How to Power the Golf Swing
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This review paper is focused on the biomechanical and physical-mechanical principles that are essential to the process of correctly powering the full golf swing. Many beginner golfers incorrectly believe that they power the golf swing with their thrusting thighs, or sliding torso or via a flipping of the right hand through the impact zone. All these simplistic beliefs are totally incorrect and the primary purpose of this review paper is to offer interested golfers a thorough understanding of the basic biomechanical mechanisms that allow a golfer to power the full golf swing in the correct manner. This review paper will be of particular interest to that subset of golfers who believe that a detailed understanding of golf biomechanics will help them improve their game.
Most of the concepts used in this review paper were derived from Homer Kelley's "The Golfing Machine" book . My understanding of these concepts was markedly enhanced by reading the archived posts in Lynn Blake's forum . Lynn Blake is a TGM instructor who has a great understanding of TGM concepts and he also has the capacity to express his thoughts clearly and unambiguously. I would never have been able to clearly understand the TGM book without his clearly expressed insights re: TGM concepts. In this review paper, I will try to express those TGM concepts in an easy-to-understand manner, so that they can be of use to the analytical type of golfer who regularly visits my website.
I will be describing a number of different swing styles in this paper, so that interested golfers can learn to understand that different golf swing styles are powered in a different way. A golfer needs to learn how to use the appropriate powering mechanics for his selected swing style and he should not mix-and-match fundamental swing concepts that are incompatible with each other. There are two basic golf swing styles - swinging and hitting. A golfer can therefore either choose to become a swinger or a hitter. I will describe how a swinger powers the full golf swing and how a hitter powers the full golf swing in great detail. It is important that a golfer not mix the fundamentals underlying a hitting action with the fundamentals underlying a swinging action because they may not be compatible. If one does mix the fundamentals, one becomes a switter (a golfer who uses an admixture of swinging and hitting actions) and a switter may be plagued by a inconsistent golf swing because his swing fundamentals may not be working synergistically together in a synchronised manner.
Before I describe the difference in biomechanical movements between a swinger and a hitter, I am going to describe the basic physics of how the clubshaft is propelled by a swinger and a hitter.
How to power the golf swing - the basic physics
The first concept that a beginner golfer needs to understand with respect to powering a golf swing is the basic concept of how power is applied to the clubshaft. There are two basic methods of causing the clubshaft to move downwards towards the ball during the downswing action.
A golfer can either pull the clubshaft down towards the ball using the left arm/hand or a golfer can push the clubshaft down towards the ball using the right arm/hand.
A golfer who pulls the clubshaft down towards the ball using the left arm/hand is a swinger. A swinger basically holds the club in his left hand and pulls the grip end of the club down towards the ball - as if he is pulling on a rope. This technique is called the rope handle technique. A golfer can simply think of a person who rang church bells in the medieval era, and imagine how they pulled on a rope attached to a church bell - they simply pulled the rope down towards the ground. A golfer who swings a golf club is essentially mimicking that rope-pulling action by pulling the grip end of the golf club down towards the ball with his left arm/hand. The major difference is that he is pulling on a solid linear object - the clubshaft - and the direction of the pull is along the longitudinal axis of the clubshaft. Another major difference is that a golfer allows the clubshaft to acquire a 90 degree angle between the left arm and the clubshaft at the end of the backstroke, before he pulls the grip end of the club down towards the ball. The movement of the left hand arc in space during the downstroke is circular when the left arm is pulled down across the front of the body and the clubshaft is therefore being pulled by a pulling force that is constantly changing direction. How does that constantly changing direction of pull-force affect the movement of the clubshaft during the downswing?
The simplest way of understanding the physics of a swinging golf club is to understand the physics of a double pendulum.
Here is a photograph of the author mimicking a left arm swing action.
Left arm golf swing action
During a golf downswing action, the left arm is swung across the front of the body from the end-backswing position (depicted in this photograph). At the end of the backswing, the clubshaft is at a right angle to the left arm. Then during the downswing, as the left arm is swung across the front of the body, the left hand moves in a circular arc (depicted by the series of red arrows) because the left arm is suspended from the body at the left shoulder socket (central hinge point). What happens to the clubshaft if the left wrist is relaxed and totally passive? The clubshaft will automatically release and seek a straight line alignment with the left arm. What causes the club to automatically/passively release if the golfer is not deliberately uncocking the left wrist during the downswing?
The mathematical explanation of why the club releases has been explained by nm golfer and you can read his explanation by clicking on the following link.
NMgolfer's mathematical explantion of the club release phenomenon
Basically, the golf club releases because the pulling force at the grip end of the club follows a circular path. A circular path can be conceived to be a series of straight line paths that are constantly changing direction so that the overall directional path is circular (depicted by the series of red arrows in the above photograph). Because the pulling force at the grip end of the club is constantly changing direction relative to the centre-of-gravity of the clubshaft, the clubshaft progressively acquires angular velocity that causes the clubshaft to release thereby allowing the clubhead to catch up to the hands.
If you find the mathematical explanation too difficult to understand, then you may find David Tutelman's explanation easier to understand.
David Tutelman's explanation of the club release action - http://www.tutelman.com/golf/design/swing1.php?ref=
David Tutelman uses the concept of a centrifugal force as causing the club release phenomenon.
Double pendulum swing model
The double pendulum swing model consists of two arms - the central arm and the peripheral arm. There is a passive hinge joint between the central arm and the peripheral arm (equivalent to the left wrist in a left arm swing). The only force applied to the double pendulum swing system is at the central hinge point - a central torque generator causes the central arm to swing in a circular arc because it is suspended from the central hinge point. As the central arm swings in a circular arc, the peripheral hinge point (at the end of the central arm) also follows a circular arc, and the peripheral arm (equivalent to the clubshaft) is passively pulled by its attachment at the peripheral hinge joint. The only force that the peripheral arm (clubshaft) experiences is indirect - it simply responds passively to the pulling motion exerted at the peripheral hinge point, which is moving in a circular direction due to the fact that the central arm is moving in a circular arc. At every moment in time the peripheral arm wants to move in a straight line (in response to the pulling force exerted by the peripheral hinge point), but because the peripheral hinge point is constantly moving in a circular direction (= a straight line direction that is constantly changing its direction in a circular fashion), a centrifugal force develops that causes the club to release. That centrifugal force is the same force described by nm golfer in his mathematical explanation. That centrifugal force causes the club to passively release so that the clubshaft becomes inline with the central arm (left arm) at the low point of the circular swingarc.
The double pendulum swing model is the fundamental swing model used to design the Iron Byron swing machine that golf club manufacturers use to test their golf clubs.
Here is an example of an Iron Byron machine - see the PingMan Machine in action.
http://homepage.mac.com/brianmanzella/.Movies/PINGMAN.mov (long download time)
For a shorter download time try this download site http://www.mediafire.com/?4tj0bn02yj1 (open the link in a separate window as the "go-back" link function doesn't work if you open this website link in this same window)
Here is a series of capture images from that video.
PingMan machine - capture images from the PingMan Machine video
Note that the PingMan machine has a single central arm that is actively rotated by some motorised mechanism at the central hinge point. The club is attached to the far end of the central arm at a passive joint. No active movements occur at this peripheral hinge joint. During the downswing, the central arm swings at an operator-determined rate of speed, and the rate of speed is user-controllable. In other words, if the machine operator wants the machine to generate faster clubhead speeds at impact, then he simply makes the central arm swing faster.
I have drawn red lines along the clubshaft and central arm, so that you can clearly see the natural release action of the clubshaft in the mid-late downswing. Note that the angle between the clubshaft and the central arm is established at 90 degrees at the end-backswing position and that it remains at 90 degrees throughout the early-mid downswing because the PingMan machine has a small latch-lock lever that prevents the early release of the clubshaft (until image 4). After that time-point in the downswing, the clubshaft releases naturally and the clubshaft is roughly in line with the central arm at the time of impact. By maintaining 90 degrees of clubshaft lag until the end of the mid-downswing, the PingMan machine's ability to increase clubhead speed is significantly increased - see David Tutelman's website for a detailed explanation . However, it is important to realise that the Pingman Machine's clubshaft release action occurs passively due to physical forces and that it is not due to any active uncocking action at the peripheral hinge joint. A beginner golfer needs to realise that he will not necessarily produce any increase in swing power by deliberately trying to uncock the wrists when the hands get to waist level. The clubshaft release action should happen automatically due to physical forces - due to the clubshaft having gained sufficient angular momentum to cause the clubshaft to release and progressively catch up to the left arm during the remainder of the downswing.
If you cannot understand the physics underlying the double pendulum swing model, then all you need to know as a swinger are three important facts - i) that you need to swing your left arm from the left shoulder socket during the downswing, and ii) that the club will be pulled passively by the left hand as the left hand traces a circular arc and iii) that the club will passively release in the correct manner if you have relaxed wrists. The primary action that a swinger really needs to learn is how to get the left arm to swing down towards the ball during the downswing so that the left arm can pull the clubshaft down towards the ball, and I will describe the underlying biomechanics in the next section.
I previously stated that a swinger pulls the club via the left hand, and that a hitter pushes the club via the right hand. How does a hitter push the club?
A hitter uses an axe handle technique whereby the right hand applies a radial force to the clubshaft at the grip end of the club. When hitting, a golfer applies an active right arm-powered force as push-pressure to the back side of the grip end of the shaft via push-pressure applied at pressure point #1 and #3.
Modified photo derived from source 
The above photo shows pressure points # 1 and #3. Pressure point #1 is the area at the back-top area of the base of the left thumb, and normally the lifeline area of the right palm nestles directly over this area of the left thumb. That allows a golfer to apply active push-presssure via the right palm to pressure point #1. That active push-pressure forces the left thumb to move away from the left shoulder socket thereby straightening a relaxed left arm via a pulling action - if the push-force at PP#1 is exerted in a direction that is along the axis fo the left arm. This active force is applied by a golfer when he tries to straighten his right arm at the right elbow joint and that active force pulls the left arm straight. This active force is called extensor action. In other words, throughout the swing (both backswing and downswing), a golfer should be trying to straighten the right elbow so that he can maintain a constant extensor pulling force on the left arm at pressure point #1 - and that extensor action allows a golfer to keep the left arm straight throughout the backswing and downswing. A golfer should not try to keep the left arm straight by tensing muscles in the left arm. The left arm should feel relaxed and it should be pulled straight via the mechanism of extensor action (in both a swinger and a hitter). Although a hitter applies a small amount of push-pressure at pressure point #1 to keep the left arm straight, he does not hit by only applying push-pressure at pressure point #1 - he also needs to apply push-pressure at pressure point #3.
Pressure point #3 is the area of proximal phalanx/middle phalanx of the right index finger neighbouring the first joint of the right index finger, and normally that area of the right index finger lies against the back of the grip end of the shaft - in other words, it is behind the shaft. A golfer can sense pressure at that pressure point (pressure point #3) if he pushes against the back of the grip end of the clubshaft with the right hand. In a golf swing (whether one is a hitter or a swinger), the right wrist is always bent back and the right wrist never bends forward (palmar flexes) at any time point during the downswing - because it would cause the left wrist to bend forward (flip).
Tiger Woods bent right wrist and flat left wrist - capture images from a Nike commercial swing video
The above photo sequence shows Tiger Woods' wrist action through the impact zone. Note that his right wrist remains bent and that his left wrist remains flat while the hands are passing through the impact zone. Whether one is a hitter or a swinger, this is a fundamental imperative of a good golf swing - the left wrist must be flat at impact. If the right wrist is allowed to bend forward in the impact zone, thereby flipping the left wrist forward, a golfer loses his ability to apply a solid compressive force to the ball at impact. Whether one is a hitter or a swinger, the clubhead should never flip past the hands while the clubhead is moving through the pre-impact zone. The clubhead should always be lagging behind the hands during the entire downswing, which means that the right wrist is always bent back. In a swinger, like Tiger Woods, the golfer can sense the clubhead lag pressure at pressure point #3 throughout the entire downswing - because the clubhead always lags behind the hands. A swinger doesn't actively apply a push-force at pressure point #3 during the downswing - he only senses and monitors the lag pressure at pressure point #3. By contrast, a hitter applies an active push-force at pressure point #3 by actively extending the right elbow during the downswing - as the right elbow actively straightens it applies an active push-force via the bent right wrist to pressure point #3. The push force is applied as a straight line thrust action against the back of the grip end of the clubshaft. Consider the following analogy.
