In order to hit the ball cleanly, the club has to return to the same place it was at address. This means the swing arc can’t be moving around during the swing.
The first part has to with the up and down location of the bottom point of your swing (Figure1). If you raise up when you take the club back, that raises the bottom point of your swing. Now you have the problem of getting it back to where it was you started–not too far back down, and not staying too far up. Who can get that right from swing to swing?
The second part has to with the side-to-side location of the bottom point (Figure 2). It’s real hard to get ball first-ground second contact when the swing keeps bottoming out in a different spot, relative to the location of the ball.
Again, the problem is to keep the swing arc from moving around during the swing. The solution was developed by Paul Runyan and explained in his book, The Short Way to Lower Scoring.
Runyan talked about the suspension point of the swing, around which the swing turns. He identified it as the big bone at the base of your neck (C7 vertebrae).
Read about it in my book, Bob’s Living Golf Book, section C16.
One year at an LPGA tournament in Portland, I stood behind the players on the first tee, so I was looking at their back. I kept my eye on the suspension point. With player after player, it didn’t move until after the ball was hit and they rose into their finish. It didn’t move up and down, it didn’t move side to side.
It didn’t move.