Movement: Lie on your back near a doorframe. With legs flat, raise your near-leg and place your heel against the wall. Without hyperextending your lower back, and keeping your leg straight, slowly move closer to the wall, placing progressively more stretch on the hamstrings.
Repetitions: Hold for the full prescribed time on one side, then switch sides and repeat. This counts as one set.
Instructions and effects for the Lying Hamstring Stretch exercise 
Movement in Sagittal Plane