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Anomalous plantar intrinsic foot muscle
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Related Threads:
Other thread tagged with stiffness
Lower extremity joint stiffness characteristics during running with different footfall patterns
Lower Limb Mechanical Properties: Determining Factors and Implications for Performance
Stiffness
Step Frequency, Clinical estimate of leg stiffness left/right differences
Leg Stiffness
Zone of Optimum Leg Stiffness (ZOOLS) -
Nice work fella. I'll pick up a couple of points later.
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There were a few things I heard myself say on playback that I wasnt delighted with. Suspected they wouldn't get past you...
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Here's a starter: if you are going to say that increase cadence = decreased step length, you need a caveat regarding velocity.
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And Claire Farley is a she not a he, btw.
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Hi Ian
Thanks for this - really enjoyed it (apart from letting everyone know what a 'young whipper snapper' you are - makes feel old before my time!)
I have a question that I hope you may have thoughts on (and obviously Simon) regarding perceived comfort of surfaces, including shoes and footwear, and stiffness modulation.
There seems to be some research that shows that perceived comfort is an extremely important factor when 'choosing' footwear etc. Also that some groups, e.g. runners, tend to perceive comfort as softer materials (Shore 3-45 density EVA for example).
This will obviously result in increased leg stiffness (unless other confounding factors are present) = greater running economy etc.
So what is the feedback mechanism that tells the body something is comfortable? Our we relying on mechanoreceptors within the foot or some other mechanism?
I have got a few other trains of thought regarding vibration frequency, natural and impact related, and there effect on stiffness modulation but will not bombard you will question - yet!
Cheers
Phil -
Phil, the concept of comfort is complex and probably relates to stimulation of temperature, pressure and pain receptors primarilly. But you can also throw in some visual and psychological factors too.
http://lowerextremityreview.com/article/rehabilitative-footwear-importance-of-comfort
http://www.ncbi.nlm.nih.gov/pubmed/11415701
http://www.ncbi.nlm.nih.gov/pubmed/24444754
http://www.ncbi.nlm.nih.gov/pubmed/16390637
http://www.ajur.uni.edu/v10n3/Barkley et al pp 7-14.pdf
http://www.ncbi.nlm.nih.gov/pubmed/22117882
http://www.sciencedirect.com/science/article/pii/0966636296828505
etc etc.
The question becomes, how does the body regulate leg stiffness in the absence of sensory input, i.e. peripheral neuropathy? -
If I am not butting in Phil
when you say will obviously result in an increase in leg stiffness, not always. Thats one of the keys as far as I am am concerned that we need to be able to workout on a patient to patient basis.
Some will and therefore keep the CoM travelling in a more similar manor to a harder material when running. This change in leg stiffness may be more efficient, but also cause a breakdown in tissue if the said tissue is pushed out of it's pysiological window.
inital comfort I would say comes from receptors at the foot surface interface, long term from many different places.
it all comes back to efficency of motion, the more efficent the body is working , say while running the more comfortable a run is. For some that might be soft surface or other hard. -
Hi Mike
I assume you are talking about Nigg's Preferred Movement pathway concept?
The issue with this is that initial perception of comfort is often static and does not relate to dynamic function e.g the individuals preferred pathway. However the patient will often rely on the initial feeling of comfort from which to judge the shoes, insole etc. and as you say it will vary between individuals on how it effects stiffness and interacts with their pathway.
From an orthotic designers perspective initial comfort is everything, especially in the retail environment, but understanding stiffness modulation in response to perceived comfort is a big topic as the credibility/effectiveness of the product is critical (for me personally!)
I am not sure that efficiency can be direct linked to comfort though. For example certain groups will feel that silicone is comfortable. However as the effects of fatigue occur and COM displacement increases, this often changes (Various reasons but personally I feel that the dampening effect of silicone insoles translates in to increased hysteresis within the silicone and the soft tissues). The comfort of the silicone at the end of a run is often different than at the beginning. (Blisters, rubbing etc)
I am starting to think that vibrations effect on stiffness modulation may play an important part in gait efficiency but has nothing to do with comfort - consequently the conundrum when designing any type of orthotic.