Wagon wheel analogy
Imagine a situation where a wagon wheel is stuck in the mud. If one wanted to dislodge the wagon wheel and get it rolling, one could apply a push force along the circumference of the wagon wheel by placing one's hands on the rim of the wheel and then pushing along a circular arc direction (the directional arc of the rim of the wagon wheel). Alternatively, one could attempt to dislodge the mud-stuck wagon wheel by pushing on one of the spokes of the wagon wheel via a straight line thrust action. It is a radial thrust action because one is pushing the radially-oriented spoke using a straight line thrust action. That's what a hitter does to power the golf club. He uses the right arm to push the clubshaft down towards the ball using a straight line thrust action against PP#1 and PP#3. I will describe the hitter's swing action in greater detail later in this review paper. At this point, a reader must simply understand how a hitter applies a straight line thrust force radially to the clubshaft at PP#1 and PP#3 (axe-handle technique) in order to power the swing.
How to power the golf swing - the basic biomechanics
In this section of the this review paper, I am going to describe the actual biomechanics of swinging and hitting - how the body and arms work to power the golf swing.
It is important that a golfer realise that the clubshaft is essentially powered by the arms, and to fully understand how this happens one needs to understand Homer Kelley's power accumulator loading and release actions.
Homer Kelley stated (1) that there are four power accumulators (numbered 1 through 4) and that three of those power accumulators are used in a set release sequence in a swinger 's full golf swing action - the sequence is 4:2:3. Homer Kelley referred to this swing action as a triple barrel action because three power accumulators are loaded and then released in the swinger's swing action. A hitter usually also has a triple barrel swing action, but he uses three different power accumulators in a different release sequence - 1:2:3. A skilled/experienced hitter can also use a four barrel action (use all the power accumulators in a set release sequence of 4:1:2:3), but a swinger cannot have a four-barrel swing action because a swinger should never actively use PA#1.
To make sense of the power accumulator loading/release concept, one first has to understand what's a power accumulator and how it works. I will start off by describing power accumulator #4 because it is the easiest to understand, and because it is the master power accumulator that is responsible for most of the power generated by a swinger.
Power accumulator #4 is loaded when the left arm is pulled across the chest wall during the backswing. At the end of the backswing, the left arm should be lying across the upper chest wall and there should be a sense of pressure at pressure point #4 - the point where the left upper arm lies tightly against the left upper pectoral area.
Power accumulator #4 loading and release - from reference number 
At the top of the backswing, note that there is an acute angle between the left arm and the upper chest wall between the shoulder sockets. The exact amount of that acute angle is not critical - it will be smaller if a golfer has a longer backswing left arm movement that gets the left arm to lie closer against the chest wall. Note that power accumulator #4 is loaded at the top of the model's backswing, and ready to be released. During the downswing, the left arm moves away from the upper torso and power accumulator #4 is regarded as being completely released when there is an approximately 90 degree angle between the straight left arm and the upper torso between the shoulder sockets - which usually happens by impact (actually at the end of the followthrough when both arms are fully straight). I will describe the different methods of releasing PA #4 during the downswing (different methods of causing the left arm to swing rapidly across the front of the torso) later in this section. At this point, a golfer merely needs to understand that the release of PA#4 supplies most of the power in a swinger's swing action - and that it is conceptually equivalent to the movement of the central arm in the double pendulum swing model.
The following photo series of Kevin Na's swing will demonstrate the next two power accumulators - PA#2 and PA#1.
Power accumulator loading and release - from reference number 
Before I discuss PAs #2 and #1, consider how Kevin Na loads and releases PA#4. Note that Kevin Na gets his left arm so far across his upper chest during the backswing that he gets his hands behind his right shoulder and his clubshaft is approximately parallel to the ball-target line at the end of the backswing (image 1). Note that his right forearm is vertical to the ground - and that is characteristic of a swinger who has a full backswing that gets to the end-of-the-backswing position (hands behind the right shoulder). By contrast, the photo of the lady model in the "power accumulator #4 photo" demonstrates that she ends her backswing when she is at the top-of-the-backswing position (defined as the time point when the hands are opposite the right shoulder, and not above/behind the right shoulder). At the top-of-the-backswing position, the right forearm is not vertical to the ground, but at an angle to the ground (roughly parallel to the bent-over spine). Note how Kevin Na's PA#4 releases in the photo sequence and how the left upper arm separates from the left pectoral area (point X in blue = pressure point #4) to become completely released by the end of the followthrough (images 2,3,4,5). PA#4 is fully released when there is approximately a 90 degree angle between the left arm and the left pectoral area of the chest wall - image 5.
Power accumulator #2 is the angle between the radial border of the straight left arm and the clubshaft, and this angle is established when the left wrist cocks upwards. PA#2 is fully loaded when there is a 90 degree angle between the clubshaft and the left arm, and a golfer loads PA#2 during the backswing. By the time the hands get to the top-of-the-backswing (or end-of-the-backswing for a more complete backswing), PA#2 should be fully loaded (red lines). Note that PA#2 releases after PA#4 in the downswing. Note that Kevin Na maintains the 90 degree PA#2 angle until his hands are passing the front of his right thigh (image 3) and that he only releases PA#2 in the late downswing. This represents a late release. If the release of PA#2 occurs from the very start of the downswing and occurs gradually (and progressively) throughout the downswing, that represents a sweep release. Most amateur golfers have a random release - which is any PA#2 release timing between a late release and a sweep release. It is critically important to understand that the release of PA#2 is passive in a swinger and due to centrifugal action - similar to the release phenomenon involving the peripheral arm in the double pendulum swing model. In other words, a swinger doesn't actively release PA#2 via an active left wrist uncocking action or via a right arm thrust action. The later the release, the faster the golfer can swing the left arm/clubshaft unit during the early-mid downswing (as explained in David Tutelman's website review) and the greater the potential clubhead speed at impact.
Power accumulator #1 is the bend-angle between the right forearm and right upper arm at the right elbow joint, and one can see that PA#1 is fully loaded at the end (or top) of the backswing and that there is a ~90 degree bend-angle at the right elbow joint (yellow lines). During the downswing, the right elbow straightens and this is only possible if a "force" causes the left hand to move away from the right shoulder. In a swinger's action, the right elbow straightens somewhat passively as the left arm/hand, and therefore the right hand, moves away from the right shoulder (due to the release of PA#4). At impact, there is still a small amount of bend in the right elbow (image 4) and the right arm only becomes fully straight after impact (at the end of the followthrough - defined as the time point when both arms are fully straight - image 5). In a swinger, the right arm doesn't actively straighten as a result of a very forceful right triceps muscular thrust action. The right triceps muscle only actively contracts with enough isotonic force during the downswing to keep the right elbow straightening slightly (in order to maintain extensor action throughout the entire downswing) and with only enough isotonic force to sense/maintain clubhead lag (a constant sense of lag pressure at PP#3) throughout the downswing (which will occur if the right hand keeps up with the left hand by traveling at the same speed). PA#1 is only actively released in a hitter's swing action - when the right triceps muscle actively contracts with a large amount of isotonic force, thereby straightening the right arm in a straight line thrust action that thrusts the right forearm downplane and drives PP#1/PP#3 towards the ball (or towards a desired aiming point in the vicinity of the ball). PA#1 is called the muscular power accumulator, because its active release depends on the active contraction of the right triceps muscle and its active release results in the active straightening of the right arm in a straight line thrust manner. PA#1's release action is the major power source in a hitter's swing action. By contrast, it provides no power thrust action in a "pure" swinger's swing action. There is no time point during the downswing when a "pure" swinger should be actively releasing PA#1 - actively straightening the right arm in a forceful thrust action. Many beginner golfers, who employ a swinger's action, try to add additional hitting power in the later downswing by actively straghtening the right elbow in a forceful thrust action, and this is a major swing fault (which I will discuss in greater detail later in this section when I describe the swinger's swing action).
Power accumulator #3 is called the transfer power accumulator and many people cannot understand how PA#3 works. One can see PA#3 at work in this slow motion swing video of Tiger Woods - the famous Nike commercial that was produced using a special camera operating at 4,000 frames/second.
Watch the back of Tiger's left hand as his club nears impact. Note how his left hand rolls over (rotates counterclockwise as viewed from above) just before impact. That rollover of the left hand occurs after the start of the release of PA#2 (uncocking of the left wrist) and that rollover motion allows the clubshaft to get into a straight line alignment with the left arm soon after impact - at low point (as seen from a face-on view). Here are a series of capture images from that swing video that demonstrate the release of PA#3.
Release of Power Accumulator #3
Image 1 shows Tiger Woods approaching the delivery position - defined as the time point when the clubshaft should be parallel to the ground and parallel to the ball-target line and roughly along the toe line. At this time point, PA#2 is still fully loaded and you can see how PA#2 releases in the time period between image 1 and image 4 (impact). However, note that there is another phenomenon happening in that same time period. Note how the back of the left hand is facing the ball-target in line in image 1, and facing the target at impact. That means that the back of the left hand (and therefore clubface, which is constantly in-line with the back of the FLW) have to rotate 90 degrees between image 1 and image 3. Note that most of the left hand rollover action occurs later in the late downswing - between image 3 and image 4. As the back of the left hand rolls over during that time period, the clubshaft is getting to become more straight-in-line with the left arm (due to the release of PA#2) - as seen from a face-on view. That specific left hand rollover action (which is primarily due to a left forearm supinatory motion) allows the back of the FLW and clubface to face the target by impact.
Addendum added February 2011: There is a much better way of understanding how PA#3 works, and that is based on the concept of the left arm flying wedge (LAFW). Once a golfer understands the concept of the LAFW, then he will realise that the release of PA#3 is nothing more than the rotation of the intact LAFW into impact during the late downswing - and that the release of PA#3 is happening while the clubshaft is being simultaneously released (due to the release of PA#2) within the plane of the LAFW.
To better understand these concepts - a website reader should view these two U-stream broadcasts that I (the author) produced in late 2010.
Q&A session number 1 - http://www.ustream.tv/recorded/10886488
Maintaining a flat left wrist post-impact - http://www.ustream.tv/recorded/10830713
Note that there is small degree of overlap between the release of PA#2 and PA#3. That's perfectly acceptable in a swinger's action as long as the start of the release of PA#2 precedes the start of the release of PA#3. The release of PA#3 is primarily due to a left forearm rotation (supination) motion and only partially due to external rotation of the left humerus in the left shoulder socket and and it represents the release swivel action. A release swivel action doesn't happen in a hitter's swing action. When I describe a hitter's swing action, you will see that PA#2 and PA#3 release near-simultaneously because their release is being driven by the active release of PA#1 (rather than being driven by a centrifugal action).
In a swinger's action, the release swivel action causes the left hand to rotate into impact so that the back of the left hand (and flat left wrist) faces the target at impact. However, impact is simply a "captured" moment-in-time, and in real-life reality the left hand should continue to rotate after impact. However, the continued rotation of the left hand post-impact is not due to independent left forearm rotation, but due to counterclockwise rotation of the entire left arm (left upper arm and left forearm) due to external rotation of the left humerus at left shoulder socket level. That counterclockwise rotation of the entire left arm causes the back of the left hand to rotate horizontally so that the FLW remains vertical to the ground and this phenomenon is called horizontal hinging. If the release swivel action (rollover release of PA#3) blends seamlessly with a horizontal hinging action, then the clubface will close steadily through impact (through the 1/4000 second time period when the ball remains in contact with the ball) and that steady clubface closing action allows the clubface to maximally compress the ball. If one doesn't employ horizontal hinging, but uses either an angled hinging or vertical hinging action, then the clubface will not be closing steadily through impact. This will result in power leakage and prevent maximum ball flight distance (for a given clubhead speed at impact). I will discuss this hinging issue in greater detail in the next section on the swinger's swing action.
