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Bending stiffness in the 1st metatarsophalangeal joint

Discussion in 'Biomechanics, Sports and Foot orthoses' started by Simon Spooner, Jun 3, 2007.


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    All,

    Something to chew over. I found this recently while doing some background research on effects of surface stiffness on foot & lower limb function:

    http://www.ncbi.nlm.nih.gov/sites/entrez?cmd=Retrieve&db=PubMed&list_uids=10694134&dopt=Abstract

    A couple of points jumped out at me:

    "The stiff shoes with the carbon fiber plates did not increase the amount of energy stored and reused at the metatarsophalangeal joint; however, they reduced the amount of energy lost at this joint during both running and jumping."

    As I've only read the abstract I may be missing something, but I keep re-reading this bit and still don't get it. If they reduced the amount of energy lost, why did they not increase the amount of energy stored? Where has that "saved" energy gone?

    And perhaps even more interesting is:

    "CONCLUSIONS: Increasing the bending stiffness of the metatarsophalangeal joint reduced the amount of energy lost at that joint and resulted in a corresponding improvement of performance."

    Since: Functional hallux limitus = Increased bending stiffness of the first metatarsophalangeal joint;

    Therefore, functional hallux limitus = reduced amount of energy lost at the first metatarsophalangeal joint and a corresponding improvement of performance.;)

    Have a nice day y'all :cool:
     
  2. CraigT

    CraigT Well-Known Member

    Hi Simon,
    I have often thought along similar lines.
    Sprinters often seem to have classically poor mechanics- I often wince when I see the slow motion reply and see the foot motion and foot position of high level spinters.
    Perhaps this is part of the make-up of a sprinter?? By having a functional hallux limitus, they are, in essence, increasing the length of their foot 'lever', and they have the power/body type to exploit this. A comparison could be with a big gear on a bike. The stiff carbon inlay in the shoe would also be like a longer lever in the sagittal plane.
    Hmmm... try to create a FHL in sprinters???
     
  3. Craig, check out the construction of sprinting spikes- solid as a rock. What I do see frequently among sprinters is subluxation of the 1st IPJ and callus on the plantar aspect of this joint- I would suggest that this observation leads to the conclusion that they are using what Bojsen Moller termed "ultra-high gear"? Interesting that the paper talks about "running" not "sprinting" though.
     
  4. Bruce Williams

    Bruce Williams Well-Known Member

    Simon;
    did they say what type of carbon firber insole they used? Was if full lenth, to the toes? Was it 3/4 lenth, etc?

    Also, the abstract talks about jumping mechanics, I did not read the entire paper so can't see any other running references, except for the lead up to the jump.

    Craig, good to see you are home again, so to speak. It was pleasure to meet you in Washington State last month.

    Finally, the interesting thing I've see about FnHL is that it is often easily over-come in short term running and sprinting. It is the longer races, 1/2 and marathon distance, plus high training mileage that I see FnHl causing problems in runners.

    I have seen articles in the past /w full length carbon plates where they see an increase in energy returned. For a jumping type lead up, I can see how that might work, especially the high jump.

    Have a nice weekend.
    Bruce Williams
     
  5. Bruce, like you I only have the abstract so can't really answer your questions. But it does say during running and vertical jumping- vertical jumping doesn't usually involve a run-up. Why do you think that FNHL becomes problematic at long distance-? Is it kinematic changes with different velocities or just increased number of cycles?

    I guess what this article says to me is that once upon a time pronation= bad, similarly (and I've not read anything other than this article which contadicts the following assumption) functional hallux limitus is seen as a "bad" thing- I think that this research shows that this assumption just isn't true. Maybe bad sometimes, but also advantageous at times. So the key is: when is it good and when is it bad? Do you know of any other research which suggests an advantage in having increased dorsiflexion stiffness of the 1st MTPJ? Taking your example, at what distance / speed does it become a problem?
     
