformation of the hippocampus. By developing the hippocampus and improving memory performance, exercise may again be helpful in combatting some of the negative impacts of heavy cannabis use.

Exercise is also being considered for recovery from broader sources of traumatic brain injuries. Exercise rehabilitation given to victims of a stroke may assist with recovery from some of the damage that has been caused.

To what extent a full recovery from such damage is possible may vary, but supplementing rehabilitation with a regular exercise regime will certainly aid the progression of a recovery.

Unanswered Questions

The idea of exercise being used as a clinical intervention is slowly gaining momentum. It is inexpensive, has relatively few adverse side-effects, and provides numerous other physical health benefits.

However more research is required for these initial findings to hold a practical relevance for clinicians. While we are confident in the benefits of exercise, some crucial questions remain unanswered and must be addressed to maximise the clinical benefit and cognitive improvement.

What type of exercise?

The majority of studies focus on aerobic exercises like running, but little is known about the comparative advantages of resistance exercises like weight training or stretch exercises such as yoga. It is possible that different forms of exercise are more appropriate to deal with different forms of brain injury, mental illness or cognitive impairment.

What intensity of exercise?

The intensity of an exercise refers to how much physical effort is required to complete that exercise, such as running at different speeds. Taking depression as an example, some studies advocate that high-intensity exercise is optimal for reducing depressive symptoms, while others suggest that the best results are achieved with a mild intensity or a moderate intensity exercise regime.

More research is required to decipher exactly what intensity of exercise is most beneficial to the brain. It’s possible that factors such as an individual’s age or the nature of the harm itself will be important in deciding what intensity of exercise is necessary.

It is currently unclear how long an exercise regime should last for optimal improvements in brain health or cognition. Too much exercise can inflict a level of stress on an individual’s brain, negatively impacting upon brain health, which in turn may inhibit the benefits of exercise.

Prescribing exercise as a treatment at all may sometimes be inappropriate. For example, exercise may actually be harmful to individuals who are taking certain medications (e.g. beta-blockers) or have a cardiovascular disease.

Exercise, Exercise, Exercise…

Exercise has a profoundly positive impact on how our brain functions. We are only just beginning to appreciate how directly applicable this may be to our daily lives. More research is required to figure out exactly how much and what type of exercise could be implemented as a clinical intervention, and for which brain disorders or injuries an exercise intervention may be most applicable.

Here we have only discussed the benefits of exercise to improving brain function in those with a mental illness or brain injury. Exercise is also effective in reducing stress and elevating mood in healthy individuals.

The potential for exercise to improve our general well-being in this way thwarts the traditional view that exercise is simply a goal-driven behaviour restricted to those who engage in a sport or wish to lose weight. Society is now recognising that exercise must be encouraged as a way to improve ones overall quality of life.

No matter who you are or what you are doing, engaging in regular exercise will ensure your brain is functioning optimally.

Aaron Kandola is a Research Assistant at Monash University, where he is examining whether regular aerobic exercise leads to recovery of the hippocampus in heavy cannabis users.