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FluidAxis from Asics

Discussion in 'Biomechanics, Sports and Foot orthoses' started by SeasonsChange, Jan 4, 2013.

  1. SeasonsChange

    SeasonsChange Member

    Members do not see these Ads. Sign Up.
    I've been a loyal Asics fan for years. I use the DS Trainer for all of my mileage and race in DS Racer. After watching the video posted about the science behind Asics' FluidAxis, I had many concerns.

    "The Game Changer"

    If FluidAxis was such a big deal why wouldn't be in more than just 2 shoes?

    "I think athletic companies design a shoes to align to the ankle because pretty much that's the way it's always done. There's no science behind it?"


    The next 4mins of the video just describe the movement of the foot and explain the different planes.

    I'm asking myself at this point, how does that small decoupling of the heel actually help a runner? It seems all diagonal flex groove is does in the 2 Asics models is to increase the rate of pronation????

    The video finishes with looks to be more marketing fluff (midfoot striking while barefoot, forefoot striking in the Kensei's, no heel striking anywhere) and is tied together using the three F's. "Form, Fit, Function."

    I would've expected this sort of pseudo science and empty claim from Saucony, but this is Asics.
    Last edited by a moderator: Sep 22, 2016
  2. A couple of quick points: the axis doesn't define the motion, the motion defines the axis and the axis isn't stationary during contact; the axis in that shoe is the equivalent of a medially deviated axis by Kirby's definition; what happens if the shoe "axial" position is different to the spatial orientation of the STJ axis?
  3. toomoon

    toomoon Well-Known Member

    Just goes to demonstrate exactly how little people understand about footwear design.
    And as usual.. a shoe can only do so much, but a decoupling aligned roughly about the estimation of a subtalar joint axis is going be way better than the way it is now, aligned with the ankle joint.
    Allowing a shoe to decouple roughly along the alignment of the subtalar joint, for someone with normal biomechanics (according to Reed Ferber 80% of all runners), will certainly not "increase the rate of pronation" as suggested by SeasonsChange. Every major footwear company has moved away from the concept of motion control, and the strategies imposed within footwear to "control motion', because there is zero science to support it.
    Every major biomechanics researcher working in the field of athletic footwear design is focussing more on the midfoot and forefoot rather than the rearfoot. Allowing the foot and shoe to move within a sphere of more normal motion is the goal. Pronation is normal motion, and to try to 'control" it is misguided.
    i am sorry SeasonsChange seems so offended by the explanation, but let's get one thing perfectly clear.. there is no shoe that can achieve all things for all people. As Simon rightly points out, the axis is not static, and whilst footwear can to a degree recognise this, and we are working on this right now, it is a difficult task.
    Footwear is and probably always will be, imperfect, but that does not mean we should accept the status quo and just go with the flow, especially if the flow is flawed. Designing around a basic grid pattern recognising the ankle joint mostly, is flawed.
    Finally in response to SeasonsChange question about if it is so great how come it is not in all shoes. Well SeasonsChange, footwear companies unfortunately are not humanitarian organisations.. they are not huge on philanthropy, and there is a very large commercial reality to building shoes for the masses (approximately 55,000 pairs every hour every day 365 days a year). The commercial reality involves something called stratification, which means if you have a good idea, like FluidAxis, you do not immediately put it into every shoe, or you kill every other existing shoe in the range. think BMW or Mercedes Benz, and the stratification of the range.
    Finally, the ultimate test is always in the wearing of the shoe and the athlete response. We have trialled Fluid Axis with thousands of wear testers. In my 30 years in this industry, I have never seen such extraordinary feedback, and never heard so many runners utter the simple phrase ..'it feels instantly completely different". That's right.. because it is!

    But that's all just marketing Bull sh*t really isn't it!
  4. Paul Bowles

    Paul Bowles Well-Known Member

    This is an interesting point - so lets for a second put aside what Simon is saying in that video as pure "advertising and marketing" jargon for the moment and take for granted we as educated professionals havent seen any of the research (which knowing how thorough and critical Simon is I am sure that there is or it is being done as we speak!).

    Lets look at the comment above which I find very interesting. Is increasing the rate of pronation such a bad thing? What does it actually achieve - and lets avoid the typical riff raff anti pronation discussion and stick with the research here taking into consideration the concepts Simon has raised in the video as well as sagittal plane function and Kevins work on sub talar joint axis.

    Its a very interesting discussion....
  5. toomoon

    toomoon Well-Known Member

    thanks Paul.. it is an interesting discussion, and I certainly would like to shift away from the commercial side of this and focus on what is achievable.
    At this bottom of this discussion for the moment (yes we are working on a new variant that looks at axial deviation) is that these shoes are designed for someone with relatively normal biomechanics, i.e. for someone who requires contact phase pronation and propulsion phase supination. For the most part, running footwear to date has tried to combat this. I strongly disagree with this premise. It is also extremely argumentative (and not supported by our data.. and once again Thank you Paul.. we have put thousands of hours of lab time into this project) to presuppose that a decoupling along the approximate line of the STJ axis will increase the rate of pronation.
    Finally.. please understand that the video you have all seen is not aimed at podiatrists or biomechanists, but is an attempt to explain a rather complex concept to the lay public, and retail in particular. It 'aint easy..
  6. SeasonsChange

    SeasonsChange Member

    Thank you Dr. Bartold for your generous reply! I always wonder how much freedom you have when making you're doing these types of videos and if you had to hold back for marketing purposes.

