Masturbation is a common practice for both men and women, but it should be done behind closed doors. Muscles grow for many reasons. Some ways to make the muscles grow is to lift weights. This seems to be the most obvious way to strengthen the muscles. Flexing the muscles also will make muscles grow because when you lift weights you are flexing the muscles. There are certain things that can be done to flex the muscles. Masturbation is one way, but this may help somewhat. It will not grow the muscles very fast.
However, this does not always work if you are not taking care of yourself. Anytime that you are trying to strengthen your muscles, you must also eat healthy and get plenty of sleep.