I don't know why, but wool helps muscle pain.
When I have really strong back pain, I lay on a sheepskin and it has good effect. If you don't want to hang around dead sheep, option #2 is lambswool directly onto the skin. They have really good soft lambswool stuff out there to wear under your other clothes, but the prickly stuff can be great too because it has double effect, it stimulates and tricks the sensory signals (as mentioned in post #4)at the same time that it warms.
In other countries, I have heard them say that cat...skin is supposed to be very beneficial to muscle pain :& but if that means you have to kill and skin a cat, I'm not going to try it...
But... I would imagine that this should probably work even better if the cat is alive, warm and furry...?
Which would mean that putting a purring cat on your aching body is excellent medicine, how about that for a feel-good cure?