Nov 18th 2020

Exercise and the brain: three ways physical activity changes its very structure

by Áine Kelly

 

Áine Kelly is Professor in Physiology at the Trinity College in Dublin

 

Regular exercise changes the structure of our bodies’ tissues in obvious ways, such as reducing the size of fat stores and increasing muscle mass. Less visible, but perhaps even more important, is the profound influence exercise has on the structure of our brains – an influence that can protect and preserve brain health and function throughout life. In fact, some experts believe that the human brain may depend on regular physical activity to function optimally throughout our lifetime.

Here are just a few ways exercise changes the structure of our brain.

Memory

Many studies suggest that exercise can help protect our memory as we age. This is because exercise has been shown to prevent the loss of total brain volume (which can lead to lower cognitive function), as well as preventing shrinkage in specific brain regions associated with memory. For example, one magnetic resonance imaging (MRI) scan study revealed that in older adults, six months of exercise training increases brain volume.

Another study showed that shrinkage of the hippocampus (a brain region essential for learning and memory) in older people can be reversed by regular walking. This change was accompanied by improved memory function and an increase of the protein brain-derived neutropic factor (BDNF) in the bloodstream.

BDNF is essential for healthy cognitive function due to its roles in cell survival, plasticity (the brain’s ability to change and adapt from experience) and function. Positive links between exercise, BDNF and memory have been widely investigated and have been demonstrated in young adults and older people.

BDNF is also one of several proteins linked with adult neurogenesis, the brain’s ability to modify its structure by developing new neurons throughout adulthood. Neurogenesis occurs only in very few brain regions – one of which is the hippocampus – and thus may be a central mechanism involved in learning and memory. Regular physical activity may protect memory in the long term by inducing neurogenesis via BDNF.

While this link between exercise, BDNF, neurogenesis, and memory is very well described in animal models, experimental and ethical constraints mean that its importance to human brain function is not quite so clear. Nevertheless exercise-induced neurogenesis is being actively researched as a potential therapy for neurological and psychiatric disorders, such as Alzheimer’s disease, Parkinson’s disease and depression.

Blood vessels

The brain is highly dependent on blood flow, receiving approximately 15% of the body’s entire supply – despite being only 2-3% of our body’s total mass. This is because our nervous tissues need a constant supply of oxygen to function and survive. When neurons become more active, blood flow in the region where these neurons are located increases to meet demand. As such, maintaining a healthy brain depends on maintaining a healthy network of blood vessels.

Regular exercise increases the growth of new blood vessels in the brain regions where neurogenesis occurs, providing the increased blood supply that supports the development of these new neurons. Exercise also improves the health and function of existing blood vessels, ensuring that brain tissue consistently receives adequate blood supply to meet its needs and preserve its function.

Finally, regular exercise can prevent, and even treat, hypertension (high blood pressure), which is a risk factor for development of dementia. Exercise works in multiple ways to enhance the health and function of blood vessels in the brain.

Inflammation

Recently, a growing body of research has centred on microglia, which are the resident immune cells of the brain. Their main function is to constantly check the brain for potential threats from microbes or dying or damaged cells, and to clear any damage they find.


Read more: Microglia: the brain’s 'immune cells' protect against diseases – but they can also cause them


With age, normal immune function declines and chronic, low-level inflammation occurs in body organs, including the brain, where it increases risk of neurodegenerative disease, such as Alzheimer’s disease. As we age, microglia become less efficient at clearing damage, and less able to prevent disease and inflammation. This means neuroinflammation can progress, impairing brain functions – including memory.

But recently, we’ve shown that exercise can reprogramme these microglia in the aged brain. Exercise was shown to make the microglia more energy efficient and capable of counteracting neuroinflammatory changes that impair brain function. Exercise can also modulate neuroinflammation in degenerative conditions like Alzheimer’s disease and multiple sclerosis. This shows us the effects of physical activity on immune function may be an important target for therapy and disease prevention.

 

So how can we ensure that we’re doing the right kind of exercise – or getting enough of it – to protect the brain? As yet, we don’t have robust enough evidence to develop specific guidelines for brain health though findings to date suggest that the greatest benefits are to be gained by aerobic exercise – such as walking, running, or cycling. It’s recommended adults get a minimum of 150 minutes per week of moderate intensity aerobic exercise, combined with activities that maintain strength and flexibility, to maintain good general health.

