1 Lie on your left side, and bend your arm and rest your head on your left hand as shown.  

2 Holding a light dumbbell in your right hand, bend your right arm 90 degrees and tuck your upper arm against your right side.

3 Let the weight hang in front of your midsection. Keep your upper arm still, and slowly rotate your forearm until it points toward the ceiling. Then rotate your forearm back to the starting position.