What action does the hamstring muscle group primarily perform?

The hamstring muscle group primarily performs knee flexion. This group consists of three muscles: the biceps femoris, semitendinosus, and semimembranosus. When these muscles contract, they pull the lower leg upwards towards the thigh, thereby reducing the angle at the knee joint, which is defined as flexion.

In addition to their role in flexing the knee, the hamstring muscles also have a secondary function in assisting with hip extension. However, their primary and most significant action is indeed flexing the knee during various movements such as running, walking, and jumping. Understanding the primary functions of muscle groups is essential for developing effective training and rehabilitation programs, highlighting the importance of hamstring function in lower extremity movement.