You often hear about the turning of the arms through impact in the golf swing. It is referred to as supination, a term that was introduced by Ben Hogan. Pronation is used to describe the turning of the arms on the backswing.
Before I get into how this relates to putting, I want you to try something. Take a normal grip and address position. Turn your shoulders slowly to 90 degrees, being careful to not let the position of your arms change in relation to the shoulder and chest.
What you will find is that the left arm appears to have rotated in relation to the ball. But is has not changed in relation to the shoulders at address. The obvious conclusion is that the arms DO NOT rotate on the way back. The turning done by the shoulders in relation to the ball causes the arms to rotate in relation to it as well. But the arms do not rotate in relation to the shoulders.
This has implications for your putting stroke. If your shoulders turn at all, so will the forearm and putter. You hear a lot of talk these days about “releasing” the putter. That simply means allowing the forearms to rotate through the putt. But it is the turning of the shoulders that turns the forearms.
They don’t do it on their own and you can’t make them with any consistency.
There is not really a big issue with allowing your shoulders to turn during the backstroke, as long as you let them turn the same way on the follow through.
But to me, that complicates things.
The important thing to remember is that the arms do not rotate. It is the turn of the shoulders that causes the arms to appear rotated and the club face open.
You should work to minimize or eliminate any shoulder turn on your short putts. Ideally, you would simply tilt them slightly along the target line.
Alternately, if you don’t feel comfortable with keeping the shoulders square while you are stroking a short putt, work on controlling the turn both back and through the ball. If you allow the shoulders to turn on the way back, you will have to allow them to turn equally on the other side of the ball.