HAMSTRING GROUP
This group is located on the posterior thigh. The most lateral of this group (a) is a two-headed muscle the biceps femoris. The semitendinosus (b) is next medially followed by the semimembranosus (c). All three muscles have as their origin the ischial tuberosity. Their insertions are on various portions of the tibia and fibula. The primary actions of these muscles are extension of the thigh and flexion of the lower leg at the knee.