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Cycle orthotics

Discussion in 'Biomechanics, Sports and Foot orthoses' started by nicpod1, Oct 26, 2011.

  1. nicpod1

    nicpod1 Active Member

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    Hi All,

    I'm coming across more demand for cycling orthoses but am struggling to find any really serious info about cycling biomechanics and the use of orthoses and, also, any courses to go on.

    Does anyone use orthoses in cyclists routinely? Do you do this as part of a complete bike fit or do you do it independently and are there any decent courses to go on to help with this?

    Thanks a million!

  2. Ian Linane

    Ian Linane Well-Known Member

    Hi Nichola
    Nice to see you on here again.

    I'm sure Kevin and others will comment but in terms of someone more local (ish) to you have a chat with Phil Wells.
  3. Admin2

    Admin2 Administrator Staff Member

  4. Griff

    Griff Moderator

    Hi Nicola,

    Both Kevin and Simon issue lots of cycling orthoses, but as they are both sunning it up in Florida at a conference I'll give you my (albeit limited by comparison) experience. I know Athol has a special interest in cycling also so maybe he'll add some gems too.

    I see a fair share of cyclists. I work quite closely in one clinic with a Physio who is an approved Retul bike fitter, so we often do it as a complete service. This can involve a number of variables including cycling orthoses, simple forefoot wedging, wedging outside of the shoe (at cleat/pedal level), and cleat pedal positional adjustments.

    There's a fair bit of literature out there on the subject (as kindly listed above by Admin2) and Kevin has done some nice Precision Intricast Newsletters on the topic which are worth reading. My advice would be to align yourself with a bike fitter, whether that be a Physio or a professional bike shop - will make the learning curve much more tolerable.

  5. PodAus

    PodAus Active Member

    Hi Nicola,

    There are products on the market that have been specifically designed for cycling, with supporting research.

    I've been working with Solestar, whom provide excellent education and technical support re: cycling biomechanics.

    Look them up.
  6. mgrig

    mgrig Active Member

    In simple terms, a Solestar orthotic is

    - a rigid prefab orthotic extending to /beyond the met heads


    - a FF valgus wedge
    - 1st ray cut out
    - met dome
    - very low profile heel cup
    - reasonably high medial arch

    Their research suggest that there is a 6.9% increase in performance.

    The question is why would they improve performance?

    would it be an increase in 1st ray dorsiflexion stiffness?

    For Kevin et al, how much influence do you feel an orthotic has beyond the contact of the pedal i.e. midfoot and rearfoot changes with orthotic intervention?
  7. Not sure if I fit in the et al but any way.

    a few things to think here

    Forefoot Center of Pressure will have a longer lever arm to the Midtarsal and Subtalar joints so a greater effect on those joints.

    Increasing the stiffness of foot will also mean greater efficiency of pedal stroke ie the stiffer the foot inside the cycling shoe will transfer greater energy through the cleat to the crank arm and produce more watts.

    A lot of the work re posting focus on the knee in better position during the power sections of the 360 degree motion. And the better position is all about watts produced/muscle fatigue/comfort/flexibility.

    There is also a large degree of neurological feedback and the use of an orthotic in cycling - ie the plastic will to a greater extent let the body know where the foot is than no device at all.
  8. Foot orthoses, whether prefab or custom, and cleat wedging (e.g. varus or valgus cleat wedging, neutral shims for limb length discrepancy) can significantly affect the biomechanics of the midtarsal, subtalar, knee and hip joints during cycling. Ideally, during a bike fitting procedure, the cyclist should be riding on their own bike on a wind trainer where they are pedalling against load at a realistic cadence (i.e. revolutions per minute).

    The main things I am looking for during a bike fit are proper sagittal plane knee angle (i.e. to ensure the knee is not too flexed or too extended), the frontal plane movement of the knee (e.g. is the knee moving medially toward the top tube too much during the power phase?), the movement of the subtalar joint (i.e. how far does the medial malleolus clear the crank arm during at bottom dead center?) and the overall position of the body on the bike (i.e. saddle height, tilt, fore-aft position, stem and handlebar position and size of frame).

