How does the lower arm bone move when lifting?

When lifting an object, the lower arm bone (ulna) moves around two joints: the elbow joint and the wrist joint.

Elbow Joint:

The elbow joint is a hinge joint that allows the arm to bend and straighten. When lifting an object, the biceps muscle contracts and pulls the ulna upwards, causing the elbow to flex (bend). As the arm straightens, the triceps muscle contracts and pulls the ulna back into its extended position.

Wrist Joint:

The wrist joint is a complex joint that allows the hand to move in several directions, including flexion, extension, radial deviation, and ulnar deviation. When lifting an object, the wrist flexors contract, pulling the hand and the ulna downward, causing the wrist to flex (bend). When the object is lowered, the wrist extensors contract, pulling the hand and the ulna back into its extended position.

Throughout these movements, the ulna moves in a combination of flexion and extension at the elbow joint, as well as flexion, extension, and some rotation at the wrist joint. The coordinated action of these muscles and joints enables us to lift objects smoothly and efficiently.