Single leg crunch
Setup: Floor space, optional chain.
Postion: Lat flat on the floor with one leg straight and the other bent to 45 degrees, arms folded in front of the body, hands on the shoulders.
Movement: Crunch the torso upward, bringing the shoulder blades off of the ground and maintaining contact with the floor by way of the low back. At the same time, lift the straight leg off the ground and raise it to the height of the bent knee, so that both knees are even. Lower the leg and torso simultaneously so that the heel barely touches the floor and you can feel the hair on the back of your head touch the floor, then repeat. If you have a chain prepared, you can loop it over the active foot.