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Thread: Jamie Sadlowski's hip rotation into impact

  1. #16
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    Quote Originally Posted by Jeff Martin View Post
    Not only is the boot-legged video Manzella posted too blurry to read the displayed numerical data, the x-axis has been shrunk relative to the y-axis, distorting all angle measurements. To add insult to injury, Manzella's Vimeo channel doesn't permit downloads, so I had to record it off the screen AGAIN so I could go through it on a video editor. For anyone else that wants to frame through and measure hip angles, I uploaded my recording to YouTube where anyone who'd like to can download it.




    To give you an idea of the x-axis distortion in Manzella's boot-legged video, the angle drawn in the screen capture below should be 45 degrees if the x-axis and y-axis were scaled properly (i.e., equally). As you can see, the angle is understated by about 8.5 degrees! That means Jamie's hips are closer to 50 degrees shut at the top of the backswing and 60 degrees open at impact.


    Attachment 1393


    Accomplishing 110 degrees of rotation in the space of 0.2 seconds requires an average rate of rotation of 550 degrees per second!!! That's insane. As you can see in the chart below of TPI data, the average peak rate of rotation for the tour pros they measured is just 434 degrees per second.

    Attachment 1394

    As you'd expect, something recorded off a video screen at least a couple times is going to be jumpy in spots and perhaps lose some frames here and there. But, this video captures the entire downswing and the story it tells is pretty simple: Sadlowski's hip rotation during the downswing is at near constant velocity, as my V1 belt-loop exercise above suggested. In fact, Jamie's hip rotation from top to impact has almost a perfect linear fit correlation (0.9990!), with drop offs in speed of rotation at just the beginning and end of the sequence.

    Below I have graphed the data I measured off of the video. The red line is Jamie's hip rotation in degrees, with negative values representing closed hips and positive being open. As I mentioned above, these angles are quite understated because of the distortion to the x-axis. As you can see, even though the slope of of the hip rotation throughout the downswing is nearly constant, the data pulled off the video by hand was pretty noisy and caused the frame-to-frame rate of rotation calculation (the blue line) to be pretty jumpy. I smoothed the ROR data (shown in green) to better reflect reality (you don't really think Jamie's hips accelerate and decelerate like a yo-yo during 0.2 seconds??).


    Attachment 1396


    So, what does this tell us? The first thing that is obvious is Jamie's hip rotational velocity does not peak when the hips are square (the vertical black line) and then rapidly drop off by a third or a half like the TPI/kinetic sequence model: there is, in fact, a second velocity peak (reflecting a second phase of acceleration) and velocity is maintained until the very last frames before impact, when his hips are nearly 60 degrees open and the upper body/arms/club moment of inertia is at its maximum.

    Second, we know that to maintain this velocity Jamie must be exerting increasing amounts of pelvic torque in the downswing. As the club and arms extend in the downswing, the upper body moment of inertia increases, putting a higher load on the body's torque generators (rotational velocity = torque times moment of inertia; if MOI goes up, torque must also go up or velocity will drop). So, from a biomechanical perspective, he is increasing his applied torque throughout the downswing, reflected in the second period of acceleration. That strongly suggests that his biomechanical intent is to accelerate the hips during the entire downswing.

    A far as I'm concerned, this data, as well as the Hogan analysis I did the other day and the 4DSwing analyses shared by Tapio, blows up claims that deceleration is essential to all good golf swings. Deceleration may be the ultimate result in most or nearly all cases, but, IMO, it should be caused by increasing moment of inertia, not decreasing torque.

    BTW, this is a 4DSwing analysis of a young European tour player with four wins. His hip rate of rotation is in blue and peaks at impact.

    Attachment 1397





    Jeff
    Dear Jeff and Kelvin,

    Thanksgiving afternoon, my beautiful wife Donna fell and broke her only remaining good hip, so since then, I have been at the hospital most of my waking hours, and on the computer late at night as I have a passionate and dedicated interest in trying to help everything getting better.

    It is with this spirit that I first say THANKS to both of you for your timely responses to my last post BUT voice and explain my disappointment in both your responses, meaning ONLY to be constructive. I will conclude with a piece of science that I believe to be the least understood BUT most affecting the confusion in this pelvis deceleration discussion.

    As to your several posts, Kelvin, it is hard to find that you have read and understand what I have written. I have tested golfers of ALL capabilities using both Flightscope and Trackman for documenting the statistical characteristics finding that better/increased lower body dynamic stability increases distance and reduces dispersion. In the cases where I had access to 3D systems, the recorded pelvic angular velocities decreased, and the appearance of the kinematic sequences improved BUT THEY WERE THE EFFECT OF THE BETTER DYNAMIC BALANCE. So Kelvin, I do not accept your "Nuf sed" salutation in the Brian Manzella Picture blog, because, in my opinion, for such an important subject to ALL golfers, you OWE US MORE.