Swinger's swing action - the biomechanics
I have previously stated that a swinger releases three power accumulators in a set sequence - 4:2:3. The release of PA#2 and PA#3 occurs passively (secondary to the centrifugal release phenomenon - a phenomenon of physical mechanics previously explained in the double pendulum swing model explanation). That means, from a power perspective, that a swinger needs to concentrate his effort on how best to actively release PA#4. There are different golf swing styles that a swinger can adopt, and they use different biomechanical methods of actively releasing PA#4.
The most common method of actively releasing PA#4 is the pivot-driven swing and it is the method used by the majority of PGA tour players.
What happens in a pivot-driven swing? Basically, a swinger pivots his torso in space in a rotational manner so that the upper torso rotates counterclockwise (as seen from above). When the swinger loads his PA#4 at the top/end of the backswing, the upper left arm gets loaded against the left pectoral area and pressure is felt at pressure point #4. During the first part of the pivot-driven downswing, when the upper torso rotates counterclockwise, the left upper arm temporarily remains in contact with the left pectoral area of the chest wall - which means that there is an increased sense of loading pressure at PP#4 and there is consequently no release of PA#4 in the early downswing. At a certain time-point in the downswing, the upper torso decelerates (speed of upper torso rotation decreases) and the inert left arm is catapulted passively away from the upper torso into a freewheeling left arm swinging motion. That represents the release of PA#4. Homer Kelley states in his TGM book , that one should "consider Pivot Thrust as Body Power blasting a Swinger's essentially inert left arm into orbit toward Impact". When a golfer initiates a pivot-driven release of PA#4, the pivot action usually starts with a pelvic shift-rotation movement, which is then immediately followed by an upper torso rotational movement. Many TGM swingers start the upper torso's rotary motion with an assertive thrust motion of the right shoulder in a downplane direction. That right shoulder thrust action causes the entire upper torso to rotate as a single unit, and the left arm is then passively pulled forward by the rotating upper torso.
Basically, there are three general types of pivot-driven swinging actions - i) an upper body swinging action where the lower body remains static and the swinger rotates only his upper body; ii) a total body swinging action where the golfer rotates his lower and upper torso at the same rotational speed - exemplified by Jim Hardy's one-plane swing (Hardy OPS); and iii) a lower body swinging action where the lower torso (pelvis) turns first followed sequentially by a secondary rotation of the upper torso (shoulders) - exemplified by Ben Hogan's and Tiger Woods swing style.
Many beginner golfers who use a pivot-driven swing unintentionally use an upper body swinging action because they have not learnt how to pivot-rotate their pelvis correctly in the backswing and/or downswing. They can still release PA#4 effectively with a great deal of force and they can often generate a great deal of clubhead speed at impact. However, they often don't hit the ball as far as they potentially could (for a given speed of release of PA#4) because their clubhead swingpath is *out-to-in and this causes the clubface (if it faces the target at impact) to hit the ball with a glancing blow that results in slice spin. If they have their clubface oriented in the same direction as their out-to-in clubhead swingpath at impact, then they will pull the ball left. The ball will often go a long way (if they rotate their upper torso at a fast speed and release PA#4 very efficiently), but the ball will likely end up in the rough well left of the left edge of the fairway. I therefore recommend that a body-swinger adopt a total body swinging action or a lower body swinging action - if physical limitations don't make this choice impossible - and they should try to avoid becoming an upper body swinger.
[* side issue - see my downswing chapter to understand why an upper body swing style usually results in an out-to-in clubhead swingpath]
There are a number of golf instructors who teach a rotary swing where the primary mantra is ABT (always be turning). That mantra applies to the rotating torso and rotary swingers primarily focus their attention on performing a fluid torso rotary movement. The prototypical rotary swing is the Hardy One-Plane Swing (Hardy OPS). If you are interested in learning the Hardy OPS, you can read his books   or purchase his DVDs .
Here is a link to a swing video of Jeff Ritter performing the Hardy OPS.
Jeff Ritter performs the Hardy OPS exceptionally well. He pivots very fluidly. Note his bent-over posture, which is very characteristic of a Hardy OPS golfer. It takes a great deal of flexibility and athleticism to perform the Hardy OPS as efficiently and fluidly as Jeff Ritter - because one has to rotate the upper and lower torso simultaneously at a fast speed.
Here is a series of capture images from that swing video.
Jeff Ritter - Release of Power Accumulator #4
Image 1 shows Jeff Ritter at the top of the backswing with his PA#4 fully loaded. What is characteristic of a good Hardy OPS golfer is how fast and assertively they rotate their torso at the start of the downswing. They generally rotate their upper and lower torso as a single rotating unit, and they rotate their torso so fast that the left arm remains in contact with their left pectoral area (pressure point #4) in the early/mid downswing (image 2). Release of PA#4 is delayed until the late downswing (image 3). However, although a Hardy OPS golfer has a delayed release of PA#4, he still has a swinger's swing action because PA#2 is released passively via a centrifugal action (double pendulum swing action model) and the PA release sequence is still 4:2:3. The arms are essentially passive in the Hardy OPS and PA#1 is not actively released in a hitting manner. In a revised version of his Hardy OPS (first described in his second book), Jim Hardy recommends an active right arm throw action at the very start of the downswing. However, this right arm throw action is not intended to drive load the clubhsaft (using a hitter's axe handle technique). Rather, it allows the right arm to keep up with the left arm during the pivot-driven downswing (during the time period when the power package assembly remains intact), and it allows the right arm to also maintain continuous extensor action at PP#1. If the right arm keeps up with the left arm, then the straightening action of the right arm in the late downswing, which causes the right forearm to paddlewheel into impact, can synergistically assist in the efficient release of PA#3.
The quintessential pivot-driven swinger's style is the Ben Hogan lower body swing style and that swing style is used by the majority of PGA tour players eg. Tiger Woods.
The characteristic feature of the Hogan lower body swing style is that the pivot action starts from the ground-up with the lower body rotating first and the upper torso secondarily.
I have produced this crude hand-drawn diagram to demonstrate certain kinetic features of the lower body swing style.
Kinetic sequence in a pivot-driven swinger's swing action
This diagram does not represent any true measurements obtained from a pivot-driven swinger who uses a lower body swing style, and it is not drawn to scale. It is merely designed to be representational of certain kinetic phenomena that occur in a swinger who uses a lower body swing style (ala Ben Hogan). Time is on the X axis. The intersection point between the X axis and Y axis represents the start of the downswing. Rv stands for rotational velocity (or angular velocity) and it roughly demonstrates the speed of rotation of the lower body (pelvis), upper body (shoulders) and left arm at different time points in the downswing. I have truncated the deceleration parts of the curves.
The first diagram represents the perfected lower body swing style - as exemplified by a swinger such as Ben Hogan or Tiger Woods. The downswing starts with a lower body (pelvis) rotation followed shortly thereafter by an upper body (shoulder) rotation - and this increases the degree of torso-pelvic separation in the early downswing (increases dynamic X-factor). The diagram suggests that the pelvis only starts rotating at the start of the downswing, but many good PGA tour players (like Tiger Woods) actually start rotating the pelvis forward even while the club is moving back to its end-backswing position. The diagram shows that at a certain time-point in the downswing, that the pelvis rotation will naturally decelerate and that the shoulder rotation will naturally decelerate a short time later. I do not want to discuss the biomechanical factors that cause deceleration of the pelvis/shoulders in this review paper. I merely want a reader to note that when the upper torso (shoulders) decelerate that the left arm will continue to rotate at a faster speed (because it has acquired enough energy to continue to acclerate throughout the late downswing) - and that this represents the release of PA#4. The left arm will eventually decelerate in the last phase of the downswing when PA#3 releases.
The second diagram represents the kinetic sequence of a swinger who uses the Hardy OPS swing style where the entire torso rotates as a single unit - ala Jeff Ritter's swing. The left arm remains in contact with the left pectoral area during the early/mid downswing and PA#4 only releases when the pivot subsides thus allowing the left arm to swing freely towards impact, and then through the impact zone.
Note that the slope of the left arm speed graph does not steepen after the shoulders slow down in a pivot-driven swing. In other words, the left arm does not accelerate at a faster speed at this time point - the left arm simply continues to move at roughly the same rate of acceleration it had acquired during the time period when it was being driven by the rotating upper torso (which applied constant push-pressure at pressure point #4). When the shoulders decelerate, the left arm can continue to swing freely and faster across the front of the body towards impact because there is no impedance to the free movement of the left arm across the front of the body.
The speed of movement of the left arm during the late downswing depends on the speed of rotational movement of the rotating upper torso in the early-mid downswing - because the left arm is inert and it acquires nearly all its energy from the rotating torso (with only a small amount of energy being supplied by the left shoulder girdle muscles). The faster the torso rotates, the faster the left arm speed, and the faster the ultimate clubhead speed at impact. If a pivot-driven swinger wants to hit the ball a long way, then he needs to rotate his upper torso faster in the early-mid downswing so that he can release PA#4 with a greater amount of velocity.
Here is a swing video of a golfer - Jamie Sadlowski - who won the 2008 World Long-Drive Competition. You can see why he can drive the ball a long way - because he rotates his upper torso super-fast in the early/mid downswing and that super-fast upper torso rotation induces his left arm to swing at a very fast speed towards impact (due to the release of PA#4).
A lower body swinger can induce PA#4 to release even earlier (before the upper torso rotation decelerates) if the upper torso rotates very fast in the early downswing and catapults the left arm off the chest wall - "essentially blasting the inert left arm into orbit". This phenomenon is more likely to occur if the golfer starts the downswing with an assertive thrust of the right shoulder downplane that triggers an earlier release of PA#4. However, an assertive right shoulder thrust that occurs independently of the speed of rotation of the entire upper torso can cause a more jerky, and too-fast release of PA#4 and a swinging left arm that travels too fast relative to the rotating torso. If the left arm swings too fast relative to the speed of rotation of the upper torso, then the left arm will whip through the impact zone too fast (relative to the rotating torso) and flip around the torso to the left - predisposing to duck-hooked (snap-hook) shots. A swinger needs to execute his pivot-driven swing very smoothly so that there is no asynchrony between the speed of movement of the upper torso and the speed of movement of the left arm across the front of the body during the downswing.
Look at how smoothly Ben Hogan rotates his upper torso in this swing video lesson - even though he starts the downswing with a lower body rotation.
If you study the swing videos of PGA tour players using a swing analyser program, you will be able to discern the exact pattern of left arm release (PA#4 release) in that individual golfer.
Here is a link to a swing video demonstration of Ben Hogan's PA#4 release pattern.
In the swing video lesson video of Ben Hogan (that I just mentioned) one can see that Ben Hogan's PA#4 release action starts in earnest when his hands get down to about waist level. The reason for the delayed release is that Ben Hogan had an assertive lower body swing action that pulled his intact power package assembly down to waist level - Ben Hogan often stated that his "arms/hands get a free-ride" when he started the downswing with a lower body swing action and his pivot action pulls his entire power package assembly (loaded PA#4 and loaded PA#2) down to waist level, thus delaying the release of PA#4. Note how the angle between the left arm and the upper torso (and distance between the hands and the right shoulder) doesn't increase in the early downswing.
At the opposite end of the spectrum to Ben Hogan's PA#4 release pattern is a PA#4 release pattern where the left arm is pulled away from the chest wall as soon as the downswing starts - and this pattern is characteristic of an arm swinger (ala Leslie King).
Here is a link to Leslie King's opinions on his method of starting the downswing with a pulling of the left arm downplane while keeping the shoulders back.
Here is a copy of Leslie King's instructional statements from that lesson.
Now, maintaining the shoulders in the fully turned position, we simply commence the downward swing of the left hand and arm. That is how the downswing starts, and nothing could be simpler!
I stress again, the SHOULDERS MUST REMAIN IN THE FULLY TURNED POSITION at the beginning of the downswing! The same left foot action that has "charged" the hands with power is enabling us to control the shoulders.
By keeping the shoulders fully turned the left hand and arm can swing freely from the left shoulder, taking the club-head down into the ball on a club line that will result in a swing into and along the line of flight through impact.
Hold your shoulders in the fully turned position as the left hand and arm begins to swing down... this ensures good club line through the ball.