    Last edited: Jun 3, 2007
  6. Simon et al.,

    I've seen a fair number of racquet players recently - badminton, squash and tennis - who have symptomatic FnHL which is mostly pain within the MTPj, IPj subluxation and callous. They have responded well with devices in everyday shoes and with medial wedging in their court-shoes (trainers) and combined with 1st MTPj mobilisation there is improvement in function and a reduction of symptoms.

    You raise an interesting point though insofar as their sports performance may be a casualty of the treatment - one patient who is a county squash player claimed his mobility and timing has suffered although his feet don't hurt afterwards. Could be he is still adjusting and compensating overly, but it will be interesting to see if the other players have noted similar. What price success, huh?

    MR
     
  7. Stiffness & energy return in walking and running

    I have a few marathon and ultramarathon runner patients that have had 1st MPJ arthrodesis procedures and don't seem to be negatively affected by the procedure during their running. In fact, many runners with functional hallux limitus (FnHL) say they have more 1st MPJ pain while walking than running.

    I have commented before on this topic a few times on Podiatry Arena. Maybe someone else can hyperlink to those discussions for all those following along. Running seems to require less 1st MPJ dorsiflexion than does walking since we "jump" off of the foot in running and "push off" of the foot in walking. In addition, during propulsion in running, the center of mass (CoM) of the body is rising while, during propulsion in walking, the CoM of the body is falling. Very different biomechanics.....that running and walking!! In fact, some very famous sports medicine doctors once said, about four decades ago:

    Sprinting is different from slower running, but there is not near as much difference mechanically as between running and walking.

    I am assuming that the researchers that Simon noted above considered that allowing 1st MPJ dorsiflexion in running, since it involved, in effect, increased compliance of the 1st MPJ, caused an energy loss. This is because the hallux "moved out of the way" of the ground.

    An easier to understand example of "energy return" and the use of elastic strain energy would be to look at the energy transfer mechanisms of a falling ball of wet clay and a falling ball made of rubber. When we drop a ball made of wet clay on the ground and see it splat flat on the ground and not bounce upwards off the ground, we are seeing a situation of increased energy loss. In this mechanical situation, the kinetic energy of the clay ball falling at a certain velocity the instant before it hits the ground is lost in its deformation as sound and heat energy. However, when a rubber ball is dropped on the ground and then bounces back up to nearly the same height from which it was dropped from, this means that the rubber ball is able to convert its kinetic energy from its final maximum velocity, the instant before it hits the ground, to a potential energy that is then stored as elastic strain energy within the ball once it maximally deforms and its velocity reaches zero. Finally, the potential energy (i.e. elastic strain energy) will again rapidly be converted into a kinetic energy that allows it to accelerate upward from the ground. A similar type of energy transfer mechanism is done with every foot strike during running, but this type of energy transfer mechanism is not present in walking (Novacheck, Tom F.: The biomechanics of running. Gait and Posture, 7:77-95, 1998).

    Using this method of performing a mechanical analysis of the foot, FnHL would decrease energy loss during propulsion since it would increase the dorsiflexion stiffness of the 1st MPJ and increase the mechanical efficiency of the 1st MPJ during propulsion during running. This makes perfect sense to me, from a mechanical standpoint, but does not, obviously, take into account the more long term possible deleterious mechanical side effects of FnHL on the foot.
     
  8. Mart

    Mart Well-Known Member

    I just happen to be reviewing some chapters of Chris Kirtly’s Clinical Gait Analysis and now you got me side tracked.

    My interpretation would be as follows.

    Most of the energy demand on intrinsic foot structures across metatarso-phalangeal joints would involve resistance to forward progression of shank/COM during walking or deceleration of COM in jumping

    Chris Kirtly states (page 192)

    Although in contrast to Kangaroos there is little evidence that significant energy can be stored in human soft tissue, energy can be stored in moving body segments.

    There are 2 mechanisms for this

    Pendulum type exchange between PE and KE within segments

    Whip type exchange between linear and rotational KE within segments.

    He then goes on to say the large amounts of power injected into shank-foot at push off raises its energy level during swing and this energy is transferred to the trunk to propel it forward ie whip type exchange. This I seem to recall figures strongly in Dannenbergs notions of FHL.

