I was studying some books and magazines...and viewing different body types of champion BB.

I notice that some like Dorian Yates, Arnold, Coleman, Haney...all seem to have a natural tendency to build Mass. (of course they do and did a lot of Juice)....But these guys are Naturally BIG!

What "enables" them to build muscle so easily...vs. someone with a Slight frame...ecotomorph?

-More Receptors?
-Joint Size?
-Tendons?

What is it?