just a thought on 3D motion analysis.....

[Michael Finney]

there is no standard way to measure the velocities and accelerations (both linear and angular) of the various body parts.....that is why every 3D apparatus will spit out different looking graphs....it doesn't make a particular graph more accurate, it just makes them different....

instantaneous screw axis theory basically says that it is very difficult to measure linear speeds (across the video screen) and angular speeds (rotational) because the body parts are CONSTANTLY changing their relationship (angles between their corresponding axes of rotation) to each other during the swing which can potentially throw off the measurements.....

 

[Matt 4-L]

I know very little about the 3d analysis machines out there for golf, can anybody list them?

K-Vest.....

 

[Martee]

Would the relationship between body parts, clubhead and ball allow to yeild accurate and consistent result within that framework?

 

[wulsy]

there is no standard way to measure the velocities and accelerations (both linear and angular) of the various body parts.....that is why every 3D apparatus will spit out different looking graphs....it doesn't make a particular graph more accurate, it just makes them different....

instantaneous screw axis theory basically says that it is very difficult to measure linear speeds (across the video screen) and angular speeds (rotational) because the body parts are CONSTANTLY changing their relationship (angles between their corresponding axes of rotation) to each other during the swing which can potentially throw off the measurements.....

Of course, when you think about it you are measuring things that may only be moving because something else is moving and that may only be moving because something else is moving and so on and so on. And that's simplifying it. Probably pretty damn inaccurate this 3D business, but it's the best we've got I suppose.

 

[SteveT]

The Future of Instantaneous Screw Axis Theory to Golf Instruction and Beyond

J.P. Carey, A.S. Vena
The Journal of Applied Golf Research - June 30, 2011

Abstract

Many golf instructional programs and institutes analyze 3D golf swing kinematics through software packages. Our group applied a promising technique, instantaneous screw axis (ISA) theory, to provide a better simulate segment rotation and a simple and practical means of looking at the kinematic golf sequence. Our work focused on identifying ISA location and orientation, and segment angular velocity of major body segments involved in the golf swing to determine ISA applicability to evaluate kinematic sequence. The method successfully demonstrated that magnitude of maximum angular velocities increased from the most proximal segment (the pelvis) to the most distal segment (the left arm), in accordance with the summation of speeds principle.

Furthermore, in most of our test cases the maximum angular velocities occur in the desired kinematic sequence, where the first maxima was achieved by the most proximal segment and followed by the more distal segments in the kinematic chain – demonstrating a range of player abilities. Furthermore, the ISA method provides clear visual representations of segment rotations, which we believe would be beneficial to instructors and players alike. Based on these findings, we believe that there is significant potential application of ISA for golf instruction and golf biomechanics analysis software. Furthermore, this approach opens a large range of potential future areas of golf research, instructional means and an additional tool for equipment design and tailorability opportunities.

The Furture of Instantaneous Screw Theory to Golf Instruction and Beyond | The Journal of Applied Golf Research - The Future of Golf

 

[SteveT]

@Finney .... are you aware of this new information on ISA theory?

 

[TeeAce]

there is no standard way to measure the velocities and accelerations (both linear and angular) of the various body parts.....that is why every 3D apparatus will spit out different looking graphs....it doesn't make a particular graph more accurate, it just makes them different....

instantaneous screw axis theory basically says that it is very difficult to measure linear speeds (across the video screen) and angular speeds (rotational) because the body parts are CONSTANTLY changing their relationship (angles between their corresponding axes of rotation) to each other during the swing which can potentially throw off the measurements.....

You are totally right and when comparing results with different devices you really have to understand the graph and its definitions, and like I've always been saying, our device is 90% to compare, 10% to analyze.

The problem starts when people start to make strong statements based on wrong conclusions and mistakes in measuring and understanding real directions of the moves.

I wonder how many really sees that when hands and club head are moving on plane, they have more than 90 degrees difference in directions. That might be good question to the summit.

 

[Brian Manzella]

I wonder how many really sees that when hands and club head are moving on plane, they have more than 90 degrees difference in directions. That might be good question to the summit.

Good one.

But, we have "been there done that."

Aaron Zick pointed out that fact almost 4 years ago at a TGM Summit, and was told to "shut up, Aaron."

I am interested in your work, "tee," and your questions about ours. Give me any two questions for the AS2, and I will make sure they are answered.

 

[TeeAce]

Good one.

But, we have "been there done that."

Aaron Zick pointed out that fact almost 4 years ago at a TGM Summit, and was told to "shut up, Aaron."

I am interested in your work, "tee," and your questions about ours. Give me any two questions for the AS2, and I will make sure they are answered.

I'm sure Brian your team knew that, but there is still few millions of people who think they move to same direction on plane. There starts the handle dragging...

 

[Brian Manzella]

....there is still few millions of people who think they move to same direction on plane. There starts the handle dragging...

You are so right.

 

[SteveT]

Big ignorant market out there... but I fear that they fear "true science", which will scare them off. There are a lot of Luddites, both golfers and teachers, who fear science and oppose change... as evidenced even on this fine forum. Your challenge will be to make true golfswing science palatable to the golffing masses. Keep up the good work at AS2.

 

[Michael Finney]

@Finney .... are you aware of this new information on ISA theory?

yes, that paper is why i wrote my second paragraph in the original post.....it's a 300 page paper with the first 175 pages about measurement and calculation errors using this "upgraded" approach......a dissenting group trying to cast doubt on the kinematic sequence and its understanding should probably take a long look at this and get back with us.....chris welch and rob neal will be asked a lot of questions the next 3 days -

by the way - there's a 5D machine on its way.....XYZ Time and a fourth grader's protractor for measuring lag

 

[SteveT]

Oh, sorry... by the tone of your second paragraph I thought the problem was insurmountable....and your first paragraph explained the deficiencies of 3D........ whereas the scientific paper promoted ISA as a solution with:

"Furthermore, the ISA method provides clear visual representations of segment rotations, which we believe would be beneficial to instructors and players alike."

My bad .....

 

[spmurph]

by the way - there's a 5D machine on its way.....XYZ Time and a fourth grader's protractor for measuring lag

now that's funny!