Final answer:
Medial or internal rotation of the forearm results in the thumbs pointing inward, a movement often associated with pronation at the shoulder and hip joints.
Step-by-step explanation:
The type of angular rotation resulting in the thumbs pointing inward is called medial rotation or internal rotation. Pronation is a movement where the palm of the hand is turned downward or backward. It is commonly observed when rotating the forearm so that the radius crosses over the ulna, resulting in the thumb pointing inward. This movement occurs at the ball-and-socket joints of the shoulder and hip, where the limb rotates around its long axis, bringing the thumb or anterior surface of the limb toward the midline of the body. When the forearm undergoes this movement, it is accompanied by the action known as pronation, in contrast to supination, where the palm is rotated to face forward and the thumb points laterally.