Arm swing illusion

Came across an interesting concept in golf: the arm swing is an illusion. It looks like the arms are doing the work, but they're mostly along for the ride. The body turns, the weight shifts, and the arms just follow. What we see as an "arm swing" is really rotation seen from the outside.

I found it really interesting, especially the biomechanics of it, and how a 3D rotation looks like a 2D arm swing when you see it from the front. It's basically an optical illusion. Worth a watch.

From Jim Waldron, Balance Point Golf.