Describing my personal interpretation of Homer Kelley's power accumulator concept, and describing which power accumulators are being used to power the golf swing in a PGA tour golfer who uses a TGM swinging technique.
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Homer Kelley in his TGM book - "The Golfing Machine" - stated that there are 4 power accumulators (PAs) that can be potentially used to power the golf swing.
He also stated that a TGM swinger should use a different combination of power accumulators to power his golf swing (PA#4 => PA#2 => PA#3) when compared to a TGM hitter (PA#1 => PA#2 => PA#3). Most PGA tour golfers use a TGM swinging technique, which means that they use a triple barrel swing technique where they sequentially unload (release) three PAs in the following sequence-: PA#4 => PA#2 => PA#3.
In this short review paper, I will describe my personal interpretation of Homer Kelley's PA concept as it applies to a TGM swinging action. It is important to note that I disagree with a number of opinions expressed by many TGM literalists regarding Homer Kelley's PA concept, and that my personal opinions (as reflected in this short review paper) should not be perceived to represent standard TGM teaching. I will explain in great detail why I have my own personal interpretation of certain aspects of the TGM's power accumulator concept (which differ to standard TGM teaching) at varying points in this short review paper.
To understand Homer Kelley's PA-concept, it is important to understand that a golfer's only connection with the golf club is through his two hands, which are basically the end-extension of his two arms. To generate swing power, and to maximise clubhead speed at impact, a golfer (who uses a TGM swinging technique) essentially powers the golf swing during the downswing by a swinging motion of the left arm (lead arm), which will pull the golf club towards the ball via the left hand's attachment to the grip handle. At address, the left arm usually hangs down near-vertically (or slightly extended away from the body) and it is connected to the body at the level of the left shoulder socket, which is the fulcrum point of the left arm swinging motion. During the backswing, the left shoulder moves backwards away from the target by a finite amount, while the left arm is simultaneously elevated and adducted across the upper body. At the end-backswing position, the left arm is adducted to a variable degree across the front of the upper torso, and it may be closely adducted against the left pectoral area or there may be a significant gap between the left upper arm and the left upper chest wall. Also, when the left arm is elevated, it can be elevated to a level where the left hand is roughly at the level of the right shoulder socket at the end-backswing position, or the left hand can end up being slightly below, or significantly above, the level of the right shoulder socket. Positioning the left arm at its end-backswing position, where the left arm is elevated and also adducted across the upper chest, represents the loading of PA#4 (which Homer Kelley called the "master" power accumulator - presumably because it supplies most of the swing power during a TGM swinger's full golf swing action).
Here is an image from Homer Kelley's TGM book showing the loaded/unloaded position of PA#4.
At the end-backswing position (top) one can see that the left arm has been elevated to a level that is roughly parallel to the shoulder turn angle, and that it is also adducted across the front of the upper torso at roughly the level of the pectoral area. Note that Homer Kelley has drawn two lines - one line representing the front of the upper torso (and that line is drawn from the left shoulder socket towards the right shoulder socket) and the second line represents the left upper arm - and that there is an acute angle between those two lines, which meet at the position of the left shoulder socket. At that end-backswing position, a golfer has a loaded PA#4.
During the downswing, the left arm will move downwards, and also away from its adducted position at P4 to become signficantly abducted away from the body at impact. Note that the angle between those two drawn lines changes to a less acute angle during the downswing, and the change in that drawn angle between the left arm relative to the upper body reflects the unloading (release) of PA#4. Many TGM literalists think of PA#4 unloading as being due to a change in that acute angle between the left arm and the upper chest wall in the plane of adduction => abduction, and they think of swing power being generated during the downswing by the left arm moving away from its adducted (loaded) position at P4 to its abducted (unloaded) position at impact. I personally harbor a slightly different opinion regarding the specific direction of unloading of PA#4, and I prefer to think of the left arm's PA#4-unloading motion happening three-dimensionally in "real life" 3-D space due to the left arm unloading motion happening simultaneously in two planes - i) moving from the left arm being adducted at P4 to the left arm becoming more abducted at impact and ii) moving from the left arm being elevated at P4 to the left arm becoming near-vertical by impact. To best measure the degree of PA#4 unloading at any time point during the downswing, I prefer to think of the distance traveled by the left hand in 3-D space away from its end-backswing position (where it was close to the right shoulder socket area) towards its impact position (where it is far away from the right shoulder socket area) and I do not only think of the change in that acute angle drawn between the left upper arm and the front of the upper chest (as depicted in that 2-D representational image from the TGM book).
