This represents my present-day thinking of the
optimum way of releasing the club through impact.
I think that it is optimum to ensure that the FLW remains flat well beyond impact - thereby ensuring that there is no flipping of the clubhead passed the left arm. If the clubhead flips soon after impact, that means that there is a
horizontal hinging motion of the left wrist superimposed on the motion of the body-arms through impact. That creates an enormous timing element problem-issue because one cannot guarantee that the horizontal left wrist hinging motion doesn't start to happen
pre-impact.
Roger Federer is eliminating any horizontal hinging motion of his lead wrist through impact, and he is maintaining a FLW from P7 to P8. The following diagram shows what is happening from a conceptual perspective.
F = fulcrum point of the lead arm/racquet swing action = Lead shoulder socket.
The blue line represents his straight lead arm.
The green line represents the straight racquet handle/racquet face.
The short black line represents the flat lead wrist (FLW).
The curved red-arrowed line represents the racquet head arc.
The curved orange-arrowed line represents the arc of motion of his FLW.
Note that the lead arm and racquet have the
same rpm speed between P7 and P7.5 - even though the racquet is traveling at a faster linear speed. That is critical to keeping a FLW after impact (between P7 and P7.5).
How is that achieved biomechanically?
I believe that the only way to achieve that goal is to
pull the lead arm/hand forward at a fast enough speed so that the lead hand moves along its circular hand arc path at the same rpm as the racquet moves along its circular path. Any slowing of the forward motion of the left hand (FLW) will result in flipping.
The same analogy applies to a golfer's swing action, but it is more complicated biomechanically/mechanically because of the presence of the right arm/hand.
A golfer uses the same swing action as demonstrated in that diagram - except one must think of the green line as being the clubshaft.
Here is Dustin Johnson's swing action through impact.
Note that DJ keeps his left wrist flat until P7.5 (image 2). I stated that it is only possible if he is maintaining forward motion of his FLW at a rpm speed that is the same as his clubshaft's rpm speed (even though his clubhead's linear speed is 120+mph through impact). How is this biomechanically possible? How does one keep the left arm/FLW moving sufficiently fast enough between P7 and P7.5 to prevent any flipping?
There are two possible power sources that will keep the FLW moving forward at a sufficient speed to prevent flipping between P7 and P7.5.
1) Left arm being pulled forward by the left shoulder girdle muscles + power derived from the catapulting of the left arm forward by the pivot action (pivot-induced release of PA#4). Both of these power sources must be diminishing between P7 and P7.5 for obvious biomechanical/mechanical reasons.
2) The straightening right arm, +/- straightening right wrist, applying a push-force at PP#1.
Note how actively DJ's right arm is straightening between P7 and P8 and it is reasonable to assume that it could help in maintaining the forward speed of the FLW from P7 to P7.5 if the push-force is applied to PP#1, and not PP#3.
That's a critical point - any right sided push-force (due a right arm straightening action) must be applied at PP#1. If it is applied at PP#3, then it will likely promote flipping.
Consider two different Freddie Couples swings.
In image 1 he is flipping - as his right arm straightens and his right wrist palmar flexes. That is not happening in the image 2 swing action. In other words, it is perfectly OK for the right wrist to straighten through impact as long as it doesn't promote flipping (by applying push-force at PP#3).
Here is Ernie Els at P7.5.
Note that his right elbow has straightened and his right wrist has straightened, but there is no flipping. If the straightening right arm/right wrist is applying a push-force in his swing action between P7 and P7.5, then it must be applying that push-force at PP#1, and not at PP#3.
I don't know to what degree any golfer (who is a swinger) is applying a push-force with the right arm/wrist-hand unit between P7 and P7.5, but I do believe that
any application of a right-sided push-force must not induce flipping if one wants to maintain a stable club motion (and intact LAFW) between P7 and P7.5.
Jeff.