Which factor contributes to flexibility based on anatomical characteristics?

Flexibility is significantly influenced by the type of joint and muscle-tendon units within the body, which establishes the mechanical capability for joints to move through a range of motion. Anatomical characteristics dictate how far a joint can move based on its structure. For instance, ball-and-socket joints, like the hip and shoulder, allow for a greater range of motion compared to hinge joints, like the knee or elbow, which have more limited movement.

Muscle-tendon units also play a crucial role in flexibility; the length, elasticity, and condition of these muscles and tendons determine how effectively they can stretch. Some individuals may have more elastic tendons or longer muscle fibers, which contribute to an increased capacity for flexibility.

While age, exercise frequency, and body mass index can all impact a person's flexibility, these factors are not directly tied to anatomical characteristics. For example, age may influence flexibility due to changes in muscle and connective tissue, and exercise frequency can improve flexibility through practice and conditioning, but these do not alter the inherent structural features of joints and muscles. Body mass index pertains to an individual's weight relative to their height and does not directly alter the anatomical aspects involved in flexibility. Thus, the type of joint and muscle-tendon units stands out as the