    Going to back to the "geometry of the fluidaxis," how does the fluid axis help overpronators? You mention in the video that by moving the fluid axis foward, you could create a more stable platform. Wouldn't removing the fluid axis all together provide the most stable platform?

    I sincerely apologize if I came off combative or rude, I truly appreciate your commentary on this forum and your work with ASICS. I'm just trying to learn more!
  7. toomoon

    toomoon Well-Known Member

    hey Seasonschange (I wish I knew your real name).. there was no offence taken and the questions you posed were completely valid. There is too much aggro at times and it is nice to kick this stuff around.. my NY resolution is to melllow out!
    In relation to what is possible with Fluid Axis.. let's remove the term from the discussion, because I am never at all comfortable discussing ASICS stuff on this, an academic forum.
    So let us for argument's sake explore the concept of manipulating the geometry of a midsole, outsole combination to see what can or might happen to motion. Let us call this concept axial geometry.
    the problem I have had with footwear design is that is has always been aligned to a basic grid, and this basic grid roughly aligns to the ankle joint axis. Think Nike free, which i always considered a pretty sound idea for its stated initial purpose, a warm up/warm down shoe.
    It should be entirely theoretically possible to have a dynamic platform, as defined by the midsole outsole and how it decouples or deforms. Now this may seem pretty radical, because what i am saying is that by shifting a decoupling of the midsole outsole, roughly aligned to the STJ axis laterally (as we might expect to see in an overpronater with a laterally deviated STJ axis), the medial base net.. or support platform if you lik, is increased, thus providing a greater resistance to pronation without the need for dual density, trusstics, propulsion plates, stiff heel counters.. etc. In short, all the "stuff' we used to think so important in a shoe for an overpronater is no longer neccessary, because the shoe is now dynamic and responding to the applied load as it exist instantaneously. The real beauty of this is that a really stable shoe can be created with a weight of less than 7 oz. Most motion control shoes are around 13oz or more.
    Now I think this is a concept to get a little excited about, because in the lab, we can easily demonstrate kinetic and kinematic advantages to this concept over something like say a Gel Foundation or Evolution.. huge , heavy stability shoes. We can show, the much lighter, much more flexible axial geometry shoe is actually far more stable than the 'motion control shoe". and the reason for this is that the shoe adapts..

    Make any sense?

    best Simon

  8. Isn't this because the direction of progression during running is principally in the sagittal plane and that the ankle joint was thought of to have it's primary role within the sagittal plane. Thus, the design intent has been to encourage sagittal plane motion via the ankle rocker (and for that matter at the forefoot rocker too) while inhibiting excessive frontal plane motion of the foot since excessive frontal plane motion has been seen as "bad" and potentially injurious?

    I quickly pulled out a few pairs of shoes from my cupboard: a Nike free which has a series of grooves which are positioned medio-laterally throughout the entire length of the sole and a single curved groove which progresses anterio-posteriorly. Which of these grooves within the grid they form aligns with the ankle axis? Certainly not all of them, if any. The other shoes I pulled were a Nike zoom elite and an Asics DS racer, both of these shoes have a series of outersole pods sitting on a blown foam midsole, I don't think any of the "grooves" between the pods nor the pods themselves align with the ankle joint axis. But as you say, this may just "demonstrate exactly how little people understand about footwear design".

    I should have thought you would expect to see medial deviation/ translation of the subtalar joint axis with pronation, not lateral deviation/ translation. Thus, I would more likely expect to see a medially deviated axis in an "overpronator" not a "laterally deviated axis" as stated above ;):morning:;)

    Can you explain exactly how having an obliquely orientated groove in the sole of a shoe influences the magnitude and position of the net ground reaction force vector during loading response and midstance please? And how such a groove influences the load/ deformation characteristics of the shoe; am I right in thinking that if I applied a bending force across the shoe sole, the axis of inflection would align with your "fluid axis"? Thanks in advance.

