You can easily block a kick with a forearm with minimal pain. Blocking a kick with a shin though hurts like hell, unless you have taken the time to condition them.
Why is that? More nerves on the shin?
I would guess that you constantly condition your forearms through your daily life.
Also, there seems to be more covering the bones in my arm than over my shin. And it isn’t as sharp either…
I’m not a doctor (although I have been kicked a lot), so if I’m mistaken on this I welcome correction: the radius and the ulna have a good bit more tissue around them to take the force of an injury, while the tibia is very close to the surface.
A round kick blocked with the forearm should strike into the meaty part of the arm, but that same kick blocked with the shin strikes onto the tibia and compresses the nerve endings up right against the bone, causing pain.
I’d have to go with pravnik. I’d also add that the shins support a lot of weight and so are under more stress regularly. They’re more likely to be sore to begin with and the blow would exacerbate that stress.
Having my legs waxed hurts a hella lot more than having my arms waxed. According to my waxer, this is typical, and she was taught in school that it was because there was less flesh over the bone. A.K.A., pravnik’s answer.
The shin bone extends in front of the muscles and tendons, while your forearm is wrapped in it. The wrist might be the closer comparison - I can personally attest to how much sharp blows to the sides of the wrist hurt.
Further, your forearm will yield at least somewhat to a blow. Your shin really won’t, at least if you have your weight on that foot.
Even if your foot is elevated, your lower leg has a lot more mass/inertia than your forearm. Likewise, someone else’s incoming shin has more mass/inertia than a forearm (and probably more speed), so a shin-to-shin collision will generate much higher impact forces than a forearm-to-forearm collision.
It hurts me more to bump a volleyball with my forearms to do high kicks on a punching bag in boxing class (where my shin hits the bag). Maybe I am backwards?
Apples and oranges. Hit the punching bag with your forearms and let us know if it hurts.
Your shins are load-bearing instruments; your forearms generally are not. They spend most of the day closer to the breaking point than your forearms. They need more nerves to let you know when you’re pushing it.
I bet this is at least part of it. If I banged my arm on something as hard as I bang my shins on the coffee table, I’d be on the floor in the fetal position.