Jim McLean's 6 degree-of-freedom 3D report and other pevis/hips commentary

[spktho]

If you want to better understand stretch shortening cycles in the lower body you'd be wise to observe.

No. I'm just trying to understand what you said because I enjoy your posts/insights.

Sorry for any condescension. That's not my intention.

I will have to take your assertion in the last two sentences as sincere, even if your first sentence implies a different sentiment.

Maybe you can try powering the pelvic turn in the downswing with only the rear hip firing with the femur going into internal rotation. Granted using external rotation of the rear femur helps pelvic rotation a bit more, it still makes it difficult for sequencing the rest of the movements.

Each hip contributes movements to rotate the pelvis. I don't see how talking about hip movement in relation to pelvic rotation is distracting. I believe you may be eluding to there being a correct sequencing for each hip individually in their roles for pelvic rotation; I was as well.

 

[GeoffDickson]

the trail side is the hinged side on the initiation of the downswing, while the lead side swings open. this trail side will at some point in the downswing break free of its 'hinge'

Great explanation. So to paraphrase: the right hip only moves towards the ball after the left hip has moved away from the ball.

 

[GaryRead]

Great explanation. So to paraphrase: the right hip only moves towards the ball after the left hip has moved away from the ball.

Yes that is the general concept I was inferring, the trail hip breaks free as a result of the lead hips active rotation. So as the left hip reaches a point of max ROM, given the nature of our stance, the right hip will have to release to take up the slack and allow the turn to come to a 'complete' finish the exact timing of which I would think would be very personal.

Remember I am not qualified in any way to say this is correct or optimal. I was simply trying to describe the movement in response to Rafared's post on how can the trail hip stay back if the lead hip is leading. In fact the more the Lead hip leads/rotates, the more the right hip stays back! In essence it all depends on where the centre of rotation for the hips is. The hips can get to 40 deg open at impact through different hips motions, either the right hip closes to the target to get to 40 deg or the left hip opens to the target to get to the 40 deg. Whether or not either of these are possible for everyone is a different debate, Im just offering up the different means to an end.

The only way to test the hypothesis and draw any meaningful conclusions would be to measure hip speeds independently of one another on elite players.

If you think that becomes complicated, imagine the same could be said for the rotation of the torso,shoulders,arms and wrists, and all the possible variations between. The research involved would be torturous and one hopes that with such a high number of possible variance in rotation, speed, timing, acceleration and all the while with different body compositions with different ratios in anatomy / muscle and fat, that some sort of correlation is formed between elite players and the rest.

And if a correlation is found, will it be attainable by the 99.999% of golfers that need help the most? We may find that the understanding of the elite swing is just for the elite and for the rest of us a personal profile which will allow the person to get the most out of their god given limits will have to be prescribed, the general theory of which may be universal, but the detail of which would be very personal.

 

[JEREMY5577]

Imagine the swing as a top view down and hips as a door with one side 'hinged' .

the trail side is the hinged side on the initiation of the downswing, while the lead side swings open. this trail side will at some point in the downswing break free of its 'hinge'

Worked on this ^^^ this morning. Holding the right hip back and having the feel of it acting like a hinge while firing the left seemed to help a ton. Held the tush line much better. Still have to focus on where to transfer the weight though. I like the feeling of jumping my belly button up onto my left femur so it's facing the target.

 

[GaryRead]

It is my idea we are not seeing individual speeds of the trail / lead hip quoted on the 3d motion capture apparatus's because for as long as you measure the speed of the hips in degrees a second (or any other rotational movement with 2 ends spanning out from a centre point) you will not be able to identify any independent speed of the 2 points (i.e each end point of the hips)

The only way to measure the speed of 2 opposing points in relation to their centre of rotation would be to calculate the Tangential Velocity at those points. Someone more in the know than me can offer up a further explanation of how to work this out, but you first need to ascertain the centre of rotation, which in 3D is harder than it sounds when you consider there is lateral movement too, you cant know it with just the rate of rotation in degrees data.

Somebody may be able to tell me that the Kvest and AMM et al dont just measure the rotational speed in degrees per second but from all the graphs I have personally seen published they do...

I came to this conclusion through the following thought processes. Please if anyone can correct me or if I have made an error call me up on it.

