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Joint moments in forefoot vs rearfoot strike running

Discussion in 'Biomechanics, Sports and Foot orthoses' started by Craig Payne, Feb 20, 2012.

  1. Craig Payne

    Craig Payne Moderator

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    {Admin Note: This thread has been broken off from: Podiatrist Recommends Forefoot Striking Versus Orthotics for Treating Running Injuries}

    Its does not matter which way you run, there is an injury risk associated with each running form!

    If you forefoot strike --> increased forefoot dorsiflexion moments on rearfoot; increased dorsiflexion moments at ankle; increased rearfoot inversion moments --> all these will do is increase the risk of injury in the structures that those moments.

    If you rearfoot strike --> increased rearfoot impacts --> increase the risk for ijury associated with higher rearfoot impacts.

    Its six of one, half a dozen of the other ... its all depends on the injury profile/history and which tissue you want to off-load.

    BTW -- have you ever tried to midfoot/forefoot strike in a military boot?
     
    Last edited by a moderator: Feb 23, 2012
  2. Re: Podiatrist Recommends Forefoot Striking Versus Orthotics for Treating Running Injuries

    Heres what I think, it's a bit "selfish gene":
    1) the body doesn't want to injure itself
    2) the body wants to be as efficient as possible to get you from a-b safely so that when you get there you are able to reproduce
    3) the kinematic pattern the body sub-consciously adopts during walking or running is the bodies best attempt to avoid injury while being as metabolically efficient as it can be. Viz. "the machine might know best"
    4) Consciously fannying about with running strike pattern is consciously overriding the bodies self-defense mechanisms and probably increases the risk of injury- now there is a prospective study... does fatigue increase the risk of injury?
     
  3. Re: Podiatrist Recommends Forefoot Striking Versus Orthotics for Treating Running Injuries

    Simon:

    I would basically agree with your summary. However, from my experience as a runner and a clinician, there does seem to be a learning process required, which requires a finite amount of time, for each individual to learn to run the most efficiently.

    Individuals who ran for many years as children and in their youth rarely need any additional coaching to run efficiently. However, adults who are just starting to run for the first time since their school gym class over 10 years ago, and who did no running sports as a youth, may require a year or more to learn to run efficiently. The neuromuscular patterns must be developed sufficiently to allow the individual to run smoothly and efficiently, given their own peculiar set of biomechanical characteristics.

    During my exercise physiology courses at UC Davis, I remember learning about how running faster speeds, as required in racing, needs to be simulated during training not only to increase the metabolic capacity of the individual but also to develop the neuromuscular coordination to run with a faster speed with better motor coordination. I certainly experienced that "neuromuscular coordination training effect" during my many cross country and track seasons when my ability to run, lets say a 440 yard interval at 70 seconds, seemed much easier mechanically to do when I had already been running these repeats for the last three to four weeks, rather than on the first 440 interval of the season.

    The same neuromuscular coordination training is required for finer motor skills such as playing piano or violin where the mechanics of playing these instruments will become more efficient with increased duration and frequencty of training of the neuromuscular system. Therefore, before we consider trying to "retrain" a runner's kinematics, consideration should be given to the amount of time that individual has been a runner and how much they have run over their lives. For these reasons, I am much less likely to suggest changes in running kinematics with experienced runners than beginning runners on "proper running form".
     
  4. Craig Payne

    Craig Payne Moderator

    Articles:
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    Re: Podiatrist Recommends Forefoot Striking Versus Orthotics for Treating Running Injuries

    Which is not surprising, based on:
    I would have assumed the the forefoot plantarflexion moments are greater in rearfoot compared to forefoot striking.
     