If one thinks of the PA#4 release (unloading) action as happening when the left hand moves further away from the area of the right shoulder socket, then when does the start of the PA#4 release action first happen?
It is obviously possible for PA#4 to start being released from the very start of the downswing if the left arm is pulled away from its adducted/elevated P4 position - as happens in Leslie King's left arm swinging methodogy where the left arm is swung independently down-and-forwards towards the ball and where the golfer uses a reactive pivot action. However, most PGA tour golfers use an active pivot action, which starts with a lower body (pelvis) rotation followed shortly thereafter by an upper torso rotation. When the upper torso starts to rotate counterclockwise around the rightwards-tilted spine, the left shoulder socket primarily moves in a horizontal (targetwards) direction and it pulls the left humeral head in the same direction. However, there is often a time delay before the left arm moves away from its adducted and elevated position during the transition phase to the downswing, which means that the distance between the left hand and the right shoulder doesn't necessarily increase in the first half of the early downswing (between P4 and P4.5). Consider an example of that phenomenon - featuring the downswing of Gary Woodland.
Capture images from a Gary Woodland swing video taken from an elevated camera-viewing perspective.
Image 1 shows Gary Woodland at his end-backswing position. Note that he has a loaded PA#4 where his left arm is both adducted and elevated so that his left hand is behind and just above his right shoulder socket area.
Image 2 shows his early downswing where he is starting to rotate his pelvis counterclockwise, but where there has been very little counterclockwise rotation of his upper torso happening during that transitional time period. Note that his PA#4 is still fully loaded.
Image 3 is at the end of his early downswing (P5 position). Note that he has already squared his pelvis, and his upper torso has started to rotate counterclockwise. Note that there is visual evidence that the distance between the left hand and the right shoulder socket is starting to increase, and this represents the start of the release of PA#4.
Image 4 is at the P5.5 position. Note that there is now clear evidence of the left hand moving away from the right shoulder socket area as the left arm moves downwards (groundwards) and also targetwards in a left arm abductory direction - secondary to the pivot action causing the left shoulder to move targetwards, which pulls the left upper arm in the same direction, and secondary to activation of the left shoulder girdle muscles, which help to pull the left arm in a more groundwards direction.
Note that he must be actively adducting his right upper arm during the P4 => P5.5 time period, so that his right elbow gets driven down-and-forwards to its pitch elbow position in front of the right hip area by P5.5. That active right arm adduction maneuver allows him to maintain a bent right arm, and an intact power package, where the RFFW can efficiently support the intact LAFW, which is moving down the inclined plane. During the P4 => P5.5 time period, as his right shoulder moves down-and-forward and as his right upper arm is actively adducted towards the right side of the torso, his right palm may be applying a finite amount of push-pressure against PP#1 over the base of his left thumb, and that push-pressure may synergistically help him to more efficiently release PA#4.
During the early downswing, the left arm is likely traveling at the same speed as his rotating upper torso, but the left arm speed will exceed the speed of rotation of his upper torso by the mid-late downswing, and it will reach its maximum speed in the late downswing before slowing down slightly in the very late downswing between P6.5 and impact.
I believe that there is a very close correlation between the speed of upper torso rotation (secondary to an active pivot action) and the speed of release of PA#4, which means that golfers who can pivot very fast can theoretically release PA#4 faster, which should result in a faster clubhead speed at impact. I believe that the maximum clubhead speed at impact is highly correlated with the maximum speed of release of PA#4, which could be the reason why Homer Kelley called it the "master" power accumulator.
