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Chi Running

Discussion in 'Biomechanics, Sports and Foot orthoses' started by James Welch, Jun 26, 2012.

  1. Nope, gravity is still tending to pull the body downwards, that is all it can ever do in isolation. The force couple of the ground reaction force with the gravitational force acting at the the centre of mass might tend to cause forward rotation of the segments which are superior to the centre of rotation in the situation, yet those inferior to it are being rotated backwards. In the absence of any other forces though, the body would just spin on the spot, without making forward progression. Thus, other forces are required to make forward progression, not just gravity and GRF. Gravity and GRF alone won't do it, unless you are descending an incline. Moreover, you have to get the centre of mass ahead of the centre of pressure and not fall over.
     
  2. This should read "pushing the body backwards" - right Eric?
     
  3. If there were no gravity, and the body were leaned forward with the feet on the ground, then the body would not rotate forward. Therefore, when this case of no gravity causing no body rotation is contrasted to the case where there is gravity and body rotation forward does occur, one could say that gravity was at least partially responsible for the observation that leaning forward on Earth will cause the body to rotate forward.

    Gravity is responsible for the acceleration of the center of mass of the body which creates the ground reaction force (GRF) acting on the plantar foot. In turn, this GRF, along with friction between the plantar foot and the ground, causes a rotational force that causes an angular acceleration of the center of mass forward when the center of pressure acting on the plantar foot is posterior a line vertically downward from the body's center of mass, which David Winter called "center of gravity" (Winter, David A.: A.B.C. (Anatomy, Biomechanics and Control) of Balance During Standing and Walking. Waterloo Biomechanics, Waterloo, Ontario, Canada, 1995).

    Therefore, to say that gravity is not responsible for the body rotating forward when one leans forward is not correct, but to say that gravity is partially responsible for the body rotating forward when one leans forward is correct.

    I feel like I am back to the "walking on ice" debate I had with Howard Dananberg and Bruce Willams from years ago.:cool:

    Here is a nearly identical thread from 5 years ago where we were talking about the same concepts.

    http://www.podiatry-arena.com/podiatry-forum/showthread.php?t=4656
     
  4. Why not turn your example around and assume the only force was gravity? Would this "pull the body forward" as "Sicknote" maintained"? I have no problem with gravity + GRF causing rotation. I do have a problem with gravity "pulling" the body forward; gravity, in isolation acts downwards end of story, hence it cannot pull the body forward. And for as much of the body that it pulls forward, it pulls some of it backward. As we have already demonstrated, gravity + ground reaction force will only cause a "forward rotation" moment of the superior segments if the centre of mass is ahead of the centre of pressure. If the centre of pressure is ahead of the centre of mass, then gravity + ground reaction force will create a "backwards rotation" moment on the superior segments. Either of these situations in isolation create spinning on the spot. Thus, something else has to drive the body forward linearly during running. It is friction which enables forward movement of the spinning object, as you note. Hence I was trying to get "sicknote" to add in the forces in diagram form.

    So the question becomes, if the centre of mass was ahead of the centre of pressure at the time of strike during running, would you fall over onto your nose? Why not?

    And in the second half of stance, during running gait, when the centre of mass is more likely to be ahead of the centre of pressure, the centre of mass is trying to rise upwards, hence gravity is working against this, so how is gravity "helping" here? How come those guys on the moon had such long strides?
     
  5. Sicknote

    Sicknote Active Member

    What is wrong with this study?.


    Runners do not push off the ground but fall forwards via a gravitational torque.
    Romanov N, Fletcher G.
    Poses Tech Corp, Coral Gables, Florida, USA.
    Link: http://www.ncbi.nlm.nih.gov/pubmed/17933203


     
  6. Admin2

    Admin2 Administrator Staff Member

  7. Sicknote

    Sicknote Active Member

  8. Craig Payne

    Craig Payne Moderator

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    ...actually it is! I have sat through a couple of presentations from biomechanists (who know a lot more about this than me) in which they went through the biomechanical underpinnings used to promote Pose Running and showed that they were flawed. ...
     
