There’s hundreds of different golfers try to putt, but putting really just boils down to two schools of thought. There are those who try to move the putter head “straight back and straight through” along the target line, and those who try to move the putter head on an arc.

Dave Pelz focuses his time and energy on the square-to-square (StS) method, while StanUtley espouses the arc stroke (AS). So which one of these heavyweight short game gurus is right ? Well, there are the positives and negatives to each method, and professional golfers have used both methods successfully.

There are two high-tech tools I use at my putting academy to examine these type of strokes on a biomechanical level: Advanced Motion Measurement’s 3D Motion Analysis System, and the SAM Puttlab by Science & Motion Sports. My putting research data has also been coordinated with the putting data derived from Lanny L. Johnson, M.D. and PGA Tour player Howard Twitty, who have tested more than 150 Tour professionals’ putting strokes during the previous several years. Together, the information we have merged contains the most accurate data to date on square-to-square and arc strokes.

It is my goal within this article to only point out the pros and cons of these strokes based on the data that was uncovered through our putting research. It is your job to decide what stroke works the best for you through experimentation on the putting green.

AMM’s 3D system measures the body’s motions during the putting stroke.

The Sam Putt Lab measures more than 28 different factors of your individual putting stroke.

The pros of each stroke

The square-to-square putting stroke: This stroke has also been called the “pure in-line putting stroke,” which leads one to believe that it is the easiest to use and the most consistent. And if you watch Loren Roberts or George Archer putt, you might believe this to be true.

The square-to-sqaure stroke focuses on making sure the setup is sound, with a golfer’s hands under his shoulders and a body and putter head that is square to the target line at address. From there, the stroke simply moves back and through along the lines established at address.

As that happens, the face of the putter will stay 90 degrees to the target line (or square to your line during the total stroke), thus making the StS stroke very simple for one to conceptualize. Golfers who use the StS stroke are seen on the putting green constantly working on their alignments at address, and putting along a chalk-line or between club shafts in order to audit their path and club face. Mentally, this style makes the 3-foot knee-knockers much easier to digest.

This stroke is virtually straight back and straight through with a square face throughout.

The arc putting stroke: The theory of an arc stroke is to allow golfers to naturally match the motions of their full swing with their putting stroke. Instructors who espouse the arc stroke believe that the inclined nature of the putter shaft, by design, necessitates the inside-square-inside movement of the putter head. As the stroke works into the backswing, the putter head tends to rotate open (as in the full swing), and at impact it returns to square. After impact, it moves back to the inside and begins to close.

The key to this motion is to keep the putter face 90 degrees (perpendicular) to the path of the arc itself. If that sounds difficult, consider this. In the uncompensated arc stroke, the shoulder motion returns the face to square as long as there is no rotation of the putter face in relation to the arc. That’s because the area of the upper back between the shoulder blades is an anatomical arc.

When the shoulder blades move back and forth on the back of the chest, a unique arc is created. This is a result of the geometry of the golfer’s posterior thorax (medical term for upper back of chest), and its movement necessitates little manipulation from the hands and forearms during the stroke. When this occurs, the rotation of the putter head matches the natural arc a golfer possess in the full swing. Thus the full swing and putting stroke are merged as one feeling. Ben Crenshaw and Tiger Woods exemplify this motion beautifully.

This example stroke has a slight arc with a square face. There are many influences of the shape of the arc, which are determined by setup and clubfitting

