There must be calluses. If your hands are tender, you will easily get bruised on the rock wall, and it is useless to wear gloves.

I often climb mountains, and my arms are not very thick. You can look at the masters of international competitions. They have reached that level and their muscles are not very big. It's just that the muscle lines of their arms are obvious. Ordinary fans don't have to worry about this arm getting thicker at all, because the training intensity of ordinary people can't reach that level.