  9. Explain the findings of this study to us... Like you said Kevin, walking on ice all over again...

    Like I said, about ten minutes ago: "And in the second half of stance, during running gait, when the centre of mass is more likely to be ahead of the centre of pressure, the centre of mass is trying to rise upwards, hence gravity is working against this, so how is gravity "helping" here? How come those guys on the moon had such long strides?"

    And of course, Romanov had no vested interest here...
     
  10. Here's a thought: gravity on earth is g = 9.81 m/s2, if we reduced the gravity to 8.81 m/s2 should we be able to run faster or slower? What about if we increased it to 10.81, faster or slower?
     
  11. fatboy

    fatboy Active Member

    i think i am going to invent/start Chai running...


    it's like normal running but with a cup of tea. (badum tish)
     
  12. Craig Payne

    Craig Payne Moderator

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    Before you start marketing it to the gullible, perhaps you should take Roberts course: Personal Improvement Starter Scheme ... it will help you become a real guru.
     
  13. efuller

    efuller MVP

    When the center of mass is anterior to the center of pressure the gravity/ground reactive force couple will tend to rotate the top of the body forward. With no friction, the inferior segment would rotate backward. The inferior segment does not rotate backward because of the posterior to anterior force from the ground acting on the foot. This force is pushing the foot/body forward. When looking at walking this is corroborated by looking at anterior posterior ground reaction shear. When the center of mass is posterior to the center of pressure the a-p shear is posteriorly directed, ground acting on the foot, and when the center of mass is anterior to the center of pressure the a-p shear is anteriorly directed ground applied to foot. It's really important to label the forces at which force is acting on what. I didn't do that in original post.

    Eric
     
  14. In order to properly understand the biomechanics of running, it is far too simplistic to use only a static assessment of the center of mass (CoM) of the body relative to the center of pressure on the plantar foot as an assessment method of this dynamic weightbearing activity.

    The first half of the support (stance) phase of constant velocity running involves a "braking action" of ground reaction force (GRF) pushing posteriorly on the plantar foot, while the second half of the support phase of running involves a "pushing forward" action of GRF pushing anteriorly on the plantar foot. During the support phase, there will be only one small instant in time when the GRF vector is vertically oriented, the whole rest of the support phase the GRF acting on the plantar foot will either be angulated posteriorly (first half of support phase) or angulated anteriorly (second half of support phase).

    In addition, during acceleration of the CoM (e.g. in the first 5 seconds or so at the start of a race) or deceleration of the CoM (e.g. after the end of a race) during a running competetion, the position of the CoM relative to the CoP and the GRF vector will be signficantly different than during constant velocity running. Also, as running velocity increases (i.e. constant velocity running) for any given runner (i.e. running first a steady 7 min/mile pace, then running a steady 6 min/mile pace, then running a steady 5 min/mile pace) the magnitude of the GRF vector will increase, and as their running velocity decreases, the GRF magnitude will also correspondingly decrease.

    Therefore, I hope that those following along do not make the mistake of assuming that one can accurately analyze still (i.e. static) photos of runners in a race or during running training activities to get any idea of the dynamics of running regarding the direction of the GRF vector, its spatial relationship to the spatial location of the CoM and the anterior-posterior shearing forces acting on the plantar foot at any instant in time during the support phase of running. Using still photographs to completely analyze the kinetics of running gait simply can not be done, however, still photography does allow to appreciate the kinematics of gait better.

    Furthermore, to suggest that a forward body lean, such as is advocated by certain running style advocates, will make you run faster, better, or even with less injury is not only pure speculation with not a shred of credible scientific evidence to back this assumption, but such speculative ideas totally ignore the large body of research in running biomechanics that has been done over the past four decades.
     
  15. Quasi- static analysis. As long as we add in and label all the forces wheres the problem? Seriously though, I just used the photo to exemplify a point, it wasn't supposed to be a full kinetic analysis. That said, a photograph of the runner moving over a force plate should provide a reasonable 2 dimensional analysis.
     
