DG,
I have spent a few days studying that Phil Cheetham Sportsbox-video.
This is the first time that I have seen a series of graphs of the lead arm-clubshaft angle between P4 => P5.5 in a lot of pro golfers. I agree that there are two major patterns - a fixed angle and a downswing-loading pattern. The third pattern - the early release pattern (= casting) is very uncommon in pro golfers.
However, I think that PC offered no insights into what causes a pro golfer to have a downswing-loading pattern. I also think that his claim that it has the advantage of inducing a stretch-shorten cycle is nonsensical because the lead wrist's forearm muscle (extensor carpi ulnaris) is not causally responsible for inducing the release of PA#2 in a pro golfer. I believe that the downswing loading pattern and the PA#2 release phenomenon is mainly controlled by the interplay of two forces acting at the level of the hands connection with the club handle - the MoF created by the lead hand pulling the club handle along the hand arc path and the hand couple phenomenon.
Here is one of Kwon's images.
The black arrow represents the MoF created by the lead hand moving down the hand arc path between P4 => P5.5. The clubshaft will tend to want to align itself with the dotted line between P4 => P5.5 and that represents the negative MoF measurement. That negative MoF will induce the phenomenon of downswing loading. The magnitude of that negative MoF between P4 => P5.5 is mainly affected by i) the direction of linear pull of the lead hand happening at the level of the club handle; the ii) the magnitude of that pulling force and the iii) the angle of the black arrow relative to the clubshaft. No golf researcher has ever attempted to calculate the combined/interactive result of those three factors and its effect on the likelihood of downswing loading.
Another major factor that will affect the phenomenon of downswing loading is the magnitude of the trail hand's positive hand couple torque that offsets the negative MoF. Downswing loading is more likely to occur if the trail hand's positive hand couple torque is small and insufficient to counterbalance the negative MoF. Biomechanical factors that may cause the trail hand's positive hand couple torque to be smaller include i) a greater degree of trail upper arm adduction, ii) a greater degree of bending of the trail elbow that decreases the distance between the trail upper arm and the train hand's position on the club handle and iii) a greater degree of trail wrist upcocking motion that can angle the club handle towards the trail side of the torso. Finally, those 3 factors will be greatly affected by the rotational alignment of the upper torso, and therefore the trail shoulder's positional alignment, at every moment in time between P4 => P5.5. No golf researcher has ever attempted to calculate the complex interactive/combined effect of those biomechanical factors on the magnitude of the trail hand's positive hand couple torque between P4 => P5.5. PC's assertion that any difference in the pattern of downswing loading between PGA male golfers and LPGA female golfers is due to differences in muscle strength is scientically unfounded/unsupported. PC has presented no "evidence" to support his claim!
I personally think that it (lead wrist angle) is a worthless Sportsbox measurement that golf instructors have no ability to correctly optimise in terms of adding (or not adding) downswing loading - because they have no idea how to alter those multiple biomechanical factors in a fruitful manner.
I also think that Chris Munson's comments on the relationship between the lead hand's grip strength and certain Sportsbox measurements was very amateurish and far too simplistic
Between the 19:48 - 19:56 minute time point of the video he shows SWK's takeaway and he incorrectly claims that SWK is getting his clubface square to his clubhead path between P1 => P2 by flexing his lead wrist. That's nonsensical! SWK is using the standard takeaway action involving lead forearm pronation that opens the clubface relative to the clubhead path. CM also incorrectly states that BS is extending his lead wrist and opening the clubface between the 19:56 - 20:03 minute of the video. That's not true! BS uses a very strong lead hand grip so any lead wrist extension between P1 => P2 mainly affects the clubshaft angle relative to the ground and it does not open the clubface. Note that BS's clubface is very closed relative to the back of his lead wrist at P2.
CM shows SWK at his P4 position at the 20:23 minute time point of the video and CM incorrectly claims that his clubface is sightly open. That's not true. SWK uses the intact LFFW/GFLW technique between P1 => P4 which means that his clubface will remain neutral, but he does slightly palmar flex his lead wrist at P4 and that will close the clubface relative to the watchface area of his lead lower forearm at P4 by a very small amount.
At the 20:31 minute time point of the video, CM shows BS at his P4 position and he calls it "open and laid-off"!!! However, his clubface is nearly horizontal relative to the ground and very closed relative to the back of the watchface area of his lead lower forearm (which is expected if a golfer adopts an very strong lead hand grip)!