If you take the following example:

I have a thin tube of metal which I can rotate screwed to a table. one side of the tube is 20cm from the centre of rotation (fixed point) the other side is 10cm from the centre of rotation.

I rotate the whole tube at the same speed 90 degrees and as I expect they both move together and stop at right angles to where they started. They both reached there at the same time and at the same 'degrees per second' however the 20 cm side traveled further distance in the same time given its further length from the center and although we can say they both traveled at the same degrees per second their speed / velocity is clearly different.

In this example, it does not matter where I put the cnetre of roatation along the tube, when I turn it, both ends turn at the same rate with regards to degrees in time, but the velocity is different.

Until these machines are programed to differentiate between tangential velocity of the 2 points and degrees of rotation we will see the the pelvis quoted as as a single unit with a single value for speed

Considering this applies to every movement that has 2 points of rotation around a point, pelvis, torso, shoulders etc, I am not sure what the implications of this are when it comes to understanding the data, but there will be some for sure.

 

[lia41985]

It means things are far more complex than we were being told....

 

[Dariusz J.]

Why overcomplicating things ? As I said, pelvis can be viewed from the up or from the down, depending on what are the intentions of a measuring person. Do you want to measure X-factor ? Do it from the up while ignoring individual hip joints action. Do you want to know what really happens with pelvis in the motion of a biped ? Measure each hip joint individually in relation to a fixed point (can be e.g. sacrum axis). It is not a rocket science. Use anatomy and fresh mind + 3-D thinking.

Cheers

 

[lia41985]

What's with the shoulder numbers? What does that say about the sequencing of the movents? What's the difference between negative acceleration and deceleration? How does that complicate the picture? What about the hips versus the pelvis as measuring points? What are the teaching implications?

 

[GaryRead]

Do you want to know what really happens with pelvis in the motion of a biped ? Measure each hip joint individually in relation to a fixed point (can be e.g. sacrum axis). It is not a rocket science. Use anatomy and fresh mind + 3-D thinking.

Cheers

Yes dariusz I do not disagree one bit with the concept you put forward on how to understand the independent speeds of the trail vs lead hip, however the determination of the fixed point in order to work out the speeds it what is complex. What you say above in theory is sound but in reality it is like saying all we have to do to find out how old God is, we need to know when he was born.

A machine has to have the right programming to be able to formulate where the centre of rotation is and if the pelvis is moving laterally at the same time the machine would be clever to seperate linear movement with rotation of each hip point measured in m/s not degrees per second. Maybe all or some do measure this. they would shed a more detailed light on things.

This all started when a post asked how you could lead with the front hip whilst keeping the trail hip back. I thibk most ppl assume the hips turn with the centre of rotation being centred, of course it can be as many times as it is not and it is when it is not that we need to be able to measure and...Well without the data I have been talking about the past few posts we wont be able to delve into this aspect of the swing, which obviously has its merits. People have reported better contact and accuracy by employing the intention of changing their hip speed independently with BBKIB and I'm trying to hilighted that this intention will not be quantified unless the machines are programmed to recieve the data required to truly understand the movements of the golf swing.

Giving a pelvis reading in degrees per second will always give 1 reading as I've explained. But what if a poor player has the same figures as an elite player but what the machine doesn't pick up is that the elite swinger rotates his lead hip 10m/s and his trail 5m/s at peak speed and the poor player has the opposite, 5m/s lead hip and 10m/s trail hip at peak impact. The rate of rotation in D/s for these examples could be identical and if we went purely on this measurement we wouldn't be silly fit thinking that the poor player has an elite attribute in this respect when in fact they are not doing any similar movement wise. The same goes for any other rotational aspect of the swing that has 2 end points of rotation.

 

[Dariusz J.]

Yes dariusz I do not disagree one bit with the concept you put forward on how to understand the independent speeds of the trail vs lead hip, however the determination of the fixed point in order to work out the speeds it what is complex. What you say above in theory is sound but in reality it is like saying all we have to do to find out how old God is, we need to know when he was born.

A machine has to have the right programming to be able to formulate where the centre of rotation is and if the pelvis is moving laterally at the same time the machine would be clever to seperate linear movement with rotation of each hip point measured in m/s not degrees per second. Maybe all or some do measure this. they would shed a more detailed light on things.

