I used to arm wrestle a lot, and so much of it is in technique. I've never had an excess of upper body strength or overall physical size. 5'9" and 165lbs is both my specs and the specs of the avg adult American male last I saw.

Idk how the broken bones happen really. You know when you are beat, you can feel it, it is better to just let the loss happen than fight the inevitable.

Even if you both have great technique, whoever does it better or implements it quicker will win.

These days I just arm wrestle my dog, as in my arm is in the usual arm wrestle position while I hang on to the toy. My dog does whatever the hell they do to get into whatever position and holds on to whatever part of the toy they want. We play tug, and sometimes they legit beat me, other times I just let go if they get my arm to the floor in either direction.