Will keep thinking at trying to find the 'perfect' material and orthotic design.
Cheers
Phil -
Hi Simon
Interesting links - especially the temperature one- socks and shoe weight made subjects feel more comfortable and cooler! You get very similar feedback from RhA patients!
Regarding the sensory input issues, I have recently seen a patient with Vestibular impairment who now feels that all her shoes are uncomfortable!
What is interesting clinically is that if we used initial comfort as a guide to prescribing our orthoses, how many rigid devices would be issued?
Cheers
Phil -
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However how would you deal with a patient whose comfort perception undermines what you need the insole to do?
Phil -
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Just out of interest how do you decide the 'stiffness' of the orthotic prior to dispensing?
I have a general rule of thumb that if the patient is 'fussy' (ticklish feet, had previous insoles that didn't like) then I use a more compliant material. If they are doing lots of standing then firmer materials are preferred.
Recently I have been looking at how footwear will maintain/control the COP progression and then using different stiffness material to try and get the COP where I think it needs to be - acceleration/deceleration. -
One of the major points of foot orthoses function is that they do not have constant load/ deformation characteristics across their interface with the foot. This is one of the methods by which they modify the reaction forces at the interface. The material selection in itself will not determine the load/ deformation characteristics, rather the geometry of the device in conjunction with the material selection will ultimately determine the orthosis stiffness at each point at the foot-orthosis interface, but only the geometry will determine the relative distribution of reaction forces unless you start using multiple density materials in parallel. So, when you ask how I decide on stiffness, we should first need to clarify: where?
Like you I am thinking in terms of "pulling" the CoP in one direction or another and in terms of preloading tissues via kinematic effects.
I think we do have reasonable ideas of optimal surface stiffness in runners- we'll talk about this privately I'm sure, Phil. There are clinical methods of estimating leg stiffness too.
While leg stiffness is interesting, we also need to think about foot stiffness. I think a reasonable starting point for this is to look at the span length of the medial longitudinal arch and the dynamic/ static navicular drop. If we have pressure plate data all to the the good, otherwise we can take a rough estimate of load based on body weight (x 1 static, x1.5ish for walking, x2 ish for running). From this we can calculate foot stiffness (or MLA stiffness). There will probably exist an optimal range of foot stiffness values- ZOOFS if you like. I talked about this some years ago.
Which reminds me, Ian in his presentation mentioned the relationship between foot type based on arch height and stiffness. He made a throw away comment in the presentation that there is not a lot we can do to change it- I disagree. Think about what foot orthoses do, Griff.
"Beam theory for dummies", anyone? "It's stiffer cause it's thicker" those that attended the seminar in Zaragoza will remember my discussion of this I hope. :drinks -
A further thought on the presentation. Ian talks about minimizing the vertical excursion of the centre of mass. Actually "flat-lining" the centre of mass has been shown to be less metabolically efficient, so some vertical displacement is required. The question becomes "how much?"
http://www-personal.umich.edu/~artkuo/Papers/HMS07.pdf -
We then need to understand which 'when' is moving the tissues out of their ZOOS and some how make the orthotic work - my head now hurts!
Phil -
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Like Simon mentioned, "shoe comfort" is complex and likely is multifactorial and may or may not be related to only the softness of the shoe. Also, different individuals may use different sensory mechanisms to rate "shoe comfort" and may even rate "shoe comfort" as to whether the shoe relieves or exacerbates preexisting painful foot and lower extremity conditions.