    This is a time-consuming process, taking at least 30 minutes, that, in years past, I did in my practice. However now, since I am so busy in my practice, I send them these patients to a local physical therapist-cyclist who has a video camera setup and specializes in bike fitting and does an excellent job. This physical therapist also refers me patients that need orthoses or other shoe modifications.

    I rarely use foot orthoses for cyclists if their foot demonstrates astable midfoot/midtarsal/subtalar joint complex (i.e. one that doesn't pronate excessively during the power phase) since I don't want to add unnecessary mass to the cycling shoe which would decrease metabolic efficiency. The most common modifications I make to cycling shoes include varying the cleat fore-aft position, varying the cleat frontal plane angle, adding a cleat shim for leg-length discrepancy and modifying the existing insole of the patient's cycling shoe.

    In general, cyclists can tolerate much higher medial arch heights from their foot orthoses than they can tolerate when walking or running in the same orthoses. Therefore, I will tend to use a more aggressively medially-arched orthosis for the patient with excessive power-phase pronation in their cycling-specific orthoses. I also commonly modify prefab orthoses to decrease compression forces at the metatarsal head level if the patient is experiencing forefoot symptoms.

    BTW, I seriously doubt any prefab orthosis has the ability to increase "performance" by 6.9% in a large range of cyclists. This smells of marketing BS, similar to the butt-toning claims of the "toning shoes" that are now being forced to refund money to their customers for their unsupportable marketing claims. Please tell the company that I made this statement publicly and that they will need to produce some good scientific research evidence in regard to their claims or be prepared to start refunding money to their customers if their 6.9% improvement in cycling performance claim doesn't hold true for the customers who purchase their pre-fab cycling orthoses.

    Hope this brief analysis helps explain some of the ways that the sports-podiatrist can help these athletes enjoy their cycling more with less pain and injury. Now, I need to continue working on my slides for the coming conference tomorrow.:drinks
  9. Hi Kevin,

    I really wonder if a bit of plastic would have a negative effect of metabolic efficiency, yes it add weight but in the down stroke the extra weight also is a positive to metabolic efficiency.

    I would also say that the added stiffness that the device adds at the foot interface would also add the metabolic efficiency which would out way the cost of the extra weight.

    PS have a good time presenting
  10. Mike:

    Cyclists spend hundreds of dollars on lighter cycling components that rotate because decreased mass on any rotating cycling component will decrease the mechanical work of cycling. The weight of rotating parts is called "inertial weight" and smart cyclists, will spend their money on lighter rims and crank arms/pedals since any increase in moment of inertia of a rotating part will require more mechanical work to accelerate it.


    Foot orthoses probably greatly improve the mechanical efficiency for some cyclists that have "unstable" feet, but would tend to decrease the mechanical efficiency of cyclists that have "stable feet" due to the added mass.
  11. nicpod1

    nicpod1 Active Member


    Thanks a million for all the feedback, I've not had time to read it but will later on today or tomorrow.

    Admin, I did search for info before I posted this reply, but nothing came up, so, sorry for repeating the issue.

    I am aligned to a bike fitter Physio, so hopefully this is something we can develop.

    I'll be back!
  12. mgrig

    mgrig Active Member

  13. Griff

    Griff Moderator

    Poor methodology.

    Everyone was tested in their own (usual) shoe environement, then issued the Solestar insert and 2 weeks later tested again. There was a difference in sprint performance. But, how do we know it was not due to between-day measurement error? How do we know it was not due to the 2 weeks extra "activity" they had done between test 1 and 2?

    Potential ways around this would've been to randomise the order of the testing (test half of the group in the solestar insert on day 1) and/or to add a control group.

    I hope this isn't the calibre of all the 'supporting research for the products on the market' which was alluded to earlier in this thread...
  14. efuller

    efuller MVP

    What Kevin said and.... What goes down must come up. The extra weight has to be lifted from bottom dead center to top dead center. Elite cyclists may add torque to the pedal when they lift their leg at this point in the pedal cycle. Even if they don't add torque they can reduce the resistance on the leg pushing down, if they lift the other leg up.

