Hi Difficult question to answer because a lot depends on the genetics of the pup, but in general a 9 month old puppy will be 'adolescent' in build - which often translates into being lanky and lean!
Muscle development will be there, especially if the pup has a great diet and the right amount of exercise, but the bones and joints are still developing and not ready to take the strain of too much muscle or carry extra weight.
As long as you feed a puppy well, give him the right amount/type of exercise and proper health care, it's best to let nature take it's course in everything else. Never try to make a pup grow bigger, stronger or bolder than comes naturally to him/her or you risk damaging the developing conformation and temperament.
MyWay LLC is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to amazon. com This site receives a small commission from all affiliate links and third-party advertising.