Although the release of PA#4 is the major source of swing power in a full golf swing, a professional golfer can get a significant amount of additional clubhead speed by impact by upcocking his left wrist during the backswing, which will load the club relative to the left arm (in the left wrist's plane of radial-ulnar deviation) so that there is a ~90 degree angle between the clubshaft and the left arm at the end-backswing position, and that club-loading phenomenon represents the loading of PA#2.
The release (unloading) of PA#2 is the release of the club, which usually happens in the later phase of the mid-downswing, often starting when the golfer reaches near the P5.5 position. When the club releases it releases within the plane of the intact LAFW, which is in the plane of radial => ulnar deviation, and the club release phenomenon therefore doesn't disrupt an intact LAFW alignment.
What causes the club to release in a TGM swinger?
I believe that the club will automatically/naturally release in a TGM swinger according to the principle-of-physics underlying the release mechanics of a double pendulum swing model, and I believe that it should not occur manually secondary to any active left wrist uncocking action, or due to any push-pressure being applied to the aft side of the club below the coupling point by the right index finger.
The best explanation that I have presently discovered to explain the physics causing the club release action was originated by "nm golfer" - see his mathematical explanation here
The mathematical explanation is complicated, so to express the mathematical club release concept in very simplistic terms, one can think of the club automatically releasing when the left hand arc path changes its directional shape from being a straight-line linear hand arc path (where the left hand and COG of the club are moving straight-in-line along the same linear path) to becoming more circular in shape, and that the club will release with a greater degree of force if the change in the circular-shaped left hand arc path is "tighter" (equivalent to having a smaller radius of an imaginary circle along which the left hand moves in its circular path manner), which means that the amount of change in left hand direction per unit distance of travel of the left hand down the hand arc path, is greater.
Here is Jamie Sadlowski's (a previous world long drive champion's) hand arc path.
The red splined path is Jamie Sadlowski's hand arc path.
Point 1 is the position of his hands at his end-backswing position. Point 2 is the position of his hands at the P5 position (when the left arm is parallel to the ground). Note that his hands are moving slightly backwards (away from the target), but mainly downwards, between point 1 and point 2 due to rotation of the upper torso that happens prior to the release PA#4. That section of the hand arc path is relatively linear, and it doesn't induce the club to release. Note that Jamie Sadlowski still has an enormous amount of lag at the P5 position.
Point 3 is when his hands are at the P5.5 position. The hands are moving targetwards, as well as downwards, between point 2 and point 3, and the change in his hand path direction is very abrupt as his left hand bypasses point 2, and this next section of the hand arc path is representative of a small radius circular hand arc path, which causes his club to release with a larger amount of club releasing-power. A club release (PA#2 release) action that happens between P5.25 and P6 represents a random release (Homer Kelley's definition) pattern.
Now, consider the hand arc path and club release pattern of another professional golfer - David Toms.
The red splined path represents his hand arc path.
Image 1 shows David Toms at his end-backswing position with his hands at point 1 on his hand arc path. Note that he has ~90 degree of clubhead lag.
Image 2 is at P4.5 and his hands are at point 2. His hands are moving mainly downwards and slightly backwards due to rotation of the upper torso which is happening prior to his release of PA#4 , and this straight line section of the hand arc path doesn't induce the club release phenomenon.
Image 3 is at P5, and he has already started to release PA#4. Note that the club has started to release soon after his hands bypass point 2 because his hand arc path is now more circular in shape, and this earlier club release pattern is called a sweep release (Homer Kelley's definition) pattern.
Image 4 is at P5.5 and his hands are at point 3 on the hand arc path. Note that his hand arc path is still mainly downwards and not directed very abruptly towards the target, and the circular shape of his hand arc path between point 2 and point 3 is equivalent to an imaginary circle with a large radius, which causes a slower club release pattern.
Professional golfers have a variable shape of their hand arc path between P4 and P5.5, and they therefore release their club at different time points and with a variable speed of club release.
