kinetic chain

[Admin]

Hi everyone,

May I be a little simplistic here for a minute.

My observations, based on my own research, but subsequently agreed by Robert, are that when the STJ is placed in neutral (or an approximation thereof) most feet invert.

To take weight upon a hard, flat surface they must evert, and this eversion internally rotates the lower limbs, which affects posture by tliting the pelvis forwards, increasing lordosis etc etc. This is easily demonstrable (and if anyone votes for me on the poll I'll take great delight in demonstrating it in January ;D).
This is entirely natural because we have a foot adapted for a multitude of surfaces, of which hard and flat is but one.
BTW we're talking static here.

OK, so far so good. Now when an insole (most insoles of whatever type will effect this, apart from the flat squashy ones) is placed under the foot, that foot is not able to evert to the same extent, = les internal ritation of the lower limb, less pelvic tilt, and less lordosis etc etc.

I really believe it's that simple

Cheers,

[robertisaacs]

Thankyou brian for breathing some life back into this thread. I love this stuff.

Brian

What you describe as neurobiomechanics is something like what i was trying (far less articulately) earlier in the thread. I think there might be something to it. However (shockingly ) i have questions / concerns (pause for you to remount your chair having fallen of it in shock and surprise).

(1) Mechanical receptors in the bottom of the feet are continuously sending information to the cerebellum regarding the position of the body in space (e.g., its posture).

I can beleive this. It strikes me that this must be quite a complex mechanism during gait as the loads on the assorted "segments" of the foot will not have a set "normative value" but rather a varied load depending on the stage of gait and the nature of the ground.

(2) If these signals are distorted, e.g., abnormal pronation, the cerebellum acts on these distorted signals, resulting in distorted (poor) posture.

Hmmm. Now we are heading into choppier water. Assuming pronation is bilateral there will still be a symmetry of a sort suggesting (to my tiny mind) that frontal plane elements of posture should not be adversly affected. So far as sagital plane is concerned... i suppose the sagital plane progression of gait could be altered (in so far as pronation affects it) and that could impact upper body function.
It strikes me that this should be possible to model, or better still observe with a force plate... Any takers?

(3) Using proprioceptive signals (insoles) underneath the feet, these distorted signals are normalized, before being sent to the cerebellum.

Now the waters become even stormier! Assuming we are talking about increased pronationas an "abnormal" sensory feedback pattern we would be looking at increased peak and impulse pressure under the medial side of the foot (or second met head depending on intermetatarsal stability). Proprioceptive insoles, and indeed traditional orthotics come to that both exert increased GRF under, yes you guessed it, the medial side of the foot! By this token would insoles (of either type) not give rise to the very pattern of pressure feedback we wish to surpress?

Damn i wish i had an F scan. This would be REALLY interesting to observe in situ.

I would much value your thoughts on the above.

Regards
Robert

[robertisaacs]

OK, so far so good. Now when an insole (most insoles of whatever type will effect this, apart from the flat squashy ones) is placed under the foot, that foot is not able to evert to the same extent, = les internal ritation of the lower limb, less pelvic tilt, and less lordosis etc etc.

I really believe it's that simple

I wish I did! ;D

This is the problem i have with this model. The whole When an insole is placed under the foot it is not able to evert to the same extent thing.

This is a beautiful theory but it is simply not bourn out by the best kinematic data we have available.

The references i provided a page back (which BTW are neither exhaustive nor, i am sure, the most up to date), show two things. One is that Rearfoot eversion / hyperpronation or whatever you want to call it DOES cause pelvic anteversion (assuming i have my ante and retro correct this time). The other is that Orthotics DO NOT have a very large if indeed any effect on position of the stj in gait.

Now if we are talking about a KINETIC chain, this presents no problem. Very few would argue that orthotics extert a kinetic effect. But the process you describe is a kinematic one which is a gait of a different pattern.

The studies which showed the increase in pelvic anteversion, 1.57 degrees in the first used 10 - 20 degree wedges. Unless we venture into the realms of the kirby skive who amoung us uses wedging of that magnitude?

Regards
Robert
PS
I've just noticed the pinto study used a 10 degree MEDIAL wedge to acheive calcaneal EVERSION and pelvic anteversion. Am i having a funny 5 minutes or is there something a bit pete tong about that?