    The concept Kevin was referring to is moment of inertia. The heavier the rotating system, the more energy it takes to accelerate the sytem.

  15. PodAus

    PodAus Active Member

    And as all athletes know, "it's what works for me, that helps me perform at my best "... measurable improvement as a result of mechanical assistance at best, and placebo at least... :drinks
  16. I going to say I don´t agree. In that I don´t think it is as simple as extra weight of the device will have a negative effect.

    Cycling pedal stroke produces the most amount of power - Watts in the downward stroke called the Power stroke. This part of the stroke is between 1 and 5 if looking at a clock. Added mass at this point will produce more watts.

    If this positive production in Watts is greater than or equal to the negative effect of the exact opposite up stroke/pull then the effect of the extra weight when just looking at the pedal stroke and watts production if this produces more watts than is lost it has to be positive or even equal itself out and thus the mass argument will be negated.

    What will happen in all feet, a greater extent in a more flexiable foot than a rigid but all feet , there will be a greater transfer of power at the power stroke - in cycling it all about the relationship between weight v´s stiffness, less stiffness and you lose power. By adding to the stiffness at the foot interface I believe that greater watts will be produced at the power stroke which is the point of where the bike is accelerated to the greatest extent if the person is more efficient at this point ie the power stroke I believe that is will have in total a positive effect for a cyclist.

    Now days cycling it is all about watts produced to weight ratio so if the device helps the cyclist produce greater watts than the negative effect then the device will in total be positive - which I believe than it does to all feet - the greater the stiffness the less.

    PS Kevin if I had the money I would own bike for all seasons can´t wait to own a cross bike and ride on the snowy roads .

    pps most cyclists would perform better by losing a few kgs of upper body mass anyway ;):drinks

    not trying to be argumentative just for discussion cause I am a bike nerd.

    So if Kevin, Eric or anyone else doesn´t agree can you answer this question for me.

    will increased mass in the power stroke or when the pedal stroke has crossed passed 12 and moving toward 6 ie not fighting against gravity will increased mass have a positive or negative effect at this point.

    Attached Files:

  17. Athol Thomson

    Athol Thomson Active Member


    At the bottom of this post is a a recent study on the incidence of overuse injuries in pro cyclists. Cycling is extremely repetitive (think 70-100RPM for a few hours) which makes being comfortable and mechanically efficient on a bike pretty important.

    Kevin has summed things up very well with respect to bike fitting or cycling analysis. I don't think you can become a so called "Master bike fitter" by paying loads of money to earn the title from a weekend course. In my opinion it takes time to read all the literature and a genuine interest in cycling to progress in this field. As Ian G said, being able to shadow a reputable physio/bike fitter etc that has experience is the go.

    There are some basic tips:

    Take both static and dynamic measurements

    A turbo trainer is essential. It is handy to be able to use decent 2D motion analysis software that allows you to track or measure angles throughout the pedal stroke on the screen. Hip angle at the top of the pedal stroke and knee extension at the bottom of the pedal stroke for starters. In an ideal world a retul or other 3D analysis system would be great.

    If you use a goniometer to measure say knee extension whilst static. Be sure to check any changes you make dynamically. I have seen cyclists start ankling or plantarflexing the foot at the bottom of the pedal stroke which then leaves the knee more flexed then you would expect after the saddle height has been raised. So knowledge on the biomechanics of the pedal stroke will help you make recommendations on technique to the rider.

    There is a window of fit
    With the margin of error involved in taking measurements there is no absolute perfect set of numbers for each cyclist. There is however a window of 'fit' for each measurement that is important to find.
    Again with knee extension measured with the pedal crank at bottom dead centre there is a 10 degree window of which the cyclist should feel comfortable and able to produce adequate output (watts). You can let the cyclist know that they can shift the seat post up or down in small increments if they feel this is needed and still be within the so-called window.

    know your anatomy and bike terminology
    Triathletes and cyclists tend to be extremely curious so you will get all manner of questions throughout a fitting session. Any fakers will be found wanting early on.