  5. Re: Podiatrist Recommends Forefoot Striking Versus Orthotics for Treating Running Injuries

    Craig can you just qualify whether you are talking about internal or external moments when you say: "If you forefoot strike --> increased forefoot dorsiflexion moments on rearfoot; increased dorsiflexion moments at ankle; increased rearfoot inversion moments -->"
     
  6. Craig Payne

    Craig Payne Moderator

    Articles:
    6
    Re: Podiatrist Recommends Forefoot Striking Versus Orthotics for Treating Running Injuries

    External
     
  7. Re: Podiatrist Recommends Forefoot Striking Versus Orthotics for Treating Running Injuries

    Then increased external rearfoot inversion moments should only occur if the centre of pressure and the resultant vector is medial to the subtalar joint axis at the time of strike, or less lateral than that which should occur with a rearfoot strike pattern. Can we evidence this?

    Anecdotal observation suggests that forefoot strike tends to occur under metatarsal heads 4-5, which should mean either the STJ axis has to be very laterally deviated at this time and or the reaction force vector contains a significant medio-lateral shear component in order for the external inversion moment to be greater in forefoot strike running when compared to rearfoot strike running :confused:
     
  8. Craig Payne

    Craig Payne Moderator

    Articles:
    6
    Re: Podiatrist Recommends Forefoot Striking Versus Orthotics for Treating Running Injuries

    Joe Hamil showed this. Its 'in press'.
     
  9. Re: Podiatrist Recommends Forefoot Striking Versus Orthotics for Treating Running Injuries

    Did he track STJ axis or use a foot "centre line"?
     
  10. Craig Payne

    Craig Payne Moderator

    Articles:
    6
    Re: Podiatrist Recommends Forefoot Striking Versus Orthotics for Treating Running Injuries

    I not sure where to look to find the abstract, but from memory he/they only looked an rearfoot/ankle moments. Inversion and dorsiflexion moments were greater in the forefoot strikers compared to rearfoot strikers.
     
  11. Re: Podiatrist Recommends Forefoot Striking Versus Orthotics for Treating Running Injuries

    Simon:

    No researcher that I know of is actually tracking the STJ axis other than Steve Piazza.

    http://www.biomechanics.psu.edu/piazza/research.html

    Everyone else is using the center line of the foot as their "inversion-eversion" axis of the foot, even though this will always produce erroneous results in regards to STJ axis external and internal moments.

    Much more work needs to be done in this regard.
     
  12. robby

    robby Active Member

    Re: Podiatrist Recommends Forefoot Striking Versus Orthotics for Treating Running Injuries

    Hi CT and Ian,

    thanks for the extra info, from my converstaion with the Physios that exactly what they were saying and they are getting large numbers with Anterior compartment injury/strains and from the refernces from Craig I would have to agree that it would reduce stresses and forces on the anterior compartment.

    although as Kevin says changing the pattern in young recruits who are generally fairly fit and usually running well without problems they may start to see other issues .

    again it probably is a horses for course issue, that is picking the correct treatment to suit the symptoms in front of you and using all available ideas as appropriate- and I guess thats the key!
     
  13. Re: Podiatrist Recommends Forefoot Striking Versus Orthotics for Treating Running Injuries

    http://w4.ub.uni-konstanz.de/cpa/article/viewFile/451/391

    Much sense in that one.

    P.S. If anyone can access and translate them from German, according to the paper these should show that injury occurs in forefoot strike runners as frequently as they do in rearfoot strike runners- just in different places.
    Kleindienst, F.I. (2003). Gradierung funktioneller Sportschuhparameter am Laufschuh. Shaker. Aachen, 234-235.
    Walther, M. (2005). Vorfußlaufen schützt nicht vor Überlastungsproblemen. Orthopädieschuhtechnik, 6, 34.

    Would be interesting to see the differences, if you can arrange it Craig.
     
  14. Re: Podiatrist Recommends Forefoot Striking Versus Orthotics for Treating Running Injuries

    The dorsiflexion I can see, still trying to get my head around that external inversion moment though. How does that sit with the greater eversion velocity observed with forefoot strike running, i.e. "FFS provoked a sig. higher eversion velocity" ?http://w4.ub.uni-konstanz.de/cpa/article/viewFile/451/391

    If the external inversion moment is higher in forefoot strike running yet the rearfoot eversion velocity is higher, it must mean that internal eversion moments are even higher in forefoot strike running- right? Which could indicate increased activation of the evertor muscles or decreased activation of the invertors- EMG anyone?
     
