You are better off training for endurance than for muscle mass. Big muscles are unhealthy, and unnatural. The human body has a limit on how much muscle mass it will carry. You can violate that limit by using steroids. All professional body builders are too big -- unnaturally big. You can't get that big without steroids, not ever. The body won't allow you to get that big, no matter how many weights you lift, because it is not good for your heart or other organs. You bones, your ligaments, your tendons, are not designed for that much muscle.