It must also be noted that researchers don’t always find exercise has beneficial effect on the brain in their studies – likely because different studies use different exercise training programmes and measures of cognitive function, making it difficult to directly compare studies and results. But regardless, plenty of research shows us that exercise is beneficial for many aspects of our health, so it’s important to make sure you’re getting enough. We need to be conscious of making time in our day to be active – our brains will thank us for it in years to come.

Áine Kelly, Professor in Physiology, Trinity College Dublin

This article is republished from The Conversation under a Creative Commons license. Read the original article.

Browse articles by author

More Essays

Feb 24th 2021
EXTRACT: "The art historian George Kubler observed that scholars in the humanities “pretend to despise measurement because of its ‘scientific’ nature.” As if to illustrate his point Robert Storr, former dean of Yale’s School of Art, declared that artistic success is “completely unquantifiable.” In fact, however, artistic success can be quantified, in several ways. One of these is based on the analysis of texts produced by art scholars, and this measure can give us a systematic understanding of how changes in recent art have produced changes in the canon of art history."
Feb 24th 2021
EXTRACT: "The most politically sensitive option we looked at was the virus escaping from a laboratory. We concluded this was extremely unlikely."
Feb 16th 2021
EXTRACT: ".... these men were completely unaware that they had put their lives in the hands of doctors who not only had no intention of healing them but were committed to observing them until the final autopsy – since it was believed that an autopsy alone could scientifically confirm the study’s findings. As one researcher wrote in a 1933 letter to a colleague, “As I see, we have no further interest in these patients until they die.” ...... The unquestionable ethical failure of Tuskegee is one with which we must grapple, and of which we must never lose sight, lest we allow such moral disasters to repeat themselves. "
Feb 14th 2021
EXTRACT: "In 2010 Carlos Rodriguez, the president of Buenos Aires' Universidad del CEMA, created the world's first - and only - Center for Creativity Economics.  During the next ten years, the CCE presented a number of short courses and seminars.  But the most important of its events was an annual lecture by an Argentine artist, who was given a Creative Career Award."
Feb 11th 2021
EXTRACT: "It’s not hard to see why. Although AI systems outperform humans in tasks that are often associated with a “high level of intelligence” (playing chess, Go, or Jeopardy), they are nowhere close to excelling at tasks that humans can master with little to no training (such as understanding jokes). What we call “common sense” is actually a massive base of tacit knowledge – the cumulative effect of experiencing the world and learning about it since childhood. Coding common-sense knowledge and feeding it into AI systems is an unresolved challenge. Although AI will continue to solve some difficult problems, it is a long way from performing many tasks that children undertake as a matter of course."
Feb 7th 2021
EXTRACT: "When it comes to being fit and healthy, we’re often reminded to aim to walk 10,000 steps per day. This can be a frustrating target to achieve, especially when we’re busy with work and other commitments. Most of us know by now that 10,000 steps is recommended everywhere as a target to achieve – and yet where did this number actually come from?"
Feb 5th 2021
EXTRACT: "This so-called elite supposedly conspires to monopolise academic employment and research grants. Its alleged objective is to deny divine authority, and the ultimate beneficiary and prime mover is Satan.Such beliefs derive from the doctrine of biblical infallibility, long accepted as integral to the faith of numerous evangelical and Baptist churches throughout the world, including the Free Church of Scotland. But I would argue that the present-day creationist movement is a fully fledged conspiracy theory. It meets all the criteria, offering a complete parallel universe with its own organisations and rules of evidence, and claims that the scientific establishment promoting evolution is an arrogant and morally corrupt elite."
Jan 29th 2021
EXTRACT: "Ageing is so far known to be caused by nine biological mechanisms, sometimes called the “hallmarks of ageing”. In order to prevent ageing in our tissues, cells, and molecules, we need to be able to slow or prevent these hallmarks of ageing from taking place. While there are numerous treatments currently being investigated, two approaches currently show the most promise in slowing the development of age-related disease. .... One area researchers are investigating is looking at whether any medicines already exist which could tackle ageing. This method is advantageous in that billions of pounds have already been spent on testing the safety and efficacy of these drugs and they are already in routine clinical use in humans. Two in particular are promising candidates."
Jan 23rd 2021