  15. Craig Payne

    Craig Payne Moderator

    Articles:
    6
    Re: Podiatrist Recommends Forefoot Striking Versus Orthotics for Treating Running Injuries

    Sorry, I racking my brains as to where the abstract is ...I know Joe is talking about this at next months iFab mtg.

    Anecdotaly, I now running 2 days/week in my NB minimus and 2 days in my Hoka maximalists shoe. When in the minumus I actively invert the rearfoot more --> post tib working harder --> does that mean the inversion moment is higher and that why post tib has to work harder???
     
  16. Re: Podiatrist Recommends Forefoot Striking Versus Orthotics for Treating Running Injuries

    It means the internal inversion moment is higher if tib post is working harder (at least while that muscle is active). If tib. post is having to work harder you'd expect that it should be in response to a higher external eversion moment (or put another way- a lower external inversion moment).

    That's the key, differentiating internal from external moment. It would make life much easier if authors would make that differentiation.

    But, if we see a higher eversion velocity with a forefoot strike it means that either the internal eversion moment is increased (which shouldn't come from your tib. post) and/ or internal inversion moment is decreased, and/ or that external inversion moment is decreased or external eversion moment is increased. See how confusing that is even when you define internal and external moments.

    I suspect that your observation of increased tib. post. activation may be accounted for by an increase in external eversion moment in association with forefoot strike (assuming that you forefoot strike in your minimalist shoes- do you?). As would the increase in eversion velocity reported by others. But lets see...

    Gets even more complex when we consider that when a muscle generates an internal moment it also generates an external counter moment when the foot is in closed chain... how is that we move again? Which I guess gives rise to the contention that muscles merely stabilise, which I think was Paul Coneely's contention a couple of weeks ago and is certainly something Dave Smith has maintained; Newtons third withstanding. I suspect the answer is by firing muscles when the leg is in open chain, but we'll leave that for another day... "pulling versus pushing revisited, yet again".
     
  17. efuller

    efuller MVP

    Re: Podiatrist Recommends Forefoot Striking Versus Orthotics for Treating Running Injuries

    If more inversion motion, then there is a greater net inversion moment acting on the foot. If the motion occurred then there is either an increased moment from the leg muscle or a decreased moment acting on the foot from the ground. So, the muscle may not necessarily be working harder.

    Eric
     
  18. efuller

    efuller MVP

    Re: Podiatrist Recommends Forefoot Striking Versus Orthotics for Treating Running Injuries

    I still think internal and external moments are less precise than describing the source of the moment and what it is acting on. With internal and external you have to carefully define, and not change, the definition of the body that moments are internal or external to. For example, you could define the body as the foot and then both the ground and the leg muscles are external forces acting on the foot.



    We move by the muscles generating motion at joints. Example: In stance, when the calf muscles contract, they create a plantar flexion moment at the ankle. When the ankle plantar flexes the center of mass of the body will rise and there will be an increase in ground reaction force on the foot that will accelerate the body upward. Yes, there will be a lot of internal equal and opposite reactions. The key to understanding and explaining the motion is in the steps of free body diagram analysis. First define the body and then examine the forces acting on the body.


    Eric
     
  19. efuller

    efuller MVP

    Re: Podiatrist Recommends Forefoot Striking Versus Orthotics for Treating Running Injuries

    I'm also having a hard time seeing this. The STJ axis is roughly in the center of the heel and passes, on average, under the first metatarsal head. If the cop is in the center of the foot with both forefoot and rearfoot contact, then the moment from ground reaction force acting on the foot about the STJ will be much higher in the direction of pronation when force is on the forefoot as opposed to the rearfoot. Using the convention that the force from ground is external to the foot, there should be a decreased external inversion (=increased external eversion) moment.