    If the outersole area of the shoe with the fluid axis is the same as a shoe without the fluid axis and subtalar joint axial position is the same in the two shoes, how does the addition of the "fluid axis" increase the "support platform" from the shoe sole which is medial to the subtalar joint axis?
  9. toomoon

    toomoon Well-Known Member

    ever dependable Simon.. thanks for the questions. I of course stand corrected no the medial vs lateral deviation of the STJ axis.. i wrote this correlating with the receipt of some very bad news and that is the only feasible explanation I can come up with for not knowing my medial from lateral... although my wife will tell you I am dyslexic!
    I think maybe the actual shoe may be being over thought here a little bit. a shoe is not like an orthosis.. it can achieve far less, but the principle, which may be wrong, is that the deep oblique split, roughly aligned with the STJ axis, will allow the shoe to decouple in a different, and hopefully better manner than nearly every other running shoe made, DS trainer included, which were to a greater or lesser extent designed to interfere with motion, not enhance it. I do not believe that fit in with where footwear research is currently positioned.
    in relation to a shoe for an over pronater, the premise is very simple.. increase the medial platform of the shoe.. rather than increasing the stiffness of the shoe. This is achieved by shifting the decoupling laterally, which allows the midsole to deform as an instantaneous 2 platform unit if you will.. one at contact, and then one immediately afterwards as the midsole deforms. Right now is where I wish you were in the room so I could show you.. anyway It may be wrong Simon, I do not know, but I do know what the 3D testing shows, and it certainly is different!
  10. Paul Bowles

    Paul Bowles Well-Known Member

    Personally I think its a great discussion - too many times I see my students and fellow colleagues throw around the term "pronation" like it is a disease or the plague of the 21st century. I think Simon Bartolds points are all extremely valid and Simon Spooner makes a very astute observation about the sagittal plane as well!

    I think the concept of pronation is misused. What does pronation of the foot actually allow - lets forget the dogma of shock absorbing platform yadda yadda yadda and use our heads a little here - doesnt the research conclude that raising the heel causes an increase in pronation throughout midstance to propulsion? If this is the case wouldnt it be logical to assume pronation is used by the foot to attain greater load at the 1st MTPJ and effective sagittal plane mechanics?

    I think there is sufficient peer reviewed published research and clinical evidence to suggest pronation may in fact simply be a method of sagitttal plane control. For example medial ILA height has an impact on sagittal plane 1st MTPJ function.

    We have all long known the relationships between medial ILA collapse and pathology but could it well be more sagittally related than we currently give it credit for? Is superior/inferior or adduction/abduction movement of the medial ILA merely a method orientating the 1st MTPJ to the ground surface?

    Let me give you an example - to attain greater functional ROM at the 1st one can easily plantarflex that joint orthomechanically. This will increase functional hallux range in line with how much plantarflexion of the joint is allowed. When you have a severe pes plano valgus foot type where the medial ILA is maximally collapsed to the ground surface and you apply a supinatory force to the foot in essence "increasing the arch" aren't you also simply plantarflexing the 1st MTPJ in the process by doing this? The basic premise of sagittal plane mechanics and arguably one of the main reasons for orthoses success in many cases relating to sagittal plane blockade could possibly be attributed to this. I hark back to the theories was it Bosch and Moller - regarding high gear and low gear propulsion?

    So in discussion above how exactly is pronation a "bad thing"? In hindsight and consideration of the what I mentioned above pronation is an essential component of the sagittal plane mechanism to allow satisfactory load to be placed on the 1st MTPJ. Unfortunately due to ground surface (the hard man made types) the load at the first ends up causing a dorsiflexion moment at propulsion instead of a plantarflexion moment - so instead of getting a plantarflexed 1st MTPJ and adequate hallux ROM on the joint we get a dorsiflexed joint leading to instability and functional (possibly even structural) hallux limitation?? Possible?

    So bringing this back into context of the shoe - what ASICS are doing here may actually make a decent deal of sense especially considering Simons comments regarding previous motion control attempts in footwear of the past.

    Load of rubbish? Possibly - but its a very interesting discussion orthomechanically and I think having people like Simon Bartold add to the knowledge pool of the subject in terms of footwear is invaluable.

    Finally - the longer I work as a Podiatrist the better I see the symmetry between all the things I was taught at University and what I see clinically. After almost 20yrs things like the Kirby Skive I no longer see as an option in an orthoses - I see it as a concept of orthomechanical care which I can apply to numerous instances and circumstances. It is work like this from Simon as well as many others such as Kevin that daily make me think about what we do and why we actually do it! Cheers guys!
  11. David Smith

    David Smith Well-Known Member

    There are number of things that don't seem to gel for me in this theory of fluid axes.

    1) In terms of the magnitude of the GRF applied to the shoe at stance phase: Is there a significant difference in flexion stiffness between the normal sole thickness and the 'decoupling' cut out (sole groove).

    2) The proposition that this is somehow a 2D/biplanar flexion action is bogus: The sole, because it is thin and flat, only significantly flexes in one plane, just because the groove is at an angle to some imaginary longitudinal line of reference is immaterial.

    3) Because the sole only flexes through one plane the the amount of flexion will be very small and insignificant to the action of the foot. I.E. The major axis of rotation for the STJ with regard to an orthogonal reference system is in the frontal plane. If the medial rotation of the STJ axis is say 20 degrees then the sine of 20 is 0.34, therefore the the amount of displacement available to flex the sole around the axis of the sole groove is only 1/3rd of the frontal plane displacement of the STJ rotation assuming the sole groove angle is also medially rotated 20dgs. If it does not match the stj medial rotation angle (as of course it will not for most of the stance phase) then the small potential advantage gained is again lost thru this mismatch..

