#4 Russian Twist on Ball 30-60 Seconds

Lay on ball with middle back on top of the stability ball. 

Knees are directly above the ankles and hips are elevated. 

Holding a free weight or kettle bell with both hands, straighten the arms without locking the elbows out directly above the chest. 

Widen the feet from one another for an easier time stabilize. 

Roll to one shoulder as the ball rolls underneath that shoulder. 

Try to keep the hips elevated evenly as you rotate. 

Center the body and fix the legs if they happen to move. 

Roll to the other direction before returning to center; repeating back and fourth for a total 30-60 seconds depending on your core stamina.