Editing Hamstring (section)

==Function==
The hamstrings cross and act upon two joints – the hip and the knee – and as such they are termed [[biarticular muscle]]s. The hamstrings contract when the knee is bent, and lengthen when the knee is extended, and when the hips are extended

Semitendinosus and semimembranosus extend the hip when the trunk is fixed; they also flex the knee and medially (inwardly) rotate the lower leg when the knee is bent.

The long head of the biceps femoris extends the hip, as when beginning to walk; both short and long heads flex the knee and laterally (outwardly) rotate the lower leg when the knee is bent.

The hamstrings play a crucial role in many daily activities such as walking, running, jumping, and controlling some movement in the [[Gluteal muscles|gluteus]]. In walking, they are most important as an [[antagonist (muscle)|antagonist]] to the [[quadriceps]] in the deceleration of knee extension.