Muscle mass, also known as muscle hypertrophy, is the increase in size of skeletal muscle fibers as a result of strength training or resistance exercise. This area of research focuses on understanding the mechanisms of muscle growth, including the role of protein synthesis, satellite cells, and hormonal factors such as testosterone and growth hormone. Muscle mass research also explores strategies for optimizing muscle growth, such as proper nutrition, supplementation, and rest and recovery. Increasing muscle mass is important for athletes looking to improve performance, individuals looking to enhance their physical appearance, and older adults looking to prevent age-related muscle loss.