Do not bounce or make rapid movements at the end of the active stretch. At that point use your hands to assist the stretch as you continue to contract stomach muscles. Move back to starting position and repeat. Exercise may also be done sitting on a chair or in a standing position if same principles are applied. Starting from a seated position with legs out straight, tuck the chin, exhale, firmly tighten the abdominals, and lean forward.
Contract quadriceps to keep knees from bending.
Do exercise slowly without bouncing. Use hands for light assisted stretch at end of movement. Resume sitting position and repeat. It is safest to do this after stretching hamstrings and long back muscles. Do not do this exercise if you have pain or disc involvement of the back.