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Proximal rocker bar on shoe can relieve tension on Achilles tendon in runners

Discussion in 'Biomechanics, Sports and Foot orthoses' started by NewsBot, Mar 28, 2013.

  1. NewsBot

    NewsBot The Admin that posts the news.

  2. Admin2

    Admin2 Administrator Staff Member

  3. Twooms

    Twooms Member

    Is there any images available of what this rocker bar looked like?
  4. sobhani_sobhan

    sobhani_sobhan Active Member

    The rocker profile shoe used in our study

    Attached Files:

  5. admin

    admin Administrator Staff Member

    Thanks to sobhani_sobhan, here is the abstract from the congress:

    A proximally placed rocker bar (profile) and external ankle moments during walking and running
    K. Postema1, S. Sobhani1, E.R. vd Heuvel2, J. Zwerver3, J.Hijmans1, R. Dekker1,3
    1) Department for Rehabilitation Medicin, Center for Rehabilitation, University Medical Center Groningen, University of Groningen
    2) Department for Epidemiology, University Medical Center Groningen, University of Groningen
    3) Center for sports medicine, University Medical Center Groningen, University of Groningen
  6. Bruce Williams

    Bruce Williams Well-Known Member

    How is that even remotely a "proximal" rocker bar?
  7. sobhani_sobhan

    sobhani_sobhan Active Member

    Dear Bruce,
    I didn`t understand your question. The apex of the rocker profile is positioned proximal to the metatarsal region. Of course the apex could be placed even more proximal.

  8. Bruce Williams

    Bruce Williams Well-Known Member

    So, are up calling a forefoot rocker a "proximal forefoot rocker" just because it is proximal to the MPJ's?

    And yes, if you truly wish to affect the forces and tension at the Achilles insertion you should move the apex even more proximal and study what affect that will have on the tendon.

    Most running shoes already have a rocker component built into them, so why the need to add a significant heel / foot lift combined with a rocker that is already present?

    Did you add lift to the opposite shoe as well to counter this affect and did you evaluate for any potential limb length prior to testing and control for that?
  9. efuller

    efuller MVP

    I had the same terminology question. I've heard of "heel rockers" where there is a thickened midsole and as viewed in the sagittal plane a curved heel that puts the contact point more anterior and allows the shoe to "roll" into forefoot contact. I've also heard this called a posterior rocker. I would tend to call the rocker in the picture in the picture above an anterior rocker. I think better terminology might be to call it a rocker at ~60-70% of shoe length. Or just a rocker just proximal to the metatarsal heads.

    The results of the study do make mechanical sense though and support the tissue stress approach to biomechanics.

  10. Bruce Williams

    Bruce Williams Well-Known Member

    I agree with you on the terminology part. I disagree with you on the mechanical part.

    If you really want to solve the issue for achilles issues then address the AJ equines that is always present AND decrease the potentially problematic forces via using a forefoot rocker as well if you feel it is necessary.

    In my opinion the heel lift will do much of what is necessary so long as it is skived to thin as it extends distally towards the mpj's. In most running shoes there is decent MPJ extension at the area of the MPJ's so why the need for the rocker?

    If the patient has a structural limitation of the 1st MPJ then I agree it is a good option. If not then w/o some sort of quantification to prove otherwise, I disagree on the need.

    I appreciate the attempt to study the change in forces in the paper, but I have seen far to many shoes modified that way and the patients limp around like they have a peg-leg. They are far better off in a cam-walker that has a real rocker bottom that is affective.

    I know this is "how it's always been done" in the pedorthic manuals but it just is rarely affective in helping the overall situation.

    I have at times used a widened medial and lateral shank in patients with sever PTTD issues and extreme lateral abduction to their feet and lower limbs. I'll then add a diagonal rocker bottom modification to assist them in their gait. If it is done correctly and at the correct proximal level of the foot they will have great benefit. It is an imperfect art no doubt, but there is a method to the madness.
  11. efuller

    efuller MVP

    Bruce, I agree with you that a heel lift might be more appropriate when there is limited ankle joint dorsiflexion as the cause of the Achilles pathology. However, the article still makes mechanical sense, as you seemed to say in your post. The results of the article did make mechanical sense in that a rocker that ends behind the metatarsal heads will reduce the lever arm of ground reaction force on the ankle joint and this will decrease dorsiflexion moment from the ground. The Achilles tendon will be working against less resistance.

