Your Muscles Have Been Talking to Your Brain

In the last post, your muscles turned out to have a much bigger job than moving your bones. When muscles start working, they use more glucose from your blood, change how your body handles fuel and send chemical messages to other parts of your body. Some of those messages are part of a conversation with somewhere you might not expect: your brain. Your brain sends instructions telling muscles to move, but working muscles also send information back.

This was a major change in how scientists understood muscle. Working muscles release chemical messengers called myokines. Some help with changes happening nearby, while others travel through the blood and become part of the communication between muscles and other parts of the body. Your brain is part of that connected system. So when you start using large muscles to walk, cycle, swim, run, dance or do squats, you are doing more than creating movement.

There is no single “exercise chemical” that leaves your leg and fixes everything. Many signals change when you become active, and scientists are still discovering exactly what they do. Your heart and blood vessels respond, your muscles use more fuel, and chemical messages travel between different parts of your body. This does not involve one heroic myokine leaving your quadriceps carrying a tiny briefcase marked URGENT: DELIVER TO BRAIN. It is a team effort happening throughout your body.

Your muscles have something to say

Scientists have even shown that regular activity changes the way muscles handle some chemicals in the blood before those chemicals reach the brain. Other research has found signals released by active muscle that affect areas of the brain involved in learning, memory and mood. Scientists are still discovering exactly how all these messages work in humans.

One brain area they are especially interested in is the hippocampus. It helps you learn and form memories, and it is also involved in how the brain responds to stress and mood. Researchers have found several ways that regular physical activity supports the health and function of this part of the brain. Some of those effects begin with what is happening in the brain itself. Others are connected with messages arriving from the active body.

This is why the old explanation that exercise helps your brain because it “releases endorphins” is far too small. Endorphins are real, but they are only one part of a much bigger response. Your muscles are communicating, your heart and circulation are responding, and your brain is receiving information from an active body. Apparently your body never agreed with the idea that physical health belongs in one box and mental health in another.

What does this have to do with thinking?

Cognitive function is simply how well your brain does its thinking jobs. Paying attention is cognitive function. Remembering information long enough to use it, solving a problem, learning something new and making a decision are too. Research with children and adolescents shows that physical activity supports several of these abilities. Even short activity breaks during long periods of sitting improve attention and help students get back on task.

Why? Your brain is made of billions of cells that constantly communicate with one another. When you learn something, groups of those cells communicate and connections between them change and strengthen. Regular physical activity supports several of the processes that help those brain cells communicate and adapt.

Blood flow is part of the story too. Your brain needs a constant supply of oxygen and fuel carried by your blood, and physical activity changes circulation throughout your body. Regular activity also supports healthy blood vessels, including the enormous network supplying the brain. Add the chemical messages arriving from an active body, and it becomes much easier to understand why movement and thinking are connected.

Unfortunately, five squats before a test will not retrieve an entire chapter you forgot to study. Your quadriceps have expanded their job description considerably, but doing your homework remains outside their current responsibilities. Activity supports the brain systems used for attention and learning. It cannot supply information you never learned in the first place.

Then you go to sleep

The connection continues after the activity is over. Research with children and adolescents shows that regular physical activity improves sleep quality. That includes spending more of the time in bed actually sleeping rather than lying there waiting for sleep to arrive. Good sleep then helps your brain store what you learned, regulate emotions and prepare for the next day.

Now we have a loop. Being regularly active supports better sleep, while better sleep helps your brain and body recover and makes being active the next day easier. A terrible night's sleep can make almost everything feel harder, including physical activity. Activity and sleep are not separate health behaviours that never meet.

That does not mean one inactive day destroys tonight's sleep or one terrible night requires an emergency jog around the neighbourhood at 2 a.m. Bodies respond much more to what happens regularly than to one imperfect day. The useful skill is noticing your own pattern. When are you active, how do you sleep, and how does the next day feel?

What about mental well-being?

Physical activity also affects mental well-being, and this is much more than saying exercise “makes you happy.” Research involving children and adolescents shows that regular exercise reduces depressive symptoms and improves self-esteem. Exercise is important enough that it is also used as part of treatment for depression. It does not replace counselling, medication or other treatment when someone needs them.

There is no single reason exercise affects mental well-being. The muscle-to-brain messages we have been exploring are one part of the story. Activity also affects sleep and the body's stress response, and it gives the brain regular experience responding to movement. Then there are things that are not happening inside a cell at all: enjoying an activity, spending time with other people, getting outside, learning a skill or noticing that you are becoming better at something.

All of those things can matter at the same time. Trying to credit one “happy chemical” for the whole effect would be like giving one hockey player credit for every pass, save and goal in the game.

Physical activity is one of those parts.

One body, not separate parts

This brings us back to the muscle that started the whole story. Start walking, cycling, swimming, playing or doing some other activity and your muscles contract. They use more fuel and send messages. Your heart and circulation respond. Your brain receives information from a body that is now active rather than sitting still.

Repeat that regularly and the effects begin reaching into more parts of your life. Your physical fitness changes, your brain gets the support that comes with regular activity, and your sleep and mental well-being benefit too. None of this requires remembering a list of chemical names. The important idea is much bigger and much easier to remember:

And then something else happens that no blood test can measure. You choose an activity, return to it and eventually discover that something you could not do before has become possible. Your body changed, but you also learned something about yourself.