Good topic though i will be the "damper..
You see, if we are talking about the APBT
/Bulldog in every sense of the word, there is no point in increasing mass muscle as it hinders the natural movement, ability and foundation that creates the working dog as intended.
In human terms, there is a reason you see leaner, muscular people doing gymnastics, sprints and many sports vs body builder type.. While building mass on structure can be beneficial to a degree, you typically lose ability in the name of muscle.
The same goes with hounds, typically your larger mass dogs are not going to perform as well as the leaner muscular dogs.. If you want larger muscle, the American Bully is a prime foundation as you already have the genetics in place to create a "bulky" animal.
IN all sense, a bulky, large mass Bulldog is useless.. Under the name APBT
, you wouldn't fair well in the show ring as it is not part of registry standard. You also, as mentioned, would not fair well in the use of test of character work or agility sport due to the amount of mass being carried.. Especially on what is typically a smaller frame.
Genetics, proper diet, proper conditioning methods and proper exercise/work is all you need to keep a dog in the best of shapes.. I'm not a fan of using "bulking products" in humans or dogs because you are relying less on natural foundation and more or less attempting to fight the grain of whats available through the dog.
It is a good topic, as i said but one that really is a dead end.. UNLESS you are looking at breeds more suited for this type of build, keep.