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Orthoses may well reduce the velocity, but I am not aware of any data that shows excessive velocity of pronation as being a risk factor for problems.
BUT, from a tissue stress perspective, if the velocity is reduced, then less force is needed to stop or slow it (assuming that this is a good thing) --> less force needed theoretically mean less force in the tissue to cause damage.
__________________
Craig Payne
Department of Podiatry
La Trobe University
Melbourne, Australia http://www.latrobe.edu.au/podiatry
__________________________________________________ ___________________________________ God put me on this earth to accomplish a certain number of things - right now I am so far behind, I will never die.
The views expressed above are those of the author and not that of La Trobe University This is where I am, where are you?
Orthoses may well reduce the velocity, but I am not aware of any data that shows excessive velocity of pronation as being a risk factor for problems.
BUT, from a tissue stress perspective, if the velocity is reduced, then less force is needed to stop or slow it (assuming that this is a good thing) --> less force needed theoretically mean less force in the tissue to cause damage.
Thanks for your perspective Craig. The slower rate of pronation though will mean that tissues such as the plantar fascia will be less stiff and therefore have a reduced capacity to store energy.
__________________ Science is the antidote to the poison of enthusiasm and superstition
Never considered that. If that is the case, then its going to be a matter of 'trade-offs'. For example, slow pronation enough to reduce tissue stress to a level below a certain threshold (assuming that is what we should be doing), but not reduce it so far that it affects the whole concept of energy return (assuming that this is a good thing).
If this is the case, then the practicalities will be problematic - its highly likely that the optimal intervention to achieve this will be very subject specific (like it is with ankle joint ROM) --- I do not have the remotest idea how to achieve that subject specificness for the ankle joint, let alone pronation velocity cotrol and energy return.
__________________
Craig Payne
Department of Podiatry
La Trobe University
Melbourne, Australia http://www.latrobe.edu.au/podiatry
__________________________________________________ ___________________________________ God put me on this earth to accomplish a certain number of things - right now I am so far behind, I will never die.
The views expressed above are those of the author and not that of La Trobe University This is where I am, where are you?
Thanks for your perspective Craig. The slower rate of pronation though will mean that tissues such as the plantar fascia will be less stiff and therefore have a reduced capacity to store energy.
The ability of our biological tissues to be both compliant in some instances and stiff in other situations is used to great effect in many human activities, whether we know it or not. For example, some recent research has shown that runners with increased knee flexion stiffness (sorry, no time to find reference) have improved running performance. In addition, our ability to decrease the knee flexion stiffness to absorb shock after jumping down from a height to prevent injury is very useful also.
As I have pointed out many times before in previous discussions with Howard Dananberg and others who get excited about possible energy return mechanisms in the plantar fascia during walking, there is no research evidence, to my knowledge, that the plantar fascia can store sufficient energy during walking to make walking more metabolically efficient. However, classic research in cadaver feet has shown that, for running, the plantar fascia and other plantar ligaments can store and release 17% of the 100 Joules of estimated kinetic energy that occurs during each running step (Ker RF, Bennett MB, Bibby SR, Kester RC, Alexander RM: The spring in the arch of the human foot. Nature, 325: 147-149, 1987).
Therefore, while increased tensile force within the plantar fascia will definitely increase its stiffness (Wright DG, Rennels DC: A study of the elastic properties of plantar fascia. U.C. Berkeley Biomechanics Laboratory, Technical memorandum, October 1961), there is no evidence that this increase in plantar fascia stiffness with increases in its tensile force can be used to effectively improve the energetics of walking. If it does improve the energetics of walking, then I would think that this effect would be minimal and much, much less than seen in running. This has probably very much to do with the diametrically opposed kinetic energy-potential energy transfer curves seen between walking and running (Novacheck, Tom F.: The biomechanics of running. Gait and Posture, 7:77-95, 1998). http://www1.elsevier.com/homepage/sa...6/fulltext.pdf
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Sincerely,
Kevin
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Kevin A. Kirby, DPM
Adjunct Associate Professor
Department of Applied Biomechanics
California School of Podiatric Medicine at Samuel Merritt College
The results of this study confirm that overpronation and increased velocity of pronation was associated with an increased incidence of ERLLP
...so I will eat humble pie. BUT, all is not lost :) - they found that in the univariate analysis, but it did not come through as a factor in the multivariate predictor model analysis.
__________________
Craig Payne
Department of Podiatry
La Trobe University
Melbourne, Australia http://www.latrobe.edu.au/podiatry
__________________________________________________ ___________________________________ God put me on this earth to accomplish a certain number of things - right now I am so far behind, I will never die.
The views expressed above are those of the author and not that of La Trobe University This is where I am, where are you?
Orthoses and pronation velocity
or feel proud 
... one of my students just emailed me to gleefully point out I am wrong !!!
Linear Mode