  12. sobhani_sobhan

    sobhani_sobhan Active Member

    I agree that there is a little confusion on terminology here. Since rocker shoes have been commonly prescribed to offload the pressure in the metatarsal region, the term “proximal” or “distal” usually relates to this region. However, I have seen in some paper terms such as “toe-rocker shoe” which according to me is distally placed rocker. The term “anterior” or "forefoot" seems too vague to me because the apex could be placed anywhere in the front.

    Just to make it more clear: a stiffened rocker profile (proximal to metatarsal region) causes a smaller dorsal flexion moment for the ankle joint (due to the reduced moment arm of ground reaction force). This external moment should be countered by the internal plantar flexion moment which is related to the Achilles tendon force. So less internal moment (less force on the Achilles tendon) is desired more proximal the apex should be positioned (as you correctly mentioned).

    We shouldn`t forget about the stiffening of the rocker profile. Although the rocker component is present almost in most type of running shoes, these rockers are not stiffened. Therefore, the bending point (apex) remains at the MTP region. The whole idea about proximally placed rocker is the shorter moment arm caused by the proximal bending point.

    For the control shoe we wanted a regular running shoe without any adaptation, therefore the other pair of shoes remained in their original shape. I believe adding extra lift to the other shoe could also give extra stiffness to shoe (probably results to different shoe mechanics?!). It was a limitation of our study though that we did not investigate the moments in the frontal plane. The thickened sole of the rocker shoe could have changed the moment arm in the frontal plane. It would be interesting in the future research to compare standard shoes with rocker shoes where they are matched for height and weight.

    Would please elaborate on “controlling the potential limb length”? After each measurement the markers were replaced, new height and weight were measured and taken into account for the new measurement. Have we missed something? :bang:

  13. Bruce Williams

    Bruce Williams Well-Known Member

    I apologize if I am being hyper-critical, I appreciate it is hard to control all aspects during a study.

    Regarding limb length: 1). If the sole of the rocker shoe is thicker than the control or opposite shoe then you very likely created an artificial LLD on the rocker side.

    One way the body will seek to decrease load a the Achilles is knee flexion. At least as far as the gastroc is concerned. How do you know that the reduced forces were not from the artificial heel lif of the rocker shoe?

    2) if the patient has a functional or structural LLD, then your unilateral rocker / heel lift could have controlled for their discrepancy, and / or made it significantly worse. If you don't examine them before hand you can't know whether this may have occurred or not.
    Again, how do you know whether this affected your results negatively or positively in your subjects?

    I'm not trying to split hairs here, I think these a very real and valid considerations and I get frustrated when the majority of studies do not take these types of things into consideration.

  14. sobhani_sobhan

    sobhani_sobhan Active Member

    Thanks for your time Bruce. No problem at all. I learn a lot from this type of discussion.

    There has been no unilateral rocker! Participants have run and walked with a pair of rocker shoes compared with a pair of standard shoes. All subjects were healthy without any discrepancy in lower limb. We are here talking about external moments around the ankle and its relationship to internal moments (produced by the Achilles tendon). How does rocker profile result in knee flexion in late phase of stance? and if it does, what is the relationship to the ankle external moments? We did not observe any changes in the knee and hip moments by the way. Probably it is better to wait until the paper gets hopefully published, then we can see the whole story. However, I am always open to the fair critics.

    All the best
  15. Bruce Williams

    Bruce Williams Well-Known Member

    My apologies for not appreciating that you used a bilateral rocker shoe vs a non-modified control shoe. I re-read the abstract and see I missed that. I was likely influenced by the picture yours posted and figured one shoe for modification. Honest mistake on my part.