    Regarding your post Jeff, I find a basic difference in trying to understand the physics you used, and I quote, " rotational velocity = torque times moment of inertia". From my understanding of the physics regarding rotational motion, the controlling and applicable equation I think you are trying to use involves angular momentum, and in written terms is " torque times time = Moment of Inertia times angular velocity". Simply transposing, this , in your terms would result in "rotational velocity = torque times time DIVIDED by moment of Inertia".

    Also, CAUTION here and my final point, the pelvic axis of rotation is constantly changing during the downswing, and therefore the visual points viewed by camera in 2D have a constantly changing 'radius' which has led to WAY TOO MUCH CONFUSION and contention for my liking, and probably all seeking 'truth' versus controversy.

    So, in conclusion, I will continue to answer any questions, and restate that my offer to meet with you, Kelvin and anyone else representing you will always BE THERE. I still FEEL, you both are very well intentioned, expending significant resources, and as I am and hope you are, anxious to discuss and change as scientifically verifiable 'golf truth' continues to become available.

    Sincerely,
    Art

  2. #17
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    Quote Originally Posted by nmgolfer View Post
    Hello Jeffy,

    Just want to take a moment and congratulate you and Kelvin for putting to rest with incontrovertible data the pervasive "kinetic chain snapping" golf swing myth. Thomas Huxley said it best:

    The great tragedy in science: the slaying of a beautiful hypothesis by an ugly fact.

    One of the reasons the one eyed Manzella banned me so many years ago is because I scoffed at that notion (which defies common sense) and he can't tolerate dissent. I can't tell you how pleased I am to see the better researchers of the golf swing such as yourself and Kelvin arriving at the same conclusion I did and are able to back it up with even more scientific data. That said, the myth will undoubtedly persist, like so many others have in the past, for a very long time come.

    nm-

    Why, thank you so much!

    There seems to be some shifting in the "theory". Advocacy of active braking ("dig in the toes", "brace the core", "quiet feet") is now being replaced by "pelvic deceleration is inevitable and fighting it will create horrendous consequences" such as an "upset in dynamic stability" and "lower clubhead speed". Tell that to Jamie!

    I also got a big laugh out of this:


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    hmmmm... I seem to recall Tapio trying to get that message across over a year ago with no success because he had an "agenda"! But when they hear the same stuff from the New Jersey Department of Transportation it becomes divine enlightenment! And now wulsy is stealing my favorite line about listening to Bman, Finney, Shields, etc...


    Thanks for stopping by!



    Jeff

  3. #18
    nmgolfer Guest
    Hello Art,

    note*

    Torque = I*alpha where alpha = angular ACCELERATION (not angular velocity).

    that said... have you documented your research results? (I seen some forum posts but consider those inadequate)

    nmgolfer

  4. #19
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    Quote Originally Posted by art View Post

    Regarding your post Jeff, I find a basic difference in trying to understand the physics you used, and I quote, " rotational velocity = torque times moment of inertia". From my understanding of the physics regarding rotational motion, the controlling and applicable equation I think you are trying to use involves angular momentum, and in written terms is " torque times time = Moment of Inertia times angular velocity". Simply transposing, this , in your terms would result in "rotational velocity = torque times time DIVIDED by moment of Inertia".
    Thanks, yeah, I really butchered that one. I should have refreshed my memory instead of relying on "the top of my head". Just as Force = Mass times Acceleration, Torque = Moment of Inertia times Rotational Acceleration. So Rotational Acceleration = Torque divided by Moment of Inertia. If the golfer's MOI increases and the torque applied remains the same, the object's rotational velocity will decelerate. So, to maintain rotational velocity in the downswing, the golfer needs to apply increasing torque in direct proportion to the increase in MOI. For nearly all of the second half of the downswing, Sadlowski appears to be doing that very well.

    As I thought some more about the Sadlowski numbers, I realized I miscounted the number of frames the first time around (last week), so in post #11 above I did not calculate the average rotational velocities in the first and second half of the downswing accurately. I also hadn't noticed then the distortion created by the shortened y-axis.

