Originally Posted by ubizmo

The rotation of the wrists--opening and closing of the club face--is an anatomically inevitable side-effect of hinging and unhinging, i.e., changing the angle between the club shaft and the leading forearm. It is the unhinging that transfers angular momentum from the arm-chest "triangle" to the club very quickly, ultimately transferring it to the ball's linear momentum.

If the human arm and wrist were jointed in such a way, like a trebuchet, to allow the same degree of hinging without any rotation, the difference in power would be too small to measure. The "late hit" just refers to "release" in the impact zone. "Release" just refers to the sudden transfer of angular momentum, which we experience as the club "whipping" through impact. Interestingly, because of this transfer of angular momentum, the hands actually go slower at impact than they were going before impact, because they are losing the angular momentum that the club head is gaining.

Proof: Set up a club next to a ball on the ground with the club face as open as you like. Now, as quickly as you can, rotate the club head using your forearms, but without swinging the club forward. Just rotate it in place, so it goes from / to . Strike the ball this way. How far does it go? Six inches? A foot? That's how much distance opening and closing the club face, in itself, adds to your golf shot. That little bit of extra motion of the club head is trivial. The power comes from the sudden change in the angle between leading forearm and club shaft, and instant before impact.