In addition, I don't think we know enough now to even include "shoe comfort" and "leg stiffness" together as relating to each other or whether they affect each other. These are interesting concepts but I think that "shoe comfort" is even less well understood than "leg stiffness" so much of what we do know is based on so few research studies that I believe we are just now starting to scratch the surface in trying to understand what makes one shoe comfortable and another shoe not comfortable. -
It would be a great research study to see the gait changes that occur by making an orthosis uncomfortable on purpose to see if different subjects respond the same kinematically to different "uncomfortable" orthosis modifications. -
One of the classic research articles on foot stiffness is the one by Ker et al (Ker RF, Bennett MB, Bibby SR, Kester RC, Alexander RMcN: The spring in the arch of the human foot. Nature, 325: 147-149, 1987) where they measured the stiffness of the longitudinal arch of the foot in simulated running conditions and then showed the changes in stiffness with transection of different tensile load-bearing structures of the longitudinal arch (see attached PowerPoint slide from my lecture on the 10 functions of the plantar fascia). Certainly, foot stiffness does play an important role in returning energy back into the runner and foot orthoses should be able to modify that stiffness to optimize energy return.
However, like Simon mentioned, "flat lining" the center of mass (CoM) is not ideal in running and too much vertical CoM excursion in running wastes energy also. There must be enough lowering of the CoM during running to "load the foot and leg springs optimally" during the early support phase of running, but not too much CoM loweing or metabolic energy will be wasted. It is up to the central nervous system to determine what optimal leg stiffness is for each different running surface with different surface stiffness. I think we are just starting to understand this and the foot does play a significant role in the stiffness of the whole lower extremity during running.
Fascinating subject! -
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Getting back to Ian's video, which I thought, Ian, was nicely done, here are a few more thoughts about leg stiffness.
1. We must remember that the measure of leg stiffness currently is only a measure of the fall and rise of the center of mass relative to the ground reaction force exerted by the foot. Therefore, it is an interesting measure, but may or may not be related to the three dimensional moments and motions that occur within the foot and lower extremity that may cause the majority of running injuries in our patients.
2. I believe the leg stiffness will be found to correlate more to performance than to injury production since leg stiffness basically measures the stiffness of the "springs" in the runner's legs. I believe, even though I don't know it has been studied yet, that runners with stronger lower extremity muscles will have stiffer legs during running. I'm not convinced measuring leg stiffness will tell us a whole lot about how to treat an injury but will tell us more about how the central nervous system alters the firing patterns of the lower extremity muscles for different shoe/orthosis/surface stiffnesses.
3. The good news is that leg stiffness is a quantifiable measure, and not a subjective measure, meaning it can be scientifically analyzed much more easily. The bad news is that there is no reliable way to measure leg stiffness during running in a clinical setting without a force plate and a 3D motion analysis system in the clinic. How many of you have that in your offices?
Good discussion. -
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Thinking out loud: if we know the stiffness of a spring and we know it's resting length, then surely we can model and predict how much load/ deformation might induce plastic deformation in a given spring? That is, there has to be a way of predicting the elastic limit of a spring, without actually physically measuring it- right?
If this is correct and I think it is, then we should be able to predict injury based on leg stiffness. Or, put another way, soft tissue injury occurs when the CNS fails to match the stiffness of the leg to the load being applied such that the deformation in the leg exceeds the limits of proportionality- I like that. -
Does the pain cause the gait or does the gait cause the pain? An age old question.
Eric -
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Just to read an article that assessed the viscosity of a muscle post stretch.
It found that when a stretch was repeatedly applied to the hamstrings for 90 secs, then the viscoelastics stress relaxation of the muscle increased by upto 30% (but did return to normal within 60 minutes) = the muscle was less stiff.
This could have implications for the CNS/mechanical modulation of stiffness if too vigorous stretching was done prior to activity requiring stiffness modulation.
