Does the tibia drive the foot or does the foot drive the tibia?

Hi all

I've only quickly read thru the Bellchanber Bogert paper and knowing a little on Van den Bogert's works I would be cautious to criticize the engineering theory however:

If they are considering power and power in terms of angular velocity x moment, which is the rotational equivalent of work/time or fd/t, where angular velocity = displacement over time and moment = the rotational expression of force.

Therefore to have a moment of interest in a mechanical system (lets call this the internal moment), then there must be an equivalent external moment to achieve equilibrium. If the internal moment is related to an angular velocity then we can characterise this as power (w*m). As there must be an equivalent external moment then; the angular velocity can not be equal otherwise there can only be zero moments about a point of interest (lets say this is a joint). So if the internal moment plus an angular velocity above the joint = -y power (if we imagine that y = the long axis of the leg and the joint is the STJ) then the angular velocity below the STJ must tend to be relatively less than above for the power to have a negative bias.

This tendency would not be an actual difference if the system is very stiff but if it has very elastic components then there may be an actual difference in angular velocities as the elastic components stretch and so give changing a bias to the power direction or flow.

Not sure if that is clear but essentially the forces at the foot can generate no mechanical power if it has no associated angular velocity the moments and forces that it generates will affect the kinetics and perhaps the kinematics of the proximal segments however. Power then may be an abstract of maths rather than an indication of real work done physiologically.

I'll let you think on and tear me up at will on that one:dizzy:

Cheers Dave

 

Dave are you saying that with internal rotation of the tibia (the angular velocity) there can not be STJ motion pronation in this case, there could be moments but not motion? and therefore no flow of power as discussed in the paper Craig mentioned.

if not, one more time for the Dumb kids in the back ie me

 

Re: Open letter to Craig Payne

Bruce, it wasn't really a statement, it was a question. That's why it had a question mark at the end of the sentence. The point being, as Craig alluded to, that the direction of flow of power is being seen by some to be evidence that a proximal approach to management should reap higher rewards when the power is flowing from proximal to distal. The antithesis being that when power is flowing from distal to proximal, distal intervention should reap higher rewards. Now, I'm not sure whether this is true, but Craig's post inferred that many see this as being the case- why? So, lets assume for one minute that this is true, if it were then targeting orthosis to the times during the contact phase when power was flowing from distal to proximal should reap higher rewards. Like I said, I'm not sure if any of this is correct. What is obvious is that there is inter/ intra subject variation and that actually the power seems to oscillate around the zero for the first 60% of stance during walking it's only really in the final 40% (propulsion) that the graph is really showing negative, proximal to distal power flow in all subjects. What does this oscillation imply given a bipedal spring mass model for walking?

What we don't know of course is what effects foot orthoses would have had on those power graphs.

Good discussion.

 

Re: Open letter to Craig Payne

Simon;

absolutely agree and sorry I did not see the question mark.

excellent discussion!
Bruce

 

Re: Open letter to Craig Payne

No worries. Can someone who is clever tell me this: if we had a spring mass model and set it oscillating (compressing and decompressing) what would we see on a power graph?

I'm interested in this statement from Geyer's PhD:
"the COM dynamics during walking may well be described
by purely elastic leg operation with the double support phase having an essential
contribution. In fact, considering a complete stance phase of one spring leg of the
spring-mass walking model, the effective load (mass) on this spring only gradually
increases after touch-down as the opposite spring still is partially supporting the
COM. Due to sufficient stiffness, the spring quickly reaches its peak compression
leading to a corresponding initial force peak in the vertical GRF. In contrast to
running, the spring does not relax completely afterwards since, following take-off of
the opposite spring, the stance spring has to bear the full body weight. Consequently,
the stance spring starts to oscillate and further force peaks occur until the ongoing
rotational motion allows the opposite spring again to contact the ground initiating
the next double support. From this instant on, the effective load on the spring under
consideration gradually decreases (as the opposite spring takes over in supporting
the COM) and, finally, the spring leg completely relaxes terminating the stance
phase."

