Start this exercise on quadruped position. Raise your pelvic and straighten your legs slowly. Keep your head between arms and try touching the heels to the ground as to stretch the hamstrings muscles (as shown in this video). Hold in this position for 10-15 seconds or as long as you feel comfortable. Then slowly return to quadruped position. Repeat this exercise for many times.
Benefits: This exercise stretches your back and legs and helps to relieve sciatica nerve pain.