Position bar on back of shoulders. Grasp bar to sides. Disengage bar by rotating bar back. Execution
Bend hips to lower torso forward until parallel to floor. Bend knees slightly during descent. Raise torso until hips are extended. Repeat.
Target muscle is exercised isometrically. Begin with light weight and add additional weight gradually to allow adequate adaptation. Throughout lift keep back straight. Knees will have to bend more with those with less hamstring flexibility. Knees can be kept bent throughout movement. Also see straight leg Goodmorning emphasising Hamstrings.
Source : EXRX.net