Phil -
Here's a prospective study which suggests leg stiffness can be employed to predict injury: https://ojs.ub.uni-konstanz.de/cpa/article/viewFile/5258/4832
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I'm not so sure that in the human leg, where the "springs" are multiple viscoelastic structures, many of them working in parallel with each other, and all contributing to the spring stiffness of the leg, that it would be possible to determine when plastic deformation would occur in any one or all of those structures simultaneously. In addition, I believe that if you want to predict the elastic limit of a spring then it would be better to know what material that spring is made of rather than just simply looking at the spring's stiffness. -
Simon, the study looks a little fishy to me. What do you think of it?
I do like the idea of measuring leg stiffness in the lab to learn more of how it correlates to lower extremity function but still think this may be difficult to measure in a clinical setting.
In addition, let's say we measure leg stiffness in a patient to be too high or too low, then what would you do to either decrease or increase leg stiffness to bring it back into more normal values for the athlete? -
Sincerely,
Daniel -
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Hi all,
Just finished a systematic review on Lower limb MSK stiffness and injury. The abstract is below. I will present the findings at the IOC conference Monaco in April and then hopefully full paper will be published soon.
Just in transit at the moment so I will tune in again later tonight and try and contribute to some of the previous posts.
In the review I looked at MTU stiffness, Leg stiffness, Vertical stiffness and joint stiffness and the possible relationship to lower limb injury in athletes.
More soon,
Athol
http://bjsm.bmj.com/content/48/7/665.1.abstract
Br J Sports Med 2014;48:665 doi:10.1136/bjsports-2014-093494.280
Abstracts from the IOC World Conference on Prevention of Injury & Illness in Sport, Monaco 2014
280
THE RELATIONSHIP BETWEEN MUSCULOSKELETAL STIFFNESS AND LOWER LIMB INJURY IN ATHLETES: A SYSTEMATIC REVIEW
A Thomson,1
+ Author Affiliations
1ASPETAR, Doha, Qatar
2Ulster Sports Academy, University of Ulster, Northern Ireland.
Abstract
Background Lower limb injuries are prevalent in sports involving running, hopping and jumping. Musculoskeletal lower limb stiffness is a modifiable mechanical property that may be related to injury risk in athletes.
Design Systematic Review.
Objective Examine the relationship between musculoskeletal stiffness and lower limb injury in athletes.
Methods Literature searching was undertaken on 3 electronic databases (MEDLINE/SPORTDiscus/google scholar) up to September 2013. All prospective and case-control studies evaluating lower limb MSK stiffness and injury in athletes were included. Two researchers independently extracted outcome data and assessed the quality of included studies using a modified Downs and Black index. Effect sizes were calculated using RevMan software (version 5.2).
Results 11 studies (6 prospective and 5 case controlled) were identified, comprising a total of 474 participants (378 M, 96 F) with a mean age range of 13–39 years. The majority of studies (9 out of 11) were undertaken on international or elite athletes. Quality index scores ranged from 13 to 16 (max 19). Athletes with a history of unilateral lower limb injury displayed less stiffness when compared to their un-injured contralateral sides. Pooled data from three case control studies also found tendon stiffness was significantly lower in athletes with tendinopathy compared to un-injured matched controls (SMD 0.70, 95% CI 0.07–1.48). Data from prospective studies could not be pooled due to clinical heterogeneity. There was a clear trend that athletes with bilateral differences in leg stiffness or higher mean leg stiffness were more likely to develop a non-contact lower limb injury.
Conclusions Case controlled studies show a clear relationship between musculoskeletal stiffness and athletic injury. Prospective research provides further evidence that musculoskeletal stiffness may have an important causal role; however this may be implicated by previous injury. -
A relation between movement pattern and free moment pattern could be seen in : Willwacher, Steffen et all. “Free Moment Patterns in Distance Running.” Footwear Science 5, no. sup1 (2013): S10–S11.
[ http://www.tandfonline.com/doi/abs/10.1080/19424280.2013.798686 ]
Another reference article is : Holden, John P., and Peter R. Cavanagh. “The Free Moment of Ground Reaction in Distance Running and Its Changes with Pronation.” Journal of Biomechanics 24, no. 10 (1991): 887–897.