    Now energy would be lost to the passive tensioning the plantar fascia and active eccentric contraction of MPJ flexors and it’s sequelae if not returned to the system (presumably lost as heat and other physiologic process of structural stress), and this energy would be lost to the system according to its recoil efficiency rather than simply transferred from the foot as Kirby illustrates above.

    Since there is no net effect of the power generation and absorption at each of the ankle, knee, and hip joints by the stiffness of the shoe midsole then there was no flow into these joints from the metatarso-phalangeal joints so this would not account for energy loss at metatarso-phalangeal joints.

    Perhaps then the effect of carbon plate is to provide passive resistance to forward progression of shank/COM during walking or deceleration of COM in jumping thereby reducing demand on musculoskeletal structures to do the same and return more energy to system by having superior elastic recoil than the foot.


    If this is the case that would be very different from assuming less energy loss because of increased resistance to MPJ motion caused by FHL.

    Am I off axis here?

    Cheers

    Martin
     
  9. Not true. Ker et al calculated a 17 Joule energy storage from the soft tissue elements of the plantar arch of the foot and a 35 J energy storage within the Achilles tendon from the foot of a 70 kg man while running.

    Ker RF, Bennett MB, Bibby SR, Kester RC, Alexander RM: The spring in the arch of the human foot. Nature, 325: 147-149, 1987.
     
  10. Mart

    Mart Well-Known Member

    Hi Kevin

    This is very interesting since Kirtly uses exectly the reference to make the opposite case - go figure :confused: !!! - I'll see if I can get a copy and check it out.

    cheers

    Martin



    Not true. Ker et al calculated a 17 Joule energy storage from the soft tissue elements of the plantar arch of the foot and a 35 J energy storage within the Achilles tendon from the foot of a 70 kg man while running.

    Ker RF, Bennett MB, Bibby SR, Kester RC, Alexander RM: The spring in the arch of the human foot. Nature, 325: 147-149, 1987.
    __________________
    Sincerely,

    Kevin
     
  11. Bruce Williams

    Bruce Williams Well-Known Member

    Simon;
    I think you are "jumping" to conclusions somewhat. ;-)
    Vertical jumping, high jumping I assume, definitely has a running start.

    My thoughts on running and FnHL, somewhat similar to Kevin K's, is that the flight phase seems to propel us through the FnHL to extend the hallux much more easily than during a walking gait. I like what Kevin says on the CoM rising thru late midstance / propulsion, this wold fit into my thinking very closely.

    I see problems later though because despite the early ease of overcoming FnHL in short running distances, I theorize that the runner w/ FnHL still is compensating at many different areas for the FnHL and will over time begin to tire much sooner at the longer distances or higher training mileage. Is it kinetic and / or kinematic, most definitely it must be at some level.

    Finally, I think that what might be happening in this study is that the carbon plate is offering a rocker bottom feedback mechanism with added MPJ propulsion. This would effectively negate most of the FnHL much as a rocker bottom addition to a shoe would do in patients with 1st mpj fusion, but more so in potential ennergy return.

    Cheers.
    Bruce
     
  12. Bruce Williams

    Bruce Williams Well-Known Member

    Martin, I think you are right on axis with your comments. Well said.
    Sincerely;
    Bruce
     
  13. Mart

    Mart Well-Known Member

    Kevin

    A bit more rumination here (before I go to the gymn try out a pair of carbon fibre plates :) )

    My assumption after looking at these papers is that Kirtly’s analysis is relative.

    Whilst the paper you quoted concludes that

    the arch of the foot stores enough strain energy to make running energy efficient,


    Kirtly’s other reference (Storage of elastic strain energy in muscle and other tissues Nature 265, 114 - 117 (13 January 1977); R. McN. Alexander† & H. C. Bennet-Clark*)

    concludes


    Storage of strain energy in elastic materials has important roles in mammal running, insect jumping and insect flight. The elastic materials involved include muscle in every case, but only in insect flight is the proportion of the energy stored in the muscle substantial.