 

Mike

I was trying to get too much into a short space of time and the terminology isn't quite right but I wasn't quite sure how Bogert et al were defining power flow (I'll need to reread and be more precise in my next post) What I'm asking is how can the power in one direction greater than the power in the opposite direction?

If one segment has a force acting in the opposite direction to the the neighbouring segment then those forces must be equal (Newtons third) and so must the moments acting across the segment. This force in the open chain would be inertial but in the closed chain may be GRF on the foot. The elastic coupling of the joint does not change the kinetic equation but the kinematics may vary i.e. the displacement over time of each can be different. Therefore if the foot has no angular displacement then mathematically GRF produces no power in that segment. We could say that the frictional forces of GRF are doing negative work since they directly oppose those forces doing positive work. Just because the work is negative does not negate the work done by friction forces of GRF it just cannot be expressed as power (work/time) since it has no real displacement.

So as an example if you lift a weight from the ground then intuitively you are driving the weight upwards. However gravity is driving the weight downwards (negative work) but the displacement is still upwards (positive work). The time it takes to move the weight a certain distance indicates the power. Gravity therefore can apply no power.

Now if you take this same example but use a spring acting horizontally then the displacement = the power so if you apply a force to the spring and it compresses then you can calculate the power. The spring has no power but definentely affects the kinetics an kinematics of the action. To show the energy used in the system you need to know the initial resting constraints e.g the spring stiffness. So if the spring force and the applied force are equal then the work done over that time is zero and so there is no power. Yet there is energy used but no change in energy so therefore the power indicates the change in energy from one body to another.
So you could say the power also flows in that direction. I find that a little abstract, I think that right but I'm writing quickly here so my theory, reasoning or terminology might be off and so I'll go away and think about it tonight.

Cheers Dave

 

I have a question about functional application of the physics here. (am I barking up the right distal/proximal tree?)

When I have a physio patient sent to me for problems related to poor lower extremity posture (contractile dysfunction), I first try to see if the posture issue is coming more from poor femoral control or more from poor foot control.

The patient stands barefooted in a pair of shorts. We usually do this in front of the mirror so I can educate at the same time. Patient sqeezes buttocks, holds belly flat, and corrects pelvic tilt; and we watch to see if that changes the posture. Patient releases the proximal muscles and then corrects the foot and ankle posture with cuing from me and the mirror; and we watch to see what that changes.

Patient will be doing exercises both proximal and distal, but this helps us decide which to emphasize more.

Is it improper to base our exercise emphasis on a static position example?
Is it ok to emphasize proximal or distal differently with each patient?
I'm looking at the internally rotating femur as dragging the tibia around which drags the foot into pronation as my proximal-to-distal pattern, is that incorrect?

Patients are usually happy and discharged within 5 or 6 visits, but if it's possible to be more efficient, I'd certainly like to pursue faster results!

(I do encourage some folks to get inexpensive OTC insoles, and for some I apply temporary medial wedges as training wheels. Usually the pod or orthopod has already screened for the need for orthotics, but I will send the patient back to the pod if I feel they need real correction.)

 

I think you need to take a little more water with it.

 

I not necessarily disagreeing with you, but in the context of the Bellchamber paper how do you know that in these studies:

1. The foot orthotics provided an inversion moment that was sufficient to supinate the foot

or

2. The foot orthotics provided and inversion moment that got it below a certian threshold, that the proximal external rotatory moments supinated the foot

 

Craig:

Excellent question.:drinks

The proper view, of course, should not be a question of whether the leg drives the foot or the foot drives the leg since this view simply does not make any mechanical sense due to the integral mechanical coupling between the leg and foot. Rather, the proper view should be that due to their close mechanical coupling with each other, both the leg and foot influence each other's kinetics and kinematics in varying amounts depending on the activity and the individual.

Subtalar joint (STJ) supination can occur, in the weightbearing foot, for the following mechanical reasons:

1. An increase in external STJ supination moment (e.g. foot orthosis shifts ground reaction force more medial on plantar foot)

2. An increase in internal STJ supination moment from any number of sources including:

A. Increase in contractile activity of extrinsic STJ supinators of the foot (i.e. increase in posterior tibial, flexor digitorum longus, flexor hallucis longus, or gastrocnemius-soleus contractile activity).

