Jack Kuykendall, a physicist, founded Natural Golf in 1986. He used many of Moe Norman's swing features. Ken Martin, PGA, described what he called the Single Axis Swing many years ago. He has a great explanation of the Single Axis Swing and differs considerably from Jim Hardy's one-plane definition.
"The Single Axis Swing fundamentally begins with the shaft angle of the club at
setup/address matching the club shaft angle at impact! First and foremost, Natural Golf uses the shaft of the golf club to define the plane of the swing. Again, we say a swing is single plane when the shaft angle at address matches the shaft angle at impact. Ideally, the shaft would stay on this inclined plane throughout the entire swing; much like the shaft movement created by the golf club testing machine, Iron Byron, used by the USGA. And much like the shaft movement of a club as swung by Moe Norman. By starting at address with your arms aligned with the club shaft, you can swing back and forward on virtually the same swing path or on one plane. I believe there is no simpler move in golf. It mimics the direct strike of driving a nail with a hammer, the way you hold the tool aligns your arm with the handle and a single plane motion is the most natural and most direct motion to use."
"Jim Hardy defines a swing as "one-plane" when the shoulders and lead arm are on the same plane at the top of the backswing. While he references a difference in setup between one and two plane swings, he does not use shaft angle as the criteria. Because the two methods use different criteria to define the One Plane, the swing mechanics of each method are not completely interchangeable." Moe Norman showed us a simple setup that produced a simple and remarkably repeatable swing. Natural Golf follows his lead and developed into a Single Axis Setup so we can use the most direct strike in golf..a One Plane Swing. Keep it simple folks!"
Martin is spot on in this statement from years ago...It's the very core of what is the One Plane Swing! In the pictures below of Moe Norman and Bryson Dechambeau, both have matched their setup shaft angle with their shaft angle at impact. That's the One Plane Swing in a nutshell: This is the key to a Single Plane Swing! Practice these positions often and with intention!
**For more information on the One Plane Swing the One Plane Golfer eBook is available for sale on the homepage of this site. It's a beautifully illustrated description of the One Plane Swing and how to apply it to your game.