    Knowing now that from the top to hips square is 17 frames and that his hips were likely at least 50 degrees closed at the top, Sadlowski's hips rotated at an average rate of about 529 degrees per second in that first half of the downswing. From square hips to impact, Jamie's hips rotate about 60 degrees open in 18 frames. That is equal to an average rate of rotation of 600 degrees per second, a 13% increase in average rotational velocity after the hips square. That doesn't exactly square (pun intended) with the following pronouncements:


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    Sorry to hear about your wife and her hips. My mom also had both hips replaced so I know it isn't much fun.

    Take care,




    Jeff

  5. #20
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    I did not know that...

    For a change, Finney posts something I hadn't seen before, although I certainly was aware of the issue discussed: the terminology he described was new:


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    In the case of my Sadlowski measurements, I used "moving": wherever the pelvis went, I measured the angle of the green hip line relative to the x-axis, and the rotational velocity was HIGHER after the hips reached square and did not "rapidly slow down" "well before impact".




    Jeff

  6. #21
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    Well, Brian, did you show Sasho my graph of the data YOU posted???

    Still in denial and creating ridiculous strawmen:

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    Jeff

  7. #22
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    It just keeps getting better!!!

    Guess what? Now that the data in the Sadlowski video has been extracted and analyzed (and thoroughly debunks Manzella's "hip rotation peaks at square hips and decelerates rapidly after that for all good golfers" theory), Finney tells us that what Brian posted can't be relied upon because it is a "VIDEO OF A VIDEO OF A VIDEO"!!! hmmmm... Why didn't they tell us that last week when they said it supported their theory???


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    This is too easy...



    Jeff

  8. #23
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    As usual, Finney has no idea what he is talking about...

    The latest from the stupidest person in golf...


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    ...and it goes on.

    What Mike seems to miss is that these ISA procedures were presumably followed by Motion Reality, so the data presented on the screen that I copied would already be in accordance with the ISA protocol! Said another way, why do I need to follow the ISA protocol if I'm just copying ISA compliant data???

    Of course, it is always possible that the ISA protocols weren't followed by Motion Reality. If so, then why did Brian post the video in the first place???

    Sorry, Mike, you can try all you want, but you can't have it both ways!!!

    Really, just stick to selling golf balls and arranging tee times. You're drowning here...




    Jeff

  9. #24
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    Strawman alert!!!

    Desperate times call for desperate measures!!! The strawmen are flying!!!

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    Let's talk about the real debate. Bman says, unequivocally, that the best swings in golf have peak hip speed "well before impact" (hips square or before) which then "decelerates rapidly" through impact. We disagree. We have posted data from 4DSwing that shows Alex Noren's hip speed accelerates after hips square and peaks at impact, we have posted video analysis of Ben Hogan that unequivocally shows hip acceleration after hips square, and we have compiled and posted data that shows Sadlowski's hips rotate faster after hips square then before. This data falsifies Bman's theory and he can spend a billion hours on the phone with Sasho Mackenzie and it won't change that fact.

    Jeff

  10. #25
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    Mike, it's real simple...

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    Depth of field and parallax issues don't factor at all into these simple facts: at the top of the backswing, Sadlowski's hips are at least 50 degrees shut. 17 frames later, the hips are square. That is a rate of rotation of about 530 degrees per second. At impact, 18 frames later, the hips are at least 60 degrees open, a rate of rotation of 600 degrees per second, 13% higher. Is that consistent with a theory that states rotation peaks at hips square and decelerates rapidly after that? No. Falsified.



    Jeff

  11. #26
    Lukman Ahmed Guest
    You're saying you're top down view (is that right?) is the proper frame of reference, is that correct?

  12. #27
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    Quote Originally Posted by lia41985 View Post
    You're saying you're top down view (is that right?) is the proper frame of reference, is that correct?
    Isn't it Manzella's top down view? Last week, it was his savior. This week? Piece of shit...only an idiot would look at it...


    Jeff

  13. #28
    Lukman Ahmed Guest
    Woah.

    Let's just stay on topic...



    What view are we talking about?

    Me asking "is that right?" was me asking for clarification, not the green light to throw a grenade...!

  14. #29
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    Quote Originally Posted by lia41985 View Post
    Woah.

    Let's just stay on topic...



    What view are we talking about?

    Me asking "is that right?" was me asking for clarification, not the green light to throw a grenade...!

    Lukman-

    Last week Bman posted data that he thought supported his theory. I actually LOOKED AT THE DATA and, in fact, it falsifies his theory. So, I would say, yes, the top down view is the proper frame of reference!



    Jeff

  15. #30
    Lukman Ahmed Guest
    Jeff,
    I'll think more about this later, hopefully. Do you mind just linking me to the footage? Are you talking about that overhead Motion Reality view? Confused and/or tired...it's late...

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