personally, after seeing dogs that are very conditioned for weight pull. it MIGHT just be the way the dog is standing but that does NOT look like Normal muscle build up even for a very well conditioned dog.
CREATINE may be a normally occuring thing in meat, however this does NOT let those that abuse things like that ff the hook. in large enough doese it can cause severe problems with the kindeys, not to mention other possible side effects.
and unfortunatly many people want super bulked up "pits" becuase they are trying to make up for something (ie look at me im so tough my dog coudl eat your child! please note these are also the people that tend to be the cause of breed based problems) and those that want this in a dog often dont give a rats arse about how their dogs health suffers for it.
ive seen dogs given excessive amounts of creatine, its not pretty, the dog looks huge but it a mess inside.
ive also met many who give their dog steroids.
a well conditioned dog involved in any strength based activity would not be so overly built, too much mass could be a downfall, the BEST weight pull dogs ive ever met are nicely conditioned, balanced with lot of drive, personally ive seen heavily mucled dog much like the one pictured do terribly in weight pull because their too built from "suppliments" but no real strength behind them.
this is NOT how any "pit bull" breed should look.
defined YES but built like that...never.