In other words, Leslie King recommends the immediate release of PA#4 at the very start of the downswing - while keeping the shoulders back. There is no pivot-thrust action in his swing methodology and the torso pivots reactively to support the movement of the left arm across the front of the body. The Leslie King swing methodology works reasonably well and it is a very legitimate way of powering the release of PA#4 - it may be especially useful for elderly, inflexible golfers who cannot perform a body pivot action efficiently. However, one cannot hope to win the World Long-Drive Competition using a left arm swing pattern, because a left arm pulling action (due to the active muscle contraction of left shoulder girdle muscles) cannot propel the left arm forward with as much speed as a world-class pivot-driven swinger can propel his left arm towards impact. The rotating upper torso is a tremendous energy source for inducing a powerful release of PA#4.
Many golfers believe that the standard body-pivot method of releasing PA#4 (ala Tiger Woods) is superior because one can torque the upper body against the resistance of the lower body during the backswing if one deliberately restricts the rotation of the lower body during the backswing. This is the basis of Jim McLean's static X factor theory - the theory that swing power can be increased by increasing the degree of torso-pelvic separation during the backswing. I have personally studied the scientific literature supporting this theory's fundamental belief in great depth, and I find the scientific evidence very unconvincing in terms of scientific conclusiveness. I believe that alternative body-pivot swing styles work equally well in terms of releasing PA#4 efficiently. Consider the classic body swing styles of Sam Snead and Phil Mickelson - they both allow their pelvis to rotate freely in the backswing and they can hit the ball as far as golfers who utilise the X-factor principle of torquing the upper body against the resistance of a lower body's restricted backswing turn.
The reason why they can both drive the ball a long way is because they have a full backswing that allows for a complete loading of power accumulator #4 (left arm loaded against the left upper chest wall during the backswing). They also have a superb downswing pivot action that allows them to fully and efficiently release power accumulator #4. If a golfer can get the left arm to swing freely and fast towards impact in the downswing, then he will hit the ball a long way.
A very convincing demonstration of how effectively one can release PA#4 without using the X-factor principle can be seen in Shawn Clement's one-leg swing video lesson.
Here is a composite capture image from that swing video lesson.
Shawn Clement's one-leg swing action
Note how freely Shawn Clement rotates his pelvis back during the backswing. He essentially has zero X-factor in his swing because he rotates his pelvis back as far as he rotates his shoulders. Yet, he can still hit the ball over 200 yards with his five-iron while swinging in this manner. If you watch his swing action in that swing video, you will understand why - it is because he loads PA#4 adequately during the backswing and unloads PA#4 very efficiently during the downswing, thereby allowing the left arm to swing at an adequate speed in the late downswing.
The important learning point, from a developing golfer's perspective, is that a swinger primarily needs to release PA#4 fluidly and efficiently and produce a free flowing left arm swing that reaches its maximum speed in the late downswing (and not the early downswing).
The timing of the release of PA#4 (the time point when the left arm separates away from the chest wall) can be early (in a left arm swinger's action ala Leslie King) or late (as in the Hardy OPS swing) or intermediate (ala Hogan's swing) and it depends on the mechanism of releasing PA#4. The main learning point is that a swinger needs to get the left arm swinging freely, and that left arm speed must progressively increase during the early-mid downswing and only reach its maximum speed in the later downswing. Over-acceleration of the left arm during the early downswing must be avoided. Left arm speed must smoothly increase until it reaches a maximum speed in the late downswing and it then needs to decelerate slightly prior to impact - so that there is enough time to complete the release of PA#2 and especially PA#3 (so that there is enough time to complete the release swivel action).
I previously stated that a swinger uses a triple barrel swing action and that he releases PA#4 and then PA#2 and then PA#3 in that set sequence. I also stated that the release of PA#2 is passive and due to centrifugal forces. I will now discuss the release of PA#2 in greater depth.
The release mechanics/physics of PA#2 is a complex subject and I have produced a 20 minute swing video presentation on that subject. I created a home made studio by simply hanging a painter's dropcloth in front of my garage door and I used my cheap camcorder to make this amateurish video lesson presentation. Hopefully, you can hear my voice clearly despite the background noises. The background noises were from construction workers who were repairing my neighbour's roof, and I didn't originally think that my cheap camcorder's microphone was sensitive enough to pick up those extraneous noises. However, I was obviously wrong!
This 20 minute swing video lesson is divided into three segments that must be viewed consecutively.
Segment 1 http://www.youtube.com/watch?v=jhAIx-DcbeU
Segment 2 http://www.youtube.com/watch?v=dxl90OLrCvo
Segment 3 http://www.youtube.com/watch?v=3BA4cE56Vfw
I am going to emphasize certain points (that I made in the swing video) in this next section on the release of PA#2.
Release of power accumulator #2
The first point that a swinger must understand is that PA#2 is released passively due to a centrifugal action and not due to any active uncocking left wrist actions. A golfer should not deliberately uncock the left wrist by using left forearm muscle power, and the left wrist should be very relaxed so that it does not impede the passive centrifugal-induced release of PA#2.
I used a double pendulum swingle stick contraption in that swing video presentation to demonstrate that passive release of PA#2 is due to the fact that the peripheral hinge joint (left wrist) moves in a circular direction in the downswing, and that passive release would not occur if the peripheral hinge point (left wrist) pull action occurred continuously along the longitudinal axis of the peripheral arm (clubshaft) - a continuous straight line pull action directionally in-line with the clubshaft. The degree of centrifugal force developed when the peripheral hinge point (left wrist) moves in a non-straight line direction is dependent on the i) degree of the change of direction of the pulling force and ii) the abruptness of the change in direction and the iii) amount of pulling force (due to hand speed) being exerted at the exact moment in time when the left wrist abruptly changes its direction of movement. One can therefore use the insights gained from studying the release pattern of a double pendulum swing model to understand why the club releases differently in different golfers. Consider a few examples.
If a beginner golfer starts the downswing with i) a very assertive pulling force exerted at the level of the left wrist from the very top of the swing and ii) he moves his left wrist down to the ball in a wide sweeping circular arc, then the club will start to release immediately. Once the club starts to release one cannot hold the club back. This early release (from the very start of the downswing) is called clubhead throwaway (casting) and the resultant release pattern will be a sweep release. In other words, the early release is due to over-acceleration of the hands at the start of the swing combined with a circular pattern of hand movement.
To achieve a later release a golfer needs to i) not exert much pulling force at the level of the left wrist in the early downswing and ii) let the left wrist move in a more straight line direction during the early-mid downswing and iii) ensure that maximum left arm/hand speed occurs at the time point when the left wrist is abruptly changing direction (changing direction to a more circular motion with a small radius = tight curve) during the later mid-downswing.
Consider Sergio Garcia's club release action - he has a very late release (often called a snap release).
Sergio Garcia's late release pattern - capture images from a swing video
Image 1 shows Sergio Garcia at the top of his backswing with PA#2 fully loaded - note the 90 degree angle between the clubshaft and the left arm.
Image 2 shows Sergio Garcia in the early downswing. He has started the downswing with an assertive pelvic shift-rotation movement that gets him to a hip-squared position. This lower body motion actually starts while the club is still moving back to its end-backswing position, and during this time period Sergio is not pulling his left arm rapidly down to the ball. Many PGA tour players state that they "feel" that they are leaving their club behind at the start of the downswing - during the time period when they are actively shift-rotating their pelvis to the left (time period of maximum pelvic rotational speed). Note that the angle between Sergio's clubshaft and his left arm has become even more acute at this time point and that phenomenon is partly due to the fact that Sergio has very relaxed wrists at the exact moment when his left hand/wrist is not being pulled very fast down towards the ball. That allows the weight of the clubshaft/clubhead to be affected by gravity and this contributes to the clubshaft-left arm angle becoming more acute.
Image 3 shows Sergio Garcia at his late release position. I used a spline tool to trace his left hand/wrist movement during the early-mid dowswing. One can see that Sergio's hand arc is U-shaped and that the middle section of the U-shape is close to a straight line. In other words, during that early-middownswing time period, the passive centrifugal releasing force that can potentially induce a release is minimal because the left wrist pulling action is directed roughly along the longitudinal axis of the clubshaft. Then, note how Sergio's hand arc abruptly changes direction when his hands pass his right thigh. At that time point, his left hand/wrist (which is merely the peripheral end of his left arm) is traveling at its maximum speed - see the hand-drawn diagram above to understand why the left arm is travelling at its maximum speed at roughly that time point in the downswing - if the kinetic sequence evolves in an optimally efficient manner. If Sergio's hands are moving at their maximum speed at the exact moment when the hand arc's motion has it smallest radius, then the passive physical force inducing a centrifugal release is at its maximum value, and that fact accounts for Sergio's ability to execute a late snap release.
What a beginner golfer, who uses a swinger's pivot-driven swing action, needs to understand is that he must get his kinetic sequencing action optimised so that the left wrist pulling action speed is maximum at the exact time point when his left hand arc's circular motion is at its tightest (smallest radius) - if he wants to achieve a late release (like Sergio Garcia).
How can a beginner golfer mimic Sergio's U-shaped left hand swingarc? The issue is complex because it involves the complex arc-of-movement of the left shoulder socket in space during the downswing, which is affected by the timing of lower body versus upper body movement and the timing of the secondary development of secondary axis tilt. As a general guideline, here is an useful method of influencing the U-shape of the left hand arc during the downswing.
The first element that a golfer, who uses a pivot-driven swinger's action, must get correct is his kinetic sequencing, so that his lower body shift-rotates to the left while his left hand/clubshaft "feel" like they are being left behind. That lower body left-lateral shift action should also create the secondary axis tilt necessary for an optimal left hand pull down action - directed by using the aiming point concept. Look at image 2 - note how Sergio's lower body shift action has produced secondary axis tilt and note that he is in a good position to pull his hands straight down towards the ball.
What do I mean by the statement "pull the hands straight down to the ball"?
The concept of pulling the hands straight down to the ball is a TGM concept , which Bobby Clampett emphasizes in his book . Here is a photo from that book.
Bobby Clampett aiming - from reference 
One can see that Bobby Clampett is aiming his eyes at a point about 4" inches ahead of the ball. He states that the aiming point concept applies to the hands - that one should aim one's hand thrust action in a straight line direction towards the aiming point so that one can get one's hands on that line at impact, thereby ensuring that the hands lead the clubhead into impact. In other words, a golfer should attempt to pull his hands in a straight line direction down towards the aiming point. Of course, it is not really possible to pull the left arm in a straight line direction down towards the aiming point - because the left arm, which is suspended from the left shoulder socket, has to move in a circular manner. However, the left shoulder socket is constantly moving leftwards during the downswing and therefore the left hand (which is merely the peripheral end of the straight left arm) must move in a U-shaped manner during the downswing. An U-shaped curve has a relatively straightish upper section and a more rounded lower section. Each individual golfer will generate a different U-shaped curve.
Here is a capture image of a superb golfer who has a more rounded U-shaped hand arc (compared to Sergio Garcia) and this results in a random release pattern.
Swing video of Anthony Kim - http://www.youtube.com/watch?v=oqmejmw-lu4&NR=1
Anthony Kim's hand arc - capture image from a swing video
One can see that Anthony Kim's hand arc movement pattern is more rounded than Sergio Garcia's (in the previous photo) and he therefore releases his club earlier - note that he has already lost the 90 degree angle between the left arm and clubshaft before his hands pass the front of the right thigh.
I don't think that a beginner golfer should obssesively attempt to acquire a late release action (like Sergio Garcia's late release action) because there is very little time in the late downswing to get the club to release fully so that the clubhead can become square by impact. It may be better to mimic Anthony Kim's random release pattern.
Each beginner golfer should experiment to find which release pattern works best for him. It is dependent on many biomechanical and alignment factors - efficacy of the lower body's shift-rotation movement in the early downswing, degree of secondary axis tilt developed in the early downswing, hand speed pattern during the downswing, degree of left wrist tension, length of the clubshaft and ball position.
Here is a photo of Aaron Baddeley's hand arc (old swing).
