So I decided to climb Snowdon mountain in Wales yesterday via the Crib Goch ridge.
It's about 2 miles up to the start of the ridge and scramble up to at some points almost vertical. I was being overstaked by skinny people who were almost hopping up the rocks.
It was supposed to be snowing so I had quite a lot of gear, about 25lbs in a back pack.
I get to the top pretty exhausted and then had to go along the ridge, which involves more up and down climbs and traverses and by this time my legs were shattered. Then another climb to the summit.
By the time I got to the top I could hardly put one foot in front of the other and was massively overheating.
Later I think what had happened was I basically I had a 4hr leg day with blood pump and had completely blown my legs out. It took 3 hrs to come down. I also got heat sickness from wearing too much winter clothes.
Anyway my point is if you only do short twitch muscle training you will be useless on anything endurance.