How exercise is good for your head

Us humans like to do crazy things: go on 40 mile hikes, dance for 4 hours straight, or bike all the way up the coast of California.

Ok, maybe not all humans enjoy doing these activities, but many humans love at least some form of physical activity. And the humans who do love extreme sports, they’re addicted.

Why?

Because exercise leaves our brains feeling euphoric. And the best part: that euphoria creates a chemical cascade in our brains that actually makes us healthier and happier. 

So if you don’t like physical activity, listen up, your brain may be craving it.

The immediate benefits of exercise are tangible: endorphins. Endorphins create a state of attentiveness and happiness, blocking out pain that may arise from the physical strain. Cue runner’s high. 

The above diagram show endorphins work. They block the pain signal, allowing the body to keep on going.

But there is so much more going on in the brain during exercise than just endorphins: the brain is actually changing.

There are two key concepts here:

 

Neuroplasticity and Neurogenesis.

 

Neuroplasticity is the brain’s ability to change and adapt, to make new synaptic connections, to learn.

Neurogenesis is the birth of a new neuron, or brain cell. Yes, it happens. Mainly in the hippocampus, a part of the brain responsible for memory.

New Neurons in the hippocampus

A 2007 study by Cotman et al. found that exercise influences both neuroplasticity and neurogenesis for the better. Cotman looked at the effects of exercise on neurogenesis in the hippocampus and found that the connection from neuron to neuron becomes stronger in the hippocampus after exercise. 

This means more learning and improved memory. The hippocampus is also responsible for spatial navigation. Therefore, if connections become stronger in this area, there is improvement in one’s ability to move through space and interact with the environment.

Not only do the connections between the neurons improve, but the structure of the neuron itself changes.

It was observed that the dendrite branches of the neuron become more rich and complex after exercise. The dendrites are the parts of the neurons that make the connections, so with more branches that are strong and rich, the more stable the connections. Yay for healthy and robust brain!

The dendrites of a neuron are like branches of a tree

How does this happen?

Good question. This is still not fully understood, but clues point to the increase of four key chemicals: synapsin, glutamate, brain derived neurotrophic factor (BDNF), and insulin growth factor-1 (IGF-1).

While there is an increase in these chemicals, there is a decrease in one huge biological player: inflammation. Inflammation is your body’s way of telling you that something is not right.

What exercise does is decreases the amount of reactive oxygen species in the body.

This is good.

This is good because less reactive oxygen species means less inflammation.

Less inflammation means less chance of diseases like diabetes and other metabolic problems that lead to cognitive decline and neurodegeneration. It also means an increase in the good things, like BDNF and IGF-1.

And you know what those two good things do? They lead to neurogenesis and neuroplasticity 🙂 We are coming full circle.

On to BDNF and IGF-1

BDNF is regulated by neurotransmitters and by the neuroendocrine system, particularly insulin growth factor-1 (IGF-1). In 1996, Schwarz showed that IGF-1 increases within an hour after exercise (Schwarz, 1996). Ok, so this leads us to assume that BDNF would also increase after exercise, right?

Yep, you got it.

A 2006 study showed that after exercise, the BDNF protein production in neurons immediately increases and remains higher even weeks after exercise (Kuipers, S.D. and Bramham, C.R., 2006).

So, this is how a lot of research works. You make a prediction, test whether there is a decrease or increase in whatever you are looking for and then make a conclusion.

Another way you can test these chemicals is by blocking a certain factor to see what happens when that chemical can no longer go about its normal course.

Studies have been conducted blocking both BDNF and IGF-1 receptors during exercise to see if these growth factors are truly important for the exercise induced benefits. What was observed was that by blocking TrkB, the BDNF receptor, the beneficial effects that are observed in the hippocampus are now dampened (Vaynman, 2004; Vaynman, 2006).

By injecting anti-TrkB in the hippocampus, researchers observed a decrease in synaptic proteins, leading to a reduction in long-term potentiation (synaptic connections). In addition, when the IGF-1 receptor is blocked in the hippocampus, spatial recall is worse.

Ok, a couple biology words and much research later and I think it has become evident that exercise = good, healthy chemicals for a happy brain.

BDNF & Depression

There’s even more evidence for this when you look at the relationship between BDNF and depression. The less BDNF, the greater the potential for depression. So, the more exercise, the more BDNF, and the less the depression. This is potentially how exercise helps reduce depressive-like symptoms.

A 2004 study infused BDNF into the hippocampus and found that this alleviated depression (Monteggia, 2004). In 2005, Hoshaw was curious to see what happens when IGF-1 is diffued into the hippocampus, so he injected IGF-1 into the ventricles of the brain and saw a decrease in depression as well, though not as strong as BDNF (Hoshaw, 2005).

So, here’s a breakdown of how exercise and these chemicals lead to a happier brain: 

What more?

If you’re not already convinced about exercise and the brain, here’s one more beautiful piece of science: more exercise means more energy and blood pumping through your brain, which means the growth of new blood vessels which carry nutrients and energy to your brain cells. 

How does this work? Well, exercise leads to vasodilation of blood vessels (the expansion of the blood canals), allowing for greater blood flow throughout the brain, but especially to the hippocampus, cortex, and cerebellum.

Not only do blood vessels get bigger, but angiogenesis also occur. Angiogenesis is the process through which new blood vessels are born and sprout from existing blood vessels.

This allows for an increased amount of oxygen and nutrient supply all throughout the brain.

A study conducted in 2007 by Pereira, A.C, et al. showed that a 12 week cardio-vascular training program in humans increased blood flow specifically to the dentate gyrus. This means better memory for you 🙂

The increase in vasodilation and angiogenesis also supports the existence and proliferation of microglia and astrocytes, the cells of the brain that help maintain and support the neurons (Cotman, 2007).

So now when you go on that hike and you’re feeling incredible, your thoughts are clear, and your brain seems to be working at it’s best, you know why.

The beautiful thing is that exercise doesn’t have to be hard. You can make it has fun or as boring as you want! The more engaged you feel in the activity, the more you lose yourself in the task. Find an activity that makes you come alive! You don’t have to run for 10 miles or do laps in the pool all day long. Your options are endless, you can mountain bike, surf, cross-country ski, climb a mountain, dance for hours, or play a game of ultimate frisbee. Get out and get the blood pumping through your body and up to your brain. Do you and your brain a favor: give yourself some love, give yourself some health.

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From my heart & brain to yours,
Hannah
www.neuroyogini.com

Hannah Heimer
Hannah Heimer

I’m a brain enthusiast and yoga fanatic. I work as a researcher at the University of California, San Diego while also running a yoga business on the side.

I use brain research and yoga as a springboard to blog about lifestyle, health, happiness, and how it all relates to your brain.

Just like the nerve cells in our brains, I love making new connections. So, feel free to reach out. For more info on yoga and the brain, take some time to explore neuroyogini.com.