By Jeff Opalewski Pitching Coach, Central Michigan University
While arm action and arm angles are two different things, they are very much related when it comes to evaluating a young pitcher. When I was an associate scout for the Atlanta Braves, we defined proper arm action as: “From the start of separation…with the thumb down while in the pivot position, the uninterrupted range of motion of hand, elbow and shoulder extending in a backward arc behind the body. Starting forward in an elliptical motion with a smooth or fluid flow with no impeding flop, hook, wrap or jerk-transmitting energy and force through hand and arm with full extension to the ball while in the physical act of throwing.”
Scout School 
While arm action and arm angles are two different things, they are very much related when it comes to evaluating a young pitcher. When I was an associate scout for the Atlanta Braves, we defined proper arm action as: “From the start of separation…with the thumb down while in the pivot position, the uninterrupted range of motion of hand, elbow and shoulder extending in a backward arc behind the body. Starting forward in an elliptical motion with a smooth or fluid flow with no impeding flop, hook, wrap or jerk-transmitting energy and force through hand and arm with full extension to the ball while in the physical act of throwing.”