I strongly suspect that professional golfers do not attempt to manually induce a club release phenomenon by applying push-pressure with PP#3 of the right hand to the aft side of the clubshaft below the coupling point. The disadvantage of using a manual club release in a golfer, who is fundamentally a TGM swinger, is that it can interfere with the natural club release phenomenon that is already happening automatically according to the laws of physics (depending on the shape of the hand arc path) and it can cause the club release phenomenon to become more jerky and more uncontrolled, and potentially less consistent from swing-to-swing.
The 3rd power accumulator that Homer Kelley recommends for a TGM swinger's swing action is the release of PA#3. Homer Kelley labeled PA#3 as representing "clubface control" or "roll power control". At address, a professional golfer's left humerus is usually internally rotated, and the left forearm is very slightly supinated if the golfer adopts a neutral left hand grip. Then, during the backswing action, when the intact LAFW is swung up the inclined plane to its end-backswing position, the left forearm must pronate by a finite amount so that the GFLW and watchface area of the left lower forearm can become parallel to the inclined plane at the P4 position. The amount of left forearm pronation required during the backswing is greater if the intact LAFW lies on a shallower inclined plane at the P4 position (as seen in Rickie Fowler's golf swing) compared to the situation where the intact LAFW lies on a steeper inclined plane at the P4 position (as seen in Bubba Watson's golf swing). Pronating the left forearm during the backswing action represents the loading of PA#3.
The release (unloading) of PA#3 occurs when the left forearm supinates in the later downswing between P6.5 and impact, so that the GFLW, and therefore the clubface, can become square to the target by impact. I personally believe that the primary function of the left forearm supinatory motion, that must happen between P6.5 and impact, is to enable the golfer to acquire a square clubface by impact, and I do not personally think of the release of PA#3 as being a source of swing power in the sense that it can potentially increase clubhead speed by a very small amount (due to the toe of the club rotating around the hosel of the club at a fast speed). Some TGM literalists seemingly believe that the release of PA#3 can increase clubhead speed at impact if the left forearm actively supinates in the later downswing so that the clubshaft can still be actively rotating around its longitudinal axis while the clubface is in contact with the ball at impact, and they mentally picture the clubface continuing to rotate counterclockwise throughout the entire impact interval and then still continuing to rotate counterclockwise in an uninterrupted manner throughout the P7 => P7.2 immediate impact zone time period. However, that mental scenario is incompatible with my idea of a drive-hold hand release action where the clubface should remain stable, and square to the clubhead arc, throughout the P7 => P7.2 time period. I believe that any left forearm supinatory motion must optimally stop at impact, and I believe that the left forearm must not continue to supinate as the club travels through the immediate impact zone between P7 => P7.2, if a golfer wants to perform a DH-hand release action, and I believe that it is physically impossible to stop the left forearm from continuing to supinate during the clubhead's travel passage through the immediate impact zone if the forces causing left forearm supination are too active (too energetic). I therefore think of the left forearm supinatory motion that happens during the late downswing as being a relatively passive phenomenon, where the amount of counterclockwise left forearm supinatory force being applied is only enough to square the clubface by impact - which means that the counterclockwise roll motion of the left forearm will not likely contribute to an increase in clubhead speed during the pre-impact phase of the golf swing. I therefore do not personally think of the release of PA#3 as being a swing power source, which can significantly increase clubhead speed at impact. I have therefore revised my thinking during the past few years and I now think that a TGM swinger should only use two power accumulators in sequence (PA#4 => PA#2) in order to generate his maximal clubhead speed at impact, and I now think that a TGM swinger should not think of the release of PA#3 as being a power source that can potentially increase clubhead speed at impact.
Finally, it is important to realise that the amount of left forearm supination happening during a PA#3 release action is inversely proportional to left hand grip strength - and that the amount of left forearm supination happening is greatest in golfers who adopt a weak or neutral left hand grip. By contrast, golfers who adopt a very strong (4+ knuckle) left grip do not need to supinate their left forearm during their late downswing, and they have the ulnar border of their left hand (and not the back of their left hand) facing the target at impact. They, therefore, cannot possibly be generating any swing power via a left forearm supinatory roll motion, which is the biomechanical basis of a PA#3 release action.