Lie face up with your arms overhead and legs extended, resting on the floor.
Keep your abs engaged by pulling your belly button into your spin and pressing your lower back into the floor.
Lift your hands and feet a few inches off of the floor into a hollow position.
Reach your arms to your right leg. Lower your arms and legs toward the floor to return to that starting hollow position (don't lower back down to the ground completely).
Reach your arms to meet your left leg, then return to the starting position. This count as one rep.