Here is my explanatory answer as to how Dustin Johnson and Keegan Bradley (
who both use a moderately strong left hand grip) can both have a square clubface at impact with very different left forearm/wrist alignments at impact.
Note that they both have their hands forward at impact with a fair amount of forward shaft lean. In that sense they are similar. However, note that KB's left forearm (image 1) is much more pronated than DJ's (image 2) and it appears that he has not completed his release of PA#3. Bv contrast, DJ's left forearm is more supinated and it "appears" that he has an AFLW. I use the word "appears" because he actually has a moderately strong left hand grip
combined with a bowed left wrist, and it looks "flat" (from a face-on viewing perspective) because his bowed left wrist is more rotated counterclockwise at impact.
How can one explain this difference in left forearm/wrist alignments needed to obtain a square clubface at impact if both golfers have a moderately strong left hand grip?
Let's start with my author-photo showing a i) weak/neutral grip (image 1) and a ii) moderately strong left hand grip (image 2).
Note that the left forearm is more pronated in image 2.
Note that if I simply slip a club in my fingers along the lifeline crease of the left palm while still holding my left arm near-vertical, that the clubshaft will
automatically have forward shaft lean in image 2 (because the lifeline is angled away from the target as a result of the left forearm pronation). That will allow a golfer to have the requisite amount of forward shaft lean at address if he simply hangs his left arm near-vertical at address and that will allow the clubface to be square to the target (remember that a small degree of forward shaft lean is inbuilt into golf clubs by the manufacturer so that the clubface can be square with a small degree of forward shaft lean).
So, consider DJ at address - image 1.
Note that DJ's left arm is near-vertical at address and he has a small amount of forward shaft lean because he adopts a moderately strong left hand grip. That allows him to have a square clubface at address.
Now, consider how DJ achieves a square clubface at impact.
First of all, remember that DJ has a bowed left wrist throughout his entire downswing from P4 to P7. At P4, a bowed left wrist (when the left wrist is radially deviated) causes clubface closure and no angulation of the clubshaft (Tapio effect), while a bowed left wrist near/at P7 (when the left wrist is more ulnarly-deviated) would have no effect on clubface closing but would angulate the club away from the target. Consider that "effect" in the next image.
The red dotted line shows how DJ's clubshaft would angle back (away from the target) if one kept his hands in the same address-position, but allowed his left wrist to be bowed. The red arrow shows that his clubface would face to the right-of-the-target due to the increased backward angulation of the clubshaft. However, DJ's hands are more forward at impact. So, let's keep that same degree of left arm-clubshaft angle (which has increased forward shaft lean due to left wrist palmar flexion) and now move his hands forward to his impact location.
I have drawn a blue line showing that his left arm is angled more towards the target at impact, which moves his left hand to a position opposite his left thigh. I have kept the same angle between the left arm (blue line) and clubshaft (dotted red line) that is secondary to the biomechanical effect of left wrist bowing (see previous image), and you can see that the clubhead now reaches the ball with a square clubface. The clubface becomes square because the clubshaft is now rotated more targetwards due to the i) change in left arm angle and ii) the fact that his left arm becomes more rotated due to the fact that his shoulders are more open to the target at impact. Note that the modified image 1 (blue line and dotted red line) matches image 2 (DJ's "real life" impact alignment) and it explains how DJ can get a square clubface at impact
with the same degree of left forearm pronation at impact as existed at address.
Now, consider how KB can have a square clubface at address and also at impact with a different combination of left forearm/wrist alignments.
At address, KB has
angled his left arm back (away from the target) so that his hands are roughly centralized between his thighs. How does he achieve a square clubface at address with a centralized hand location?
Consider this modified DJ image.
I have drawn a blue line to demonstrate a left arm that is angled back (away from the target) so that the hands are more centralized between the thighs at address. The red dotted line represents the clubshaft. Note that I have kept the degree of forward shaft lean (angle between the left arm and clubshaft due to a moderately strong left hand grip) constant, which means that the clubshaft would be angled away from the ball at address, which also means that the clubface would face to the right-of-the-target (red arrow). However, KB has his clubhead positioned at the ball at address with a square clubface. How does he achieve that goal. The next image shows the needed biomechanical modification required to achieve that goal.
The pink dotted line shows a clubshaft that is near-vertical at address, and the pink arrow shows that angling the club more targetwards would automatically square the clubface. What biomechanical mechanism would allow that change in clubshaft angulation (from the red dotted line to the pink dotted line). The answer is left wrist bending. Note that the modified "blue line + pink-dotted line" image matches image 2 (KB's "real life" address position - and note that KB has a bent left wrist in image 2).
Now, has does KB achieve a square clubface at impact?
KG maintains an intact LAFW/GFLW between P4 and P7+ and he doesn't bow his left wrist like DJ. So his left arm-angle clubshaft angle at impact will not have more forward shaft lean due to the presence of left wrist palmar flexion.
Consider this modified DJ image.
I have drawn a blue line showing that the left arm is angled forward at impact to get the hands opposite the left mid-thigh at impact. The dotted red line represents his clubshaft. Note that I have kept the left arm-clubshaft angle constant (because KB has a GFLW at address and also at impact) which means that the degree of forward shaft lean due to the adoption of a moderately strong left hand grip will remain constant. However, note that the clubhead will be ahead of the ball and the clubface (red arrow) will be closed to the target. So, KB has to use a biomechanical swing modification to get his clubhead positioned at the ball at impact with a square clubface. What type of biomechanical modification would solve this problem?
Consider this next modified DJ image.
See this hyperlink if the image doesn't automatically appear -
perfectgolfswingreview.net/JohnsonAddressImpactSeven.jpgImagine keeping the left arm angled forward to the same degree (blue line) which means that the hands (represented by the junction between the blue line and the dotted red line) remain in the same position, but now imagine what effect increased left forearm pronation (curved pink arrow) would have on the clubshaft angle and clubface. If the left forearm is pronated it would angle the clubshaft more away from the target (due to the clockwise rotation of the GFLW and clubshaft) and the amount of angulation would depend on the magnitude of the accumulator #3 angle - see dotted pink line. That would get the clubhead to be positioned at the ball. That same clockwise rotation of the clubshaft (due to left forearm pronation) would open the "closed clubface" so that the clubface would become square at impact. The next image shows that this is what KB actually does in his "real life" golf swing.
Note that the blue line/pink dotted line image in image 1 exactly matches KB's "real life" left arm/clubshaft alignment in image 2. Note that KB comes into impact with a more pronated left forearm (biomechanically equivalent to an incomplete release of PA#3) and that allows him to have square clubface at impact.
Jeff.