Which type of exercise is primarily aimed at increasing muscle size?

Hypertrophy training is specifically designed to increase muscle size. This type of training typically involves lifting moderate to heavy weights for a moderate number of repetitions (usually in the range of 6 to 12 reps) with the goal of maximizing muscle fiber recruitment and stimulating muscle growth. The principle behind this training method is to create enough tension and stress on the muscle fibers that it leads to microtears, which then heal and make the muscles larger and stronger.

Endurance training primarily focuses on improving the ability to sustain prolonged exercise, often involving lower weights with higher repetitions or duration. Plyometrics, on the other hand, are explosive movements aimed at improving power and speed rather than directly increasing muscle size. Flexibility training focuses on improving the range of motion of muscles and joints and does not contribute significantly to muscle hypertrophy. Therefore, hypertrophy training is the appropriate choice for increasing muscle size among the options provided.