Aiming point concept - capture image from an Aaron Baddeley swing video
One can envisage Aaron Baddeley aiming his straight line hand thrust motion towards an aiming point well ahead of the ball - yellow arrowed line. That allows him to generate a distinct U-shaped handarc.
If a beginner golfer attempts to aim at an aiming point well ahead of the ball and finds that he cannot square the clubhead by impact (because of physical limitations and/or inefficiencies in his kinetic sequencing), then he should use an aiming point further back - blue arrowed line. That will produce a more rounded U-shaped handarc and an earlier release pattern, which may be particularly useful for longer clubs which have a wider clubhead swingarc eg. driver.
Whatever release pattern a golfer uses in his swinger's action - the fundamental rule is that the release of PA#2 must be passive, and not primarily due to any active left wrist uncocking action or any push action from an active release of PA#1 (actively straightening right elbow).
Release of power accumulator #3
The release of PA#3 is also passive and it should happen naturally without any need for a conscious thought-action.
How does the release of PA#3 happen in a swinger's swing action?
To understand the release of PA#3, one first needs to understand that a swinger should always incorporate a start-up takeaway swivel action in his takeaway action. There are two major swivel actions in a swinger's backswing/downswing action - i) during the backswing's start-up takeaway swivel action the left forearm rotates clockwise and this rolls the left hand (pronates the left hand) and ii) during the release swivel action phase of the downswing the left forearm rotates counterclockwise thereby reversing the roll action of the left hand (reverses the pronation that occurred during the takeaway swivel action). To understand this concept, first consider consider the takeaway swivel action.
The takeaway swivel action and the release swivel action can be clearly seen in this swing video of Anthony Kim's swing.
Anthony Kim is a quintessential swinger and he has a superb swinger's action.
Anthony Kim - takeaway and release swivel actions
Image 1 shows Anthony Kim at address. At address, his left humerus is neutral (neither internally rotated or externally rotated at the left shoulder socket joint). His left forearm is also neutral (neither pronated or supinated) and the back of his left hand faces the target.
At the end of the takeaway (image 2) his left hand (and therefore clubface) has undergone a 90 degree rotation so that the back of the left hand approximately faces the ball-target line. That left hand rotation is due to two factors - i) some internal rotation of the left humerus at the left shoulder socket joint, which is made easier due to the fact that the left shoulder socket is simultaneously moving down-and-around to the right; and ii) some clockwise rotation of the left forearm (a pronatory movement of the left forearm).
Image 3 shows Anthony Kim at the delivery position in his downswing - his clubshaft is parallel to the ball-target line, parallel to the ground, and along the toeline. Note that the club's toe is pointing upwards and that the back of the left hand is roughly facing the ball-target line. That means that from a biomechanical perspective he is in the same position where he was at the end-takeaway position (his left forearm is slightly pronated and his left humerus is slightly internally rotated at the level of the left shoulder socket joint). From the delivery position to the impact position, his left hand must undergo a 90 degree rotation so that the back of his left hand faces the target at impact - and this 90 degree rotation represents the release swivel action. Image 3,4,5 shows how the back of the left hand (and clubface) rotates 90 degrees into impact and this represents the passive release of PA#3 (plus passive release of PA#2 because the left wrist is also uncocking during the release swivel phase of the downswing). During the release swivel action, the left humerus is externally rotating at the level of the left shoulder socket and the left forearm is rotating counterclockwise (left forearm is undergoing a supinating = reverse-pronating roll-over action). These biomechanical actions happen naturally/automatically/passively as the left humerus/left forearm rotate back to their neutral positions by impact, and these biomechnical actions do not require a conscious thought action. In other words, a golfer does not have to think of actively releasing PA#3. Instead, he should merely let the release swivel phenomenon happen without interference (eg. an example of interference = actively resisting the roll action of the left hand into impact by deliberately trying to keep the clubface open through the impact zone - which can conceived to be a "steering" action, or "holding the clubface open" action, that should be avoided).
Note how the right elbow straightens progressively during the release swivel phase of the downswing. The right elbow straightening is NOT due to an active release of PA#1, but it is due to enough right triceps isotonic muscle action that allows the right hand to keep up with the left hand. Note how Anthony Kim's right forearm is "on-plane during the late release swivel phase of the downswing - it is aligned in-line with the clubshaft along the elbow plane line at impact (see my review paper on the swingplane to understand the subject of plane lines and the concept of being "on-plane"). If the right forearm is on-plane at this stage of the downswing, then it will cause the right palm to face the target as the hands reach their impact location. In other words, the on-plane movement of the right forearm synergistically helps to direct the accurate/timely release of PA#3 (roll-over rotation of the left hand) into impact.
Now consider a very important point about the release of PA#3.
Consider this composite image from the slow motion swing video of Tiger Woods' swing .
Capture images from the Nike commercial of Tiger Woods' swing
This video was captured at 4,000 frames/second (which is 8x the speed of the BizHub Swing Vision camera that apparently operates at 500 frames/second). I used the spline tool in my swing analyser program to follow the sequential movement of Tiger's lower left arm in the late downswing (from just before the delivery position to the impact position) - each white dot represents 10 frames, or 1/400th second. One can therefore see how fast Tiger's left arm is moving during the late downswing. Note that the white dots get closer together as he approaches impact, which means that Tiger's left arm speed is decreasing as he nears impact. This happens naturally in a skilled swinger's swing action and it occurs while the left hand is rotating into impact (due to the release of PA#3). What is the importance of this fact?
It is important that the left arm decelerate slightly in the last phase of the downswing (as the clubshaft approaches impact) for there to be enough time for the left hand to rotate into impact so that the clubface can get square by impact. If a golfer moves the left arm and therefore the hands too fast through the pre-impact zone, there may insufficient time to complete the release swivel action prior to impact, and the clubface will be open at impact thus producing a push or push-slice ball flight. In other words, a golfer must not over-accelerate the left arm/hands through the impact zone - the clubshaft must accelerate through the impact zone, but the hands have to decelerate slightly prior to impact. Over-acceleration of the hands through the impact zone is a common problem in high handicap, developing golfers - and it will predispose to a failure to complete the release action of PA#2 and PA#3 and it will result in an open clubface at impact. One of the most frequent causes of this problem is switting - a tendency for a swinger to apply an active right arm hitting action in the late downswing in an attempt to supply more power. A golfer must avoid this switting problem by preventing the right hand from providing any excessive push-force in the downswing. A swinger's action is a left-sided pull action - the left arm pulls the club's grip via the left hand (a process called drag loading), and the club release phenomenon (release of PA#2) must occur with optimum efficiency and timing so that the clubhead can reach maximum speed at impact (or just past impact when all the power accumulators have fully released their load). In my swing video lesson, I demonstrated a left arm-only swing and I demonstrated how a swinger must get his release timing correct - so that the clubshaft swishes through the impact zone (thereby getting the clubhead to travel at its maximum speed through the impact zone), and this is achieved by an optimised release of PA#4 and then PA#2 in a set sequence, and it is not due to the application of any right arm power. If one is a swinger with an optimised release of PA#4 and PA#2 that results in a very fast centrifugal release of the clubshaft in the late downswing, then there is no practical method of getting the clubshaft to travel faster through the impact zone by adding right arm power in the late downswing - the right arm/hand can only interfere with the clubshaft's motion in the late downswing if they attempt to add additional push-power.
In my swing video lesson, I demonstrate how an urge to hit with the right arm/hand at some time-point in the mid-late downswing can produce deleterious effects. There are two right arm hit actions that switters frequently use in an attempt to add more "hit power" to their golf swing, and they are both potentially destructive.
Switting - the use of a right arm hitting action in a swinger's action - from the author's swing video lesson
Image 1 demonstrates how the hands/clubshaft should appear just prior to impact in an optimised swinger's action (when the sequential release of PA#4 and PA#2/3 occurs with optimal timing). The hands should be leading the clubshaft into impact, so that clubhead lag is maintained all the way into impact. The left wrist should be flat and in-line with the straight left arm at impact. The right wrist should be slightly bent back (dorsiflexed).
Image 2 shows what usually happens if a switter tries to supply additional "right-sided hit power" by actively palmar flexing the right wrist as the hands approach impact. The straightening right wrist bends the left wrist and flips the clubhead past the hands. This is a disaster! If the flipped clubhead hits the ball, it will do so with a lack of solid compressive power (due to the loss of clubhead lag) and with a loss of directional control (it will often cause the ball to be pull-hooked left to a variable degree).
Image 3 shows what happens if a switter maintains a bent right wrist but attempts to add "right-sided hit power" by actively straightening the right arm (actively straightening the right elbow via a very active right triceps muscle contraction) in the late downswing. The actively straightening right arm pushes the left hand forward by applying push-pressure at pressure point #1 and this results in the hands being pushed too fast through the impact zone. The hands get too far ahead of the ball before the club releases completely => the clubface is open at impact => the ball is push-sliced to the right.
Essential Advice for Swingers = Do not become a Switter = Do not attempt to "hit" with the right arm/hand in the late downswing in order to produce more swing power.
A beginner golfer can easily assess whether he is using "right-sided" push power in his swing action by first performing a left arm-only swing. Grip the club firmly with the 3rd, 4th, and 5th fingers of the left hand (which are collectively called pressure point #2) and load PA#4 and PA#2 by swinging the left arm across the upper chest in a backswing motion while ensuring that there is a 90 degree angle between the left arm and clubshaft at the top of the backswing. Then swing the left arm down to impact while pulling actively on pressure point #2. Allow PA#2 to passively release and get a "feel" of the clubhead swishing at a fast speed through the impact zone. Then gently place the right palm over the left thumb with minimum pressure and repeat the downswing action making sure that the right palm does not provide any push-pressure on pressure point #1 during the downswing. If you can swing faster with a more effective centrifugal release of PA#2 (that allows the clubhead to swish at maximum speed through the impact zone) compared to your usual swing action - then you may have been a switter and your right arm/hand has been interfering with your swinger's action. The right arm/forearm should only provide enough active push-power to keep the right hand on the club to a sufficient degree that allows a golfer to use PP#3 to sense lag pressure and prevent clubhead throwaway (see role number 2 below) and with enough low-level force to apply constant extensor action throughout the downswing and followthrough.
Here is an example of "pure" drag loading - where the golfer swings with only one arm. This in an example of a golf swing where the swing is entirely powered by the release of PA#4 (pivot-driven) and where PA#2 and PA#3 release occurs passively.
Can you imagine that golfer adding right arm power to his swing by applying right arm/forearm push-pressure at some time point in the mid-downswing? How would he efficiently synchronise the left arm's pull power with the sudden supplementary application of active push power from a right arm action? I am not implying that it is impossible to be an efficient switter, but I think that it is technically much more difficult compared to being a pure swinger or a pure hitter.
Addendum added February 2011:
I have significantly revised my opinions regarding the use of the right arm in a swinger's action. I now believe that there is a subset of golfers who will perform a full golf swing better if they actively use their right arm to actively assisist in the release PA#3 +/- PA#2 in the late downswing - my latest/updated opinions regarding this issue are available in my new review paper called The Power Mechanics of Swinging, Hitting and Swing-Hitting.
The right arm/hand have a number of critically important functions in a swinger's swing action - but the right arm/hand should not be used to supply additional swing power via a push action.
The right arm/hand have three important functions to perform in a swinger's swing action and I have produced a 12 minute swing video lesson to demonstrate the role of the right arm/hand in a swinger's swing action.
I created a home made studio by simply hanging a painter's dropcloth in front of my garage door and I used my cheap camcorder to make this amateurish video lesson presentation. Hopefully, you can hear my voice clearly despite the background noises. The background noises were from construction workers who were repairing my neighbour's roof, and I didn't originally think that my cheap camcorder's microphone was sensitive enough to pick up those extraneous noises. However, I was obviously wrong!
The 12 minute swing video lesson is divided into two segments that must be viewed consecutively.
Segment 1 http://www.youtube.com/watch?v=vizRrBGfiSs
Segment 2 http://www.youtube.com/watch?v=Kc07lLEPyOo
The right arm/hand have three major roles to play in a swinger's swing action.
