What motion is accomplished when the upper extremity is brought to midline from full extension?

When the upper extremity is brought to midline from a position of full extension, the movement being performed is adduction. This motion involves drawing the arm closer to the body's central axis. In the anatomical position, full extension places the arm away from the body, and transitioning it towards midline signifies that the arm is moving inward, which is characteristic of adduction.

Adduction specifically refers to movements that occur along the frontal plane, where limbs are moved toward the midline of the body. Understanding this motion is crucial in fields like orthotics and rehabilitation, as it often relates to the function and alignment of prosthetic devices and body mechanics during various activities.

The other movements listed do not accurately describe the action of bringing the arm to the midline from an extended position. Internal rotation involves the rotation of the arm towards the center of the body but does not necessarily relate to the lateral movement towards midline. Abduction refers to moving the arm away from the midline, which is the opposite of what occurs in this scenario. External rotation also describes a rotational movement that does not pertain to the lateral movement towards the midline. Therefore, adduction is the most appropriate and accurate term for the motion described in the question.