    So if max pronation is 21 degrees in the frontal plane then the amount of flexion around the sole groove is only 7 degrees. Let's assume the vertical dimension from the centre of the STJ to the ground is 50mm then for the 21 degree angular deflection there is 3mm linear deflection and so in the plane of the sole groove there is only 1mm of linear deflection. Now I'm sure no matter how good a fit the shoe is to the foot there is going to be more than 1mm of slip between the interface of the shoe inner and foot.

    To me it appears like the sole groove is very unlikely to make any difference to the 'uncoupling' forces between the rearfoot and forefoot.

    4) Now considering No.3: the exact position of the sole groove relative to the spatial position of the STJ for the shoe wearer would be crucial since the difference in stiffness between the optimal position and the actual position would negate any advantage gained by the availability of a very small amount of sole deflection around the groove. I.E.

    Assuming the groove angle matches the wearers STJ angle then the relative horizontal position of the groove would be very important and would be relative to the vertical height of the STJ centre from the plantar heel of the foot and the width of the heel. If there was not a match then rather than a pure angular deflection about the sole groove there would be tension (stretching) or compression or the flexion moments would not about the sole groove at all. This again would negate any small advantage gained by the action considered in No.3.

    Just my initial thoughts, sorry if my explanation is a bit difficult to get to grips with a robust unambiguous description is difficult to come up with.

    regards Dave Smith
  12. David Smith

    David Smith Well-Known Member

    Another thing occurs to me

    If you want a shoe that is going to have a 'Fluid axis' that suits as many individual wearers as possible the why not make the sole groove really wide i.e. perhaps 30mm then there is plenty of scope for the foot, or every foot, to uncouple and flex just where it wants to and not restricted to the silly 2mm slot provided in the Asics shoe.

  13. That's kinda' what I was asking: what does the testing show?
  14. toomoon

    toomoon Well-Known Member

    Can you wait till we publish it in a couple of months?
  15. toomoon

    toomoon Well-Known Member

    i think you are completely missing the point David.
    FluidAxis is not claiming to be the second coming of Christ. I will say again that a shoe can only achieve so much, and that so much for the majority involves major interference with normal foot function. Fluidaxis is a design protocol that provides a vehicle for the foot to move on a more interactive platform than is currently available based on outdated and disproved design protocols like stiffness, weight and inflexibility. Nothing more.. nothing less. A majority of current running footwear is based on technology that is 40 years old and does not help the runner.
    It might also be worth considering that this is the first attempt, and that we have been working hard to refine the concept. it is a shame to disregard a concept until you have had the opportunity to evaluate it in the flesh
    Of course you and everyone else is entitled to believe it is "bogus', however, i disagree, and hope that in due course, when we publish our research, you may perhaps change your mind.
    I will also be presenting most of our data at the International Society of Biomechanics Conference in Natal Brazil this year. Put it in your diary and we can chat there.
  16. This is an interesting discussion. Simon Bartold has been discussing the idea for this shoe design, the "Fluid Axis", with me for at least a year now. I have yet to see the shoe in the flesh or even try one on to see how it performs. Therefore, until I do, I know from previous experience that it is very difficult to determine how a shoe will perform until I have tried it on, walked and ran with it, and then watched a number of other individuals doing the same. It could be the greatest shoe to be made in the last 20 years, could be a shoe that causes problems for many runners or, more likely than not, could be somewhere in between these two extremes of performance.

    After reading the other comments, I feel that both David Smith and Simon Spooner have quite valid comments regarding this new style of running shoe sole design, especially considering the video that I viewed that had my good friend, and fellow member of the famous Tarsal Coalition, Mature-Adult-Boy-Band, Simon Bartold, explaining the concepts of the shoe, obviously for the layperson. The video looks like a good marketing tool for the layperson to me, nothing more, nothing less. Therefore, I wouldn't get too excited about what Simon says here in this video since he is obviously trying to dumb down the concepts of the shoe for the layperson who wouldn't know the ankle joint from the STJ, rather than explaining the concepts to a group of biomechanics PhDs or biomechanically-oriented podiatrists.

    The shoe sole construction in the "Fluid Axis" shoe is definitely unique, as Simon Bartold stated in the video. However, I am uncertain whether a split in the shoe sole approximately along the course of the subtalar joint (STJ) axis will cause that much change in shoe performance when compared to the same shoe sole construction when there is no STJ-axis oriented groove in the shoe sole.

    I would think, however, from a theoretical basis, that modifying the midsole durometer within the rearfoot and midfoot portion of sole would have much more kinetic effect on the foot and lower extremity than putting a STJ-axis groove into the sole of the shoe. However, modifying the shoe sole durometer medial and lateral to the STJ axis and then combining this along with a groove in the shoe sole oriented approximately along the STJ axis may have quite profound effects on shoe performance and on running kinetics rather than just modifying shoe midsole durometer by itself.

    Even though I love to theorize regarding the effects of shoe construction parameters on shoe biomechanics and shoe performance, I have been wrong before on such matters, especially with new and unique shoe designs. It would probably be best that a pair of size 12 (US) of these shoes were sent to me so I could inspect them, try them on and walk and run in them (hint.... hint.... Bartold) before I make any other guesses as to how these shoes will perform on my feet and other individual's feet.