Role number 1 - Extensor action
In my swing video lesson, I demonstrate how the lifeline of the right palm rests over the left thumb in the standard grip - and the right palm is therefore capable of applying push-pressure force at pressure point #1. Extensor action is applied at address by a gentle straightening action of the right elbow (straightening of the right arm as a result of gentle right triceps muscle activity) which causes the right palm to apply a slight push-force at pressure point #1 => this push-force pushes the left thumb, and therefore the left hand, away from the left shoulder socket thereby pulling the left arm straight. The amount of force being applied is very small - equivalent to tugging on the left sleeve of your shirt to straighten the left shirt sleeve when wearing a jacket that has crumpled up the left shirt sleeve.
Extensor action is a small force that is applied continuously throughout the entire backswing and downswing, and it keeps the left arm continuously straight.
Extensor action force in play during the backswing
In my swing video lesson, you can see that my left arm bends readily at the left elbow joint when I swing the small, lightweighted club with my left arm alone (image 1). That's because I am resisting any tendency to "artificially" straighten my left arm by tensing up the muscles of my left arm. When I swing with both arms, you can see that I can more readily keep my left arm straight by applying an extensor action force at pressure point #1 (image 2). Extensor action is applied continuously throughout the backswing when a golfer gently attempts to straighten the right elbow - even while the right elbow is folding during the backswing. Extensor action is also applied during the entire downswing, but the amount of extensor action force required becomes progressively less as the downswing proceeds because the centrifugal-induced release of the club has a synergistic "effect" in helping extensor action keep the left arm straight.
Role number 2 - Sensing clubhead lag
During the backswing, a flexible swinger frequently tries to get his club to the end-of-the-backswing position - where the clubshaft is parallel to the ball-target line.
Tiger Woods and Adam Scott at the end-backswing position - capture image from a swing video
Note that Tiger Woods and Adam Scott have the flexibility to get to the end-of-the-backswing position - where the hands are behind the right shoulder and the clubshaft is parallel to the ball-target line. That's a very desirable end of backswing position when hitting a driver or long iron. In that end-backswing position, note that the right forearm is vertical to the ground and the right palm faces the sky - like a waiter holding up a tray of dishes. In that position, the grip end of the clubshaft is resting on the right palm.
Capture photo from the author's swing video lesson
In this photo, I am demonstrating the position of the right hand at the end-backswing position. The right palm faces the sky and the grip end of the club rests on the right palm and against pressure point #3. In other words, an advanced golfer can sense a "feel" of pressure at pressure point #3 at the end-of-the-backswing position due to the weight of the clubhead (due to the effect of gravity on the club). When the downswing starts, the hands are pulled down towards the ball and this motion increases the sense of lag pressure at pressure point #3 because the clubhead has inherent inertia and it momentarily resists any tendency to be pulled down towards the ball. During the entire downswing, the clubhead is always lagging behind the hands and a sense of clubhead lag pressure is always felt at pressure point #3 (which is always under or behind the shaft). The amount of lag pressure felt at pressure point #3 during the downswing varies at different time-points - and it is maximum when the hands are travelling at maximum speed (usually in the mid-downswing). After the club starts to release, the sense of lag pressure diminishes because the clubhead is propressively catching up to the hands. However, a sense of lag pressure at pressure point #3 is never lost during the late downswing because the clubhead always lags behind the hands and the clubhead never passes the hands. If the clubhead passes the hands (a condition called clubhead throwaway) the sense of lag pressure is lost. This happens frequently in high handicap, developing golfers who over-accelerate their hands at the start of the downswing and swing their hands in a circular arc out-and-away from their body - this causes clubhead throwaway (casting) and a loss of clubhead lag pressure at pressure point #3. Advanced golfers can develop a heightened awareness of a sense of lag pressure at pressure point #3 and this can help them avoid the problem of clubhead throwaway, or premature release of the club. A heightened awareness of the sense of clubhead lag pressure at pressure point #3 also allows an advanced golfer to swing at variable speeds in a controlled fashion. Annika Sorenstam has stated that she normally swings her driver at a swing speed level of 6 on a scale of 1-to-10, and she has presumably developed an acute sense of the required amount of "felt" clubhead lag pressure at pressure point #3 for that particular swing speed. If she wants to swing faster (eg, at a level of 8 on a scale of 1-to-10) in order to hit the ball further, she can use a "felt" sense of increased lag pressure at pressure point #3 to monitor, and thereby modulate, her arm swing speed.
Role number 3 - Keeping the clubshaft on-plane
The right forearm and right hand conjointly act in a manner that allows the golfer to keep the clubshaft on-plane during the backswing and downswing. I demonstrate this process in my swing video lesson.
Here is a golfer who has his clubshaft on-plane during the entire downswing.
Anthony Kim's on-plane clubshaft during the downswing - capture images from a swing video
A clubshaft is on-plane when the end of the clubshaft nearest the ground always points at the ball-target line (or an extension of the ball-target line) - except when the clubshaft is parallel to the ball-target line.
If one looks at the yellow dotted lines in those capture images of Anthony Kim's downswing, you can see that they always point at the ball-target line (or its extension) - you have to use your mental capacity for 3-D mental imagery when mentally projecting the direction of that dotted yellow line, because when the clubshaft is not parallel to the surface of the photo, the yellow dotted line projects into, or out of, the photo). That indicates that Anthony Kim's clubshaft in on-plane during the entire downswing. It's the controlled three-dimensional movement of the right forearm/bent right wrist unit (RAFW) that keeps the clubshaft on-plane. I discussed this complex on-plane issue in great detail in my How to Hit the Ball Straight review paper. A golfer has to learn how to fold/unfold the right elbow and bend the level right wrist in a controlled manner during both the backswing and downswing, so that he can always keep the right index finger's first joint area (pressure point #3) pointing at the straight plane line throughout the downswing - PP#3 must trace the straight plane line (which is the base of the inclined plane, and also the ball-target line when a golfer has a square stance).
Now, there is another aspect of a swinger's swing action that requires detailed discussion - the overall swing pattern.
A swinger's swing pattern is very different to a hitter's swing pattern in the sense that a swinger uses three swivel actions and a horizontal hinging action, while a hitter doesn't use any swivel actions and he uses angled hinging.
Swinger's swing pattern
I have produced a swing video segment to illustrate the swing pattern of a swinger's swing action.
Swinging action http://www.youtube.com/watch?v=6AdzRVKUa8g
I have used my friend Scott as a subject, and he is demonstrating the swinger's swing pattern. I am providing the audio commentary in this swing video segment. I repeated the entire process twice so that a viewer could experience a repeat viewing of the entire swing pattern.
Swinger's swing pattern video lesson
Swinging pattern in a swinger - capture images from a swing video
This series of capture images from Scott's swing video presentation demonstrates the different phases of a swinger's swing pattern, which occur in the following sequence:- takeaway swivel action (image 1) => clubshaft moves up-plane to the end-backswing position (image 2) => clubshaft moves down-plane to the delivery position (image 3) => release swivel action delivering the clubshaft to impact (image 4) => horizontal hinging action to the end of the followthrough (image 5) => finish swivel action (image 6).
Image 1 - this demonstrates the start-up takeaway swivel action. Note that the back of the left hand, and therefore the clubface, roughly points at the ball-target line at the end of the takeaway - and this represents a 90 degree rotation of the left hand during the start-up takeaway swivel action. See my backswing chapter for more details.
Image 2 - shows the end of the backswing position. The right forearm is nearly vertical to the ground and the right palm is under the clubshaft. Scott has a slightly shortened backswing action relative to Tiger Woods/Adam Scott's driver swing - his clubshaft doesn't quite get to the parallel-to-the-target line position.
Image 3 - shows how the back of the left hand moves down the inclined plane line during the mid-downswing so that the back of the left hand is parallel to the surface of the inclined plane. His clubshaft is on-plane - because the butt end of the club is pointing at the ball-target line. His clubshaft is cutting across the lower half of the right upper arm - indicating a shallow clubshaft attack angle (roughly on the elbow plane line). Moments later, he will reach the delivery position - where the clubshaft will be parallel to the ground and parallel to the ball-target line. See my swingplane review paper for further details.
Image 4 - shows the hands approaching impact. The back of the left hand faces the target, which means that the left hand, and clubface, underwent a 90 rotation during the release swivel phase of the downswing.
Image 5 - shows the roll-over of the clubface so that the clubface is vertical to the ground (toe of the club has rotated 90 degrees relative to its impact position). The roll-over of the clubface is due to the biomechanical process of horizontal hinging. See my impact chapter for further details on hinging actions.
Image 6 - finish swivel phase where the left elbow folds slightly while the left hand supinates so that the back of the left hand lies against the surface of the inclined plane. See my followthrough chapter for further details.
A swinger must go through all these swing action phases in a standard swinger's swing pattern.
Here is a swing video of Anthony Kim in slow motion.
You can readily see that he goes through all the swing action phases that constitute the swinger's swing pattern (including a start-up takeaway swivel action phase - release swivel action phase - horizontal hinging phase - finish swivel action phase). His swing pattern is identical to the swing pattern demonstrated by Scott in his swing video presentation.
Many golfers, and many golf instructors, do not really understand what is happening biomechanically during the followthrough phase of the swing - during the time period when the clubface rolls over so that toe of the club passes the heel of the club (you can clearly see the toe of the club passing the heel of the club in image 5 above).
This diagram demonstrates what happens to the clubface in the pre-impact and post-impact phase of the swinger's golf swing (red dot = ball).
Diagram showing the clubface orientation during the followthrough in a swinger who employs a horizontal hinging action
I have previously explained the biomechanics of the release swivel action phase of the golf swing - and I explained how the clubface closes prior to impact due to the timely release of PA#3, and I also explained the biomechanics underlying the release of PA#3.
The above diagram demonstrates that the clubface continues to rotate post-impact - so that during the followthrough phase of the golf swing the toe of the club starts to pass the heel. Many golfers, and many golf instructors, incorrectly believe that it is due to a wrist-activated hand-crossover release action through impact, and they incorrectly believe that the right hand should actively roll over the left hand through impact. Many golf instructors even teach this foolish practice.
AJ Bonar's Magic Move - from reference number 
I explained why AJ Bonar's Magic Move of deliberately rolling the right hand over the left hand is a foolish golf instructional recommendation in my impact chapter.
It is important that a swinger understand the "correct" biomechanics that cause the toe of the club to pass the heel of the club during the followthrough phase of the swing, so that he can master this biomechanical action - which is called horizontal hinging.
Horizontal hinging is a biomechanical action where the swinger rotates the back of the left hand leftwards so that the back of the flat left wrist moves around to the left while remaining vertically oriented relative to the ground - in other words, the back of the flat left wrist, which remains vertical to the ground, rotates to the left like a door opening. The AJ Bonar photo gives a swinger the impression that the left wrist rollover occurs at the level of the wrists/hands. However, that is totally incorrect! The roll over action must occur at the level of the left shoulder socket, and the entire left upper arm, left forearm, flat left wrist and left hand must rotate around to the left as a single unit - at the same rpm as the rotating clubshaft/clubhead. This explanation becomes clearly understandable if you consider the next photo of Anthony Kim's horizontal hinging action.
Anthony Kim's horizontal hinging action - capture images from a swing video
Image 1 shows Anthony Kim at impact and image 2 shows Anthony Kim at the end of the followthrough (defined as the time point when both arms are fully straight and all the power accumulators have fully released). Note that the clubface has rotated 90 degrees to the left so that the clubface (and back of the left hand) is vertical to the ground. What causes this 90 degree rotation of the back of the left hand and clubface? The answer is clearly discernible in the above photos.