    This compares compliant vs contractile structures however.


    If you consider the study below modeling the roles of compliant structures vs contractile components in the foot during jumps it is consistent with the notion that the carbon fibre plate as a more compliant surrogate plantar fascia is more efficient than the real thing which is the essence of my interpretation.



    Increasing tendon compliance in the model led to an increase in elastic energy storage and utilization, but it also decreased the amount of energy delivered by the contractile elements to the skeleton. Jump height therefore remained almost the same for both jumps. These results suggest that elastic energy storage and utilization enhance jumping efficiency much more than overall jumping performance.




    cheers


    Martin






    Abstract:
    Based upon the optimal control solutions to a maximum-height countermovement jump (CMJ) and a maximum-height squat jump (SJ), this paper provides a quantitative description of how tendons and the elastic elements of muscle store and deliver energy during vertical jumping. After confirming the ability of the model to replicate the major features of each jump (i.e. muscle activation patterns, body-segmental motions, ground reaction forces, jump height, and total ground contact time), the time histories of the forces and shortening velocities of all the musculotendon actuators in the model were used to calculate the work done on the skeleton by tendons as well as the series-elastic elements, the parallel-elastic elements, and the contractile elements of muscle. We found that all the elastic tissues delivered nearly the same amount of energy to the skeleton during a CMJ and an SJ. The reason is twofold: first, nearly as much elastic strain energy was stored during the SJ as the CMJ; second, more stored elastic strain energy was lost as heat during the CMJ. There was also a difference in the way energy was stored during each jump. During the CMJ, strain energy stored in the elastic tissues came primarily from the gravitational potential energy of the skeleton as the more proximal extensor muscles were stretched during the downward phase of the jump. During the SJ, on the other hand, energy stored in the elastic tissues came primarily from the contractile elements as they did work to stretch the tendons and the series-elastic elements of the muscles. Increasing tendon compliance in the model led to an increase in elastic energy storage and utilization, but it also decreased the amount of energy delivered by the contractile elements to the skeleton. Jump height therefore remained almost the same for both jumps. These results suggest that elastic energy storage and utilization enhance jumping efficiency much more than overall jumping performance.
    1: J Biomech. 1993 Dec;26(12):1413-27. Links
    Storage and utilization of elastic strain energy during jumping.
    • Anderson FC,
    • Pandy MG.
    Department of Kinesiology and Health Education, University of Texas at Austin 78712.
     
  14. Just a little story which some of you may find interesting here on stiff MPJ sole sprinting spikes and their "effectiveness".

    In February 2000 I was invited to lecture with a world renowned biomechanics researcher at his lab for a meeting of podiatrists. After the meeting, while walking to lunch, the researcher was saying to me and others walking along that he was willing to bet $100.00 to anyone that the spring plate racing spikes that he had helped develop for a famous athletic shoe company (that funded his research) would result in a new world record in the 100 meter dash for the upcoming 2000 Olympics in Sydney since it was so much more energy efficient than other shoes http://www.popularmechanics.com/outdoors/adventures/1277586.html

    Unfortunately, for the runner wearing the "magic shoes" a sprinter from the US took first, and the sprinter wearing the "magic shoes" took second. By the way, neither sprinter broke the record.....I guess I should have bet him. :rolleyes:
     
  15. Martin, Simon, Bruce and Colleagues:

    This is a subject I am fascinated by and have done quite a lot of reading on.

    The forward dynamics study you quoted does not show that countermovement (CM) jumps produce much higher jumps than do squat jumps. Unfortunately, this is not what is seen in real life by real athletes who nearly always can jump higher with a CM jump than a squat jump. Try it yourself and see. I can jump over an inch high using CM versus squat technique. Most younger athletes can jump about 2 inches higher using CM jump technique.

    The reason CM jumps are thought to lead to increased "spring" from the legs when compared to squat jumps is that there is increased elastic strain energy stored in the elastic elements of the muscle and tendons during CM jumps than in squat jumps. The initial rapid downward squatting motion of the CM jump "preloads" the elastic elements of the lower extremities as potential energy that is then returned back during the upward leap from the ground as kinetic energy.