[rothbart]

Ciao All,

To date, no single or double blind randomized tests have been published regarding the foot - cerebellum link, that is, how abnormal foot motion is interpreted by the Cerebellum (if indeed, it actually occurs at all). What I am suggesting, and what Posturologists have been writing about over the past 20 years, is a possible explanation of what we are seeing clinically. For example, I have demonstrated an immediate response of the levator (eye) muscle when a signal is applied to the bottom of the foot. I would argue that we are changing the tonus pattern of that muscle. But how is that happening. From a biomechanical point of view, it would be difficult to explain. But from a neurobiomechanical point of view, an explanation is easier to provide.

I suggest that during stance phase, if the foot motion follows the pelvic oscillations, the mechanical receptors in the bottom of the foot provide an accurate picture of the body's posture in space. However, if the foot does not sync with the pelvic oscillations (e.g., abnormal pronation), the mechanical receptors in the bottom of the feet fire in a different pattern (mechanical receptors are tactile sensitive). This change in the pattern of firing is what I referred to as a distorted signal. And this distorted signal, initiated in the foot, is transmitted to the cerebellum. The cerebellum reads this signal as being an accurate description of the body's posture and makes the appropriate adjustments. A distorted posture is the result.

Understand, this explanation is theoretical. No scientific studies done to date, to prove or disprove it. However, it is consistent with my clinical experience using proprioceptive insoles. You can access my clinical research at www.rothbartsfoot.info

Prof B

[robertisaacs]

I suggest that during stance phase, if the foot motion follows the pelvic oscillations, the mechanical receptors in the bottom of the foot provide an accurate picture of the body's posture in space. However, if the foot does not sync with the pelvic oscillations (e.g., abnormal pronation), the mechanical receptors in the bottom of the feet fire in a different pattern (mechanical receptors are tactile sensitive). This change in the pattern of firing is what I referred to as a distorted signal. And this distorted signal, initiated in the foot, is transmitted to the cerebellum. The cerebellum reads this signal as being an accurate description of the body's posture and makes the appropriate adjustments. A distorted posture is the result.

Understand, this explanation is theoretical. No scientific studies done to date, to prove or disprove it. However, it is consistent with my clinical experience using proprioceptive insoles. You can access my clinical research at www.rothbartsfoot.info

You did'nt answer my question

Assuming we are talking about increased pronationas an "abnormal" sensory feedback pattern we would be looking at increased peak and impulse pressure under the medial side of the foot (or second met head depending on intermetatarsal stability). Proprioceptive insoles, and indeed traditional orthotics come to that both exert increased GRF under, yes you guessed it, the medial side of the foot! By this token would insoles (of either type) not give rise to the very pattern of pressure feedback we wish to surpress?

.

I'm not looking for research just now, a model or more detail will do!


Regards
Robert

PS
We've all got the link to your site Brian, we've all been there. Its lovely. You can quit putting the link up now. Otherwise it looks like a plug if you link to your site with every post.

[ianl]

Hi

Brian used the term "abnormal foot motion" which of course need not be linked (and I'm sure Brian does not implies this) with excessive pronation but with other aspects of foot function as well.

Equally focus is placed so much upon the amount of heel eversion and attempts to possibly control it.

My difficulty is that I am not convinced that we can talk about abnormal foot motions in these instances. We have an individuals foot function but to describe it as abnormal is possibly (?) to go to far and have us looking how to introduce normality.

For many years in my assessments I have noted the level of static and dynamic eversion of pts heels when assessing them but made no real attempt to address this other than including occasional medial skives or deepening the heel cup. When making my own devices the aim was always to bring resistance to what I would have considered excessive in-roll of the MTJ at early and mid heel lift. This for me has never been an issue of them having abnormal foot function but an issue of using the device to produce (paradox coming up) a "stability" (or resistance) that moves a person from one point of instability to a different type of instability but one where hopefully their own musculoskeletal and neurological intelligence is allowed to function more helpfully.

Equally I have used lateral heel skives to alter "instability". Would expand this but I have now got an unexpected pt arrive (must put people in diary!)

Ian

[Admin]

What ian said (apart from the patient bit ;D).

Robert,
What I'm talking about is stance only, no gait involved. I should have mentioned that the pt is shod too (obviously) and that I believe the heel of a shoe exerts some anti- lower limb internal rotation too.

Robert,
In stance it is very easy to straighten a pt up (I did it yesterday and only had her with and without shoes - the difference was easly observable. I'm not brave enough to suggest this can be quantified during gait .

Re- overpronation (hate that too ) have you considered how much overpronation would occur on an uneven surface? Most "overpronators" are simply feet which don't work well on those flat rocks we call pavements.
Cheers,

[robertisaacs]

Interesting idea. Normal / Abnormal function. Deserving of its own thread.