    The result posted could be possible with the use of the longitudinal axis of the foot instead of the STJ axis. That's the problem with assuming the axis of motion is the long axis of the foot.

    Eric
     
  20. Craig Payne

    Craig Payne Moderator

    Articles:
    6
    Re: Podiatrist Recommends Forefoot Striking Versus Orthotics for Treating Running Injuries

    Sorry, I think in a previous post I should have said internal moments and not external.
     
  21. Re: Podiatrist Recommends Forefoot Striking Versus Orthotics for Treating Running Injuries

    In stance, when the calf muscles contract, they create an internal plantar flexion moment at the ankle and an external dorsiflexion moment. Are these equal and opposite?
     
  22. Re: Podiatrist Recommends Forefoot Striking Versus Orthotics for Treating Running Injuries

    the net moment must be equal and opposite unless the joint is under motion ie accelerating

    but the moments created by the contraction of the tricep surea ( internal plantarflexion moments ) does not mean the external dorsiflexion moments acting on the forefoot need to be equal and opposite.
     
  23. Re: Podiatrist Recommends Forefoot Striking Versus Orthotics for Treating Running Injuries

    Newton might disagree with you Mike since for every action there is an equal and opposite reaction. Hopefully Dave Smith will contribute to this. But like I said, it's probably a discussion for another day.
     
  24. Re: Podiatrist Recommends Forefoot Striking Versus Orthotics for Treating Running Injuries

    Maybe, re another day

    I did have a small discussion with Eric about net moments and acceleration, and the thing that stuck was Eric saying that they will be equal and opposite unless the joint is under acceleration

    1. I could not find the discussion

    2. I could be wrong with what I remember Eric wrote

    3. I am just wrong all together.
     
  25. Re: Podiatrist Recommends Forefoot Striking Versus Orthotics for Treating Running Injuries

    Here's an interesting little game: stand in rcsp. Now elevate the heel of your right foot without flexing your knee or hip- in other words elevate your heel using only internal ankle plantarflexion moment generated by gastroc/ soleus. Bet you can't. The only way you can is by leaning the head and torso forward- but that's cheating.

    Why can't you do it?
     
  26. Re: Podiatrist Recommends Forefoot Striking Versus Orthotics for Treating Running Injuries

    Because the internal plantarflexion moment is unable to overcome the net dorsiflexion moments acting around the ankle joint axis.

    why ? where does the dorsiflexion forces come from - GRF - therefore the ankle joint plantarflexers are able to overcome the dorsiflexion forces ( GRF ) without the help of other muscles etc , the result is no kinematic change ( no acceleration ) but there has been a change in where the net forces come from on the plantarflexion side and probably the dorsiflexion side as well, but mainly through an increase in external dorsiflexion forces acting around the ankle joint axis
     
  27. timharmey

    timharmey Active Member

    Re: Podiatrist Recommends Forefoot Striking Versus Orthotics for Treating Running Injuries

    I can but it is harder than I thought
    Tim
     
  28. Re: Podiatrist Recommends Forefoot Striking Versus Orthotics for Treating Running Injuries

    Sorry making devices today - I do a lot of my thinking there

    of course they must be equal and opposite at all time :eek:

    the change in axis position defines the point at which the forces on either side would be for them to be equal and opposite.

    so we have acceleration ie kinematic change during this process the axial equilibrium position will change so that the forces are always equal and opposite, the change is the make up of the net forces on each side of the axial position.

    the result kinematic change ie joint motion or acceleration will result in a new rotational axial position which defines the point at which the forces acting on the joint are equal and opposite.

    sorry slow moment - pun intended

    plus it means I need to rewrite a section
     
  29. efuller

    efuller MVP

    Re: Podiatrist Recommends Forefoot Striking Versus Orthotics for Treating Running Injuries

    Again, we need to be careful in describing the source of the moment and the body that it is acting on. With the calf muscle example: one body is the leg and the other is the foot. The leg applies a force couple to the foot of an upward force from the muscle at the insertion of the Achilles tendon, and a downward force from the tibia acting on the talus. The equal and opposite reaction is from the foot acting on the leg causing a moment that will tend to rotate the top of tibia posteriorly in the sagittal plane. The foot is applying a downward force at the end of the achilles tendon and an upward force from the talus acting on the bottom of the tibia. (It might be helpful to draw a leg with the bottom of the tibia and the end of the achilles tendon and a foot with a top of a talus and an achilles tendon insertion and then draw the forces from the other body.) Both of those moments can be described as a plantarflexion moment of the ankle. (This is how an equinus can cause a genu recruvatum.)