    If you want a great book to read about how animals use "springs" in their legs, hop on over ;) and buy R. McNeil Alexander's book "Principles of Animal Locomotion" (Alexander, R. McNeill: Principles of Animal Locomotion. Princeton University Press, New Jersey, 2003). It goes into great detail about these mechanisms in animals and is a fascinating read. Nearly all jumping, galloping and pronging http://video.google.com/videoplay?docid=-5555230278824938747&q=deer jumping (a bouncy, four-footed pogo-stick gait) animals use elastic strain energy storage in their long tendons of their lower extremities to perform higher, more efficient jumps, gallops, and prongs and with very little muscle contractile movement required.

    As a matter of fact, in kangaroos and wallabies, their energy storage mechanisms in their leg tendons are so efficient that they actually consume the same amount of oxygen as they move faster over the ground as when they are moving slower (Kram R, Dawson TJ: Review: Energetics and biomechanics of locomotion by red kangaroos (Macropus rufus). Comparative Biochemistry and Physiology, Part B. 120:41-19, 1998). http://spot.colorado.edu/~kram/kangaroo.pdf

    Great topic, Simon!!
     
    Last edited: Jun 4, 2007
  16. efuller

    efuller MVP

    Hi Simon,

    Interesting question. I have not read the paper, but may have an idea to explain what was seen. It would depend on if the energy value reported was a net for the whole step or just part of the step.

    Energy is power/time. Power = joint moment x angular velocity. When the moment is in the same direction as the velocity there is energy gain. When in opposite directions energy is lost. Without the plate, from the time the hallux starts to dorsiflex to max dorsiflexion there is a power loss because there is a plantarflexion moment with a dorsiflexion motion. Some of this energy is lost to heat and some is presumably stored in the elastic tissues of the arch, iinclduing the muscle. Then duirng the rest of the step where the toe is plantar flexing with a plantar flexion moment power is added. They may be only looking at the power loss part of the step when they reported the results and not ne energy over the entire step.

    When, a carbon fiber insert is put into the shoe, I would assume that there is less dorsiflexion and probably a lower angular velocity and therefore a lower amount of energy loss when compared to no carbon fiber plate. With less dorsiflexion there would be less storage of energy in the tissues of the arch.

    I would also bet that there is not 100% energy return. That is power lost with orsiflexion is greater than power gain with plantar flexion. So, if less power is absorbed by the mpj when there is a plate more power goes into the jjump and performance is improved.



    Quote from abstract.
    "The data showed that energy generation and absorption at each of the ankle, knee, and hip joints was not influenced by the stiffness of the shoe midsole."

    This is really interesting in terms of the results. If the lever arm was increased by preventing dorsiflexion then there would have to be a change somewhere else to make the ankle energy remain the same. The increase in lever arm at the ankle and hence moment could have been accompanied by a decrease in angular velocity. This puts a hole in the Bosjen-Moeller long gear short gear idea. That theory assumes constant angular velocity.

    The results, as reported in the abstract point the notion that the carbon fiber just prevents the energy lost in hallux dorsiflexion and the elimination of that loss alows increased performance.

    Regards,

    Eric Fuller
     
  17. Craig Payne

    Craig Payne Moderator

    Articles:
    6
    I know this is somewhat off-topic for this thread, but we were data collecting on a female runner's study and have been told (though the actual data has not been passed on to me for stat analysis yet) that the first mpj dorsiflexion stiffness appeared to vary during the menstrual cycle...
     
  18. Bruce Williams

    Bruce Williams Well-Known Member

    Craig;
    I've seen some papers stating that relaxin levels increase in peri-menopausal women equal to or greater than women in their 2nd-3rd trimesters of pregnancy.

    The Relaxin hormone is used to loosen the firbrocartilage in the birth canal, and this firbrocartilage is made up of the same material that is in the spring ligament.

