Whenever there is a discussion of the kinetic chain action in a golf swing there will be invariably someone who brings up the question - how on earth can one gain from a braking action?  Others will simply stop thinking all together and refer to it being a new myth for the golf swing. So what is it what is so difficult to understand about the action of a kinetic chain?  Just hang on and before long it will all become clear.

The reason many have so much trouble with  the kinetic chain action is, surprisingly perhaps for some, partially due to science and scientists themselves. We all have been educated almost exclusively with spring forces as if there were no other type of forces present around us. Another reason is the aversion of scientists for reaction and inertial forces as if they only want to acknowledge as existing,  forces which are 'cause' and rapidly shovel under the carpet forces being 'effect'.

Yet there is no escape there is and remains the fundamental third law of Newton.
III - Actioni contrariam semper et æqualem esse reactionem: sive corporum duorum actiones in se mutuo semper esse æquales et in partes contrarias dirigi.
For a force there is always an equal and opposite reaction: or the forces of two bodies on each other are always equal and are directed in opposite directions.
    
The third law basically means that all forces are interactions, and thus that there is no such thing as a unidirectional force. Forces therefore always come in pairs. Hence the centrifugal force is as real as is the centripetal force. Yet there is big time confusion about the centrifugal force, forever being denied to exist for real except as some fictitious force in rotating frames, another dada of scientists used to mask their lack of empathy for inertial reaction forces. Inertial reaction forces often are hardly discussed or seriously acknowledged in text books, yet they are omnipresent.  

Due to this particular flaw in scientific education the average golfer is frequently lead to believe to only consider as real the forces and torques he himself employs in the swing and does not have a clue that there are also very big and very real inertial reaction forces at work in the down swing. Acknowledging this basic fact is the first step towards being able to more readily understand the real and useful action of the kinetic chain in the golf down swing. Using the kinetic chain action is really acknowledging there existence, not getting in their way and letting them play their part.

We  will use the double pendulum model in our analysis. Let us assume it to be an iron byron and use the terms wrists, arms or shoulders to make it a bit more pleasant to discuss things. We have modeled a dead stop at the wrists and no active wrist torque is applied. The only external torque applied is a shoulder torque.  Naturally there is a small contribution  due to gravity. Four different shoulder torques have been used in the analysis but modulated such that they resulted nevertheless in the same clubhead velocity of 160 km/h at impact.

Below we have put together the result of the analysis in graphical form for the four different shoulder torques, showing the pendulum swing (Figs 1a,1b,1c,1d), the shoulder torque (Figs 2a,2b,2c,2d), the work expended by the shoulder torque (Figs 3a,3b,3c,3d), and the hands speed (Figs 4a,4b,4c,4d), Vertically the graphs are associated with one particular shoulder torque, (Figs 1a,2a,3a,4a), (Figs 1b,2b,3b,4b), Figs 1c,2c,3c,4c) and (Figs 1d,2d,3d,4d). Hence graphs are arranged to facilitate rapid comparison.

Iron byron is programmed to swing away with only one external torque, applied at the shoulders. A dead stop, Fig1, is programmed to prevent jack-knifing of the arms onto the shoulders. As shown below four different time histories for this torque are used but are modulated such that the same clubhead speed of 160 km/h is reached at impact. There is a different shaft angle at impact and I could have eliminated it but it involves a considerable amount of work, but having not really any impact on the main issue at hand, I left the angle alone.

Notice the systematic progression for the applied shoulder torque from Fig2a to Fig2d - increasing, constant, decreasing and finally constant but near zero torque through impact. The Figs 1a to 1d show the resulting down swing of iron byron. Except for a different angle at impact there is 'seemingly' not much difference for the rest of the down swing. Yet there is. The torques shown are readily produced by an iron bryon and are specifically chosen to gradually show the influence of the weighting of the torque at impact vs at the top.

Figs 3a to 3d show a considerable difference in the work expended by iron byron for the four swings yet producing identical clubhead impact speeds of 160 km/h. Those who believe that one should fire hard through impact better have a closer look! The Figures 3a to 3d show in a nutshell convincingly the validity of the kinetic chain action. 'Free-wheeling' through impact (Fig3d) is 25.7 % more efficient when compared to a smooth start and firing hard through impact (Fig3a).

Why is there from left to right progressively a more efficient swing? Figs 4a to 4d show his quite clearly. The arms slow down more in the down swing giving up progressively more energy to the club. This is the typical action of a kinetic chain - energy transferring from proximal to distal elements. However notice that the more torque is present at impact the less it occurs. For it to happen it should not be interfered with, it has to happen by itself. Hence active (yang) from the top and free-wheeling (yin) through impact.

Conclusion

The conclusion of the analysis above is self evident - kinetic chain action is truly acting and effective in a golf swing. Also it is clear that it is most effective when not being interfered with with external torques. Indeed Bobby Jone's 'free wheeling' approach seems to be the most efficient way to swing for an iron byron golfer.

Notice that nowhere I used the term 'braking' often used to criticize the validity of the kinetic action in a golf swing. Indeed take note that the four different torques used are always positive, therefore there is never any braking going on. As long as the torque is positive there remains an effort to keep accelerating, hence speeding up the swing.

It is here where I tie in to the introductory remarks. The inertial forces generated in the down swing are large and most effective when there is no interference. A helping torque at impact is counter productive. The only efficient way to still increase clubhead speed close to impact is not by applying a torque but rather a very brisk upward linear force.

Above we have shown that the kinetic chain action is closely related to free wheeling through impact. Definitely no deliberate 'braking' is required. This is a basic error made by some taking an effect to be an cause. Hence for an efficient golf swing, expend adequate effort (yang) early on in the down swing and then let go through impact (yin).

mandrin