What is “Muscle Memory”?

Axon Sketch

What is “Muscle Memory?”

If you have any involvement with self-defense training, athletics or the development of any type of physical skill, you’ve probably heard the term “Muscle Memory” used before. It’s the term most commonly used to express the idea of developing refined motor-skill, efficiency and repeatability in a defined physical skill. Want to throw a better punch? Practice throwing a good one until it becomes “muscle memory.” Want to smoothly perform magazine changes? Practice a smooth mag change again and again until it becomes “muscle memory.” Want a great fastball, golf swing or rod cast? “Muscle memory.”

But if you’re like me, the term “Muscle Memory” just doesn’t sit quite right. Maybe it causes some confusion and seems hard to really define. That’s probably because most of us know from grade school biology that muscles don’t actually store memories (or any sort of data). That’s the brain’s job. But at the same time, it’s clear that practicing a skill allows you to perform that skill more easily and quickly than a beginner. That can seem like a contradiction.

So what actually happens in our bodies when we practice a skill? If it’s not accurate to say we are building muscle memory, than what are we actually building?

Well break out the lab coats, ladies and gentlemen, because I’m about to knock the dust off my scientist credentials. (Those of you who read the Ebola post will recall that I was an honest to God scientist, once upon a time).

The first thing we need to talk about is Neurons. These are the cells that make up your nervous system. Neurons are special because they can transmit chemical and electrical signals to other cells. They can send a signal through the body by running it down a chain of other neurons, resulting in actions in another part of the body. So when you perform a physical act, like practicing your mag changes, your brain sends the signal to do it down a chain of neurons.

Neurons are shaped differently from the round cells you remember from your biology text book. They’ve got a long arm that projects from the side of the cell. That long arm, called an “Axon” is what the signal travels down when it’s sent to another neuron. So in an extremely simplified way, you could think of a neuron like a set of jumper cables: two ends that send and receive, with an insulated cord in between.

With me so far? Good. Now let’s talk some more about the axon.

The axon is wrapped in a fatty substance called Myelin. Myelin is awesome. It’s what separates us from the invertebrates. (No, seriously, myelin is considered a defining characteristic of vertebrates. Got a spine? You’ve got myelin). But what makes myelin really cool is that it insulates the axon and allows for more efficient and rapid transmission of signals along the nervous system. In fact, it’s only because of myelin that we have massive creatures (like whales, elephants and politicians) because without the efficiency myelin adds to the nervous system, large organisms can’t send signals around the body fast enough to stay alive.

So the myelin sheath around a neural pathway is pretty important. In a pathway with a thin myelin sheath, impulses travel slowly in a wave, like shaking one end of a rope. In pathways with thick myelin sheathing, the impulse hops along, like throwing a ball. Neural pathways with thick myelin sheaths are much faster and more efficient.

So what does this have to do with “muscle memory” and developing physical skills?

You know how you can make a muscle grow bigger by using it more often and under a heavier load? If you want a big bicep, you can do lots of curls and make it grow. The muscular system is responsive like that… and the nervous system is too, in its own way, through a process called myelination.

When you perform a particular action, the command to do so runs down a particular neural pathway (or sets of neural pathways). The more that pathway gets used, the thicker the myelin sheath becomes. The thicker the myelin sheath becomes, the faster and more efficiently the signal for that action travels. That’s why frequently practiced actions become “second nature.”

In addition to physical actions, myelination may also contribute to decision making, stimulus-response and thought patterns. Ever hear your cellphone ring and immediately stick your hand in your pocket to answer, only to learn your phone is on the table a few feet away? You knew the phone wasn’t in your pocket, but the neural pathway of [phone rings = reach into pocket] is already so well established (in part via myelination) that your body acts almost without thought.

Once you know about myelination, you can start to understand how repetition in practice works to build skill. (And why “practice makes permanent” is much closer to the truth than “practice makes perfect”). It also explains why the answers to familiar scenarios, in life and in training, come easily and the answers to unfamiliar circumstances take longer to produce. It may even explain why bad habits are hard to break and good habits take time to form.

How myelination affects neural pathways can lead us down a heckuva rabbit hole, so I’ll end with this: What we call muscle memory is really a change in, and reinforcement of, specific neural pathways in the brain and peripheral nervous system. Just like you can change your skeletal-muscular system by how you use it, you can change (to a degree) your nervous system with your repeated actions and thoughts.

And I think that’s extremely cool.

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