[ http://www.sciencedirect.com/science/article/pii/002192909190167L ]
Sincerely,
Daniel -
Whereas the more specific measures such as MTU stiffness, joint stiffness are more location specific and in the case of MTU stiffness, require the use of ultrasound of a tendon to measure the change in length of the tendon or aponeurosis for a given force .
There are two excellent reviews of the types of stiffness and the mathematical models used to calculate stiffness for each method below.
http://www.ncbi.nlm.nih.gov/pubmed/18282225
http://www.ncbi.nlm.nih.gov/pubmed/22845059
Happy to email PDF of these if you PM me.
Reliability of these measurements is an issue. A friend called Corey Joseph has studied the reliability of each method and his findings are attached.
On the point about measuring stiffness in the clinic. It can be done with a contact type-mat (pressure mat) with one of the models covered in the reviews above.
However, The most reliable method seems to be hopping on a "proper" force plate. You don't need kinematic data for vertical stiffness as you can do a double integration to work out the COM displacement using the kinetic data only. (again see reviews if interested). I think this is not far away for pre-season screening in elite sport and with Australian rules football already trying this in two prospective studies.
There are studies that have shown how certain types of training alter lower-limb stiffness such as plyometric, power, strength, endurance, eccentric or heavy slow-resistance training. Each type of training has a certain effect on lower limb stiffness or MTU stiffness.
So if we can measure the stiffness as podiatrists/biomechanics specialists we might then be consulting with physiotherapy and strength & conditioning colleagues to tailor a treatment plan that we can then objectively measure again after a given amount of training or time.
All the best,
AtholAttached Files:
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:good: Great posting.
By the way, for those following along MTU means "muscle-tendon unit".
Let's say I want to measure leg stiffness of a patient in my clinic and don't have a force plate in my office. How do I measure leg stiffness in my patients without this rather expensive piece of equipment? How reliable would this measure be? In addition, how does body weight affect stiffness? Is there any correlation?
Thanks for the information! -
You could use a contact/pressure mat to calculate vertical or even leg stiffness in clinic. Some studies have used in-shoe pressure (e.g pedar-x) and even an optojump system to work out flight times and contact times. These values are then put into a large equation or some software with the function set-up already to calculate stiffness measure you require. I emailed you the Brughelli et al. review which outlines all the methods used in previous literature very well.
I think it is still a stretch to calculate stiffness in a clinical setting with time constraints. There are some clinical tests that seem to correlate well with leg stiffness such as a 3-single leg hop test for distance. These are the tests that will give an inference to what the actual leg or vertical stiffness is while being clinically useful.
I'll try and find the study that used the hoping test for distance and post a link.
When using the force plate methods for calculation you can "normalise" for body mass so the stiffness is not dependent on just the mass.
I imagine that this can be done with all the methods.
Cheers,
Athol -
As far as I know I haven't seen the following article cited on this forum... doesn't seem to be on this thread (which is probably the more appropriate thread out of the "Leg Stiffness" threads)...
Warm-up with a weighted vest improves running performance via leg stiffness and running economy (link):
Journal of Science and Medicine in Sport:
K.R. Barnes, W.G. Hopkins, M.R. McGuigan, A.E. Kilding.
- Received 24 June 2013; received in revised form 5 December 2013; accepted 13 December 2013. published online 27 January 2014.
In fact, now that I think about it... there was a distance runner from the U.S - Hobie Call (marathon PR of 2:16.39 as of 2012) who believes he could be the first to break 2:00hr in the marathon; article here: http://www.runnersworld.com/elite-runners/hobie-call-would-be-sub-200-marathoner...
I use the following...
MiR Weighted Vests.
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Anomalous plantar intrinsic foot muscle
|
Arch Supports should NOT be used in treating a Flexible Flatfoot
>
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