Here's a fun, easy and very effective way to firm and tighten your abdominals while gently stretching the muscles in your back. Be sure to practice this move on a padded surface so your spine is protected and comfortable.
Sit upright on a level, padded surface or mat. Bend your knees and hug them loosely toward your chest, hands holding your lower shins. Tighten your abdominals and lean back slightly until your feet are off the floor. Inhale and pause.