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 creates small tears in the muscle fibers. As the body repairs these fibers, they become thicker and stronger. 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.