    I rarely use custom orthotics for cyclists any more. Customised pre-fabs and shims between the cleats and shoes seem to cover most frontal plane issues. Sigma sport is one company in the UK that sell the shims to match various pedal models (SPD, Speedplay, Look).

    At the moment there is a move towards opening the hip angle at the top of the pedal stroke because it improves power output. This has been a great development because riders are a little less concerned with their frontal profile (aerodynamic position) if they know they can push higher wattage with a more open hip angle (or less spinal flexion). This allows the use of stems with more upsweep etc to obtain a more comfortable position.

    Mike, the weight of a heavier pedal/shoe/orthotic may very well help generate watts on the down-stoke only but not with overall rotation of the pedal. The overall weight of the bike, rider and clothing etc has to be pushed up hills. So mentally a serious cyclist or triathlete will always take the lightest option so they know that when the dark moments come during nasty climbs the niggling thought of heavy orthotics will not break them!


    Overuse Injuries in Professional
    Road Cyclists

    Benjamin Clarsen,*y PT, MSc, Tron Krosshaug,y PhD, and Roald Bahr,y MD, PhD
    Investigation performed at Oslo Sports Trauma Research Centre, Department of Sports Medicine,
    Norwegian School of Sports Sciences, Oslo, Norway

    Background: Little epidemiological information exists on overuse injuries in elite road cyclists. Anecdotal reports indicate anterior
    knee pain and lower back pain may be common problems.

    Purpose: This study was conducted to register overuse injuries among professional road cyclists with special focus on anterior
    knee and lower back pain.

    Study Design: Descriptive epidemiology study.
    Methods: We attended training camps of 7 professional teams and interviewed 109 of 116 cyclists (94%) on overuse injuries they
    had experienced in the previous 12 months. Injuries that required attention from medical personnel or involved time loss from cycling
    were registered. Additional information on anterior knee pain and lower back pain was collected using specific questionnaires.

    Results: A total of 94 injuries were registered; 45% were in the lower back and 23% in the knee. Twenty-three time-loss injuries
    were registered—57% in the knee, 22% in the lower back, and 13% in the lower leg. Fifty-eight percent of all cyclists had experienced
    lower back pain in the previous 12 months, and 41% of all cyclists had sought medical attention for it. Thirty-six percent
    had experienced anterior knee pain and 19% had sought medical attention for it. Few cyclists had missed competitions because
    of pain in the lower back (6%) or anterior knee (9%).

    Conclusion: Lower back pain and anterior knee pain were the most prevalent overuse injuries, with knee injuries most likely to
    cause time loss and lower back pain causing the highest rates of functional impairment and medical attention.
    Last edited: Oct 28, 2011
  18. efuller

    efuller MVP

    We are talking about very small amounts of force here, but bikers spend a lot to decrease the weight of their bike by a few ounces.

    You would get perpetual motion if you got greater power in on the downstroke than you lost in the upstroke. At constant velocity, you would theoretically have no effect from the extra mass. However, that is a problematic assumption, because there is resistance frictional or in attempting to make the bike go up a hill. Since it would be very hard to have constant power output with constant resistance, there will be acceleration. The more mass, the more energy input is needed to accelerate. We are talking about very small amounts of energy either way.

    If your device made the foot lever more rigid than the shoe alone then I would agree with arguement here. In a very flexible foot/shoe segment it is possible to lose some energy as heat. However, cycling shoes tend to be quite rigid, so I don't know if it is really possible to make the foot and shoe more rigid. There may be some fatigue issues that an orthotic would address. I'll have to think about that a bit.

    To pick a nit, you are right that it power to mass for climbing. But for flat, it's power to wind resistance.

    This is why I buy cheaper, heavier components for my bike. I realize that the difference between the heavier part and the lighter part is much less than the extra weight that I'm carrying around.

