Thanks for this info..... I see - so lever 1 is the upper arm (short) and lever 2 is the forearm plus club (very long).
In pure biomechanics terms this makes sense. From a skill-learning perspective though it feels unnatural (I tried it) and most of us want things to 'feel right'. So I guess it's just down to the individual.
Interestingly, one of the greatest ever golfers - Harry Vardon - played with a bent left elbow.... Maybe he knew something....?
Once again, thanks for the update
Chris, absolutely right about the "unnatural feel". Kuykendall sells a contraption that imobilizes the front wrist and he says when you can hit the ball about 90% of your distance without it on you know you've got it. And he's right ,it took me weeks to even hit the ball 50 yards then it dawned on me that the front arm must bend at the elbow to get that :laggy" feel you get in trad golf. The feeling in the front arm is like this. Imagine you've got a punching bag hanging just in front of your lead shoulder. The aim is to smack it with the back of your front hand as hard as you can. So you bend the elbow back until your palm is against your rear shoulder, then using your triceps smack the bag with the back of your hand. Once you get that feeling you realize there's power in the triceps that's unused in the conventional swing. PS, I'm no sports scientist or anything.....just my observations.