    Good discussion.:drinks
  17. By the way, here is Simon Bartold in Boston from over eight years ago, at a time when he was first thinking about the idea of the fluid axis shoe....nothing like beer and paper airplanes to get the get the cerebral gears going.....:rolleyes:
  18. Even Simon Spooner was deep in thought regarding these types of topics at a PFOLA conference the year before....;)
  19. toomoon

    toomoon Well-Known Member

    pretty cutting edge hairstyle from Simon for the day I must say!
  20. toomoon

    toomoon Well-Known Member

    I am very, very disturbed Dr. Kirby.. have you at some stage planted a covert listening device upon my personage? Your comments in relation to construction and density indicate that you possess knowledge you should not unless you have had access to our top secret planning and research sessions!!
    I would be more than happy to arrange delivery of a pair of the 'ol size 12's to you, and also to Simon and David should they wish to check 'em out, which really is the best way (Simon and David, if you are keen, let me know sizes in US sizing). The proof is always in the puddin' I guess.
    Shoe hits market very soon, so stand by
  21. CraigT

    CraigT Well-Known Member

    I would have to echo the thoughts of Simon S and Kevin above... Possibly Dave's too, but I have think a lot to understand what you are exactly saying!
    Kevin in particular said-
    So it is aligned to the axis of a 'neutral' type foot, but for a 'pronated' foot where the axis is generally more medially translated, the axis of the shoe moves more laterally? And supinated/ laterally deviated axis foot vice versa??

    Geez Simon... I agree with your first sentence, but then you start to talk like you are trying to appeal to the minimalist advocates. Outdated and disproved??? Doesn't help the runner???You make it sound like we should throw out all our running shoes!!!

    Are you telling me that you have never had a patient have a significant improvement in symptoms simply by advising them to choose a particular type of shoe as opposed to their current choice?

    Do we need a revolution or should we continue with the evolution in running shoes? I think we have had quite some evolution in the past few years as we have moved away from shoes trying to control the foot... because we have seen that there is a limit to their effectiveness at doing this. However they are still an important component in managing lower limb mechanical problems. I still believe there is a place for a heavy motion control shoe like a Brooks Beast... but I there probably has been a shift away from using this shoe for many people who have may have previously been advised this.

    I look forward to seeing the new design before I pass judgement...
  22. CraigT

    CraigT Well-Known Member

    Kevin said-
    Or we can individually tailor an insert which could be put inside the shoe. We could base this insert on the shape of that person's foot and alter the geometry in all 3 body planes to influence how the GRFs are applied. We could also use a variety of materials according to individual's needs.
    This insert could be moved from one shoe to another- then each pair of shoes would be essentially customised to that person!
    Hang on a minute...;)
  23. toomoon

    toomoon Well-Known Member

    Not at all Craig.. and I have to be a little careful here.. I am saying dual density midsoles were invented by Barry Bates in 1974, and first appeared in an ASICS shoe. I have been publicly critical of design focus from the company that pays me, to my peril Craig, but did so because I believe the company owes it to the athlete and because it is my job.... there is no evidence they (dual density midsoles) do anything other than make the shoe heavy. Stiff, heavy shoes will suit maybe 1 in 100 runners, probably less. If you believe Reed Ferber, whom I chatted to in Austin 4 weeks ago.. the number is 1 in 500. There will be challenges to paradigms mate, and some of these will hit hard. i think the questions you asked me were rhetorical because you know me well and know how I have practised over many years. You have also heard me go against the trend many years ago.. and yet I am still speaking to podiatrists regularly who ONLY prescribe the Beast and will not have it any other way.
    Craig.. am I not getting the message across here properly? Currently.. for at least the next 18 months, Fluid Axis will be in 2 shoes only, and they are both designed for neutral runners. One of the 2 is off a 6 mm platform and is designed primarily for short fast mix up sessions on different surface and terrain, something I personally believe is a very important injury prevention strategy.
    I have not, and never will be advocating a "revolution", nor am I suggesting you should throw out all your runners! If you read my response to Season Change, you will see the specific comment about stratification. I am not saying this is the answer.. I am saying it is different, just like a Brooks beast is different, and it just might be that it really helps some runners, especially given that both shoes are performance based running shoes coming in at around 7 oz and one of the 2 still has a 10mm platform. Hardly minimalist.
    Craig.. you need to visualise the way the shoe decouples.. not visualise the axis. of course the shoe does not replicate the axis,,and of course it is not fluid.. geez mate, I do not make up the names and I do not do the marketing. the working name I used for this project was axial geometry just to demonstrate the importance of midsole geometry, nothing more, nothing less.
    You of all people know I am not advocating minimalism.
    i am advocating a 'theory' that manipulating midsole geometry may well be more important than any of the traditional 'motion control' strategies.
    now I am very aware that i am now put in a position where i am having to defend a decision made by a commercial entity that i have studied in a lab and on the road extensively.
    i do not wish to do this on this arena, because I do not see myself as the defender of ASICS and never have. In fact that is the exact reason that this has arisen, because I have been so critical of all the 'stuff' that has been put into shoes that did nothing but add weight.
    Sorry guys.. all that crap addressed rearfoot or contact phase pronation, which is stone dead normal.. I am far interested in the midfoot and forefoot.
    I think i shall bail out of this discussion for the moment, because I feel I am on a hiding to nothing, with none of you actually able to see the shoe. No point in hanging it out to dry until you have had a chance to hold it and hopefully run in it.

