Earlier quoted context omitted.
I suspect a lot of this is habituation due to repeated practise. As long as one climbs well within one's abilities, the actual level of danger is comparatively low. But the fear is still there and needs to be trained away.
I don't think it required much training for Alex, I think he just has an under active amygdala or something
https://nautil.us/the-strange-brain-of-the-worlds-greatest-s...