  16. efuller

    efuller MVP

    I would agree that it is simplistic, but not far too simplistic. You just have to know the limitations of your model.


    You very accurately describe the limitations of the static model. If you know the anterior component and the vertical component then you can add them in to make the model more accurate.

    Eric
     
  17. Simon and Eric:

    I have no problem with sagittal plane quasi-static analyses of a dynamic activity such as running as long there is sufficient data to make a meaningful kinetic analysis. My point was that knowing where the center of mass of the body (CoM) is relative to the support phase foot in a dynamic activity such as running tells us very little, if anything, about the relative position of the CoM to the GRF vector during that instant of the running activity (i.e. dropping a plumb line from the CoM to the foot certainly doesn't tell us whether there is a posterior or anterior shearing component to the GRF vector in a photograph of a runner).

    However, if you were to draw the GRF vector relative to the plantar foot and the CoM in such a photo of a runner, then we could make some more meaningful conclusions regarding the forces and moments acting on the plantar foot and other joints axes of the foot and lower extremity and whether that runner's CoM was likely being accelerated or decelerated by the GRF vector.

    Currently back in the good ol' USA...at Dulles Int'l Airport in Washington, DC. Home sweet....my own bed tonight!!
     
  18. phil

    phil Active Member

    If we think about the passive dynamic walker challange discussed in this thread- http://www.podiatry-arena.com/podiatry-forum/showthread.php?t=79426 we have eccentially created a situation where gravity is the only force causing forward motion (if we ignore the little tap you give it to start!).

    However, for these machines to achieve sustained forward momentum you need a continuously decending slope. These machines don't work uphill, or on a flat surface. They technically do use gravity alone to propell them forwards.

    Human bipedal locomotion however can occur on flat surfaces and even up hills! I've seen it with my own eyes.

    My hypothesis is this (correct me if i'm wrong)- Gravity can only "pull you forward" if you are heading down a hill. (not counting falling over, which will technically "pulll you forward", but only as far as you can fall.)

    I believe this is always true, whether you are a passive dynamic walking machine or a bipedal human with fancy joints and muscles and stuff. However, if you're on a flat or inclined surface, gravity will either pull you into the ground, or backwards down the hill. And if you're a bipedal human with muscles and stuff, now would be a good time to use them.
     
  19. Yep, I didn't start that thread randomly.;) As I said:
    What about building a walker, Phil- you getting involved?
     
  20. Craig Payne

    Craig Payne Moderator

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    Just a follow up on this.

    Have a look at the first two finishers in the Womens marathon @ London (esp the one in second place at the finish line):



    How many of the guru's would want to try and change there 'form'? .... these runners are the best of the best ... just confirms there is no one best way to run.
     
    Last edited by a moderator: Sep 22, 2016
  21. Craig Payne

    Craig Payne Moderator

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    This just turned up in my alerts: Biomechanics of Running: Have you stopped and thought to yourself: Am I running correctly?
     
  22. Craig Payne

    Craig Payne Moderator

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    Like the email Kevin got, I get my fair share of them and one thing they have in common is that they all prove me right! What brought this up now is I just got one from a Chi runner in response to what I wrote in this thread.

    Firstly, they obviously can't read as I did not say what they accused me of (ie they proved me right)
    Secondly, they used many of the argumentative fallacies such as the appeal to the natural fallacy, cheery picking, appeal to authority** etc (ie they proved me right)
    Thirdly, when I replied and pointed these things out to them, the abusive email came back (ie they proved me right)

    ....been through that same pattern many a time!

    **The appeal to authority in this one was also quite typical. They said If I would just read the Chi Running books by Danny Dreyer, then I will become a believer! ... well, I actually own two of them Chi Running and Chi Marathon and rather than make me a believer, they make me roll my eyes and wonder how people fall for it!