  24. Perhaps if you could describe how it "decouples", and provide a description of how this decoupling might (or was designed to) influence the ground reaction forces we might be able to make better judgement?

    As for my hairdo back in Boston.... this from the man who appears to be styling himself on Chris Evans these days ;):D

    Attached Files:

  25. OK, I appreciate Simon's position of having to wear two hat's here (he might want to consider one to cover up that new hair colour too ;)) and his reasons for wishing to step back on this discussion. So lets see what we can speculate upon ourselves.

    As I recall Adidas introduced a decoupled heel with their formotion shoe, the idea was that at heel strike, the strike plate section of the shoe hit the ground first and it's forward (mainly sagittal plane) motion was arrested due to friction between the shoe and the ground, while the rest of the shoe could still translate forward anteriorly due to the "decoupling" between the strike plate and the rest of the sole unit.

    This new Asics design seems to be similar in concept, except the coupling line, axis call it what you will, is offset more obliquely and extends forward further into the midfoot on the medial side of the shoe.

    So, we strike the ground on the decoupled rearfoot section of the shoe which arrests the forward translation of the shoe in an area roughly medial to the subtalar joint axis (STJ) (lets model it so the decoupling axis of the shoe aligns exactly with the STJ axis for now), while the rest of the shoe sole (which lies lateral to the STJ axis) is allowed to continue to translate forward. However, due to oblique nature of the coupling axis the translation should be antero-lateral (lets assume the foot is glued to the shoe). This should allow the forefoot to abduct and the medial longitudinal arch to lower. But the two section of the shoe sole can only move so much relative to one another because the material which bridges the gap between the medial and lateral sections of the sole will restrain it; this material deforms and stores elastic energy along the decoupling axis. As the material recoils, the forefoot should adduct and medial longitudinal arch should increase in height due to the angular relationship of the decoupling axis, and because the foot is glued to the shoe. Viz. the shoe allows the foot to pronate at strike and then aids in resupination (or limits excessive pronation) by storing and returning elastic strain energy within the material that bridges the decoupling axis.

    You can give me a nod privately if I'm understanding the design intent correctly, Simon.
  26. CraigT

    CraigT Well-Known Member

    I am all for questioning paradigms, but I do not want the baby to be thrown out with the bath water. Lay people read all propaganda from the so called minimalist movement and would think that we haven't a clue what we are doing... I do believe that the right shoe can make a difference to many people because I have seen it so many times. Is it always the solution? Of course not...

    Yes- being rhetorical mate... and agree with the problem of Pods and others only advising one shoe without having a good hard look at the shoe and its suitability.

    Have a better idea now! Certainly not hanging it out to dry... look forward to seeing it in the flesh.
  27. David Smith

    David Smith Well-Known Member

    Simon AKA TooMoon

    Could you explain what is the benefit to decouple the rearfoot from the forefoot or isolate the STJ motion?

    At what part of the stance phase do you envisage the decoupling would be most advantageous?

    I.E. should it work best at heel strike, mid stance or propulsive phase or would it work better with a forefoot strike?

    Perhaps in the forefoot strike or the propulsive phase condition the sole groove might allow more or less inhibited supination of the STJ. I have cut a similar groove in a pair of Slazenger sports shoes and it does reduce the stiffness of the sole in a simulated supination action acting on the sole when performed by hand

    The groove I cut is about 3mm wide and goes about half way thru the mid sole in an approximate V shape cross section. It is cut in a similar position to the Asics shoe i.e. it goes from medial arch mid foot to lateral anterior heel. The problem is that when a pronation action is performed the gap closes and the increased compliance is lost, to maintain the flexibility it is necessary to cut a groove in the opposite direction crossing the original cut, i.e. from lateral aspect mid foot to medial heel.

    Considering, as mentioned earlier, that the sole groove only allows 1 degree of freedom about its long axis: the next thing I considered was that during midstance it is impossible for the sole to flex about the axis of the sole groove. This is because it (the shoe sole) is fixed by bodyweight onto the ground and can only flex about an axis that is horizontal with and parallel to the ground and so unless the floor is flexible the sole cannot flex in that direction, which by definition would be pushing through the ground.

    Now I'm not a runner by any stretch of the imagination but I had a run in the Slazenger shoes with the groove cut in the left one and couldn't notice any difference in terms of STJ freedom to move. I felt this was because of aforementioned reasons, i.e. the relative difference in sole stiffness in terms of the magnitude of GRF is insignificant and the amount of slip between shoe inner and foot. I do notice the difference between the thin flexible soles of the Slazenger compared to he stiff thick sole of my Sketchers.

