The bicep moves the arm primarily through flexion at the elbow joint and supination of the forearm.
Here's a breakdown of how the bicep facilitates these movements:
-
Flexion at the Elbow: The bicep brachii muscle, located on the front of the upper arm, crosses the elbow joint. When the bicep contracts, it shortens, pulling the forearm towards the upper arm. This action bends the arm at the elbow, allowing you to lift objects or bring your hand closer to your shoulder. While the bicep is a flexor, it isn't the only flexor; other muscles like the brachialis assist.
-
Supination of the Forearm: The bicep also plays a crucial role in supination, which is the rotation of the forearm so that the palm faces upward. This action is facilitated by the bicep's attachment to the radius bone in the forearm and the unique angle at which it inserts. When you turn a doorknob or unscrew a jar, you're using your bicep to supinate your forearm.
Key Points:
- The bicep originates at two points near the shoulder (hence "bi-cep," meaning two heads) and inserts on the radius bone in the forearm.
- When the bicep contracts, it pulls the radius bone upwards and rotates it.
- The bicep works in coordination with other muscles, like the brachialis and brachioradialis, to accomplish arm movements.
In summary, the bicep contributes to arm movement primarily by flexing the elbow and supinating the forearm, allowing for a wide range of actions involving lifting, pulling, and rotating the hand.