    Even though both books are on my desk at the moment, I will admit that I have not read Chi Marathon as I just can't bring myself to pick it up again. I told this story earlier, but when the book first arrived I opened it to a random page - on that page Dreyer was talking about Leibermann's study published in Nature. He talked about how the authors compared the foot strike pattern of runners from Africa and USA .... when in reality they actually eliminated the African runners from the analysis..... this book is off to a bad start, so I turned to another random page and it was discussing plantar fasciitis .... and stated "plantar fasciitis was due to heel striking" .... really? There is not one shred of evidence for this and we all see plantar fasciitis in midfoot and forefoot strikers! .. I had to put the book down after that and really have to wonder about the information in the book if there is this bull**** on the first two random pages I turned to ..... I have not found the inclination to pick it up again to read it.

    Why do people fall for this for?
     
  23. admin

    admin Administrator Staff Member

    For completeness, here is a post from the Pose Running thread that is relevant to this topic:
     
  24. They want to believe.

     
  25. NewsBot

    NewsBot The Admin that posts the news.

    Articles:
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    A Comparison of Eccentric Joint Work and Vertical Ground Reaction Force Loading Rates between Chi Runners and Traditional Rearfoot Striking Runners
    Goss, Donald L.; Yu, Bing; Lewek, Michael D.; Teyhen, Deydre S.; Ware, William B.; Gross, Michael T.
    Combined Societies Mtg; American Physical Therapy Association; San Diego January 21-24. 2013
     
  26. NewsBot

    NewsBot The Admin that posts the news.

    Articles:
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    Effect Of Training In Chi-running On Running Biomechanics
    Deepak Kumar, Kelly McDermott, Haojun Feng, Veronica
    Goldman, Anthony Luke, FACSM, Richard Souza, Frederick M.
    Hecht.
    Presented at 2013 ACSM Mtg
     
  27. Craig Payne

    Craig Payne Moderator

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  28. Craig Payne

    Craig Payne Moderator

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    If you want to see what is exactly wrong with "Chi Running", then have a read at what they fan boy is posting in the comments section to what I wrote - they just don't get it!
     
  29. NewsBot

    NewsBot The Admin that posts the news.

    Articles:
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    Training in ChiRunning to reduce blood pressure: a randomized controlled pilot study
    Kelly McDermott, Deepak Kumar, Veronica Goldman, Haojun Feng, Wolf Mehling, Judith T. Moskowitz, Richard B. Souza and Frederick M. Hecht
    BMC Complementary and Alternative Medicine 2015, 15:368 doi:10.1186/s12906-015-0895-x
     
  30. Craig Payne

    Craig Payne Moderator

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    Blogged about this study here:
    http://www.runresearchjunkie.com/chi-running-did-not-lead-to-less-injuries/

    There were more injuries in the Chi running group, but it was not stat significant.
     
  31. In my lecture on footstrike patterns in running, I show this image of Danny Dreyer from the cover of his book running with his foot ahead of his center of mass. Unfortunately, for Danny, he emphasizes that you should never let your foot get ahead of our CoM during running. Instead, he is emphatic that the foot should land underneath the CoM or even slightly behind it during running...what a joke!!! See 2:50 into Danny's video.

     
    Last edited by a moderator: Sep 22, 2016
  32. NewsBot

    NewsBot The Admin that posts the news.

    Articles:
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    Press Release:
    ChiRunning School 2.0 will include DVDs, webinars, video lessons and audio downloads with Danny Dreyer's most updated teaching methods.
     
  33. Craig Payne

    Craig Payne Moderator

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    They obviously learnt nothing from the class action that Vibram had to settle. Anyone who has got an injury from taking up Chi running probably has a case against them. The actual evidence contracts the health claim that those who promote Chi running make. You can not make health claims for a "product" unless you have evidence to back it up. Testimonials are not evidence.
    Vibram (class action) and Skechers (class actions and FTC fines of >$100 million) found that out the hard way. Some companies never learn (and yes, 'Chi Running' is a registered company).
     
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