Image 1 shows Anthony Kim at impact. Note that he has a strong left hand grip, which means that his flat left wrist/back of left hand is not quite facing the target at impact. Note that one can clearly see the back of his left forearm and note that the radial border of his left forearm is still facing slightly rightwards. Note what happens to his left forearm during the followthrough - the back of his left forearm rotates counterclockwise (as viewed from above) so that it faces the target at the end of the followthrough and the radial border of the left forearm faces the ball-target line. The left forearm's counterclockwise rotation is not due to any independent left forearm rotatory movements, but it is due to an external rotation of the left humerus (bone of the left upper arm) in the left shoulder socket joint (which has itself moved upwards during the followthrough phase of the swing - thereby making it easier for external rotation of the left humerus to occur naturally). Note that the left upper arm has rotated to the same degree as the left forearm, and that the left forearm has rotated to the same degree as the flat left wrist, and that the flat left wrist has rotated to the same degree as the clubface. That's what happens in a horizontal hinging action - the entire left upper limb rotates as a single unit at the same rpm as the rotating clubface, and the rotation occurs as if there is vertical hinge joint at left shoulder socket level thereby allowing the entire left arm unit to rotate horizontally like a door opening. If a swinger understands this biomechanical phenomenon, and understands that the left hand controls the clubface during the followthrough, then he can control the horizontal hinging action during the followthrough phase of the golf swing.
I am constantly stupefied by the foolish golf instructional advice that one can find on the web. Here is a link to a swing video by Tom Betrand who claims to have discovered one of Ben Hogan's missing secrets that wasn't divulged to the public before Ben Hogan died. Tom Betrand claims to have discovered this "missing link" Hogan secret!
Tom Bertrand claims that the "missing link" to Hogan's secret is the "active turning-in of the left elbow towards the left hip" through impact. He claims that this is not a natural action and that one has to train oneself to perform this "unnatural" action. This claim is unadulterated nonsense! What he is doing is nothing more than a "forced" external rotation of the left humerus, and he is performing the action unnaturally in a contrived manner. External rotation of the left humerus (at the level of the left shoulder socket joint) occurs naturally during the release swivel phase of the golf swing and also during a horizontal hinging action. It's a natural biomechanical action that occurs automatically/naturally in a swinger's biomechanically-natural swing action. The left hand controls the clubface, and when one performs a horizontal hinging action by rotating the entire left upper limb counterclockwise post-impact, the back of the left hand will remain vertical to the ground as it rotates around to the left (like a door opening).
Consider this diagram again.
Diagram showing the clubface orientation during the followthrough in a swinger who employs a horizontal hinging action
Note that the clubface is slightly open to the clubhead arc as it approaches the ball and that it closes (relative to the clubhead arc) during the release swivel phase of the downswing (due to the release of PA#3). After impact, it continues to close (relative to the clubhead arc) due to a different biomechanical action - the action of horizontal hinging. Therefore the biomechanical action of horizontal hinging must blend seamlessly with the biomechanical actions causing the release of PA#3, so that the clubface can close smoothly while the clubface remains in contact with the ball. If the clubface continues to close smoothly while it is in contact with the ball, then it will impart an optimum compressive blow to the ball and it will cause the ball flight to be optimised for distance - the ball flight will be low and penetrating with a slight draw tendency at the end of the ball flight. However, there is one potential complication. How does one get the ball to go straight if the clubface is closing slightly while it remains in contact with the ball?
If the clubface is closing slightly while the clubface remains in contact with the ball (which lasts about 1/4000th of a second and a clubhead travel distance of about 0.75"), and if he ball will only go straight towards the target if the clubface faces the target at the exact moment of ball-clubface separation, then the clubface must be slightly open at the exact moment of first ball contact.
Position of clubface at address - square or open
The above photo shows a square clubface and a slightly open clubface. A swinger will often need to have a slightly open clubface at address - to ensure that the clubface is square to the target at the exact moment of ball-clubface separation. The amount that the clubface needs to be open at address is individual golfer-dependent - and it depends on the amount of clubface closing that occurs while the ball remains in contact with the clubface during impact. Each individal swinger needs to experiment to find the optimum clubface orientation at address when using a horizontal hinging action in his overall swing action. The clubface will have to be less open at address if a swinger uses angled hinging to produce a power fade shot - because the clubface closes less per unit time during angled hinging, and an overly open clubface at address will result in an excessive amount of fade. However, most golfers want to maximise their driving distance by having a low, penetrating ball flight with a tendency to draw at the end of the ball flight trajectory, and they should therefore utilise horizontal hinging in their swinging action - and only experimentation and gained experience will allow an individual golfer to determine the correct amount of open clubface alignment at address for his individual degree of horizontal hinging action.
Addendum added February 2011:
I now believe that the TGM-idea of the clubface significantly closing during the impact interval of 1/4,000th second is incorrect. Recent scientific evidence shows that the clubface doesn't close >1 degree during the impact interval time period, and that small amount of clubface closure during the impact interval doesn't independently cause a draw flight pattern. A draw flight pattern occurs if the clubhead path is more open to the ball-target line at impact - relative to the clubface orientation at impact. I have discussed this complex issue in great detail in my Ball Flight Laws review paper.
To maximally compress the ball, a golfer also needs to ensure that he hits the ball while the clubshaft is travelling on a descending path - and a golfer achieves that condition by ensuring that the hands lead the clubhead into impact. A golfer first needs to determine where's the low point of his clubhead swingarc for each club, and he needs to position the ball just behind the low point to ensure that the clubhead hits the ball first and then produces a shallow divot secondarily. The depth of the divot usually depends on the club - being very shallow for long irons (which have a shallow attack angle) and deeper for short irons (which have a steeper attack angle). With fairway woods, the divot is often so shallow that a golfer merely scuffs the grass without producing a distinct divot.
The following diagram demonstrates the principle of the low point and the attack angle (the imaginary straight line drawn between the impact point and the low point).
Angle of approach diagram
This diagram is not drawn to scale and it is merely representative of the principle of the attack angle and the angle of approach. One can see that the low point of the swinger's clubhead arc is roughly opposite the left shoulder and it occurs when the left arm/clubshaft radius (distance from the left shoulder socket) is at its greatest value. If one places the ball behind the low point, then the impact point will occur when the clubhead is on its descending path down to the low point. The impact point is at ground level (where the ball is placed) and the low point is below ground level. The low point is the deepest path of the divot. If one draws an imaginary straight line on the inclined plane (the imaginary inclined plane the clubshaft is situated on as it travels through the impact zone) between the impact point and the low point, then that line is called the attack angle line. The angle of approach line is the same imaginary line (between the impact point and the low point) as viewed on the ground from the golfer's eye position.
If a reader wants to understand the difference between the attack angle line and the angle of approach line better, then he can view this online video demonstration (which has delightfully soothing music in the background to calm your mind while your mind wrestles with the complexity of understanding this concept).
The attack angle line is drawn on the glass perspex pane, and the angle of the glass pane (relative to the tabletop) represents the angle of the inclined plane for a particular golf club. When the demonstrator shines the laserlight through the glass pane, while tracing the attack angle line, the laser light produces an imaginary light track on the table top, and that imaginary line is the angle of approach line as viewed from above.
It not critically important that a golfer clearly understand these attack angle/angle of approach concepts - as long as he understands why he needs to hit down on the ball, and not up at the ball.
If a beginner golfer wants to view a swing video lesson on how to hit down on the ball and produce divots, I have provided two links to two swing video lessons on the basics of how to ensure that the low point of the clubhead swingarc is in front of the ball.
Brain Manzella Swing Video Lesson
Shawn Clement Swing Video lesson
Finally, there is one critical element that is the key element in a swinger's action - and that is timing. When I describe a hitter's action, a reader will understand that it is a much simpler golf swing action with "less moving parts". The swinger's swing action is much more complicated because there so many body/limb actions occurring either simultaneously or sequentially and these body/limb actions must be perfectly timed. To execute a perfect swinger's swing action that results in an optimal ball flight, all these body/limb actions have to be perfectly timed. However, timing cannot be taught, and it is acquired through personal practice and gained practical experience. When I am playing a round of golf (rather than practicing at a golf practice facility), timing becomes my primary swing thought - I primarily concentrate on timing and I try not to think of complex golf mechanics/biomechanics. I would recommend that all swinger's adopt the same appproach - learn golf biomechanics at the practice facility and primarily think of timing when playing golf on a golf course.
Hitter's swing action - the biomechanics
In this section, I will describe a hitter's swing action. This section will not be as lengthy as the swinger's section, because hitting is a much simpler procedure.
I have produced two video lessons that pertain to hitting. Readers can view these swing videos before, or after, reading my written section on hitting. Video lesson 1 should be viewed before video lesson 2.
Video lesson 1 - Hitting Fundamentals. This is a 30 minute video lesson divided into four U-tube segments and I describe the general principles of hitting, the address hitting position, the backswing actions, the downswing actions, and the followthrough actions.
Segment 1 http://www.youtube.com/watch?v=vnjp-O-2DTg
Segment 2 http://www.youtube.com/watch?v=muqpd_hTBHM
Segment 3 http://www.youtube.com/watch?v=e_b6ydQcA8s
Segment 4 http://www.youtube.com/watch?v=jyVoCjpbgRk
Video lesson 2 - Hitting in "real life" action using my friend Scott as a role model hitter. Scott is using a 9-iron and he has positioned his ball slightly back of the center of his stance.
Segment 1 http://www.youtube.com/watch?v=08k4R6SlbZI
I have already described the physical principles and basic mechanics of hitting in the first section of this review paper, and in this section, I am going to describe the biomechanics of the hitting action.
Here is an image of Scott at address.
Scott in his hitting address position - capture images from a swing video
A swinger normally stands at address with his hands and clubshaft more-or-less centralised between his thighs. By contrast, a hitter adopts an impact fix alignment position at address. In this impact fix alignment position, the hands are moved forward slightly and this causes the clubshaft to have some forward shaft lean. This motion causes the left wrist to appear more flat, and the right wrist is slightly bent. Note that the right forearm is held on roughly the same inclined plane as the clubshaft-at-address plane, and this plane is usually the elbow plane (or close to the elbow plane).
The rest of the address postural alignments - including a small degree of rightwards spinal tilt which gets the head behind the ball - are the same as a swinger's postural alignments.
The backswing starts with a takeaway action whereby the hitter takes his right forearm straight back (away from the target) without performing a start-up swivel action (characteristic of a swinger) where a swinger deliberately rotates the left forerarm clockwise (as seen from above) in order to get the club toe-up at the end-takeaway position. By contrast, a hitter should have the "feeling" that the clubface is always looking at the ball during the takeaway.
Scott at the end-takeaway position - capture images from a swing video
In this photo of Scott at the end-takeaway position, one can that his clubface is slightly closed - due to the lack of a takeaway swivel action. Note that Scott has not yet folded his right elbow and that he has the same amount of right wrist bend as he had at address. He is simply carrying the grip end of the club away towards his end-backswing position by moving his right forearm away from the target (while his upper torso is rotating).
From the end-takeaway position, the right elbow will progressively fold during the remainder of the backswing and the right elbow will acquire a 90 degree angle between the right upper arm and right forearm by the end of the backswing actions.
Scott at the top-of-the-backswing position - capture image from a swing video
Note that Scott has a 90 degree right elbow bend at the end-backswing position. In that position, one can see that PA#1 is fully loaded. Note that the right forearm is at a right angle to the clubshaft and the left arm. The V-shaped combination of the straight left arm and the clubshaft (which is at a 90 degree angle to the left arm) is referred to as the left arm flying wedge . The V-shaped combination of the right forearm and right wrist being at a right angle to the clubshaft also forms a wedge-like structure, called the right forearm flying wedge, and one can see that the right forearm flying wedge is approximately at a right angle to the left arm flying wedge. If the clubshaft component of the left arm flying wedge can be thought of as a small Cessna airplane's wing, then the right arm flying wedge can be thought of as a strut supporting the airplane wing . A hitter needs to adopt that described flying wedge inter-relationship at the top-of-the-backswing position - where the right forearm is at right angles to the left arm flying wedge. Note that the hands are opposite the right shoulder and that the clubshaft appears laid-off (it does not get to a position where the clubshaft is parallel to the ball-target line). It is important that a hitter does not try and get further back than this top-of-the-backswing position. By contrast, a swinger (if flexible) will often get to the end-of-the-backswing position where the right forearm is vertical to the ground, and the right palm is directly underneath the clubshaft (that is parallel to the ball-target line). A hitter's right forearm should never be vertical at the top-of-the-backswing position. It should be angled relative to the ground and it will often be close to being parallel to the bent-over spine (as seen from a down-the-line viewpoint).
