How exercise makes your brain better: 7 mechanisms

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You know exercise is good for the brain. But… Do you know what exactly is happening to your brain because of exercise?

Let’s start with the basics. Physical activity of any form creates widespread changes to the brain, as confirmed by MRI scans[1]. These changes occur at the whole “system” level of the brain (the organizational layout), the microstructures (smaller neural circuits), myelin sheath (fatty deposits on neurons that improve signal efficiency), and blood supply inside the brain. This essentially says the changes occur everywhere in the brain. Now, we’ll explore the specific changes that bring out the biggest benefits of exercise.

exercise and brain function (1)

Exercise triggers many biological processes that, at the very least, temporarily improve brain function and give us better memory, learning potential, perception, reaction time, and emotional regulation.

1. Hippocampus size increases

The hippocampus is a small brain area that creates new neurons and accommodates new learning via new neural connections to existing circuits. When this area shrinks in size and density, we see symptoms like memory loss or inability to perform things we’ve previously learned. Research done via brain imaging[2] shows those who exercise regularly have about 2% more hippocampal volume compared to those who don’t. To compare it to how the hippocampus also shrinks with age, this growth is equal to offsetting the shrinkage in 1-2 years of aging. Even low-intensity activity like daily walking[3] promotes hippocampal volume.

An analysis of 13 studies[4] assessing the relationship between hippocampus size and physical exercise found a robust increase in hippocampus size in those who exercise regularly. This held across a wide age range, spanning young adults to elders, with and without Alzheimer’s. The study concludes exercise has the potential to prevent and treat the loss of volume in the hippocampus in healthy adults and those with Alzheimer’s.

Credit: In the P.S.

2. Amygdala activity reduces

The amygdala is quite a popular brain area because it processes emotions. Activity in the amygdala directly corresponds to our emotional state, including anxiety, stress, calmness, joy, fear, etc. One common finding[5] is that exercise regulates the amygdala and reduces its sensitivity and baseline activity, which manifests as fewer volatile emotions and more diluted emotions. In a way, this means exercise is a mood stabilizer and a protective barrier against regular emotions turning into anxiety.

A small study on adolescents using MRI data[6] on a 6-month-long habitual exercising group and a control group shows that habitually exercising adolescents had more plasticity in their amygdala. Plasticity refers to the changeability of activity and neural connections. It suggests exercise allows people to positively change their emotional responses to stress, especially when their responses are previously unhealthy. This means exercise is a valid way to protect against mental health issues characterized by negative thoughts, unhealthy emotional patterns, rigid emotions, anger, anxiety, depression, and stress.

3. BDNF growth

Exercising muscles releases myokines from the muscles, a protein that signals the genes in the hippocampus (brain region governing the birth of new neurons and learning) to synthesize a protein called BDNF[7]. It also protects neurons from damage. The concept of brain reserve is more relevant here because BDNF is a critical requirement for it. The brain reserve is an extra set of resources that fortify the brain with extra neural connections, stronger neural circuits, healthier cells, etc. Brain reserve protects the brain against age-related decline and provides compensatory mechanisms for normal functioning during brain injury and deterioration.

BDNF is a mind-and-body connection mechanism. BDNF is triggered through exercise, but its primary job is to promote new neural connections and fortify existing ones. This creates a “dual action[8]” phenomenon – BDNF can be maximized with mind-body exercises such as sports, which require many decisions. Another alternative is doing cognitive tasks like recitation or mental calculations during yoga. The dual action here is that neuroplasticity (the biological neural domain expansion that gives us learning and memory) increases through physical activity AND cognitive activity.

4. Incubating creative thoughts

Stuck with a problem at work? Go run or walk for 15 minutes.” This advice works because exercise and short physical activity enhance creativity in many cases (but it’s hard to test in a lab).

In one study[9], researchers observed that a 15-minute treadmill, sitting down for 15 minutes, and 15 minutes of listening to music did not improve creativity in their tests. However, these tests are not particularly known for being a good measure of creativity, nor is creativity easily measured without a real-world context. So YMMV, big time.

A more reliable observation is that exercise unlocks existing creativity by removing recently formed mental blocks. For that, studies are few, but anecdotes are many. A study using the same test as the previous study[10] found that exercise improves creativity and mood, but it improves creativity independent of mood improvements.