    What I do also notice, with any shoe that I wear is that at heel of as the rearfoot supinates then the rearfoot just rotates in the shoe and the stiffness of the sole appears to have no bearing on the ability of the STJ to supinate.

    Regards Dave Smith
  28. Dana Roueche

    Dana Roueche Well-Known Member

    I am encouraged that Asics recognizes the shortcomings of having a sole that is rigid from the heel all the way through the mid-foot. If I understand what Simon B. is stating, FluidAxis compensates for the shortcomings of a rigid sole. A rigid sole is necessary to provide a stable platform to compensate for the shortcomings of having cushioning. Starting to sound like "design dominos".

    If the layer of cushioning was thin enough with a durometor firm enough to allow for the omission of a rigid sole, there wouldn't be a need for the "hinge" in the sole.

    I'm really struggling with the need for a soft midsole/rigid sole design combination. I would imagine using a hinge would help greatly but how do you place the hinge in a fixed position that will always align properly with the joint movement of the foot?

    I would think that by configuring the midsole to allow for a fully flexible sole from heel to toe that it would allow the foot and ankle to move freely and function as it was anatomically designed to do would be the best option for "neutral" runners. (neutral = lack of motion pathology)

  29. David Smith

    David Smith Well-Known Member

    Makes sense in terms of this discussion.

    Regards Dave
  30. SeasonsChange

    SeasonsChange Member

    Are you a minimalist advocate?
  31. Dana Roueche

    Dana Roueche Well-Known Member

    Mr. Change, what is a minimalist agenda? I have been running big miles since the early 1970's. I have had the opportunity to wear and experience most running shoe design principles for entire history of the modern running shoe. For that matter, my experience begins before running shoe companies started building up foam then EVA mid soles and finding they needed to add a firm platform to the shoe. That firm platform was made of a hardened piece of cardboard that ran from the heel through the midfoot. Some shoes actually had it run the entire length of the sole. The "technology" was called "board last". One of the shoes that had a board last the entire length of the shoe was The Onitsuka Tiger, X-Caliber GT. Asics bought out Onitsuka. Simon B. actually referenced this shoe in one of his posts, it was the first shoe to include dual density foam. A break through for the time and here we are 30 yrs later with shoes that still use the same technology.

    Getting back to my agenda, I have always found shoes that have had flexible soles running the entire length of the shoe to work the best. In the beginning, these shoes where labeled "slip lasted" or even more to my preference was a type of "slip last" known as "curve last". The curve lasted shoe tended to be the lightest, most flexible and most conforming to the shape of the foot. Even so, a lot of the flexibility in the heel was lost to the thick heel which was hard to get away from at the time.

    I am reminded of the Nike Terra TC, a super light, curve lasted flexible shoe that was available in the early 1980's which was one of my all time favorites. It hasn't been until the Nike Free that Nike has been able to come close to replicating the feel.

    With time, materials have changed, design points have changed and the jargon has changed with it. What was once a shoe built on a piece of cardboard, they dropped the cardboard for a piece of rigid plastic. Since we are talking about Asics, they have coined the term "trustic system" for this piece of plastic that is fitted at the midfoot to ensure stiffness from the heel through the midfoot.

    I have been a big consumer of running shoes for 40 years, yet the the label "minimalist shoe" has only been around for about 4 yrs or one tenth of the life of the modern running shoe. No I do not have a minimalist agenda, rather I am interested in shoe design that optimizes the runners experience, not what sells the most shoes or uses the most marketing buzzwords to label it's technology.

    Frankly, I dislike the term minimal, it is ambiguous and often incorrectly implies certain characteristics about a shoe that don't exist.

    I confess, I was never an enthusiast of the board last of the 1970's and here we are now and I'm still not an enthusiast of shoes that possess rigid soles. This has nothing to do with "minimal" shoes. As I mentioned in the first sentence in my post, I was encouraged by the fact that Asics after 40 years is finally recognizing the short comings of rigid soles, THANK YOU Simon. I have disliked rigid soles for 40 years.

    There will always be customers who want or possibly need cushioned shoes and with cushioned shoes comes the need for a rigid platform. And there will always be shoe companies providing this type of design. My point is those design points have shortcomings and the easiest and simplest way to fix the design points is to dump them in favor of design that doesn't require design fixes on top of design fixes.

    In my mind, the "game changer" is not FluidAxis, it has to do with the fact that the shoe companies finally recognized that people don't necessarily need all of that cushioning. Without all of that cushioning, there isn't necessarily a need for a rigid sole. Without a rigid sole, the foot can function more effectively......Just like Simon is trying to accomplish but with a much simpler, more direct path.

    Maybe I should start my own shoe category, the "Flexible Shoe"!

    Other than that, I don't have much of an opinion.

  32. Paul Bowles

    Paul Bowles Well-Known Member

    Function more effectively on the......rigid ground?
  33. Dana Roueche

    Dana Roueche Well-Known Member

    Paul, you are joking, right?

