how... do... they do it...
amazing. if only they found a way to work legs as well 
Pretty sure they avoid leg work entirely, more weight to carry. Certainly not well rounded in that respect, but it's a sport about specialization, and in fact is much less specialized than sports like climbing which are almost all about vertical pulling and grip strength.
I used to do almost all bodyweight strength, but these maximum strength elements are very hard on the joints. Imagine doing weights you can only hold isometrically for a few seconds, it's beyond even a 1rm. Now I do a more standard bodybuilding workout.
There are guys who are more balance and do a lot of 1 leg squat variations, but they are not nearly as strong on the upper body elements. Also they're probably not juiced like some of the thicker street work-out guys.