    Maybe the hormone levels are performing a similar result at the time of menstruation? I have nothing to back this up, but it might be worth a look.

    Cheers,
    Bruce
     
  19. Schuster and Port (1977) considered the female hormones: progesterone, oestrogen and relaxin to play a significant role in the aetiology of "abnormal" pronation by relaxation of ligamentous structures. But, more recently:http://ajpendo.physiology.org/cgi/content/full/290/5/E1034.

    Back on topic- as anyone got the whole paper: Influence of midsole bending stiffness on joint energy and jump height performance.

    by Stefanyshyn DJ, Nigg BM.?
     
    Last edited: Jun 4, 2007
  20. Simon:

    Do you have the full reference on the Schuster and Port article??

    Thanks.
     
  21. Schuster, R.O., Port, M: Abnormal pronation in children. An hormonal etiology. JAPA 177; 67: 613-615

    As I recall they didn't really offer much in the way of hard data! And as memory serves they were saying that it is the females relaxin influencing the childrens feet. Something similar being hypothesised for congenital hip displacements I believe.
     
    Last edited: Jun 4, 2007
  22. Bruce Williams

    Bruce Williams Well-Known Member

    Kevin;
    were you able to get the JAPMA site to offer the abstract on that paper?
    I saw the listing, but only the top paper of Dr. Schusters was listed available for abstract.

    Finally, the paper / Abstract Simon listed is on knee ligaments. I admit that I am not pathologically inclined to know the exact makeup of knee ligament tissue, but I do recall that the spring ligament has been correlated with potential effects from relaxin hormones.

    Sincerely;
    Bruce
     
  23. Some years ago we followed a group of females through pregnancy in a longitudinal study measuring HA angle- this increased throughout pregnancy but increased rapidly around and following the time the relaxin hormone is supposed to kick in. Never really found any hard data to support the contentions though, and given the other major changes occuring around this time, not least weight gain and shift in CoM t'was difficult to draw definitive conclusions.

    Bruce, if you have references re: spring lig I'd love to read them.
     
  24. Bruce Williams

    Bruce Williams Well-Known Member

    Simon;
    I wish I could find them myself right now. There was a paper on the internets a couple of years ago that sighted an increase in relaxin hormone in peri-menopause, norwegian study. I think I mistakenly threw it out and did not have an electronic backup.

    I really don't know now where I read or heard about spring ligament reference, but I think there was a japma paper on it? I know that every time I've brought this up others have heard the same claim. Kevin, do you recall this claim?

    I am really sorry that I don't have a reference at hand Simon. I might solicit the podiatry list serve or the primary Podiatry email list in the US and see if anyone has the reference. Give me a week or so to do this. Please accept my apologies.
    Sincerely;
    Bruce
     
  25. I may need to go digging in boxes in my garage to find that reference from 1977 (Schuster RO, Port M: Abnormal pronation in children. An hormonal etiology. JAPA 177: 613-615, 1977.)

    However, if you want the definitive paper on the spring ligament then you need to read this paper:

    Davis WH, Sobel M, DiCarlo EF, et al: Gross, histological, microvascular anatomy and biomechanical testing of the spring ligament complex. Foot Ankle Int. 17:95-102, 1996.

    I don't know of any spring ligament papers that talk about hormonal influence, but my research on this subject is not that extensive.
     
  26. All,

    Thanks to the pack-rat known as Kirby I now have the full paper- see attached.

    Yep, you right me jumping to wrong conclusions the paper clearly states they used a run up. Being pedantic, this isn't vertical jumping- momentum and all that. But I concide the point Bruce. Note to self- Don't write about papers before you've read the whole paper.

    However, the analysis of running and jumping were two discreet parts of the methodology, i.e. they didn't use the run up for the jump to analyse running data.


    Now you jumping to the wrong conclusions Bruce- carbon fiber was a flat plate.
     
