very intresting, I see what you are saying with the shoulder pulling back which in turn accelerates the arm circle. The sling shot (David and goliath reference) is very fitting. Thank you for taking the time to respond. This was very helpful.The role of the shoulder plays in the arm circle goes largely unnoticed. This is not surprising since most pitchers perform it adequately and it is a "no teach". The shoulder leads the arm in it's circle and is responsible for generating some velocity. This is especially important in the 4 o'clock to 1 o'clock part of the arm circle. What is generally thought of as "opening up" is more of a pull back action which adds speed to the arm circle. Shoulder/arm/hand action is similar to that of a sling (as in David and Goliath). A sling has a pocket for the stone and two strings that are held in the hand. As the pocket/stone is whirled in a near vertical circle to build velocity the hand which holds the strings also moves in a small circle and leads the pocket/stone. Similarly in pitching the shoulder leads the arm in it's circle. Look at first 20 seconds of this video of Amanda Scarborough and focus on her shoulder, you will see that it makes a circle. At 9 o'clock she is open, from 6-4 she is about square/closed, from 4-1 you can see her pull back with the shoulder which accelerates the arm/hand. If the timing of this sequence is incorrect, such as opening up early, there is a loss of velocity. This same pull back action is very noticeable in the 17 second video of Cat Osterman
If you dont mind me asking what brand of Neoprene sleeve do you use for youth. My DD is 10 but is 5'3 and about 106 pounds?