    When the ankle joint plantar flexes (motion and acceleration) there will be an anterior shift in the location of center of pressure of ground reaction force. This anterior shift in the location of ground reaction force will cause a dorsiflexion moment. If the plantar flexion moment from the muscle acting on the foot is greater than the dorsiflexion moment from ground reaction force acting on the foot then the foot will plantar flex because the net moment is not zero.

    In stance, the tension in the achilles tendon can be gradually increased. There will be a gradual shift of the center of pressure anteriorly as it is possible to keep the net moment on foot at zero, for a while. At some point the ankle plantar flexion moment from the muscle will be greater than the ankle dorsiflexion moment from the ground and then there will be a net moment, at which acceleration will occur.

    Some of the confusion occurs because we do a lot of free body diagram analysis when there is no motion. When there is no motion the net force and net moment has to equal zero. That is often where the equal and opposite confusion comes from. That is different than Newton's 1st law which is for every action there is an equal and opposite reaction.

    Eric
     
  30. Re: Podiatrist Recommends Forefoot Striking Versus Orthotics for Treating Running Injuries

    Why? How does the plantarflexion moment from muscle become greater than the dorsiflexion moment from the ground? Why doesn't the dorsiflexion moment from the ground keep increasing as the centre of pressure keeps shifting anteriorly and the magnitude of the reaction force keep increasing in response to the increased internal ankle plantarflexion moment?

    If I had a see saw and lifted up one end until the other end was in contact with the ground (i.e. the see-saw is now in closed chain) if I keep lifting up the free end it doesn't move any further, rather the ground reaction forces keep increasing at the contact point- isn't this the same thing?
     
  31. efuller

    efuller MVP

    Re: Podiatrist Recommends Forefoot Striking Versus Orthotics for Treating Running Injuries

    Balance.

    You can do it, if your calf muscle is strong enough, if you put your center of mass over the ball of the foot that you are trying to plantar flex. (Raising up on the ball of one foot is an excellent way to assess a patient's balance.) If you don't lean, then gravity acting on the center of mass and ground reaction force will create a force couple that will cause you to fall over, and people usually choose not to fall over.

    Eric
     
  32. efuller

    efuller MVP

    Re: Podiatrist Recommends Forefoot Striking Versus Orthotics for Treating Running Injuries

    The maximum moment from ground reaction force is body weight x the distance of the center of pressure from the axis. Both of those numbers are finite and, at some point, will be less than the force in the tendon x the lever arm of the tendon. I'll have to check the next few people that come in to the office to see if they can stand on their tip toes.;)

    Eric
     
  33. Re: Podiatrist Recommends Forefoot Striking Versus Orthotics for Treating Running Injuries

    But the only way you can put your centre of mass over the ball of your foot is by using muscles over than gastroc/ soleus. I could lift mine, but only by firing muscles in my lower back on that side. Tim put your hand on your erector spinae as you do it- bet he firing
     
  34. efuller

    efuller MVP

    Re: Podiatrist Recommends Forefoot Striking Versus Orthotics for Treating Running Injuries

    Balance is the reason that you cannot do it. If you allow contraction of the other muscles you can. You could also do it if you stood in a corner so that the wall could push you toward the foot that was plantar flexing and the other wall would prevent you from falling over backwards. (Low friction walls)

    Eric
     
  35. Re: Podiatrist Recommends Forefoot Striking Versus Orthotics for Treating Running Injuries

    That doesn't seem right. Since the forefoot plantarflexion force resulting from the internal ankle plantarflexion moment should be equal to the rearfoot dorsiflexion force exerted by the Achilles tendon, the magnitude of the ground reaction force at the forefoot x the distance of the center of pressure should be used to calculate the external moment, not the body weight, and since the harder the gastroc-soleus pulls at the rearfoot, the greater the reaction force at the forefoot...

