The function of the golf swing is to consistently deliver the club head on a desired path, on an incline plane oriented at the ball at maximum velocity, while striking the ball in the center of the clubface and square to the chosen target. Players have different sizes, shapes, abilities, and desires and many parameters enter in the swing motion and particularly in the swing plane. To understand their interactions we must check some specific information.

1 - Identification of your body type: ectomorph, endomorph, or mesomorph.

Ectomorph - An ectomorph is a typical skinny player. Tall with maximum flexibility - think charl Chwartzel, Julie Inkster, Matt Kuchar and Phil Mickelson. An Ectomorph, often tall but more importantly has long legs in relation to the torso. Usually very flexible, and with a high height / weight ratio. This is the profile of the "Arc" player.


Mesomorph - A mesomorph has a large bone structure, large muscles and a naturally athletic physique. Average build with average flexibility -  think Rory Mc Ilroy,  Annika Sorenstam. A Mesomorph has arms and legs in proportion,giving the appearance of symetry. Moderately flexible, with a medium height/weight ratio. This is the profile of  "Leverage" player.

Endomorph - The endomorph body type is solid and generally soft. Endomorphs gain fat very easily. They are usually shorter built with thick arms and legs. Thicker torso and minimum flexibility -  think JB Holmes, Kevin Stadler, Inbee Park. The tendency for this body type is a low height/weight ratio (heavy for their height). This is the profile of the "Width" player.

2 - Measurement of arm length, leg length, trunk length, shoulders width.

3 - Evaluation of flexibility, range of motion, chest thickness, spine curvature (C, S or I), physical deformity or anomaly (both structural and muscular caused by injurie or birth), physical limitations and imbalances, physical strengths, athletic vs nonathletic, other sports and activities that you have played, the way you learned to play, all these parameters will contribute to how you swing the club.

Every golfer is unique, and this individuality has biomechanics consequences, so the way to train must be adapted to each one. How biomechanics relates to swing plane?

In order to analyze which backswing plane fits your body the best, you need to measure your wingspan from finger tips of the right hand to finger tips of the left hand. (Stand up and hold your arms stretched out at shoulder height.)

1.    If your wingspan and height are the same lengths, then you will have a top of the backswing position that aligns the lead arm through your trailing shoulder. This is much like what is taught in "one-plane theories".
2.    As the wingspan becomes longer than the height, the lead arm will elevate more above the shoulder line into what has been described as a "two-plane" position at the top of the backswing.
3.    If the wingspan is shorter than the height, the lead arm will align below the shoulder line at the top of the backswing in what is commonly called a "flat" backswing.

Note that there is a range in which the lead arm will be set at the top of the backswing. If the wingspan is 4 inches shorter than the height, the lead arm will set very low across the chest and below the shoulder line. If the wingspan is 4 inches longer than the height, then the lead arm will set well above the shoulder line into a high two-plane type of alignment.

There are three different top of the backswing planes and three different downswing planes. At the top of the backswing, the golfer can achieve a position that aligns the lead arm either above the shoulder line (high-plane), through the shoulder line (mid-plane) or below the shoulder line (low-plane). This is shown explicitly in the picture below of Matt Kuchar, Tiger Woods and Jim Furyk when they are at the top of their backswing. During the downswing it is possible to deliver the club along the hip plane, the torso plane or the shoulder plane.

Now, how to reach that top-set position will vary from player to player. For example, some will swing inside and then elevate upward like Matt Kuchar. Others will swing up along an outside path, like Fred Couples, and then loop the club into the top-set before transitioning into the slot. Then there will be golfers that swing up the same path they will slot along during the downswing. This is based upon how the arms fold in the backswing.

To figure what downswing plane fits your body’s mechanics, measure your forearm from the middle knuckle to the elbow and then measure the upper arm from the elbow to the shoulder socket. Based upon their relationship, you will swing on one of the three swing planes seen above. Here are your three options:

1.    Hip-Plane Downswing: The distance from the middle knuckle to forearm is SHORTER than the distance from the elbow to the shoulder socket (Heath Slocum).

2.    Torso-Plane Downswing: The distance from the middle knuckle to forearm is EQUAL TO the distance from the elbow to the shoulder socket (Ernie Els, Hunter Mahan, Adam Scott).

3.    Shoulder-Plane Downswing: The distance from the middle knuckle to forearm is LONGER than the distance from the elbow to the shoulder socket (Martin Kaymer, Camilo Villegas, John Senden).

The easiest way to think about this is that if the forearm is longer than the upper arm, the hands will ridehigher and farther out, so they should come down on a steeper plane than if they were shorter. If the upper arm is longer and the forearm is shorter, then the hands will ride lower and closer to the body. That will produce a more shallow delivery plane.

History proves the club head, shaft, or grip does not have to be on a specific 'plane whilst the backswing is in progress.

Yet all we hear today is instructors and commentators talking about keeping the butt of the club pointing at the ball going back and coming down.  Why? Let's have a look at some of history's greatest ever ball strikers and see what they do

Bobby Jones, Sam Snead, Ben Hogan, Moe Norman, Jack Nicklaus, Lee Trevino, Tony Lema, Byron Nelson, Gary Player.

None of them respect the theory to have the shaft of the club pointing to the ball.

Trying to keep the club on a specific plane is wrong, but on your natural plane is right!