Which muscle is primarily responsible for elbow flexion?

The muscle primarily responsible for elbow flexion is the biceps brachii. This muscle, located at the front of the upper arm, plays a key role in flexing the elbow joint. When the biceps contracts, it pulls the forearm closer to the shoulder, effectively bending the elbow. The biceps are particularly active during lifting and pulling movements that require bringing the forearm up.

While the brachialis, located underneath the biceps, also contributes significantly to elbow flexion, the biceps brachii is often considered the main muscle due to its larger size and more prominent role in this action. The triceps, located on the back of the arm, are responsible for extending the elbow rather than flexing it. The hamstrings, a group of muscles located at the back of the thigh, are not involved in elbow flexion at all, as they are primarily responsible for bending the knee.

Thus, the biceps brachii is rightly identified as the key muscle responsible for elbow flexion.