The biceps muscle is the large muscle over the front of the arm that extends from the elbow to the shoulder joint. The biceps muscle is especially important both with bending the elbow, and also turning the forearm to have the palm facing upwards. This movement, called supination, may not seem particularly important, but when going to open a door knob or when turning a screwdriver, the importance becomes quite apparent!
Source: Verywell Health
