Casting is releasing the hand's and arm's 90 degree or so's angle while still at the top of the swing. This is usually done because the body is not in on the swing first...just the hands and arms are the main focus of making the powerful action to the ball.

Fixing it, is the idea that this release of the hands and arms HAVE to be last. The body will deliver the rotational acceleration to the ball, and the arms and hands get to finish the job. They are flung at the ball with greater force then if just the arms and hands did it alone...a "whip affect" so to speak.

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I'm a golfaholic, no question about that. Counseling wouldn't help me. They'd have to put me in prison, and then I'd talk the warden into building a hole or two and teach him how to play. ~Lee Trevino