    Me too. Before the arena and JISC mail I hung out on bike newsgroups. I even build my own wheels. Building a rear wheel is a real lesson in physics. No bike jewelry though.

    Looking from which side? See, my discussion of acceleration above. If you had increased mass in one shoe, the additional mass would help in the down stroke and hinder in the up stroke. The reason that toe clips/ or clipless shoes, are more efficient is that they help keep the foot on the pedal so that you can lift up when going from bottom dead center to top dead center. You may not add much power with that lift, but you will decrease the power needed on the downstroke of the other leg. Another way of saying that the leg going from bottom dead center to top dead center has to be lifted by something. One possibility is that the leg pushing down lifts the leg going up in addition to propelling the bike.

  19. Eric, Mike and Others,

    I believe that foot orthoses do have the potential to increase the mechanical efficiency of cycling in the foot that has a overly-compliant medial and/or lateral longitudinal arch.

    During the power phase, as the pedal is being pushed by the plantar forefoot from top dead center (TDC) to bottom dead center (BDC), the mechanically ideal human foot and lower extremity for cycling would only be constructed with joints that would allow rotational and translational motions within the sagittal plane with no wasted transverse, frontal or sagittal plane rotational or translational motions.

    To accomplish this goal of having the most mechanically efficient foot and lower extremity for cycling, with no wasted motion, I have long described the ideal cycling foot and lower extremity as having only four joints:

    1. Hip joint
    2. Knee joint
    3. Ankle joint
    4. Metatarsophalangeal joints

    In other words, motions at the subtalar, midtarsal, naviculo-cuneiform and LisFranc's joints are wasted motions during cycling where the increased compliance resulting from motion at these joints during the power phase of cycling is detrimental to the mechanical efficiency of the driving muscle power coming from the hip extensors, knee extensors and ankle joint plantarflexors within the cyclist's lower extremity.

    Therefore, when the gastrocnemius-soleus (GS) muscles are firing to create an ankle joint plantarflexion moment during the power phase, we ideally want this force from the GS muscles to plantarflex the calcaneus, talus and rest of the osseous structures of the foot simultaneously the same degree, or, in other words, with high longitudinal arch stiffness. In this fashion, the tensile force within the Achilles tendon can be more directly and efficiently transmitted to the plantar forefoot as a pedal pushing force.

    The attached illustration simplifies the plantar ligaments, plantar fascia, plantar intrinsic muscles, PT, PL, FDL and FHL muscles into a plantar arch spring. This plantar arch spring needs to be infinitely stiff in order to create the most mechanically efficient cycling foot. Too much compliance within the plantar arch spring will decrease the mechanical efficiency of cycling.

    Well formed foot orthoses for cycling effectively increases the stiffness of the longitudinal arch of the foot so that even feet with more compliant "plantar arch springs" will have decreased longitudinal arch flattening motion during the power phase which will result in a more efficient mechanical transfer of GS power to the pedal during the power phase of cycling.

    Attached Files:

  20. Frederick George

    Frederick George Active Member

    Hi NicPod 1

    All good posts, information has really developed over the years.

    With sponsored riders, you can have the shoe manufacturer (sponsor) copy your orthotic design into the sole. When I treated Greg Lemond (name drop) I was somewhat disappointed that the shoe sponsor didn't want Greg to have orthotics in his shoes, not because of weight, but because the sponsor didn't want word to get out that the shoes weren't "good enough." Paul at Precision Intricast made these first ever bike orthotics for free, but they were eventually used for skiing!

    As I recall, Lance Armstrong (name drop, again) had a limb length discrepancy, and rather than have a spacer on his pedal/cleat, I had him use a shorter crank arm on the short side. It is a more elegant solution to the biomechanics, lighter, and no spacers to loosen.

    Hope this helps.


  21. Jonathan

    Jonathan Active Member

    Frederick - Shorter crank arm on the shorter side - this doesn't make sense?
  22. Nor is name dropping Armstrongs name and thinking it is a good thing.