B. Increase in contractile activity of muscles that shift ground reaction force medially on the plantar foot (e.g. plantar intrinsics to medial column have increased contractile activity which causes increased medial column dorsiflexion stiffness)

B. Increase in external rotation moment acting on tibia and fibula by way of talar trochlea (which may occur from thigh or hip/pelvic or trunk musculature that places an external rotation moment on the femur).


Now, given these various sources that may cause STJ supination, we then must allow for the approximate 10 degree of range of external rotation motion of the talus relative to the tibia within the transverse plane before the tibia is forced to externally rotate with the talus (from Chris Nester's research). Then once this approximate 10 degrees of "slop"is taken up with the talar trochlea, STJ supination should produce external tibial rotation.

So, the external tibial rotation that was seen to occur during the weightbearing activity could have come from any combination of the above external or internal factors that can cause STJ supination moment. It basically comes down to an equilibrium equation across the STJ axis where all the supination moments are added and all the pronation moments are subtracted to equal the net supination or pronation moment that has produced the observed motion of the foot and/or leg (Kirby KA: Rotational equilibrium across the subtalar joint axis. JAPMA, 79: 1-14, 1989). For example, some STJ supination moment from the orthosis may have been combined with some hip muscle contractile force that caused an external rotation moment on the femur that was also combined with a contractile force from the posterior tibial muscle that caused the net increase in STJ supination moment that resulted in the calcaneal inversion and tibial external rotation we saw during the observed weigthbearing activity.

The bottom line is that we know the foot orthoses can theoretically increase external STJ supination moment using the theory of STJ axis location and we have plenty of research now that shows that foot orthoses can alter both the kinematics and kinetics of the rearfoot. However, we as podiatrists, who tend to focus primarily on foot mechanics, must also realize that the foot is at the end of the relatively long kinematic chain where proximal influences can have a profound mechanical influence on whether the foot supinates or pronates during gait. Neither the foot by itself drives the leg nor does the leg by itself drive the foot, they both drive each other.

Best discussion of the year!

 

Thanks for the rest of the post Kevin with that and Dave´s post I think the fog is starting to clear.

would it be safe to say this? for anyone

Tibia internal and external rotation in CKC (closed kinetic chain)from a proximal aspect is most influenced by knee flexion/extension ( this is important for leg stiffness discussions)

STJ supination or pronation moments most likely to effect tibia internal and external roation in CKC would come from a Ground reaction force vector. or in treatment case and Orthotic reaction force

 

So what is the significance of the direction of power flow?

 

Can I ask another question...

if we take a spring as in Daves example and one side we have the tibia and the other GRF. If the tibia compresses the spring we have a positive powerflow ?

Now if this spring compresses but cannot be compressed anymore the powerflow would be in balance or 0 ?

say it takes 4 newton of force to compress and 4 seconds, said spring to where is cannot be compressed any more, we now add something which reduced the length of the spring it might take say 4 newtons of pressure to compress the spring but only 2 seconds to get to the balance or 0.

does that make sense?

so if so, the tibia internally rotates STJ pronates there would be positive power flow or proximal to distal power flow and a certain point the STJ will run out of ROM or STJ supination moments equal STJ pronation moments and the power flow must be in balance or 0 ?

if our device reduces the time it takes for the positive power flow to reach 0 would not the internal forces created by the body have a greater effect to create a negative power flow (distal to proxiamal) in this case ?

so in the study if the subjects had, good to increased ROM of foot and ankle joints the amount and timing of positive and negative flow would be different from those with reduced ROM of foot and ankle joints ?

so what we are looking at is another Zone ie Zones Of Optimal Power Flow ZOOPF at which timing and direction of power flow are important for the body preferred motion pathways.

and this would then fit with the spring mass model where positive power flow is associated with loading of the spring and negative power flow with energy return from the spring mass model.

ie knee flexion - internal tibia roation - STJ pronation proximal to distal power flow or positive power flow decreased leg stiffness

STJ supination - external tibia rotation - knee extension distal to proximal power flow increased leg stiffness.

