hm hab noch eine erklärung gefunden :

Quite frankly, it didn’t make any sense until I watched him do it. He would chalk up, put on chinning straps and with his hands facing away at about shoulder width he would get his palms as far over the bar as possible. Then hanging from the bar he slowly raised his rib box as high as he could as if he was trying to touch the chinning bar without bending his arms... all the time keeping his scapula slightly adducted (pulled in),

then right at the top of the movement he would suddenly throw his lats forward real hard.
(hier hab ich wieder keine ahnung was die meinen)

When he did this, you could see the very bottom of his lats jump right out at you. Then he would hold them... standing out... like the arc of a circle while he slowly lowered his rib box again as far as possible.
When he dropped off the bar the bottom of his lats had this funny little pumped shelf under them. You could stick a couple of fingers under this shelf and... lift it up and down. It made you want a set like that so bad it hurt.

so ne art klimmzug ohne arme ist schon klar aber was machen die mit dem schulterplatt??