The controversy regarding these two putting strokes

• StS theory states that the shaft angle at address does not affect the motion of the putter head, and goes on to say that if the hands hang directly under the shoulders, then the path will always tend to be StS.
• AS theory states that the angle of the club shaft by design innately causes the putter head to move in a slight arc just as your full swing does.
• StS theory states that the face should remain square to the target line naturally, with no physical manipulation of the hands. And if the path is StS, then this will happen naturally.
• AS theory states that the club face cannot stay square to the target line during the entire putting stroke because the putter head works in an arc. Try to keep the path and club head square to the target line, as the StS players try to do, requires a physiological manipulation of your hands, wrists and forearms in order to do so.
• StS theory states that with no putter-head rotation back and through, controlling the ball’s direction will become much easier as ball position is not as crucial.
• AS theory states that strokes with face rotations that match up are 90 degree to the arc’s direction at all times and require no physical manipulations. They are a natural result of the inclined nature of the club shaft at address; thus, directional control will be much easier.
• StS theory states that the putter should be face balanced and have around 2 degrees of loft to make the ball roll and not skid quite as quickly off the start. It must be noted that all balls “skid” off the start. The key is to eliminate as much unnecessary skid as possible.
• AS theory wants a golfer to use some type of toe-hang putter with around 5 degrees of loft. Using an AS stroke is the best solution for someone who wants to get the ball on top of the grass much quicker.

What the data says

Angle of the shaft v. hand position: Testing with the 3D Motion Analysis System has shown that the angle of the shaft, coupled with the player’s physiology, does indeed cause the putter to work on a slight arc very naturally. However, this can be altered greatly by changing one’s set-up posture and putter lie angle, thus placing the hands more under the shoulders. In fact, the more the player bends over at the waist, the flatter the arc and the less putter-head rotation occurs.

The player who stands in a more upright posture will produce a more curved arc, and usually will have more putter-head rotation. The more upright the putter’s lie angle and the more the putter is in the lifeline of the top hand, the less curved its path will be. If the player’s back was 90 degrees to the ground, it would be very possible for his arc to be almost straight back and straight through with no manipulations necessary.

The amount of forward bending at address for most players is between 35 to 40 degrees with the lie of the putter being somewhere around 70 to 72 degrees at a 34-inch length.

The conclusion: Every natural, non-manipulated putting stroke has some degree of arc.  The only way to eliminate this arc would be to set the body in a very bent-over posture and/or make a stroke manipulation during the transition period of the stroke. The key is to minimize the amount of arc that you have within your own putting stroke. To do so, you must assume an address position that places your eyes over the ball, your hands under your shoulders, as well as one that set you up with the proper amount of forward bending when you approach the ball with a properly fit putter.

Square to Square vs. Arc Stroke dynamics

In biomechanical testing, the StS stroke is much more difficult to perform than originally thought. It requires intentional rotation of the putter face to take it away closed on the back swing and open after impact to stay square on the follow through. It is, in fact, a reverse parabolic curve that looks like the inside of a saucer. However, some elite putters achieve a straight putter path on the forward swing by looping the putter head to the inside and then at the end of the backswing bringing it down over the top to accommodate a straight path to the ball.

Minimizing the magnitude of the arc would provide a better opportunity to deliver the putter head to square at impact. And the Sam Putt Lab has shown that a “straight-back-and-straight-though” putter-head path is possible, but it requires a manipulation of the putter as discussed above. Biomechanical studies have recently shown that no PGA Tour player recorded has a putter path that was exactly straight back and straight through. Thus, it is natural to have a slight arc to the putter-head path due to the inclined nature of the putter shaft by design. However, a very important negative of the arc stroke to consider is that this arc can be over exaggerated very easily with a poor putter fit, additional hand action and/or extreme shoulder rotation during the stroke. You must remember that this over rotation stems from overactive forearm rotation.

Biomechanical 3D Motion Analysis studies have shown that when you form a triangle with your arms and the putter grip, it is impossible to rotate the putter face with your glenohumeral joint (upper arm) or the scapula independently or together. If you allow any of these things to happen your arc stroke will implode!

With a path manipulation, the putter can stay StS. Note the over-the-top transition.

A poorly fit putter, coupled with poor posture and excessive forearm rotation action, can cause an over-exaggerated arc stroke with a ton of face rotation.

The conclusion: The less curvature a stroke has, the easier it is to control the putter. But in all players, there is naturally some type of arc to the stroke unless a manipulation is made during the transition. Use your set-up posture, putter fit and putter type help to determine the shape of your stroke innately.