This above discribed coulping or summation of force can able be effected through internal and external moments acting on individual joint not just from the most distal or proximal starting the chain reaction ?

??? this is thinking out loud I maybe :sinking: trying to get my head around it all.

 

Great discussion here.

I think I agree with Kevin that there is a large influence from both proximal and distal structures, and I think someone mentioned earlier in the discussion, that it may have more significance when discussing the specific phase of gait. I would think that from heel strike to foot flat that proximal structures will have a significant influence, but from foot flat to propulsion, that the effect of FFO will have a large effect on proximal structures.

There has to be a very large individual component with this also, and cannot be generalised to say that either proximal or distal structures are doing the same thing for everybody.

What I see clinically is that patients are very poor with their own rehab, and also it takes a long time to get good lumbopelvic muscular control. However, foot orthoses have a good clinical response in the PFS and aid in the lumbopelvic rehab... why not do both if the clinical examination warrants it?

 

Good point, Simon. What I should have said is that neither the leg nor the foot drives the other all the time. And, once I have a little more time, I want to more completely discuss the problems with the ideas, methods and conclusions of the Bellchamber/van den Bogert paper.

 

Good point Kevin. I was thinking that it might be interesting to explore this concept (of what drives what?) by using a different joint but still looking at the relationship between the foot and the leg. Could doing this make it easier for us to understand or might it add to our understanding of the original question?

What if we analyzed an individual in bipedal stance who is standing in their angle and base of gait and who then raises their heel and stands on their toes; and then allows the foot to return to the original position? We have four phases to consider that are different mechanically. The first phase is the relaxed stance phase. The second phase is the upward phase in which the ankle is actively plantarflexing in order to raise the center of mass. The third phase is instant the center of mass reaches its maximum height and there is no motion at the ankle joint. The fourth phase is the return phase in which the ankle is actively dorsiflexing in order to enable the feet to return to their original resting stance position.

So if we look at each phase and ask the question does the foot drive the foot, leg and body up, or does the leg drive the foot, leg and body up? Conversely, what drives it back down? This is an entirely closed chain example of the relationship between the foot and leg and I would like it to focus on ankle joint motion.

I'm willing to bet that if we explore this example, we will find as Kevin implied above, that there is a basic flaw in the question itself. I think we need to expose that flaw better than we did in the original discussion of what drive what? Anyone care to take a stab at this other example of the same concept?

Respectfully,
Jeff

 

Jeff, I've said before that I'm rubbish at energetics- note to self, do some learning. Lets see if I can start that learning here:

1. Relaxed standing: assuming no muscle contraction power = zero. If postural control being maintained via muscle action= negative power- power flows from proximal to distal.
2. Tip-toe rise- equivalent to propulsive phase, so given the power profiles from the paper under discussion, we should see a big negative peak- power flows from proximal to distal.
3. Hold the position, awkward because no change in position- hence no work, however, muscles must be contracting to maintain the position- I'm guessing though that due to the way it's calculated we'd see a zero????

4. Lowering back down, eccentric work by the plantarflexors- I don't know, should be another negative peak because the same muscles are doing the work but this time being assisted by gravity- so it depends on the rate of lowering and the muscle force being employed??

Somebody learn me about it- I need to do some basic physics reading, but there you go, head on the block; for all of you that have been waiting to shoot me down, now would be a good time.

 

Simon:

Don't have a lot of time now...celebrating my 30 year wedding anniversary tonight with my lovely wife...but you may want to read this classic paper by David Winter first to get a better handle on things.

 

The method used in the paper was that used for angular motion which is power = moment x angular velocity.
There is an equation for linear motion and that is: power = force x time.

Dave, I agree with most of what you said, but have a few minor points. "We could say that the frictional forces of GRF are doing negative work since they directly oppose those forces doing positive work." Since work = force x distance, unless the foot is sliding there is no work done because the distance = 0. Now, the question is whether or not the there is work done by the ground between heel contact and foot flat. There is angular motion of the foot relative to the ground. (With "rolling of the heel" there is a little bit of translational motion.) The work of the ground on the foot may be negligible. During this time at the ankle there is power flow from the leg to the foot. The anterior tibial muscle is creating a dorsiflexion moment at a time when the foot is plantar flexing.