Creativity is fundamentally taking a new perspective, re-connecting ideas in unexpected ways, and stepping back from a situation that gave you a mental block. All 3 of these are achieved by the brain’s default mode network. It is a network of neural circuits spread across the brain that re-analyze memories and simulate ideas with a lot of random activity, which creates creative insights. The resting moment of the brain comes with high activity in the default mode network. It’s a moment where a thought is cooking in the background for a creative insight. This process, known as incubation is a well-supported process of creativity. I highly recommend reading this thesis to know more[11].

5. Memory boost

The effect of exercise on memory is widely studied and in no way will it give you a permanent boost. There is always a ceiling effect regarding trainable skills where more effort starts giving diminishing returns. The same goes for exercise. But here’s what we know so far.[12]

  1. Regular exercise triggers multiple cellular processes that do the brain’s biological upkeep and, as a result, keep memory intact.
  2. Short exercise bursts improve recall if the exercise is done after some form of new learning.
  3. Just 1 session or a few days of intense exercise is enough to dramatically improve long-term and short-term memory.

The reason we see these effects is not clear, but researchers have proposed potential mechanisms[13]. One is that exercise increases available resources in the brain (blood supply, glucose, default mode network activity, etc.), which helps recently formed memories consolidate. Another theory is that exercise prevents one memory trace from interfering with another trace by separating the 2, biologically speaking. A third possibility is the physical movements that happen to occur during exercise are themselves the foundational blocks of memory (a new direction called “embodied cognition“).

Related: Lifestyle factors that affect memory and what you can do about it

6. Slows aging

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Not strictly exercise per se, physical activity is one of the main reasons people “super age” – leading a satisfying, well-adjusted, independent life well beyond 80 years. Physical activity is the broader determining factor, but for most of us in a fast-paced urban life, dedicated exercise sessions such as gym routines and sports are a way to achieve it. The Insta-famous 10,000 steps a day advice is also to that end – have a lot of physical movement in the day. The same goes with the advice – “move 10 minutes after every 45 minutes of sitting screen-time.”

Exercise can increase life expectancy by over 6 years[14] and dramatically reduce (by 30-35%) the chances of death by a wide range of factors like violence, accidents, disease, etc. The most commonly talked about contributing factor is physical health, namely cardiac health. But brain health – the ability to remember, focus, avoid physical accidents, adapt, make sound judgments, etc., also contributes to lifespan. These changes happen via every other actor discussed in this article (neuroplasticity, healthy emotional makeup, BDNF, brain reserve, hippocampus volume, reaction time, etc.)

7. Reaction time reduces

Exercise, with its progressive overload and increasingly faster/complex movements, begins to train our reaction time. Sports coaches could say, “You should spot the ball and grab it as a reflex, 100% muscle memory.” The statement is not technically wrong, although, here, the reflex means fast reaction times and habits. Those who exercise generally have faster reaction times, and not just for those types of movements they practice. The value of reaction time is not just a personal flex in sports – it is the ability to avoid accidents, spontaneous decision-making, adjusting to unfamiliar scenarios, etc. Driving in a new country, for example.

Reaction time – the time it takes for us to respond to a stimulus – indicates a healthy and efficient central nervous system (brain and nerves to the body included). One study[15] suggests that a short burst of just a 5-minute exercise that doubles the resting heart rate is enough to decrease reaction time after exercise. Auditory and Visual reaction times are most relevant in everyday life – quickly responding to others, spotting errors, seeing oddities on the road, avoiding injury, responding to unpredictable sounds, etc. Research shows regular aerobic exercise improves auditory and visual reaction[16] time.

However, there is a limit to this benefit. Another study[17] that looked at those who exercised for much longer – 10 months – did not show an improvement in reaction time when it was measured at the start and end of the 10-month exercise routine. The exercise benefit on reaction time may be temporary and more about increasing the nervous system arousal, which readily puts the brain into a vigilant and fluid state. This is because during high arousal moments[18], like seeing a threat or preparing for it or even being hopeful and excited, faster reaction times helped us survive, so our “fight or flight” mode gives us better reaction times.

Summary

How exercise improves the brain:

  1. Hippocampus grows
  2. Reduces negative emotions
  3. Signals BDNF
  4. Increases creativity
  5. Improves recall
  6. Slows aging
  7. Reaction time reduces (you get faster)

P.S. By Images are generated by Life Science Databases(LSDB). – from Anatomography, website maintained by Life Science Databases(LSDB). You can get this image through URL below. 次のアドレスからこのファイルで使用している画像を取得できますURL., CC BY-SA 2.1 jp, https://commons.wikimedia.org/w/index.php?curid=9808812

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