  27. Bruce Williams

    Bruce Williams Well-Known Member

    Simon;

    not sure I jumped to the wrong conclusion on the carbon fiber plate. :)
    I said it would potentially provide a rocker bottom effect, not be rocker bottom shaped! ;-)

    what I meant, though it was obviously not clear on my end, was that there more than likely would be enough flexiblilty in the plate at the MPJ's to flex, not break, and apparently provide enough energy return to overcome any potential FnHL in the studied patients. I believe that there is an article referenced below by the Admin that states that a lot more clearly than I.

    And yes, it does us all well to actually read an article before commenting on it, myself included.

    Thanks for the attachment to you Simon and to Pack Rat Kevin K.

    Cheers!
    Bruce
     
  28. I knew you'd say that Bruce. Couldn't see an article reference by admin. How flexible is 5mm of carbon fibre? To allow me to get my head around this can you give a comparative material of a similar stiffness of that measured in the shoes of 0.38 N.M.deg-1? Concrete? Rubber? Butter?
     
  29. Bruce Williams

    Bruce Williams Well-Known Member

    Simon;
    actually, if you read the paper that you so nicely attached to your post, the carbon fiber plates, there were three of them at 1mm each, totalled 3mm. The researchers welled out 5mm of EVA from the test shoes, and filled this in the stiff shoe w/ 3mm of the carbon fiber and another 2mm of EVA.

    Also, further into the paper it states quite plainly that despite the carbon fibre plates, the mpj portion of the shoe bent, "Even with the stiffer shoes, the MP joint remained in a dorsiflexed position at take-off and was unable to generate any energy during jumping and only a very small amount of energy during running. Thes, the shoe does not straighten until after take off when the return of energy is too late to have an influence on performance".

    Also, "One trend was present for the ankle joint, which absorbed and generated less energy with the stiff shoes. This was true for both running and jumping."

    So, as you can see, my comment on the rocker bottom action is pretty much correct. 3mm of carbon fiber is not unflexible and nothing like cement as you alluded.

    From my sagittal plane perspective, I see very little of surprise in this paper or abstract. The ankle joint decreae in energy would be a usual compensation for loss of 1st mpj ROM. I see this on a regular basis.

    Finally, the article I suggested is the one posted by Admin in blue at the end of teh postings page.

    Good reading to you Simon! ;-)
    Bruce
     
  30. Bruce,

    If I could refer you to page 472 of the article: Methods section, Para 2, line 13: "For the very stiff shoe, five flat carbon fiber plates (total thickness of 5mm) were placed in the pocket." See also "table 1" Page 472. So nice reading to you too. Perhaps a little less arrogance and a little more accuracy next time you reply Bruce?

    And your ability to edit does indeed enable you to try and spin this paper into a positive for your cause. However, let me do my own selective editing as you have in your post previously:

    "there were no significant differences in the energy production and generation at the ankle, knee, and hip joints for the different midsole stiffnesses."

    The authors did indeed speculate upon a trend as you noted previously, but this was not statistically significant. Which may or may not have been due to n. Within the limits of the study there were no significant differences Bruce. Hence, the authors conclude:

    "the stiffer shoes decreased the amount of energy absorbed and dissipated at the MP joint but did not affect the energy production at the other joints of the lower extremity."

    From my less blinkered, more holistic perspective of foot and lower extremity biomechanics, I see very little of surprise in this paper or abstract. That functional hallux limitus doesn't necessarilly have a negative effect on performance, and as the paper demonstrated may indeed have a positive effect. I see this on a regular basis.

    Finally Bruce, I don't know what or where the "teh postings page" is.;)
     
    Last edited: Jun 6, 2007
  31. Bruce Williams

    Bruce Williams Well-Known Member

     

  32. I do not feel any conflict toward you Bruce, and I'm sorry you feel that way. I do enjoy academic debate with you since our points of view are often somewhat dichotomous.

    Bruce, here's another quote from the paper, p. 465 para 2:
    "Increased bending stiffness of the shoes lead to large decreases in MP dorsiflexion (figs 2-4). The result was a decrease in the energy absorbed at the MP joint." Within this paragraph the author's then go on to say how this reduction in energy lost corresponded to an increase in performance.

