The behind the back pass is another great excercise for the arms
Step 1. Stand with your legs slightly wider than hip distance apart and your knees slightly bent. Look straight ahead, and keep your back upright. Hold a ball in your hands, behind your back.
Step 2. Transfer the ball to your right hand, and then extend your arms up in the air. Pass the ball from your right hand to your left hand over your head.
Step 3. Bring arms back down behind your back and start over. Continue the up and down ball-passing motion so your arms move in a circle like a windmill.
Step 4. Repeat the series 20 times. Go slowly; don't let your momentum do the work.