The hamstrings are a set of three (plus one) muscles on the back of your leg, from pelvis to lower leg. If you reach behind and palpate the back of your leg, starting from the medial (inner) side, the first pair of hamstrings muscles are the “semi sister”, semimembranosus and semitendinosus.
Hamstrings are a biarticular muscles as they cross and act upon two major joints: hips and knees.
Actions: Hip extension, knee flexion, and to a lesser extent lateral and medical hip rotation.
Tightness can limit anterior pelvic tilt and potentially lead to excess pressure in the spine during forward flexion movements.
Since the hamstrings are used in nearly every human movement activity hence injury is common, and even more common is a slow and challenging healing process as it’s difficult not to reinjure a damaged hamstring muscle.