Forearm supination involves which of the following movements?

Forearm supination is the movement that turns the palm of the hand upward or forward, depending on the position of the arm. This action involves the rotation of the radius and ulna bones around each other in such a way that the palmar surface of the hand faces upwards. When you supinate your forearm, you are effectively rotating it to a palm-up position, which is crucial for various activities, such as holding a bowl of soup or performing certain lifts in a gym setting.

The other movements mentioned in the options do not describe supination. For example, rotation to the palm-down position refers to pronation, moving the arm across the body does not specifically relate to supination or pronation, and extending the elbow is a separate action involving the straightening of the arm rather than the rotation of the forearm. Understanding these distinctions is essential for grasping how forearm movements function during various exercises and everyday tasks.