This all started when a post asked how you could lead with the front hip whilst keeping the trail hip back. I thibk most ppl assume the hips turn with the centre of rotation being centred, of course it can be as many times as it is not and it is when it is not that we need to be able to measure and...Well without the data I have been talking about the past few posts we wont be able to delve into this aspect of the swing, which obviously has its merits. People have reported better contact and accuracy by employing the intention of changing their hip speed independently with BBKIB and I'm trying to hilighted that this intention will not be quantified unless the machines are programmed to recieve the data required to truly understand the movements of the golf swing.

Giving a pelvis reading in degrees per second will always give 1 reading as I've explained. But what if a poor player has the same figures as an elite player but what the machine doesn't pick up is that the elite swinger rotates his lead hip 10m/s and his trail 5m/s at peak speed and the poor player has the opposite, 5m/s lead hip and 10m/s trail hip at peak impact. The rate of rotation in D/s for these examples could be identical and if we went purely on this measurement we wouldn't be silly fit thinking that the poor player has an elite attribute in this respect when in fact they are not doing any similar movement wise. The same goes for any other rotational aspect of the swing that has 2 end points of rotation.

Gary, I am theorist. AMATEUR THEORIST. I do not want to be all-knowing source, rather a help when its needed. I won't construct a machine, I am too stupid for this. What I can do is to point out some facts that can be useful. Watched many times details were forgotten and the whole result was f**ked up.

Cheers

 

[lia41985]

Whereditgo?
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[lia41985]

Each hip moves independently (e.g. rate of rotation) of the other. Speaking of just the pelvis obscures the complexity.

Thanks for the post-humous like of this above quoted post, Manz. Tricky bird.

 

[Brian Manzella]

Like lots of long threads, thing sometimes deteriorate into internet blather....edited now, there is hope for this one...back to golf.

 

[Brian Manzella]

Here are the elements as I see them (after being away from home and the forum for Christmas)...

There is the pelvis...it is rotating during the swing. Speeding up and slowing down on the backswing, speeding up and slowing down and then speeding up again on the downswing.

The upper legs (Femurs) are attached to the pelvis.

The 3D systems create a STICK THAT DOESN'T EXIST from one "hip" to the other.

To me, it is much easier to think of the pelvis as what it is, and the hip as just the upper leg.

As plain as day, you can "leave the right upper leg back" near it's top of the backswing location, and rotate the pelvis...for a time.

Probably to near the last phase of the downswing.

Then the pelvis is going to "take the upper leg" (hip) with it.

Then, there is going to be a small amount of time where the two (upper leg [hip]) is going near the speed as the pelvis.

But, after some sliding (but not as much as many believe), the pelvis is going to start losing it's tilt and after a certain amount of rotating, the torso starts looking for some stability and well...the pelvis is going to slow down.

But that's how all of this got started, eh?


So, no doubt there are a least three different speeds that could be measured. And probably many more.

 

[lia41985]

the pelvis is going to slow down

Negative acceleration, deceleration, or acceleration?

You sure it's not velocity? Positive or negative?

Why do teachers like John Jacobs, who you agree plenty with, speak of a "turn and release"?

As we've learned, the club, shoulders, hips, arms, hands, all move in different planes. The hips and shoulders rotate on much "flatter planes" than some instruct...

The tilters...

Jacobs used to say turn, don't tilt.

Was he "right"?

 

[Brian Manzella]

Negative acceleration, deceleration, or acceleration?

Tell us why you think it matters so much.

It doesn't seem to with Art or Sasho. All ears....

 

[lia41985]

We are being told the pelvis decelerates.

Does the pelvis experience negative acceleration, acceleration, or deceleration?

How is this not obviously important...?

 

[Brian Manzella]

At some point, you have to say why it (the word) matters in a golf lesson. That's what I am asking...

 

[Brian Manzella]

Why do teachers like John Jacobs, who you agree plenty with, speak of a "turn and release"?

That's how he viewed the swing.

"Two turns and a swish."

As we've learned, the club, shoulders, hips, arms, hands, all move in different planes. The hips and shoulders rotate on much "flatter planes" than some instruct...

Yes.

And yes.

Jacobs used to say turn, don't tilt.

Was he "right"?

In my opinion, in what he was actually trying to say (also in my opinion)—yes.

 

[Brian Manzella]

Oh, ok.

Like Negative Alpha down by the ball....

Yup...you are correct Lia. It matters a lot!