Bench Knee Tucks

Sit on the end of a flat bench or edge of big chair and lean your torso back to a 45 degree angle to the floor.
 
Extend your legs out at a 45 degree angle and stabilize your body by gripping the sides of the bench or chair.
 
Pull your knees into your chest and then lower your knees back down to the starting position.
 
The entire motion should be done in a smooth, controlled manner that lasts about 3 seconds, with the downward movement no faster than the upward.