What is so different that i am able to do way more chin ups (palms facing me) and curls than pull ups (palms facing away) or reverse curls? They all use bicep muscle, but why does it make such a huge difference?
The biceps is the prime mover when you have your palms facing you. When you have your palms facing away, the brachialis is the prime mover. And when you have your palms turned inward, the brachioradialis is the prime mover.