    I'm sure people can stand on their tippy toes, I'm just not convinced that they achieve it using the ankle plantarflexors in isolation which you've already conceded, Eric. Some other part of the body, which isn't in contact with floor has to move to enable heel lift or an external force is needed to jump start it- interesting. Cheers.
     
  36. efuller

    efuller MVP

    Re: Podiatrist Recommends Forefoot Striking Versus Orthotics for Treating Running Injuries

    Don't know how I missed this in the other post. No they are not the same thing. Body weight and the length of the foot (lever arm to the ankle) are finite. So, the resistance to a plantar flexion moment is finite (well, less than the moment that can easily be created by the muscle.) Whereas, the force from the ground acting on the bottom of the see saw is essentially infinite.

    Eric
     
  37. efuller

    efuller MVP

    Re: Podiatrist Recommends Forefoot Striking Versus Orthotics for Treating Running Injuries

    I'm getting a little confused by terminology here as you are talking about forefoot and rearfoot. So, I'm going to restate what I think you said. The plantar flexion moment applied by the leg to the foot should be equal to the dorsiflexion moment from the ground applied to the foot. That is true when the acceleration is equal to zero. However, what allows us to move is that we can produce a greater plantar flexion moment on the foot than the ground can create a dorsiflexion moment. The maximum dorsiflexion moment that can be applied to the foot, without upward acceleration of the body, will be body weight x the length of the tip of the foot from the ankle axis. If the force from the ground acting on the foot goes above body weight then the body will accelerate upward. Net force = mass x acceleration.

    Eric
     
  38. Re: Podiatrist Recommends Forefoot Striking Versus Orthotics for Treating Running Injuries

    Yes, I agree that was a poor analogy, I thought I'd deleted it.:eek:

    But it still doesn't explain how the internal rearfoot plantarflexion moment ever overcomes the external forefoot dorsiflexion moment acting at the ankle. Yes the lever arm is finite but the ground can push back on the forefoot just as hard as the ankle plantarflexion moment can attempt to push the forefoot through the ground and the distance of the contact area of the foot distal to the ankle joint axis is much greater than the lever arm available to the Achilles . The harder the Achilles pulls the rearfoot into plantarflexion, the harder the ground then pushes back on the forefoot to create external ankle dorsiflexion moment. Both the external dorsiflexion moment and internal plantarflexion moment are limited only by tissue failure. So how is movement initiated; how is acceleration toward plantarflexion ever achieved at the ankle? My conjecture- not by the ankle plantarflexors in isolation. Rather it is initiated/ aided by muscles acting upon segments which are not in direct contact with the ground.
     
  39. efuller

    efuller MVP

    Re: Podiatrist Recommends Forefoot Striking Versus Orthotics for Treating Running Injuries

    Ankle plantar flexion is not just the forefoot going down. It is also the rearfoot and leg moving upward with the ball of the foot staying on the ground. When the force from the talus acting on the bottom of the tibia is greater than the force of gravity acting on the rest of the body, the body will accelerate upward and motion is initiatied by the muscles creating tension in the Achilles tendon.

    Eric
     
  40. Re: Podiatrist Recommends Forefoot Striking Versus Orthotics for Treating Running Injuries

    Yeah, but in order for the force on the talus to initiate it to accelerate upwards on the tibia, the force on the talus from the forefoot resisting the upward acceleration and pulling the leg back down has to be exceeded. I just can't see how the ankle plantarflexors can ever do this in isolation since the internal forces they create will always be matched, equal and opposite, by the external forces they create. Something else has to jump start the system- thats why the erector spinae fires.
     
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