Center of pressure index and running strike pattern

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Hi all, I am starting out on a research project in a local sports medicine facility. My area of interest is in whether customised orthotic intervention differs in efficacy in runners with different strike patterns ie forefoot midfoot and rearfoot. I would love to do a kinetic and kinematic study on that, however, resources are limited as for now, and I only have an Fscan machine that can allow me to do mainly center of pressure calculations.

I have looked everywhere for any journal papers revealing moderate or high validity of evaluating foot and orthosis function with center of pressure, but I have found none. I do have high hopes of using center of pressure as a tool in evaluation, and sees a link between center of pressure and tissue stress theory which kinda makes sense to me and am trying to use it in my daily practice

I admit that my knowledge of biomechanics is very limited and would really appreciate anyone's input in this. Is it possible to quantify orthotic success with center of pressure measurements in a research setting? Any views on that? Thank you for any help!

Yen

 

My initial response to that is: why? What will it mean if you find differences or not? I would have thought a more appropriate parameter to investigate would be a parameter that has been shown to be a risk factor for injury with the research question being: can foot orthoses alter that parameter and is there a difference with strike pattern.

It will be easy to show the effects that foot orthoses have on the center of pressure; its just what does it mean?; we do have a fairly good theoretical idea and anecdotal experience about where the center of pressure should go and how a foot orthoses could change that; but what has that got to do with clinical success (ie symptom reduction); it may have a lot to do with it, but we just do not know (apart from that theoretical understanding and anecdotal experience).

I would have thought that its a 4 'prong' approach:
1. Show a correlation between the parameter of interest in a cross-sectional study
2. Show that the parameter of interest is a risk factor for injury in a prospective study
3. Show foot orthoses can alter the parameter
4. Do a RCT comparing foot orthoses that alter and do not alter parameter have on clinical symptoms.
(5. Large enough sample size in 1,2,3 & 4 so that a subanalysis can compare differences in forefoot strike pattern)

What you are proposing is just doing 3 ... nothing wrong with that, but it needs to be done in the context of no data from 1,2 & 4.

 

I tend to concur with Craig, there have already been studies that show the CoP position can be altered by orthoses. Here's a thought experiment which highlights one of the big problems that comes from looking at CoP position in isolation. Lets say we see a medial shift in the CoP in conjunction with an orthosis- what conclusions can we draw from this?

 

Yen:

There is so much research to be done in this regard, that you could spend a lifetime doing just the basic research that we all need. If you only have an in-shoe pressure insole system at your disposal, then you will only be able to measure the temporal parameters of pressure and/or load distribution on the plantar foot during weightbearing activities. However, you will not be able to determine the kinetics of the foot and lower extremity since the F-scan will not give you the three-dimensional (3D) orientation of the ground reaction force (GRF) vector acting on the plantar foot during weightbearing activities or the locations of the important joint axes of the foot and lower extremity. You would need a force plate to measure the 3D location of the GRF vector and would need 3D motion analysis to determine the 3D location of the joint axes at any instant in time.

Bart Van Gheluwe, Friso Hagman (two PhD biomechanics researchers from Belgium) and I did a study a few years ago where a pressure mat was placed on top of a force plate to determine not only the location of the center of pressure relative to the plantar foot but also the 3D location of the GRF vector in order to estimate the moments acting across the subtalar joint during simulated genu varum and genu valgus walking (Van Gheluwe B, Kirby KA, Hagman F: Effects of simulated genu valgum and genu varum on ground reaction forces and subtalar joint function during gait. JAPMA, 95:531-541, 2005.) Bart will be presenting a lecture on the collaboration that has occured over the last 20 years between the research and clinical world (we have collaborated together on a few clinical-biomechanics research projects/papers) in a few months at the Footwear Biomechanics Symposium in South Africa in July 2009. Unfortunately, I won't be able to share giving the lecture with Bart since I can't attend, but it should be a great seminar.

One great research idea would be use the F-scan to measure the difference in response of both rearfoot and forefoot striking runners to running in shoes of various heel height differentials. [Heel height differential is the difference between the thickness of the sole below the heel and the thickness of the sole below the forefoot.] There is a lot of interest and controversy now within the international running community with the Pose and Chi running methods that emphasize forefoot striking, even for slow running, as being a "better and more efficient" method of running. It would be interesting to see if those runners who have naturally selected to run in a rearfoot striking pattern change their plantar pressure patterns of running in a similar fashion to those runners who have selected to run in a forefoot striking pattern when they run in shoes with varying heel height differentials. Rearfoot wedges could be added under the sockliner of the running shoe to increase heel height differential in both groups.

This is just one idea I have for you. If you have any other directions you would rather proceed with your research, I am familiar with most of the running research that has been done over the past 30 years. Maybe we can help you do some meaningful research that could eventually be published and, therefore, be of service to the running research and clinical communities.

 

You can conclude that there is "a medial shift in the CoP in conjunction with an orthosis" which is only of importance if a lateral shift in the CoP is a risk factor for an injury (with due credit to CP for teaching me that!).