Gain muscle mass for improved metabolism, better athletic performance and defined physique. Improving your body’s muscle mass will relieve regular daily aches and pains, work-related stress and backaches. Common aches and pains often result from under-defined muscles that lack the ability to support that portion of the body, resulting in pain and discomfort and also injury. Increased muscle mass improves metabolism which can help break through weight-loss plateaus as well. Even if you don’t have access to a full gym, you can gain muscle mass with standard weights, and use your own body for added resistance.