Lay on your back with your knees bent. Bring one knee up and place your opposite palm on the inside of your thigh above your knee. Keep your elbow straight. Push your hand into your leg and pull your leg into your hand; do not move. Tighten your abdominals and obliques to produce the force you are putting into the push from your hand and leg. The more intensely you press the harder it will be. Start with about 50% of max effort and adjust accordingly form there. Do this for 10-30 seconds.
Muscle Targeted: (1) abdominals (2) obliques (3) hip flexors (4) adductors