Climbing feels like to me the least aggressive form of martial arts; except it’s not player v player, it’s player v environment. 

Incredible amounts of discipline and proof of work. The entire environment is a problem to solve. The efficiency of your energy moving through the problem/routes (space).

The state of flow and focus when you are locked in to a climb is the ultimate zen. Enduring the pain of the crux is an indescribable reward.