comes not from the muslce, but from the nerve system and I feel the love right here. So, actually it is the nerve systems ability to control the muscles. That means that muscle, nerve system and focus are the three elements that need to be balanced to create strength.
If someone lifts a curl to train the bizeps, the better the supporting machine is prepared up to having even weights on both sides of the curl, the armrest perfectly adjusted and so the budd rest, the wrisk stretched out straight to pull up slowly until the arm is bended to hold for a moment and slowley dropping the weight, every single part and the combination is important for perfect results.
If you get into bizeps curls, instead of Pain and Gain, you will understand A Beautiful mind stating that the best for each part is the best for each part and all parts involved as in too much weight will destroy the perfect execution as much as the wrong position of your ass.
In Love and perfect balance!
I keep jumping up and down.
PS: Imagine that assholes face in the gym when he is asking stupidly while you stare at the bizeps "What are you doing" and you reply "Getting into applied chaos theory". A moment you want to look up when the arm is holding for a short sec!