  16. sobhani_sobhan

    sobhani_sobhan Active Member

    No need to apologize! Probably the abstract was not clear enough. I will send you the article when it is published. Again, thanks for your time and consideration

    All the best
  17. Twooms

    Twooms Member

    The modified shoe looks very like a Hoka, was this intended or have comparisons been drawn with these shoes? They too have a rocker and a very high midsole, had you considered just using that rather than a modified shoe?
  18. sobhani_sobhan

    sobhani_sobhan Active Member

    Indeed they are similar! No we were not aware of this model! That`s why we designed our own. Have you tried them? Is the sole stiffeness adequate to be effective during push-off? There were two drawbacks regarding our model: weight and too much stiffness at the heel (perhaps results in higher impact forces). To me this model could be an alternative for our future research. Thanks so much for this information.

    All the best
  19. Twooms

    Twooms Member

    The Hoka shoes are extremely light for their size. There are two main models for road running, the Bondi B and the Stinson Tarmac. The Bondi has a heel-to-toe differential of 4.5mm and the Stinson 6mm. I believe the midsole stiffness to be almost identical in both perhaps the Stinson slightly stiffer. I have tested them out on a treadmill a few times but do not own a pair. Most people I know who have a pair love them but I imagine they would find it hard to run in other shoes afterwards. I know a few people on this site rotate them into training like they would with a minimalist trainer. What you really need is some boost midsole from Adidas, then your patients will be bounding around the roads with no problem ;) Hope this helps.
  20. We talked about the Hoka One One shoes last year here:


    I have two pairs of them, my wife wears them and my son runs in them also. They have also become a very popular shoe for trail runners here in Northern California. I think these "maximalist shoes" will become more and more popular as time goes on.....for both running and walking.

    My guess is that the Hokas are one half the weight of the shoes used in Sobhan's experiment..they are amazingly light for their size.
  21. sobhani_sobhan

    sobhani_sobhan Active Member

    Thank you all for useful information. I am really curious to try them. This new concept (maximialist shoes) was really new to me although apparantely I have done some research on them (or similar one) :))

    There are two other studies done by our group on the rocker shoes:
    1) plantar pressure distribution during running with the rocker shoes
    2) Running economy (comparing rocker shoe with minimalist and standard shoes)
    I would love to see how our findings would differ when using the Hoka as the rocker shoes.
    Probably for our future research!
  22. Twooms

    Twooms Member

    Where are you researching? I am very keen to get involved in this area of research also. Do you know are there any research PhD positions available, would be very keen to have a more detailed chat and throw some ideas at each other. I work as a biomechanist within the running industry in Australia and our store is the sole distributor of Hoka in Victoria so I have had quite a bit of interest in them for the past 18 months and have heard so many great things about them. I am, similar to you, intrigued by the shoe and its properties.
  23. Boots n all

    Boots n all Well-Known Member

    Last year we modified 20 left shoes like the above picture for a research project.

    To keep the weight down we created a number of cavities inside the build up material.

    This is common practice in any build up greater than 20mm for us.
  24. sobhani_sobhan

    sobhani_sobhan Active Member

    I am a PhD student in the department of Rehabilitation Medicine in University Medical Center Groningen, Netherlands. I sent you a message. Check your inbox.
  25. sobhani_sobhan

    sobhani_sobhan Active Member

    Great idea! These cavities had no effect on the rigidity of the rocker?
    What was the research about?
  26. Boots n all

    Boots n all Well-Known Member

    l am not the researcher, just the supplier of the footwear & modifications, it was a research project that a Physio student was undertaking, left shoe modified the right was not.

    The cavities will effect the flexibility if you place the cavities at the fulcrum, of course the amount of flexibility created is not as the product was before modification, to retain the stiffness simply stop the cavity proximal of the fulcrum.

    Once you get past the 20mm of build up the question of flexibility, cavity or not, is questionable in gait with children and small adults.
  27. sobhani_sobhan

    sobhani_sobhan Active Member

    ok! I guess you are right. Probabely these cavities should be avoided at the apex.
    Thanks you for the response.

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