    Anyways I guess longer crank ARM for shorter side seems the likely meaning
  23. Jonathan

    Jonathan Active Member

    Cycling and drugs!!!!!! - No, don't believe it. Next you'll be telling me they cheat at cricket!!

    I have heard from (Jan Ulrichs bike builder) that if you measure power output at the crank/spindle, you will see an improvement with an orthotic. This translates into improved acceleration - but not always comfort. Bearing in mind he is looking for a biomechanical advantage - comfort isn't that important.
  24. Athol Thomson

    Athol Thomson Active Member

    On other cycling threads here there has been studies with links to improved power output with the use of orthotics or varus shims. (Mike Weber might be able to locate these?)

    One that comes to mind is below. Always lots of reference to the old forefoot varus in cycling literature....I think due to Andy Pruitt and specialzed quoting that 87% of all feet have a forefoot varus. Never seen a reference to back this up.

    International Scientific Journal of Kinesiology

    Nicholas J. Dinsdale & Alun G. Williams
    Institute for Performance Research, Manchester Metropolitan University, Crewe, CW1 5DU, United Kingdom
    There is limited research relating to cycling biomechanics, and more specifically, the use of foot orthotics to enhance cycling
    performance. Therefore, this study investigated the effect of forefoot varus wedges (foot orthotics) on cycling performance, as
    measured by anaerobic power output in a population of untrained males presenting with forefoot varus. Six untrained males
    (forefoot varus mean ± SD; 6.1 ± 1.7°) completed two separate 30 s Wingate Anaerobic tests (WAnT) on a Monark 824E cycle
    ergometer, one with and one without varus wedges, in a counterbalanced order. Although paired-sample t-tests revealed no
    significant difference P > .05 in mean power, peak power, and anaerobic fatigue between the two conditions, a Pearson’s productmoment
    correlation coefficient (r = .957, n = 6, P = .003) demonstrated that varus wedges offer greater performance benefits to
    riders with greater forefoot varus. These preliminary data suggest that correcting forefoot varus using wedges may improve shortterm
    power output during cycling for individuals possessing high levels of forefoot varus.
  25. Athol:

    It is not so much "forefoot varus" that is so common among cyclists, but "varus forefoot to transverse plane angle" which is relatively common and which will be increased with tibial varum, rearfoot varus and/or forefoot varus deformities. This is the parameter I came up with and one that we measured and correlated to knee joint loading forces in our Journal of Biomechanics study on cyclists on knee joint loading forces from 19 years ago.

  26. Full text found here - http://www.podiatry-arena.com/podiatry-forum/showpost.php?p=224431&postcount=7


    The Influence of Seat Configuration on Maximal Average Crank Power During Pedaling: A Simulation Study
  27. Non-driving intersegmental knee moments in cycling computed using a model that includes three-dimensional kinematics of the shank/foot and the effect of simplifying assumptions

    no full text IG an chance of an emailed PDF ?
  28. The problem with using a shorter crank arm to treat a short limb in cycling is that at top dead center you are making the limb length discrepancy worse but at bottom dead center you are equalizing out the limb lengths. Most clinicians will use cleat shims (i.e. thin plates between the sole of shoe and cleat) to treat limb length discrepancies in cyclists since this will keep the limbs equalized throughout the power phase and recovery phase of cycling.
  29. Athol Thomson

    Athol Thomson Active Member

    Hi Kevin,

    I agree. I read your study when you kindly uploaded it on an earlier cycling thread on PA.

    On another note;

    As I am sure you would know, Sanderson et al believe that different strategies are used for cycling at different cadence and power output. (Study attached)

    They found that cycling at higher cadence leads to decreased plantar pressure at the 1st metatarsal and Hallux. And cycling with higher power output leads to increased plantar pressure at the medial plantar foot.

    So, tibial varum and rearfoot varus aside for the moment, could both strategies lead to a more inverted forefoot position when examining an experienced cyclist non-weight bearing?

    1. With cyclists who prefer increased power output due to pedal/shoe reactive force applying a dorsiflexion moment to the first metatarsal with increased medial plantar loading.