Note that that the pelvis has rotated about 45 degrees and the shoulders about 90 degrees, and that is similar to a swinger's torso movements.
The downswing must start with a shift-rotation movement of the pelvis towards the target. During that movement, the entire torso will move leftwards towards the target.
Downswing actions in the early downswing - capture image from a swing video
This photograph of Scott's early downswing actions demonstrates a number of biomechanical actions that occur near-simultaneously at the start of the downswing. i) The pelvis slides left-laterally as weight is replanted onto the left foot. ii) While the pelvis slides left-laterally, the pelvis rotates about 45 degrees so that the pelvis becomes parallel to the ball-target line (hip squaring action). iii) The right upper arm is adducted against the right side of the torso and this action pulls the right elbow to a position alongside the right hip area.
Note that the right arm flying wedge remains intact and its perpendicular relationship to the left arm flying wedge remains constant. At this time point, PA#1 has not released - there is still a ~90 degree relationship between the right upper arm and right forearm at the right elbow joint.
Note that the right shoulder has moved closer to the ball (moved downplane) during this pelvic shift-rotation movement. The right shoulder is not actively thrusting downplane, but it is being pulled passively downplane towards the ball by the lower body's shift-rotation movement. The right shoulder must get closer to the ball before the right elbow actively straightens so that the hitter does not "run-out-of-right arm". If PA#1 releases too soon (before the right shoulder moves closer to the ball) then the hands will not reach the impact location during the right arm straightening action - and this phenomenon is called "running-out-of-right-arm". The right shoulder should be conceived as being the launching pad for the release of PA#1 , and the launching pad must get close enough to the ball before the right arm straightening action is initiated.
At this point in the downswing, a hitter is in a perfect position to release PA#1 in a right arm thrust action towards the ball. The release of PA#1 is due to a very active triceps muscle contraction that actively straightens the right elbow in a forceful thrust action that pushes the right forearm and bent right wrist towards their impact fix position. The straightening right arm applies push-pressure to pressure point #1 and pressure point #3 via the right forearm/bent right wrist/right palm and this push-pressure pushes the clubshaft towards impact. In other words, the clubshaft is pushed (driven) into impact via the biomechanical actions involved in the active release of PA#1. When the clubshaft is pushed into impact secondary to the release of PA#1, then the left wrist obviously uncocks (release of PA#2) and the left hand obviously rotates into impact (release of PA#3). In other words, the release of PA#2 and #3 is driven by the release of PA#1. There is no centrifugal action involved in the release of PA#2 because the clubshaft is driven into impact by right arm push-pressure (axe handle technique) and not pulled towards impact (rope-handle technique). There is no release swivel action in a hitter's swing action, because at the delivery position the clubface is slightly closed relative to the clubhead arc - remember that there was no start-up takeaway swivel action during the takeaway action to open the clubface relative to the clubhead arc, and therefore there is no need for a reverse-swivel action during the downswing (as occurs in a swinger's action).
The clubshaft doesn't whip into impact because there is no centrifugal release action in a hitter's action. The clubshaft is pushed/driven into impact - and the clubshaft motion should appear to be slower, and more deliberate, and more controlled to an outside observer. The clubshaft should progressively gain speed during the downswing and the hitter must avoid over-accelerating the club at the start of the downswing.
Note the position of the right elbow at this time-point. It is very close to the right hip area - being either just behind or just alongside the right hip. When PA#1 releases and the right elbow straightens, it will cause the right forearm to *paddlewheel towards impact and during the last few moments before impact, the right forearm should be "on-plane"' (roughly on, or near, the elbow plane) just behind the clubshaft. At impact, the right forearm will be in-line with the clubshaft (see next photo), supporting the thrust action of the clubshaft into impact.
(* the term "paddlewheel" is a useful conceptual term to describe the right forearm's three-dimensional movement into impact - because it can be perceived to resemble the movement of the right forearm of a canoeist who uses that forward-directed motion to slow down the canoe, or help turn the canoe to the same side, by reversing the normal backward-directed movement of the canoeist's paddle action)
Individual hitters will usually release PA#1 when the right elbow is in close vicinity to the right hip area. Skilled hitters, who want to have a delayed release, can delay their PA#1 release to a time-point when the hands pass an imaginary line drawn between their eyes and the ball. However, a delayed release gives a golfer very little time to complete the release of PA#2 and PA#3 and one will need to perform a well-executed release of PA#1 to get the clubface sufficiently closed by impact. An incomplete release of PA#2/#3 will result in pushed/push-sliced shots. Each individual golfer must find the optimum release point, which is dependent on his physical capacity and coordination. A good PA#1 release action should result in the hands being just ahead of the clubhead at impact.
Scott demonstrating optimum impact alignments - capture images from a swing video
Note that the right forearm is "on-plane"' at impact - supporting the clubshaft as the straightening right arm applies thrust force to the clubshaft in a radial direction. Note that the hands lead the clubhead into impact thereby ensuring that clubhead lag is maintained through the impact zone. The clubhead is traveling down at this time point towards the low point of its arc. The clubhead should also be traveling slightly outwards (towards right field in a crossline manner). That is due to the thrust direction of the right elbow straightening action and the paddlewheeling path of the right forearm. A hitter should have the "feeling" at the top-of-the-backswing that he is going to thrust his hands in a straight-line direction towards the aiming point (which is usually in proximity to the ball) and this straight line thrust action is down-and-out-and-forwards towards the ball.
Note that the right arm is not completely straight at impact, and that PA#1 has not completely released at impact. The "true" endpoint of the release of the right arm thrust action occurs after impact - when both arms are fully straight. The end of the followthrough is defined as the time point when both arms are fully straight.
The following composite photo shows the author demonstrating the end of the followthrough position.
Author simulating the end-followthrough position - capture images from a swing video
In the first image, I have my right hand off the club - because I am simply demonstrating how a hitter straightens his right arm in a straight line thrust action and how that active thrust motion drives the clubshaft through the impact zone. The direction of the right arm thrust action is down-and-out-and-forward. The second image shows the outward component of the right elbow straightening thrust action, and a viewer can see that the clubface angle is at an approximately 45 degrees angle to the ground and that the clubshaft is still moving along the inclined plane. During the followthrough phase of the hitter's swing action, the back of the flat left wrist/hand is moving perpendicularly to the inclined plane (see above photo) which means that the clubface is also moving perpendicularly to the inclined plane while the clubshaft travels up the inclined plane. What I have described = Angled hinging. In other words, a hitter doesn't use a horizontal hinging action (like a swinger). Instead, his natural followthrough action is an angled hinging action.
During an angled hinging action, the clubface is not closing as fast as it closes during a horizontal hinging action. Consider a swinger's horizontal hinging action.
Clubface closing action during the horizontal hinging action phase of the followthrough
I previously mentioned that a swinger uses a horizontal hinging action during the followthrough phase of the swing, and that the horizontal hinging action causes the clubface to be constantly closing while the clubface remains in contact with ball. I also mentioned that swinger may need to open his clubface slightly at address to compensate for this fact. By contrast, a hitter has the opposite problem because he is using a crossline thrust action and angled hinging (where the rate of clubface closing per unit time is less than the amount that occurs in horizontal hinging). That combination results in the clubface being slightly open during the entire time period of ball-clubface contact, and a slightly open clubface alignment at the exact moment of ball-clubface separation can predispose to a push-slice ball flight trajectory. A hitter may therefore have to compensate by closing his clubface slightly at address to ensure a straight ball flight.
Position of clubface at address - square or closed
If the clubface is slightly closed at address, a golfer should be able to envisage how the clubface will be facing straight towards the target at the exact moment of ball-clubface separation if a hitter uses angled hinging and a slight crossline thrust of the clubhead through the impact zone. The amount that the clubface needs to be closed at address is individual golfer-dependent, and a hitter has to experiment to find the optimum clubface angle at address for his particular hitting action.
Addendum added February 2011:
I now believe that the TGM-idea of the clubface significantly closing during the impact interval of 1/4,000th second is incorrect. Recent scientific evidence shows that the clubface doesn't close >1 degree during the impact interval time period - irrespective of whether a golfer uses horizontal hinging or angled hinging. The major reason for adopting a slightly closed clubface at address is primarily related to the fact that a hitting action is a crossline procedure, where the clubhead path is directed slightly to the right-of-the-target as a result of the straight line thrust action that occurs during the active release of PA#1. However, an individual golfer may choose to produce a baby draw ball flight, and not a straight ball flight, and he may therefore prefer to have the clubface slightly open to the ball-target line at address.
Finish phase actions
During the finish phase of the swing, a hitter doesn't need to perform a finish swivel action that causes the back of the left hand to be positioned against the inclined plane (due to the combination of left elbow folding and a left forearm supinatory movement).
Here is a photo showing how a swinger supinates his left hand onto the inclined plane during a finish swivel action.
Author demonstrating the left hand's movement during a finish swivel action - capture image from a swing video
In this photo, I am demonstrating how the back of the left hand will lie against the surface of the inclined plane, thus causing the butt end of the clubshaft to point at the ball-target line (direction that my right index finger is pointing), if the left elbow folds and the left forearm supinates correctly during a finish swivel action.
A hitter doesn't normally perform a finish swivel action (like a swinger) and the arms are usually extended more down-the-line in a direction that is left-of-the-target.
Scott's finish action - capture image from his swing video demonstrating a hitting action
Note how both of his arms are still extended-out towards the target and note that he has still maintained a bent right wrist and flat left wrist through to his finish position. A hitter can wrap the club around his torso if his full swing action has generated a lot of clubhead momentum, but many hitters prefer to finish their swing action like Scott.
Note that Scott has maintained a bent right wrist (which is called a "frozen" right wrist) throughout his entire swing - backswing, downswing, followthrough and finish - and that he doesn't change the degree of right wrist bend at any time point throughout the swing. In other words, there are no "active hands" in a hitter's action (any hand manipulation through the impact zone at the level of the wrists - as recommended by AJ Bonar).
Addendum added February 2011:
I have written a new review called Power Mechanics of Swinging, Hitting and Swing-Hitting. In that review paper, I have provided more newly-acquired insights regarding the technique of executing a hitting action, and I have described three types of hitting action - i) a triple-barrel TGM hitting action; ii) a four-barrel TGM hitting action and iii) a non-TGM hitting action using a reactive pivot action.
Hopefully, a reader will have acquired a great deal of useful information from this review paper on "how to power the golf swing". Each individual golfer first needs to decide whether he wants to be a hitter or a swinger. That's an individual choice that partly depends on the individual golfer's physical makeup (his physical strengths and weaknesses) and partly depends on personal whim.
In my original/first version of this review paper, I didactically stated that a golfer should not mix swinging elements with hitting elements in the same swing action - based on Homer Kelley's belief  that swinging and hitting are mutually exclusive techniques. However, I now believe that it is practically possible to mix swinging elements with hitting elements in the same swing, and thereby become a swing-hitter. The difference between a swing-hitter and a switter is that a swing-hitter has succesfully mixed swinging elements with hitting elements in a synchronised/coordinated manner, while a switter has mixed swinging elements with hitting elements in an uncoordinated/asynchronous manner. I have described the optional approach of executing a swing-hitting technique in my new review paper called Power Mechanics of Swinging, Hitting and Swing-Hitting. Although it is possible to successfully become a swing-hitter, I still personally prefer the techniques of swinging and hitting, which are based on a totally different set of mechanical/biomechanical fundamentals.
First version of this review paper: December 2008.
Revised version - February 2011.
1. The Golfing Machine. Homer Kelley.
Available at http://www.thegolfingmachine.com
The Golfing Machine website also provides information on TGM golf instructional schools and authorised TGM instructors in your local area.
2. Lynn Blake's Golf Website (free registration required to view contents).
3. David Tutelman's Golf Website.
4. Golf's Critical Details. George Hibbard.
5. Kevin Na Swing Video
6. The Plane Truth for Golfers. Jim Hardy.
7. The Plane truth for Golfers Master Class. Jim Hardy.
8. Jim Hardy's websites.
9. The Impact Zone. Bobby Clampett.
10. Tiger Woods Slow Motion Swing Video - Nike Commercial
With audio remix
11. AJ Bonar's Magic Move.