Building muscle??

look into somthing calles a spring pole i use that on my dogs and it helps build muscles and stamina ant same time theres videos on youtube and i have a few pics in my profile pics and u can see my two pitss playing on the toy at a very yound age and they still do it today also thiers something calles a flirt pole you might like that also

You have a pup, just let him be a damn pup and worry about stupid #$@! later. Why is chest width so damned important? Why not worry about a stable temperament or things that actually matter?

he already has a good temperament. I am wanting to train him as a pulling dog for competitions not to fight or anything other stupid #$@!. I was looking for advise not your opinion. Chest size matters in the competiton world but you probably don't know that.

He's just a baby. All pups go through at least 2 lanky growth spurts their first year. Don't rush him. If you know what his parents look like then he will end up looking very similar to them. He'll completely fill out by the time he is 2-2 1/2yr old.

My female razors edge was so small when she was a pup, but i just let her do her puppy thing for about a year, got her training down, socialization down, and now her chest is almost 2 ft wide, and pulls 4000 lbs at 2 yrs old... I did alot of conditioning and cardio first then we hit the gym! Let the pup be a pup....