    2. With cyclists who prefer higher cadence due to internal moments generated by muscles unloading the hallux and first metatarsal. Which possibly becomes an accommodated position in experienced cyclists.

    I could be way off here but just thinking out loud.

    Have a good weekend,
  30. Athol Thomson

    Athol Thomson Active Member

    Again I agree. I would just add that using a shim to treat the short leg for cycling works best if you are lucky enough to have the main difference in length at the tibia.

    With a shim added this will be ok at both the top and bottom dead centre.

    Where as a femoral length issue is not as easier to account for at top dead centre.

  31. Athol:

    I have seen this concept described, but have never heard a good, mechanically-sound explanation of why this would be the case. I have always treated both tibial and femoral shortness with cleat shims and/or moving the cleat more anteriorly on the shoe.

    Can you please explain why cleat shims or moving the cleats more anteriorly on the shoe can't also be used to effectively treat a femoral length discrepancy?
  32. Athol Thomson

    Athol Thomson Active Member

    Hi Kevin,

    I think femoral length discrepancy can be treated effectively using a shim and most likely place the rider in a decent enough position to decrease tissue stress. I use shims to treat femoral length discrepancy.

    At Bottom dead centre you can get the knee extension fairly similar on each side by using a shim for this. As you know.

    However, the knee over pedal axle alignment (with the pedal horizontal) cannot be symmetrical with a femoral length difference. Some cyclists are concerned about this.

    The force/symmetry ratio will be altered by the shorter femur to leave a difference in power output at each leg.

    This would be the case with a short tibia also but I always assumed with the quadriceps, hamstring and gluteal muscles about the femur that a femoral length difference may affect force symmetry when pedaling more than a tibial difference.

    I need to maybe stop "assuming" and start doing some research to back things up!

    Also, when commencing the down stroke pedal action from TDC there may be more transverse hip motion or rocking on the saddle on the side with the short femur. This will not be an issue with a short tibia that has been corrected by a shim.

    Moving the cleat too far forward may cause nerve or MTP joint irritation

    BTW, I remember a patient with a short femur who had been told by a well known bike fitting outfit that his best option was to have his long leg shortened by femoral osteotomy as this was the only way to get his bikefit right. The guy had minimal pain and a pretty meagre LLD. Just nuts.

    Last edited: Nov 5, 2011
  33. Athol:

    I agree with everything you say other than the following:

    The rocking on the saddle, I believe, occurs due to the saddle being too high for the total limb length (i.e. measured from the hip joint center to cleat/pedal interface), not just the femur length, not just the tibia length and not just the ankle joint to cleat distance.

    I know of no reasonable biomechanical factor which would cause the cyclist to rock on the saddle only with a short femur, but not with a short tibia, do you? In other words, a correctly adjusted shim and saddle height should be able to correct not only for asymmetries in tibial length but also for asymmetries in femoral length.

    I don't believe half of what I have read on bicycle fitting...there way too much of "I'm just telling you what the experts have done in the past" in bike fitting and too little research and logical biomechanical reasoning, from what I have seen over the past quarter century.

    One of the keys to more efficient cycling biomechanics is equalizing pronation and supination moments (i.e. rotational equlibrium) at the STJ during the power phase and recovery phase in order to keep the knee tracking as straight up and down as possible....when have you ever read that concept in a bike magazine or fitting blog?!
  34. Hi Gents,

    I have also been considering compensation of LLD thru increased plantarflexion at the ankle of the short side at 6 O´clock at the end of the power stroke. The long term effects of this could lead to muscle imbalance between legs and differing reliance of muscle groups which generate Power in the pedal.

