Wind up position

[ManInBlue]

Had a buddy taking a test for the Private school association. One of his questions was "Which one of the following is a legal move by the pitcher?"

One of the possibilities was "in the wind up position turning the shoulders to check a runner." I don't believe he marked this as the legal move, but it got me to thinking...

Fed rules. F1 has to step off the rubber before throwing to a base from the wind up. So what difference does it make if he turns his shoulders? He hasn't made any motion associated with the pitch.

Is it legal for a pitcher to turn his shoulders in the wind up to check a runner? I've over-thought this I know. Please give rule sites etc.