When it comes to most of your body, it’s true…if you don’t use it, you lose it in at least some sense. And if you do use it, it gets bigger, thicker and stronger. (Unfortunately, there are exceptions to the rule though 😞) Your body is efficient and strengthens what it uses most and doesn’t waste resources on what it doesn’t use. If you lift heavy weights, your arms will get bigger to tolerate that. If you’re in an arm cast for months, your muscles will get smaller and weaker, your arm bones will get thinner, and your tendons and ligaments will get weaker as well. Since you’re not using your arm, your body will use the resources to maintain your arm in other places where you’ll actually use them.
There’s also a weird thing that happens when you don’t use a body part which can increase the chance of feeling pain. If you don’t use your body, the neurological muscle and sensory connection between your body and your brain gets hazy.
Your brain has a map of your whole body in order to feel something coming from that body part (sensory map) and in order to move that body part (motor map). These are separate parts of the brain. Your hands have a bigger sensory map and a motor map since you use your hands a lot to feel around and you need to be able to move your hands and fingers very specifically for different tasks. Where as your trunk (torso) doesn’t take up a lot of space in either since you don’t use your trunk to feel around (that’s why the game where you have to guess what someone is writing on your back is so tough, especially if the written word gets smaller and smaller) and you usually perform big general movements with your body like twisting left or right or sitting up.
We know that if you tape your index finger together with your middle finger for 30 minutes, your brain will “smudge” these two fingers into one in its maps. Smudging means the maps representing each finger will start to overlap. It’ll become harder for you to distinguish between whether someone is touching your index finger or middle finger and it’ll be harder to move your fingers individually. So all it took was 30 minutes of not moving and feeling your fingers individually to screw up your brain maps. This is important because if your maps aren’t detailed and your brain doesn’t have an accurate representation of your body, this can lead to an increased chance of feeling pain. That makes sense because if your brain doesn’t have an accurate representation of whats going on, it can increase the chance of your brain wanting to protect that body part and make you experience pain.
This is a big reason why I try to avoid immobilizing body parts the best that I can. If I broke my arm and it was an UNSTABLE break (my bones are moving where they shouldn’t be moving, your upper arm bone should be moving as one piece), yes, I would probably cast it and immobilize it as the risks of moving my bones further and further away from each other outweigh the benefits of keeping my neurological connections intact (there are still ways to use your motor connections without moving your body though).
But let’s say I sprained my ankle (tore a ligament either completely or partially), there would be danger messengers (not pain nerves) coming from my ankle to my brain that would increase the chance of me feeling pain. My ankle would be sensitive, which is a good thing, since I want to protect it somewhat and let it heal. But if I overprotected my sprained ankle and I put on an ankle brace when I didn’t need to, I could have unnecessary issues. This becomes a lot worse if I start using crutches and I’m too scared to put weight on my foot at all. My sensory and motor maps in my brain representing my ankle would likely get more smudged the longer I used a brace and crutches. My brain would have no idea what’s going on with my ankle. My brain would feel threatened and want to protect it and when I took the brace off, it’s possible that even the smallest movement can cause pain. I wouldn’t feel pain because I’m harming my ankle but because my brain would be OVERPROTECTIVE of my ankle since it doesn’t know what’s going on there. Overprotecting your own body will lead to your brain overprotecting YOU and can lead to long term pain (not injury).
Each person’s injury is unique to them so I can’t say you should NEVER use a brace or crutches. You just want to be sure you ABSOLUTELY need to. In cases where you do need to, you want to be sure you are maintaining your neurological connections the best you can so you can get back to a normal pain free life as fast as you can. The best thing to do is to use your body to the best of your tolerance all the time. There is always a way to use it, at least a little bit, even if you’re in a cast.
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