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

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...."
Nov 4th 2020
EXTRACT: "I imagined America as the land of the free that gave voice to the forgotten. Where race, color, and creed do not matter and human rights are guarded with zeal. Where the ingathering of all cultures and people made it richer and human resources and talent knew no limits or constraints. Where opportunity awaits the able and generosity is extended to the needy. Where everyone is equal before the law and political differences are valued to make America better. Where sacrifices are willingly made to right the wrong morals and fortitude guide its leaders. Where caring about friends and allies is the hallmark of the nation and opposing oppression near and far is the emblem that distinguished America. This is the character of America. This is the soul of America. This is what made America great. The America that gave me a home. The America that fulfilled my dreams."
Oct 15th 2020
EXTRACT: "“The paintings which I propose to do will depict the struggles of a people to create a nation and their attempt to build a democracy” – this is how Jacob Lawrence described his project in 1954. Over sixty-five years later his proposal has, if anything, become only more urgent. Two days after this exhibition closes, Americans will vote in what is arguably the most significant election in a generation, an election that will measure our commitment to preserving that democracy, the struggle for which was Lawrence’s mighty theme."
Oct 15th 2020
EXTRACT: "There are also other ways our life stories can be passed down through generations, besides being inscribed in our DNA...... One 2014 study looked at epigenetic changes in mice. Mice love the sweet smell of cherries, so when a waft reaches their nose, a pleasure zone in the brain lights up, motivating them to scurry around and hunt out the treat.... The researchers decided to pair this smell with a mild electric shock, and the mice quickly learned to freeze in anticipation....... The study found this new memory was transmitted across the generations. The mice’s grandchildren were fearful of cherries, despite not having experienced the electric shocks themselves. The grandfather’s sperm DNA changed its shape, leaving a blueprint of the experience entwined in the genes."
Oct 1st 2020
EXTRACT: "As we Americans face the potential loss of a peaceful transition of power after the election and the possible end of democracy as we know it, we are reminded that discourse matters, that words matter and that the one who quotes poetry is a man who reads—and that matters."
Sep 25th 2020
EXTRACT: "We now know the potentially appalling long-term effects of suffering cruelty from others, including damage to both physical and mental health. The benefits of being compassionate towards oneself, rather than treating oneself cruelly, are also increasingly recognised..... And the idea that we must suffer to grow is questionable. Positive life events, such as falling in love, having children and achieving cherished goals can lead to growth..... Teaching through cruelty invites abuses of power and selfish sadism. Yet Buddhism offers an alternative - wrathful compassion. Here, we act from love to confront others to protect them from their greed, hatred and fear. Life can be cruel, truth can be cruel, but we can choose not to be."
Sep 19th 2020
EXTRACT: "Over his incredible career, David Attenborough has seen more of earth’s natural wonders than almost anyone. To hear him talk, with such clarity, about how bad things are getting is deeply moving. Scientists have recently demonstrated what would be needed to bend the curve on biodiversity loss. As Attenborough says in the final scene, “What happens next, is up to every one of us”. "
Sep 15th 2020
EXTRACTS: "The Anglo-Australian multinational company Rio Tinto – the largest iron ore mining company in the world – demolished two 46,000-year-old Aboriginal rock shelters in May.......The Dampier Archipelago of Western Australia is home to thousands of Aboriginal pictographs, and perhaps the oldest surviving rock art in the world. Indeed, Australia’s Indigenous art represents the longest uninterrupted tradition of art in the world – going back over 50,000 years......Aboriginal people represent the oldest continuous culture in the world...."
Sep 13th 2020
EXTRACT: "Iran’s 1979 Islamic revolution was a defining event that changed how we think about the relationship between religion and modernity. Ayatollah Khomeini’s mass mobilisation of Islam showed that modernisation by no means implies a linear process of religious decline.....Reliable large-scale data on Iranians’ post-revolutionary religious beliefs, however, has always been lacking...........In June 2020, our research institute, the Group for Analyzing and Measuring Attitudes in IRAN...conducted an online survey......The results verify Iranian society’s unprecedented secularisation."