  34. Paul Bowles

    Paul Bowles Well-Known Member

    I don't know if I should be or not - maybe I am being a tad facetious! I am simply taking what you said and applying day to day logic to it - is that incorrect?
  35. Dana Roueche

    Dana Roueche Well-Known Member

    OK, now that I know you are not kidding, I have an idea of your level of understanding. Rigid soles and ground compliance are barely remotely related.

    There is an optimal thickness and an optimal durometer of sole cushioning in a running shoe. Optimal being defined as that resulting in the greatest efficiency and efficiency being measured by oxygen consumption. Optimal thickness and durometer varies across individuals, running form, pace, terrain, ground compliance and I'm sure a bunch of other variables as well.

    As the thickness increases and the durometer becomes softer, the relationship between the foot, the shoe and the ground become less stable. I like to think of this in a highly technical term, "mush factor". As the shoes become mushier, there is more of a need for a stable platform to keep the runner from undesired motion issues such as falling off the sides of the shoe. A stable platform in which to place thick, soft cushioning is easily solved by introducing a plate to the sole of the shoe. This plate used to be very stiff cardboard which ultimately was traded for thermo plastic. In shoes that contain a plate, it can run from the heel through the midfoot. Other times the plate might just be located in the midfoot that bridges the heel to the forefoot. Often the outer sole combined with a thick, firm heel provides enough stiffness in the heel area to only need the plate at the midfoot where the sole transitions to thinner and narrower and has the least structural integrity.

    The relationship between a rigid sole and ground compliance is indirect. Ground compliance MIGHT influence the choice of thickness and durometer of cushioning. The thickness and durometer influences the requirement for a rigid sole.

    A rigid sole laced to the foot can inhibit the range of motion of the moving parts of the foot and for my next highly technical term, has a "cast effect". Think of a splint on a broken finger. A flexible sole can allow freedom of motion of the foot allowing it to move/function more effectively. The assumption is the foot is non pathological and doesn't need a cast to restrict motion. FluidAxis recognizes the shortcomings of the cast effect and is attempting to allow movement in a key location of the rigid sole to allow effective function of the STJ.

    The ground, whether it is compliant or non-compliant ground or "rigid" in your language has no influence on the movement or function of the foot.

    My point in this discussion has been about what thickness and durometer of the cushioning is really required for most runners. Does it really need to be mushy enough to require a rigid sole?

    The reason I was asking if you where joking is that these principles seem rather obvious.

  36. SeasonsChange

    SeasonsChange Member

    Yeah, for you.

    On the net there's tons of minimalist advocates, including Steve Larson, who proclaim that a certain form or style of running shoes is the best. But the fact is they're all pretty slow and most aren't even competitive at a local level.

    I've never seen a fast runner who wears <7oz shoes for all of their training. Most of the faster runners wear traditional trainers. Have you tried running >70mpw at <7min/mi pace in a shoe you suggest? I wouldn't make it past 35mpw.

    How many athletes have you coached or patients you've seen who have had their symptoms improve from switching from a traditional shoe to a lesser one?
  37. Dana Roueche

    Dana Roueche Well-Known Member

    Mr. Change, who is talking about less than 7 oz shoes? Not once have I referenced shoe weight in the discussion. Because you haven't seen a "fast" runner wear less than 7 oz shoes for all of their training doesn't mean they don't exist. But, it's a mute point, I'm not talking about shoe weight.

    There are few people who can run over 70mpw at less than 7mpm pace regardless of the shoe they wear. Does it matter how far you can make it? I suggested flexible soled shoes over rigid soles, nothing more, nothing less. I can't control how much you incorrectly read into what I've written.

    I have coached many, many runners for compensation for years on how to successfully run a 100 mile trail ultramarathon. Not once, not ever have I suggested what shoes they should wear.

    Again who is talking about "traditional" shoes vs a "lesser" shoe?

    You brought up the Asics DS Racer in your first post on this thread. They weigh 7.9 OZ for a mens US size 9. Do you consider them a "minimal" shoe? Keeping with Asics, they have a trail shoe the Fuji Racer which has a flexible sole with some very slight stiffeners to the midfoot area add some structural integrity to keep it consistent with the heel and toe but it most certainly has a flexible sole. It weighs 8.8 OZ for a mens US size 9. Do you consider that a "minimal shoe?

    Mr. Change, define what a minimal shoe is to me and secondly show me a thread of evidence that supports the use of rigid soles as being more effective for a neutral runner defined as someone without motion pathology.

  38. David Wedemeyer

    David Wedemeyer Well-Known Member


    Are there any RCT's or studies where patient's with say Plantar Fasciitis where "minimalist" or "barefoot" are compared to traditional shoes?

    Does any governing body or clincial guideline of any health profession recommend either as a treatment for any foot condition?

  39. Craig Payne

    Craig Payne Moderator

    There was this study in which the minimalist group did worse than the traditionally shod group (despite the authors actually claiming the opposite).
  40. Paul Bowles

    Paul Bowles Well-Known Member

    ...and thanks for your post because it gives me a very good understanding of your level of knowledge.


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