How to weaken the interaction of bones?

Question

Unity

Hello. My character has animations (idle, running, holding a weapon). In order for the character to hold the same weapon while standing and running, I created the necessary masks (Body (legs, torso, head) and hands (only hands)) and divided the animations into layers. When running, the body body tilts a little, therefore the arms also go down, but I don’t need this, I need the arms to always be straight, I turned off the torso from the Body mask, but nothing has changed. As I understand it, this did not help due to the fact that the animation of the torso itself stopped, but the torso itself was pulled down not because of the animation, but because of the lower bone that is attached to the legs (more precisely, due to the strength of the connection that prevents the bones from moving away by quite a distance apart). As far as I understand, this problem is solved in the Avatara section of the Muscles model.