    Power generation from lower back Gluteals through to ankle plantarflexion - ie summation of force, but with a LLD which is not treated with a shim - the cyclist will either increase the medial to lateral rock - lose power output or increase the plantarflexion of the ankle - which may either lead to Achilles tendon overuse ( common in folks whose saddle it too high) or increased strength of the gastroc/Sol complex which through a training effect may lead to the person relying of the Gastroc/Sol complex more on the short side to generate power - which over time may lead to a Muscle imbalce in the Gluteals and lower back because of the adjustment made by the cyclist in muscle recruitment.

    what do you think ?
  35. Mike:

    I think most cyclists will adjust for leg length differences by a combination of methods including increasing their knee joint and anke joint angles on the short side. I haven't seen many Achilles or gastroc-soleus strains in cyclists since cycling is a concentric activity for all muscles involved and concentric contractions are much less likely to produce tendon/muscle tears than are eccentric contractions. In fact, in many of my runners with Achilles tendon injuries, cycling is one of the few activities they can do with making their Achilles pain worse.

    When I find a limb length discrepancy (LLD) in a cyclist, regardless of whether the LLD is caused by a short tibia or short femur, I will shim the short side and then raise the saddle height about half the distance of the shim added as a starting point. If the pelvis is rocking excessively within the frontal plane on the saddle (viewed from posterior) then I first will lower the saddle height a few millimeters until this abnormal pelvic movement is reduced.

    As I mentioned to Athol, I also focus on trying to get the STJ pronation/supination moments normalized in the cyclist so that excessive STJ pronation/internal knee rotation/knee adduction does not occur during the power phase. Getting the lower extremity to function so that the knee tracks more vertically and less from side to side is where, I believe, we as podiatrists have a marked edge over many others in improving bike fit and function. Maybe I will need to do another set of newsletters on this subject some time in the near future.

  36. Hi Kevin,

    While rare I agree Achilles Tendon issues do occur but I wonder about the muscle recruitment if the LLD is not treated.

    Be a nice study EMG with differing Crank arm lengths on one side to stimulate LLD

    Get the person to produce the same watts over each study for the same time and see where the compensation occurs and what muscle are recruited to produce the same power.
  37. Frederick George

    Frederick George Active Member

    Jonathan, Kevin, Mike - Yes it does. As Kevin realised, at the bottom, the shorter crank on the short side doesn't drop down as far - it fits the short leg.

    But Kevin, you got it half right. Shorter cranks are usually used for racers with shorter legs. The shorter leg is just that, shorter. It has less elongation and shortening with the same amount of knee flex. So using a shorter crank is the better option.

    Nicola - to keep it simple, just remember that you are simply trying to maintain the foot as a rigid lever for transferring force most efficiently. Therefore, you want to try to keep the foot in neutral position at all times.

    And Mike Weber you got it completely wrong.

    And Mike re: "this doesn't make sense" you wrote
    What does that mean? How do you know what I think? Do you think you are the only one who is an egotist on this blog?

    Methinks me smells a whiff of envy. Ha! Ha!


  38. Perhaps my ego is too big for my boots, but maybe we should both not destroy the best cycling thread we have had on PA with point scoring and discussing if Armstrong is the fraud in sporting history or not. I am enjoying the learning and thinking this thread is bringing and would be sad to see bickering destroy the thread imo.

    Hopefully Eric, Athol,Kevin and yourself and anyone else will keep the tread going

    Kevin wrote

    If you shorten the crank arm then there will be only 1 point in the 360 degree that the LLD would be neutralised.

    Also and maybe the crank arm the pedal on the shorter side would have to travel at different RPM to the longer side to reach the same point at the same time - I maybe be wrong here - but we did this project at School a warn car tire will need to go through more revolutions than a new car tire to travel the same distance - wouldn´t this be the same here if each power stroke produces the same watts. So during the power stroke the form 1 side to the other we would have

    power stroke faster v´s power stroke slower rather than a more constant RPM of the 2 pedals.

    Does that make sense ?

    If each power stroke does not produce the same watts for energy expenditure then the cyclist will compensate and start working harder with 1 side , after the training effect there will be a imbalance in sides in muscle strength - which plays a huge role in cycling overuse injuries

    where as the shim would mean the pedal will travel at the same speed per revolution to be at the same point.

    remove the bold bit and I think we would all agree.

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