GOLF'S EFFICIENCY WEDGE
In identifying the most efficient way to swing a golf club you must first take into account the design of a golf club. The angle between the sole of the club and the shaft has the most influence in determining how to efficiently swing a golf club. This angle is referred to as the club's 'lie angle', a standard 5 iron has a 60 degree lie angle.
Machines that have been designed to test golf clubs and balls use this principle. In simple terms, 'Iron Byron' swings the club shaft on the same angle as the lie angle.
We all know golf is not that simple....
Swinging the club this way is not practical for humans given the way our levers and joints work. In particular the folding in the right arm (RH Golfer) lifts the clubs shaft up above the original lie angle.
PGA Tour professional Matt Kuchar has a good crack at keeping his shaft on the original shaft angle.
I suggest, rather than trying to swing your shaft on an exact angle it is better to have the concept of swinging your shaft within what I call the 'efficiency wedge'.
The bottom line of the wedge is determined by the club-shaft’s position at address and the top line runs from the ball up and rests on the right shoulder at address. The wedge is approximate 20 degrees wide.
The vast majority of PGA and LPGA tour players stay within the efficiency wedge throughout their entire swing. Like anything though, there are exceptions to rule. You will see the odd world class golfer swing outside the wedge on the backswing. However, to date I have not seen any quality golfer swing outside the wedge on the downswing.
If you haven't already, I suggest you get a friend or a golf professional to video your swing to check how efficiently you are swinging.