Most of us know that exercise will help us live longer and have a better quality of life. According to the latest research, exercise can even help to combat mental illness and improve our focus, memory, mood and protect our brain as we age. Erin Gray investigates what is really going on inside our brains when we exercise.
Many of us know all too well the heartache of seeing an elderly loved one affected by dementia. We are forced to watch helplessly as the wisdom that guided our youth and shaped golden childhood memories fades away into confusion. For patients diagnosed with Alzheimer’s disease, the most common form of dementia, the prognosis is poor. The disease is progressive and debilitating, and there is no known cure.
However, emerging evidence from the field of neuroscience is suggesting that we might be able to reduce our risk of developing dementia by being physically active. An extensive body of research now tells us that regular exercise can also improve the symptoms of other mental and neurodegenerative disorders, such as depression, anxiety and Parkinson’s, and can even reduce the risk of developing one of these diseases. “Exercise can make you smarter, happier and have more neurons depending on the [intensity] of the training program,” say researchers from Spain’s Cajal Institute (Frontiers in Neuroscience, vol 10, article 93, p1). So what exactly is happening in our brains while we exercise?
Made to move
Research into the neuroscience of exercise is ongoing, but scientists are getting closer to finding out why and how our brains respond so positively to exercise. One popular theory is based on our evolutionary history. Many of our day-to-day activities that are essential for sustaining life once involved a significant amount of physical activity. These are basic survival functions like finding food or escaping from predators. While this is no longer the case for most of us, our bodies have evolved to be physically active. These survival activities required early humans to think, assess the environment and plan accordingly. So it is perhaps no surprise that we are seeing links between exercise and cognition.
There are many ways that exercise can influence the biology of our brains, and this research remains one of the frontiers of neuroscience. What we do know is that during acute exercise, blood flow to the brain increases and parts of our brain become more active. Chemicals called neurotransmitters and growth factors are released.
Neurotransmitters help to transmit messages between nerve cells in the brain. Reduced levels and activity of specific neurotransmitters are implicated in the underlying causes of diseases such as major depression and Parkinson’s disease. Exercise increases the availability and effectiveness of these neurotransmitters, explaining why we see an improvement in symptoms associated with these illnesses when exercise is part of the treatment regime. The mood boost we receive when we exercise is also caused by the release of these neurotransmitters, and the increased blood flow improves our ability to focus.
“Exercise can make you smarter, happier and have more neurons.”
Growth factors, which are responsible for maintaining and supporting nerve cell function, are also released during exercise. Growth factors stimulate the growth of new blood vessels and nerve cells, and promote improved connections between nerve cells. Collectively, these effects contribute to something called neuroplasticity.
Neuroplasticity is the ability of our brain to rewire connections and change its’ structure so it can adapt to new situations. Neuroplasticity is important for learning, thinking and the protection of our cognitive abilities as we age. Exercised promotes neuroplasticity in a particular region called the hippocampus (one of the regions of the brain associated with long-term memory) resulting in the memory improvements we see in people who regularly exercise.
The protective effects of exercise on our brains may, in part, come from an unsuspecting source. Exercise causes the body to release an inflammatory chemical called reactive oxygen species. Counterintuitively, low level exposure to this chemical can stimulate the release of antioxidants and trigger the repair of DNA. Much like the exposure to low doses of inactive viruses in vaccines can strengthen our immune systems, regular exercise can make our brains and bodies more resilient to further stress.
Pleasure and pain
So far, we have seen that exercise improves our memory, focus and mood, and can protect our brains from ageing. Along with the known physical effects, that is a pretty long list of benefits. It’s fairly clear that our brains really like exercise. In fact, our brains like exercise so much, we are wired to seek it out regularly.
Exercise activates our pleasure and reward system, driven by the neurotransmitter dopamine. When we exercise at a moderate to high intensity, receptors in the reward centres in our brains are activated enhancing the release of dopamine. Dopamine causes feelings of euphoria, and reduces pain and anxiety levels. If you have ever experienced the exhilaration of a ‘runner’s high’, you might have first-hand experience of this neurotransmitter rush.
Not only does exercise make us feel good, but it can also reduce our levels of pain. During exercise, a different group of neurotransmitters also act on the nerve endings outside our brain. These neurotransmitters can reduce the activity of special nerve endings that sense tissue danger and contribute to pain.
There are other convincing arguments to get up and get moving. People who are physically fit have a reduced risk of developing age-related cognitive disorders and are more mentally healthy. The harmful effects of being physical inactive are also sobering. Physical inactivity has been likened to that of moderate cigarette smoking when it comes to your risk of dying.
The good news is you don’t need to be running marathons. Benefits can be gained simply doing by low to moderate intensity exercise such as walking. Of course, this depends on how fit you are to begin with, and the effect does level out with large amounts of exercise. Nonetheless, the benefits are clear.
So while we may have little control over the suffering of loved ones at the hands of neurodegenerative diseases, we may be able to influence our own fate and that of generations to come. Exercising consistently over long periods of time can protect our bodies and our brains. Future research into these effects may also lead researchers to improvements in treatments and drugs, as they uncover the incredible inner workings of our brains.
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