Between the 21:00 - 21:29 minute time points of the video, their clubface will be in their naturally expected positions at P5.5 and P6 - as a direct result of their different lead hand grip strengths. From P6 => P7, SWK will have to use much more lead forearm supination during his PA#3 release action because he uses a weak lead hand grip, while BS will naturally use much less due to the fact that he uses a very strong lead hand grip.
Between the 23:00 - 23:45 minute time point of the video, CM incorrectly states that SWK has to slow down his body rotation and stall his lead hand's speed down the hand arc path in order to square his clubface by impact. However, that causal connection is not related to his lead hand grip strength!
Here is SWK's driver swing video.
Watch SWK's hand release action through impact at the 1:34 minute time point of the video. Note how he stalls the forward motion of his lead arm and straightens his trail arm/wrist through impact as he performs a flip-roll subtype of non-DH hand release action through impact. That can explain why he manifests a slow lead hand speed between P6 => P7+.
However, not all pro golfers who adopt a weak lead hand grip slow their lead hand speed and/or their torso rotation between P6 => P7+.
Here is Will Zalatoris's DH-hand release action.
Note that WZ (who uses a very weak lead hand grip) has a very open pelvis/upper torso alignment through impact and note that he does not stall his lead hand's targetwards motion through impact.
CM also incorrectly claims that BS hits his 7-iron further than SWK because he "turns his clubface down". That's not true! BS comes into impact with a lot more forward shaft lean than SWK (8 degrees difference) and that will cause the dynamic loft of the clubface to be decreased. However, the fact that SWK's clubface is more lofted at impact is not due to the fact that adopts a weak lead hand grip, but it is due to the fact that he comes into impact with very little forward shaft lean. It is entirely possible to come into impact with much more forward shaft lean than seen in SWK's golf swing when a golfer also uses a weak lead hand grip - by either bowing the lead wrist or by pronating the lead forearm more.
Here is Collin Morikawa at impact.
He has lot of forward shaft lean at impact despite using a weak lead hand grip - because he bows his lead wrist a lot at impact (compared to SWK).
Here is Justin Thomas at impact.
He has a lot of forward shaft lean at impact despite using a weak lead hand grip - because he allows his lead forearm to be more pronated at impact (compared to SWK).
Look at the measurements CM presents at the 26:27 minutes time point of the Sportsbox video.
He claims that SWK must have a slow pelvis/torso rotation between P4 => P6 (see measurements in the purple zone) to allow his clubhead to catch up!!!! That's crazy talk!!!!
Then CM discusses their comparative measurements at P6 (red zone measurements). CM asserts that there is a causal relationship between SWK's slower lead hand speed at P6 and the fact that his lead wrist angle is greater by 14 degrees at P6 (compared to BS). However, CM does not explain why he believes that there is a causal relationship between those two factors!!!
CM's comments are even crazier when he discusses their differences at impact (yellow zone).
Between the 29:00 - 29:07 minute time point of the video, CM claims that BS is extending his lead wrist in order to keep his clubface more open while he is simultaneously creating more forward shaft lean. That's totally nonsensical!!! BS adopts a very strong lead hand grip so any lead wrist extension between P6 => P7 only changes his accumulator #3 angle and it does not cause his clubface angle to become more open relative to the clubhead path. Also, BS naturally acquires forward shaft lean at impact because his lead wrist is going to be slightly less ulnar deviated at impact secondary to his very strong lead hand grip and it is not due to any wrist/hand manipulation maneuver.
CM also incorrectly asserts that BS is rotating his pelvis/upper torso more actively into impact than SWK, but the measurements in the yellow zone do not support his wild claim! Note that they have similar changes in pelvis/upper torso rotation between P6 => P7 and there is no evidence that SWK is slowing his upper torso rotation more than BS between P6 => P7. CM also incorrectly asserts that SWK must slow his upper torso rotation between P6 => P7 in order to get a square clubface by impact!!! That's not true because SWK's PA#3 release action is causally responsible for squaring his clubface by impact and its efficiency can be independent of the degree of upper torso rotation happening between P6 => P7.
Finally, between the 33:0 - 33:23 minute time point of the video, CM incorrectly claims that SWK must let his clubhead bypass his lead hand faster (compared to BS)!!! Why?
Will Zalatoris uses a weak lead hand grip and he does not have to let his clubhead rapidly bypass his lead hand through impact!
Jeff.