Shock attenuation from foot orthoses

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Hi everyone,

Im currently researching the effectiveness of different methods of increasing shock attenuation in lower limb orthoses.

Although I have found about 25 relevent articles including well documented ones (eg. withnall et al), they are all research based on foot orthotics or 'insoles'. I have only one that mentions AFO's.

Has there been significant research done based on polypropylene orthoses?? I know this is a podiatry arena so AFO's are not your thing, but I thought it would be similar to a UCBL???

I have read through the threads on GRF and impact forces and have already found the journal articles cited.

Can anyone help??

thanks
Aideen:morning:

 

Re: shock attenuation

I would think not.

AFOs have a far greater effect on the angle / velocity of heel strike. Lets face it, in peads they are generally used to acheive heel strike. UCBLs by contrast do not controll the TC joint.

Hard to study because apart from the effect of the material one would have to consider the effect of the device on function and the function in patients who need AFOs will be radically different to those needing UCBLs (or indeed FFOs).

Regards
Robert

 

Re: shock attenuation

The first question I would ask is why? Not one prospective study has linked poor shock attenuation to any problem. The data on increased shock absorption decreasing injury is not good either.

See this thread on Do “cushioning” shoes really cushion impacts? for more. What is appearing to be important is the 'tuning' of impact to the vibration frequency of the soft tissues.

 

Re: shock attenuation

Why? Because I was given the topic by your fellow staff members at latrobe!

Tuning to the frequency of soft tissues.... is that achieved in the orthoses? How?

thanks for the help

 

Re: shock attenuation

Shock attenuation and shock absorption have become such a dated concept now. Check some of Beno Niggs stuff on muscle tuning - it not soecific to foot orthoses - its specific to anything under the foot (orthotics; shoes; surface). There is some infor on the link thread on running shoes.

Check this lecture of Beno Nigg's:
Click on 2007-10-Impact-Australia.pdf on this page: http://www.biomechanigg.com/bricontent/applications.htm

 

Thanks Craig, I checked that out. A little over my head but I get the idea of it.

I desperately want this journal article but I cant access the full text!

"The shock attenuation characteristics of four different insoles when worn in a military boot during running and marching"

Carol M. Windlea, , , Sarah M. Gregorya and Sharon J. Dixonb

This is the link to it:

http://www.sciencedirect.com/scienc...serid=10&md5=87c41c5f5b4aac9d596e7cb1ab1bc22f

has anyone got this article???

thanks again

 

Log on to Science Direct via a computer on-campus at LTU (they recognise the IP address)and you should be able to get the .pdf of that article.

 

Aideen

I'm not quite sure what you are asking for Aideen. The AFO is used where one specifically wishes to control some aspect of the kinetics and / or kinematics of the ankle joint and STJ. It may be used to control supination ad pronation or plantarflexion and dorsiflexion. So if one were addressing a foot drop then the AFO might also reduce shock attenuation and if one were to use an AFO where there was a weak Tibialis Anterior but not foot drop IE foot slap then this might increase shock attenuation.

Describing the Shock attenuation characteristics of a certain material in terms of how this affects the force impulse or integral (force time curve) during gait can be difficult since the characteristics of gait may also change with the change in material and design.

So to give an example, this is how I would see some of the problems of answering your quesion.

First, jump of a 20cm high platform onto a steel force plate, then do the same off a 50cm high platform. You will probably notice that the peak force is similar and the force impulse for the second jump is longer. Now do the same with 5cm of medium density foam on top of the force plate. The peak force will probably still be similar and the force impulse somewhere between the first two curves. Which one is best in terms of shock attenuation?

This question is difficult to answer until you know the requirements of the activity to be performed and which part of the body is the focus of interest for your study. The body will subconsciously attempt to limit peak forces during a given activity. If the forces applied do not reach a peak where proximal compensations to achieve shock attenuation is required then this may not happen. This may also be overcome consciously when required. E.G. you could walk over cobbles in bare feet without limping but its difficult.

If you wanted to jump quickly back onto the platform after landing using the stored energy of the Achilles tendon, you may not want to have a thick piece of soft foam absorbing the energy required to spring up.

If you wanted to land on the heel and not flex the knee and reduce the chances of injury then some foam might be a good solution.

If you landed like a parachutist the foam probably wouldn't make any difference at all.

All the force impulses would be different and which type of landing would cause the most pathology to which joint or tissue is difficult to determine.

An ant can run across a crash mat quite easily but a human would find running on such a surface very difficult. The attenuation properties need to be matched to the activity and the body parameters of the subject.


When you have an orthosis, FFO or AFO, it will have many laminations of interfaces to the ground. EG 1) Fibro-fatty pad, 2) Polyprop, 3) EVA, 4) Wool, 5) foam, 6) leather, 7) shoe sole material. All these will have different attenuation properties intrinsic to the material. The shape of the material, e.g. the shoe and point of application of the applied forces all will affect the deformation properties and this will determine to some extent how the body reacts to the forces applied.

All these confounding variables make it difficult to determine how effective one type of material or design is in terms of shock attenuation.

So you can see that you would have to be very specific in your research question before you could collect and evaluate data that would give a reasonable conclusion.

Cheers Dave

 

Re: shock attenuation

Is this for an undergrad assignment? If so, what is the title? Or is it for something other?

 

Aideen

Reading the abstract of the Army boots insole research

Local pressure reduction is not necessarily the same a shock attenuation.

A soft insole may increase the surface area contact of the foot / insole interface and this will reduce the force per unit area (pressure) the force impulse as measured by a force plate may still be the same as without an insole. Therefore the joint forces at the knee for instance may still be the same.

Cheers Dave

 

wow I clearly have a lot to learn! (I'm only in 2nd year P&O tho!!)

Thank you so much for your feedback!

I'm beginning to think that this topic is doomed yet I have to submit it in 4 weeks!

I completely acknowledge your points David, in that there are far too many variables to take into account with such a broad research question.

Unfortunately my assignment topic reads as follows:

"Discuss the relative effectiveness of different methods for increasing shock attenuation in lower limb Orthoses"

Also the word "method" is throwing me a bit.

 

Aideen

Ok! I see the merit of this question.

By reviewing the various methods used for a proposed increase in shock attenuation you will reveal how effective each method was.

So you could identify X number of methods used (these may already have been outlined in your course work). Lets say you identify 6 methods.

Establish exactly what is "shock attenuation" and how it might be useful for a biomechanical application.

What are these applications - Rehab, Performance, injury prevention etc.

Review the method and results for each and perhaps some statistics if required.

Discuss the limitations and shortcomings of each method.

Conclude which is best, in terms of absolute attenuation or for the activity described, or if is possible to do this considerig the many variables inter and intra experiment.

Recommend further research to improve the reasonableness of the outcomes.

I think the point is "relative effectiveness ". Perhaps what is good for one application is not so good for another, why is this?

Just my suggestion.


Cheers Dave