In reply to I like climbing:
> You are correct. It should be done on the out breath which is a pilates principle.
What a deep insight. Can you imagine an inhaling power scream?
Mmmmhhhhhhhhhrrrrrrgghhhhhhhhhhhfffffff ???
Joking aside, as in the martial arts, screaming can help increase core tension and give you a bit of extra power for a short spike.
Obviously screaming is traditionally only used to attract climbers of the opposite sex. To establish a crag pecking order same sex climbers should instead be intimidated into submission by power grunting, especially on offwidth routes.
CB