quote:Chris, can you describe the "early pronation" as it relates to hand position relative to the ball? It appears in your video that as the hand is behind the body, the palm is underneath the ball with fingers pointing up. Is that correct?
Early pronation is related more to the orientation of the forearm than to the ball. However, you can tell how pronated the forearm is by looking at the position of the ball.
In the video my hand is under the ball. This puts the forearm in a relatively supinated position. Since my forearm is supinated at this moment, I am then forced to pronate my forearm to get my palm facing the target. Pronating while the elbow is rapidly extending will protect the UCL by enabling the Pronator Teres muscle to take up some of the load that is normally focused on the UCL.
If my forearm was supinated at this point (e.g. fingers on top of the ball and showing the ball to Center Field), then my forearm would have to be extremely pronated. Since I would be pronated at this moment, I would have to supinate my forearm to get my palm to face the target. This would focus the load on the UCL.