The Majority Of Fitness Suggestions Still Concentrates On Building Muscle. I know that a lot of fitness instructors mean well. Regrettably, the majority of the fitness instructors at commercial fitness centers are young men in their early 20s who want to gain as much muscle as possible. Im not sure why, but that type of guy seems to be the one most likely to take up personal training. They assume that everyone they train wants to gain muscle and their guidance is mostly geared towards ...