Tip from your hip for perfect putting posture
There's a very good reason for the putter being the shortest club in the bag. While the the driver encourages a long, flat rolling type of movement, the reason the putter is short is that we want to have what's called an upright swing plane, where the putter head seems to go almost straight back and straight through.
And because of that, your posture must be good. As you can see in the video, once I aim the putter head, I tip forwards from the hip to set my body in the correct position where my arms can hang naturally underneath my shoulders. Now I can make a stroke where the putter head comes back fairly straight back and through.
If your posture is soft or slack, your elbows go soft and then you get a situation where the putter face ’rolls – ‘and that's bad news. So the putter is short because you want an upright stroke – and an upright stroke demands good posture.
When you have those two factors lined up, your forearms behave during the stroke. Because absolutely the last thing you want in your putting stroke is forearm rotation.