No face rotation vs. natural face rotation

SAM shows that it is more effective to minimize the amount of putter-head rotation you have naturally and to keep your putter head perpendicular to the arc you are using. Simply stated, the more manipulations you possess within your stroke the more the inconsistencies you will have to overcome in the end. This is not to say that you cannot putt well with either stroke type, but you must make the proper compensations in order to make them work.

The rotation of the putter head is measured relative to the player’s arc. Zero rotation is when the putter face remains square to the arc at any given point throughout the swing. In other words, the rotation is measured at any given point on the arc and should remain perpendicular to the tangent of the arc. The elite PGA Tour putters have minimal rotation of the putter path. Most will open the putter face less than 6 degrees on the back stroke and close less than 6 degrees on the follow through. The very best putters have less than 1 degree of rotation in both directions. To reemphasize, this is independent of the nature of their arc.

StS putters come over the top during their transitions to put the putter head on a straight through line and tend to “hang on” through impact to reduce the natural actions of the putter head wanting to close through impact. This is the reason why a face-balanced putter tends to work best for these types of players, due to its aversion to closing through impact. AS putters must make sure that within their strokes their hands and forearm rotation do not take over (as we see in the example below), or over-rotation of the putter head will result making it harder to control the ball’s starting direction.

The face alignment at impact transmits 83 percent of error to the ball and is five times more important than your stroke’s path while putting.

StS shows “holding on” through the impact zone
4 inches to impact -0.1 degree of rotation
4 inches after impact -0.8 degrees of rotation

AS shows that added hand action through the impact zone can make it hard to control the ball’s starting direction
4 inches to impact 2.5 degrees of rotation
4 inches after impact 2.9 degrees of rotation

2 degrees of loft vs. 5 degrees of loft

The most important discovery within the last few years within the ranks of putting lies within the ability for us to track the ball’s skid and roll just after impact. Golfers can do everything just right with either stroke type, but if they have the wrong rise angle and/or dynamic putter loft at impact they will NEVER be a good putter. The final key is to have the ball leaving the face correctly and rolling very quickly after impact. And this fact is controlled by the rise angle of your putter head and the dynamic loft of your putter at impact.

Rise angle shows how much the putter is moving up or down through the ball in relation to the bottom of its vertical arc as viewed from the side of the ball.

Dynamic loft is measured by taking the factory loft of your putter plus/minus the shaft angle at impact. Example 1 (pictured below) shows a TaylorMade Rossa being used that is designed with 4 degrees of loft, and the player returns it to impact with + 0 degrees of added/reduced loft, thus the putter maintains its original 4 degrees of loft. And when it comes to the loft of your putter, several things must be taken into account: your spine angle (side to side), your center of gravity, the amount of hand action you have and the center of gravity of the putter you currently use.

In a perfect world, with greens running about 10 to 11 on the stimpmeter, the data suggests that your dynamic loft should be around 2-to-3 degrees and your rise angle should be about 3-to-4 degrees in order to give you the best roll possible. When the rise angle is slightly greater than the dynamic loft of the putter, the ball will begin to roll very quickly off the start as shown below.

Example 1

Tour professionals show a rise angle of 3-to-4 degrees and dynamic Lofts of two to three degrees.

Example 2

The average amateur adds loft at impact by flipping his hands through impact.

In Example 2 (above), the TMAG putter used had 4 degrees of static loft and the player added 3.1 degrees of loft at impact for a total dynamic loft of 7.1 degrees. When the rise angle (6.4) is lower than your dynamic loft at impact (7.1), the ball will jump into the air just after impact, bounce, skid and the begin to roll. This lowers your consistency. The key is to match your putter’s static loft to your stroke type for the greens you normally play.

The Conclusion

Whether you use a StS or an AS is of no consequence as it pertains to the ball’s skid and roll. The determining factor of your ball’s actions just after impact are 100 percent determined by your set-up fundamentals, which influence your impact alignments. Matching the putter’s static loft and center of gravity (by design) at address with your impact shaft angle during impact is the key to making the ball roll just after impact.

All these factors considered, the bottom line for direction remains to be able to answer this question in the affirmative, “Was the putter square to the target at impact?”