    So, with the greatest respect, I am not sure how you can make the statements you make above since within the limits of this study a relationship between FnHL and its positive effects on running and jumping was demonstrated.
     
    Last edited: Jun 6, 2007
  33. Bruce Williams

    Bruce Williams Well-Known Member

    Simon;

    in my practice I will utilize a rocker bottom modification on shoes to overcome the structural loss of the MPJ pivot.

    It appears quite obvious to me that the authors of this study achieved that outcome, despite decreasing the actual extension motion of the subjects MPJ's.

    They also got a very slight increase in jump and running performance.

    My contention, as from the beginning is that the rocker bottom shoe function that they created negated the supposed FnHL that they achieved.

    I stand by my previous statement that they proved nothing in this study. They showed that a nMPJ pivoting shoe reinforced with multiple energy returning carbon fiber inlays gives a very slight energy return. That still shows the importance of the MPJ pivot!

    cheers!
    Bruce
     
  34. Bruce,
    I knew you would say this which is why I kept my powder dry on the quote that I "left out". Let's revisit that paragraph now: Even in the stiffer shoes, the MP joint remained in a dorsiflexed position at take off and was unable to generate any energy during jumping and only a very small amount of energy during running"

    Ok so the the joint was dorsiflexed, we know from their previous statement that the stiff shoes resulted in "large decreases in MP dorsiflexion". An MPJ which is dorsiflexed by 1 degree is still in a dorsiflexed position. Yes the joints remained dorsiflexed, but I think most people would agree that a joint who's range of motion is decreased by over 50% is being limited.

    Now here's the key to why I believe your contention above is wrong: The paragraph continues:

    "Thus the shoe does not straighten until after take-off when the return of energy is too late to have an influence on performance."

    In other words, any energy stored in the carbon fiber plates and the shoe did not contribute to the increased performance. What the authors were basically saying is that it wasn't the shoe springing back which propelled the subjects to improved performance.
     
  35. Bruce Williams

    Bruce Williams Well-Known Member

    Simon;

    Ok, so less energy was "lost", but the mpj still was extended and the pivot still functioned.

    My contention has never been that the shoe springing back is what made the difference. My contention is that the shoe is rocker bottom in function and that the mpj pivot still functioned as it was supposed to.

    If the MPJ extended as the paper says, then the carbon fiber plates extended as well. This will create a very stable rocker bottom w/ flexibility which perpetuates the MPJ pivot and apparently allows less energy loss!

    Hooray for the MPJ pivot!

    Bruce
     
  36. What you are basically trying to extrapolate here Bruce is that a shoe that bends at the MPJ's is the same as a rocker bottom shoe. I don't think so. Moreover, that it doesn't matter that the range of motion of the MPJ is reduced by 50% as long as it bends a bit, then function is normal. Perhaps then we need to go back a step; perhaps you could define functional hallux limitus. What's the difference between normal, limitus and rigidus?
     
  37. Bruce Williams

    Bruce Williams Well-Known Member

    Simon;
    the one big flaw in this study is that they did not establish the actual range of motion at the mpj's while in the shoe. No where does it state what the extension range of motion was from their calculated zero point. They only determine whether their was any motion from that zero point.

    Most running shoes have a certain heel height and rocker bottom modification built in that will allow a degree of mpj extension automatically.

    The study did not calculate for that as far as I can see.

    Bruce
     
  38. Bruce, see figure 3
     
  39. Bruce,

    Bruce, energetics has never been my strong point hence my first question in this thread, but how is the energy that is stored in the carbon fibre plates returned in this situation if it is not through them "springing back" because the authors statement that: "Thus the shoe does not straighten until after take-off when the return of energy is too late to have an influence on performance." has lead me to think that the authors believe it is the staightening from it's deformed shape i.e springing back, that returns the energy? Since you clearly believe that the energy return is significant (as evidenced by the number of times you have referred to this) I should be grateful if you could explain this energy return process to me.
     
    Last edited: Jun 6, 2007
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