Hypertrophy refers to the increase in the size of muscle cells, leading to overall muscle growth. This process occurs when muscles are subjected to resistance training, such as weightlifting, which causes small tears in the muscle fibers. As these fibers repair, they grow larger and stronger, resulting in increased muscle mass. There are two main types of hypertrophy: myofibrillar and sarcoplasmic. Myofibrillar hypertrophy focuses on increasing the density of muscle fibers, enhancing strength, while sarcoplasmic hypertrophy increases the volume of the fluid and energy sources within the muscle cells, improving endurance. Both types contribute to overall muscle development.