Dear 300Drive,
To me, the chief advantage of left-hand low is the consistency of a stroke path that rolls the ball straight away from the putter face. The interesting thing is why this would be the case in general for the human body in putting, as compared to a conventional grip with the right hand low, such as the reverse overlap grip.
What's different in the body setup and motion between the left-hand low and the conventional right-hand low grips? List just list some things.
Left hand lower than right
Right hand higher than left
Left arm straighter than right
Right arm crooked at elbow
Left arm not crooked at elbow
Left arm forearm in line with shaft
Right arm forearm not in line with shaft
Bottom of stroke closer to left shoulder than middle of body
Shoulders more level with left-hand low and ball-ahead in stance
Shoulders tilted left-up and right-down with right-hand low and ball-ahead in stance
Right-hand power / guidance influence lessened in left-hand low stroke
Left-hand guidance influence increased with left-hand low
Guiding hand on same side as target with left-hand low
Left shoulder of guiding hand on front side of body towards target in stroke
Back of left hand / forearm square to target at address
These aspects of setup and motion are pretty interesting when you consider a few points in how targeting and motion is controlled by the brain and how the body works in a putting stroke.
First, the left hand may be more accurate in moving toward the target than the right. The right side of the brain controls the left side of the body (and vice versa) for muscle activiation and movement. In almost all people, the left side of the brain is where most thoughts, words, internal dialogue, analysis, and parts-rather-than-the-whole are processed; the right side handles most of the awareness of space and the body in space, targeting, the whole-rather-than-the-parts, the "gist" of a situation, and certain rhythmic and musical senses. Of course, both halves of the brain are connected and cooperate in these disparate processes, but most people develop certain tendecies in one side of the body that more closely reflect the characteristics of that body side's brain hemisphere for muscle action. And in terms of muscle activiation and control, the opposite side of the brain pretty much handles one side of the body to the exclusion of the other hemisphere. For example, when a stroke affects the right "motor" or "sensory" cortex, only one side of the body is affected with loss of sensation or muscle control.
According to some researchers, the right brain is more accurate and reliable in locating a target and in moving the left side of the body at the target. This to me means that the left hand is more accurate in "drawing" a straight line at a target to the left than the right hand can "push" a line at the same target. Some instructors have compared this to pushing a donkey cart versus pulling the cart. To the extent the hands participate in "powering" the stroke and guiding the stroke, as is the case with putting style having some hand action or manipulation and even only with some armsiness, the left-hand low style starts with a little advantage.
This concept is a little more subtle. Targeting is the foundation of movement. And targeting is more body knowledge than visually finding the target. That is, targeting is how we orient and position the body with relation to a target for purpose of making a forthcoming, well-practice motion to roll the ball at and to the target. Targeting is much more body and much less eyes than almost everyone seems to realize, particularly including certain recent "scientists" in academia. And in this sense, orienting the setup to a target vests the left hand with a clearer capacity for moving straight at the target than the right hand.
Second, the way the body works suits left-hand low a little better for a consistent and accurate straight stroke. Whether the stroke style is a shoulder stroke or more of an arms stroke, it is easier to move one hand alone straight away at a target to the side than it is to move two arms connected together at the hands. This is mostly due to the tension in the upper back that comes along with putting the hands together at the lap. While this tension may be very mild or hard to detect, it is there. Also, the shoulder joint acting alone makes it easier to move the arm towards a target, especially if the target is off to the left and the left arm is being moved (since the arm does not have to cross the chest). In contrast, when the arms are joined together with equal influence and relations between hands and associated shoulders for power and guidance, the body will most comfortably move the hands in an arc fabout the feet. It is a lot easier to move the so-called "triangle" of shoulders-plus-arms to the target when the rear hand does not have much influence or control. I think this directly relates to a little more tightness in the right shoulder and lower right side when the right arm and hand have a power / guiding role in the stroke. And finally, when the key side is moving UP thru impact, as is the case with left-hand low, the body can more reliably move the limb at the target. This latter point is closely related to the idea of pulling a cart versus pushing a cart, with the vertical dimension added in (pulling up versus pushing down).
So, to me, there are basically two reasons why the left side should dominate in the putting stroke for a right-handed conventional putting stroke -- the right brain is in control of the target and the influence of the right hand is diminished so that the left side can move more accurately.
Because of all this, I personally believe that the left-hand low grip is very good, but the "low" part is not all that responsible for the benefits. In my preferred style, the grip of both hands ends up with the left hand on the handle, the right hand on the left, and both about the same height above the ground. This gives a nice level-shoulders setup and a nice body symmetry and balance in the stroke. Playing the ball a little forward of the middle of the stance promotes a rising left shoulder, lagging the left arm, hand, and putter straight up and sending the putter face squarely down the straight line of the putt. The "low" aspect of this style does not necessarily result in the left hand being the one most on the handle, since left-hand low by itself does not choose this. And the "low" aspect of the left hand versus the right tends to tilt the shoulder frame, which alters the bottom of the stroke and the sense of balance in setup and motion. This tilt also promotes a descending blow. So, give me left-hand only, not left-hand low.
I have recently been spending a lot of time experimenting with a differential grip pressure at address, having the left hand more "on" while the right hand is deliberately kept out of the picture grip-pressure wise. I would call the left hand pressure about 2-3 on a scale of 1 to 10, with the right hand between 1 and 2.
Also, the right thumb seems to be a key to getting the right hand's influence reduced. The fine-control "precision grip" of the hand is a matter og thumb and index finger pincering together. Thus, deliberately lightening the grip pressure of the right thumb tip on the handle neutralizes the right hand's control in the stroke. This gives control to the left side and permits a more accurate motion at the target.
I should say in conclusion that what I am describing is a shoulder motion, and not a left-hand motion. Although the left hand "knows" the target location, the left hand is not what I am intending to move. My stroke style is a motion of the shoulder frame as a whole, powered and guided by dipping and then raising the left shoulder socket. This action is powered and controlled in the midrift / abdomen / lower back muscles, and the muscles of the shoulders, pecs, upper arms, forearms, wrists, and hands are all inactive albeit with a steady tonic setup tension for form. The action of the left shoulder moves the whole left arm and hand and putter as a unit, and the "bad" influence of the right side is kept at bay.
I hope this answers your questions, at least in terms of my personal understanding.
Cheers!
Geoff Mangum
Putting Theorist and Instructor
PuttingZone.com
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