Building muscle

build is a genetic thing. like any athlete, the stronger they are the better they feel. the better they feel the better they perform. that being said, a little muscle gain most likely isn't going to slow him down or decrease his stamina. the way you describe the dog, he's probably not gonna gain enough muscle to hurt him. time and age are gonna put some muscle on him, that's just nature. more muscle means his heart has to work harder to pump more blood which means he burns more energy trying to the necessary oxygen to the extra tissue and it means that he will get hotter because his body is working harder. so too much is a bad thing in this case. muscles grow when they are in shock. if they get in a routine they have the tendacy to reach a stalemate. i rotate the dogs that want to make stronger from a heavy chain to a kennel. a day on the chain then a day in the kennel. i always keep the time frames changed up though. don't stop there though or you take the chance of making him tight. make sure you get him out let him stretch out really good by running him. not at a trot because he don't have to reach out when he trots or lopes. you should do this daily. your dog food will also play a big role. too high of protein is hard on the kidneys. they can only use so much of it. the victor 24/20 is a good feed. enough protein from useable protein sources and high fat so that he has something to burn for fuel. if he don't get enough usable protein, he will break down muscle for fuel and store the fat as fat. chicken by-products are a poor source of protein as is corn. the protein is there but the dog can't break it down to use it. soy is also bad in my opinion as lots of problems have been associated with it. check your first 5 ingrediants. they are the bulk of your food and the most important. keeping them wormed and clean is the other part. i don't know it all though. hope i was a help.