EXTRACT: "The ageing global population is the greatest challenge faced by 21st-century healthcare systems. Even COVID-19 is, in a sense, a disease of ageing. The risk of death from the virus roughly doubles for every nine years of life, a pattern that is almost identical to a host of other illnesses. But why are old people vulnerable to so many different things? It turns out that a major hallmark of the ageing process in many mammals is inflammation. By that, I don’t mean intense local response we typically associate with an infected wound, but a low grade, grinding, inflammatory background noise that grows louder the longer we live. This “inflammaging” has been shown to contribute to the development of atherosclerosis (the buildup of fat in arteries), diabetes, high blood pressure , frailty, cancer and cognitive decline."
Jan 20th 2021
EXTRACT: "Anthropos is Greek for human.... The term is used to convey how, for the first time in history, the Earth is being transformed by one species – homo sapiens. ...... The idea of the Anthropocene can seem overwhelming and can generate anxiety and fear. It can be hard to see past notions of imminent apocalypse or technological salvation. Both, in a sense, are equally paralysing – requiring us to do nothing. .. I consider the Anthropocene as an invitation to think differently about human relationships with nature and other species. Evidence suggests this reorientation is already happening and there are grounds for optimism."
Jan 7th 2021
EXTRACT: "During the second world war, Nazi Germany banned all listening to foreign radio stations. Germans who overlooked their duty to ignore foreign broadcasts faced penalties ranging from imprisonment to execution. The British government imposed no comparable ban which would have been incompatible with the principles for which it had gone to war. That’s not to say, though, that it wasn’t alarmed by the popularity of German stations. Most effective among the Nazis broadcasting to the UK was William Joyce. This Irish-American fascist, known in Britain as “Lord Haw-Haw”, won a large audience during the “phoney war” in 1939 and early 1940, with his trademark call sign delivered in his unmistakable accent: 'Jairmany calling, Jairmany calling'. "
Jan 6th 2021
EXTRACTS: "The revelation of Trump’s hour-long recorded call with Brad Raffensperger, Georgia’s Secretary of State, over this past weekend crossed a new line – a line that not only set a high-water mark of moral reprehensibility, but a legal line as well, specifically in his pressuring Raffensperger to 'find the 11,780 votes' that would hand Trump the state and his veiled threat (' it’s going to be very costly…') if Raffensperger failed to comply. ........ Raffensperger – who has been forced to endure intense pressure, intimidation and threats – has proven himself to be a man of integrity and principle."
Jan 6th 2021
EXTRACT: "A final, perhaps more sinister, possibility is that Johnson knows exactly what he is doing. His political style evokes a unique blend of dishevelled buffoon and privileged Etonian. He is someone who likes to bring good news and doesn’t take life too seriously. Making tough, controversial decisions threatens this persona and so hiding in the shadows until his hand is forced helps him to reconcile his identity threat."
Dec 21st 2020
EXTRACT: "The resultant loss of land, the growing impoverishment of its citizens, and the hostile actions of Israeli occupation forces and settlers have forced many Bethlehemites to leave their beloved city and homeland. Given these accumulated violations of human rights and their impact on Christians and Muslims, alike, one might expect Christians in the West to speak out in defense of these residents of the little town they celebrate each year.  That, sadly, is not to be – most especially (and I might add ironically) among powerful Christian conservative groups in the US which, after all, claim to be the defenders of their co-religionists world-wide."
Dec 7th 2020
EXTRACT: "Worldwide, people donate hundreds of billions of dollars to charity. In the United States alone, charitable donations amounted to about $450 billion last year. As 2020 draws to a close, perhaps you or members of your family are considering giving to charity. But there are, literally, millions of charities. Which should you choose?"
Dec 1st 2020
EXTRACT: " The Museum of Modern Art is currently presenting Félix Fénéon: The Anarchist and the Avant-Garde – From Signac to Matisse and Beyond, examining the immense influence of this art critic, editor, publisher, collector and anarchist............A crucial feature of anarchism is the emphasis on the individual as the fundamental building block, the essential point of departure for any human association whatever. The individual was characterized by Grave in 1899 as a social creature who should be “left free to attach himself according to his tendencies, his affinities, free to seek out those with him whom his liberty and aptitudes can agree.” "
Nov 25th 2020
EXTRACT: "As the pandemic raged in April, churchgoers in Ohio defied warnings not to congregate. Some argued that their religion conferred them immunity from COVID-19. In one memorable CNN clip, a woman insisted she would not catch the virus because she was “covered in Jesus’ blood”. "
Nov 18th 2020
EXTRACT: "Here are just a few ways exercise changes the structure of our brain."
Nov 15th 2020
EXTRACT: "Perhaps it is Piller’s discovery that when it comes to war there is no such thing as innocence...."