Originally Posted by Brandon Oto
I thought that good climbers rely mainly on their lower body. Does that become less true as the difficulty of the route increases?
generally speaking, no, it is not less true. there ARE exceptions...there are some difficult routes or problems that require ridiculous campus moves (climbing using only arms). most very difficult routes actually require even MORE precise footwork than easier ones.
the best climbers use their footwork to position their body in a way that maximizes their reach and grip endurance. good footwork also allows them to use available handholds in the best or only way possible.