Again the power equation for linear motion is power = force times time. As you drop the weight the force of gravity is applied over time and the weight gains kinetic energy over that period of time. So, gravity can change the energy.

I'm not sure I'm entirely correct in all my analyses either. It's really hard to determine where the energy comes from as the power flows.


Regards,
Eric

 

It sounds more like you are in the realm of patient outcomes than in the realm of physics. If you get the patient to increase strength in core muscles and they feel better after that you have a success. Explaining it in terms of physics may be entertaining, but not always necessary. There are so many variables between the foot and the trunk, you can come up with an explanation, but it is really hard to be sure that you are right.

Eric

 

Agree entirely.

Stand up now while staring at your computer and try it yourself. Don't you just love the KISS principle?

 

But thats static stance. How do you explain the results of the above study re the tibia doing the driving during dynamic gait?

 

Re: Open letter to Craig Payne

Re: muscle activity in response to orthotics.
The arch of the foot would hurt if the muscles tried to lower the arch when standing on an orthotic. I agree with Jeff's comments below, that part of the effect of the orthotic is to apply pressure to the arch. However, another part of how orthotics work is a change in muscle activation. Some patients will notice muscle soreness when first using orthotics and there are other observations that support this idea. One observation that would support it is what we've been talking about on this thread. If you saw an increase in power with increase in external leg rotation that would be the muscles supplying that rotation.

Re Arch height of orthotics:
Most orthotics, maybe even the vast majority, made from neutral suspension casts will have higher arches than the foot in static stance. (I don't recall if a study has been done to compare the height of the arch in static stance to the height at midstance in gait. I would bet that it is not too far off, in most feet.) So, what we are talking about is a matter of degree between neutral suspension casts and MASS casts. I've made myself some orthotics from full weight bearing foam box casts and they just don't push in the arch enough.

Re Bruce's quote: "Also, the muscles are no more than supporting players stabilizing the lever that is the foot that the body must vault or pivot over at this time."
I think we have talked about this before in does the swing leg power gait debate. Joint powers answer this question as well. Winter's papers have shown that some of the time the ankle pushes the swing leg forward.

``

Agreed.

Eric

 

The question was not whether or not the motion was coupled, but what drives the motion.
Eric

 

I was just saying I agreed with Brad Randazzo. I didn't say I had all the answers.

Cheers,

 

I'll take a stab.

Tibial internal and external rotation is probably not related to knee flexion extension. There was a theory proposed that the knee flexion was coupled with internal rotation. A paper that I saw that I thought refuted this notion looked at the envelope of motion of the knee. (Sorry don't have site at this point.) As the knee went from fully extended to partially flexed the amount of internal and external rotation available increased. From that you can infer that the direction of motion seen depends on the forces acting on leg. That is if you observed internal leg rotation with knee flexion it is because the leg was being torqued in that direction at a time ligaments allowed more motion because of the knee flexion. If the torques on the leg were such that the knee would go external as the knee flexed you would see external rotation.

This is also another reason to question the proximal control of motion at the foot. The knee is not a very good torque translator. The tibial surface at the knee is essentially flat in the transverse plane. How do you stop transverse plane motion on that flat surface. In other words if you apply a moment to the femur, you have to wind up the ligaments of the knee before the moments applied to the femur will be high enough to overcome any internal rotation moments acting on the tibia from below.


RE: STJ moments and internal and external rotation.
Yes moments about the STJ from ground reaction force will influence leg internal and external rotation of the leg because of STJ coupling. (Better coupling than at the knee) However, moments from the lower leg muscles are also very important in causing internal and external rotation of the tibia.

Remember that old test that people used to do where they would have people rotate their pelvis to show that the twist goes all the way down from the pelvis to cause external rotation of the leg on one side and internal rotation on the other. Well, if you watch people do the pelvis twist you will see that they will contract either their peroneal muscles or their posterior tibial muscles to achieve that twist. Try doing the pelvic twist without contracting those lower leg muscles. It starts to get pretty uncomfortable at the knee.

Regards,

Eric

 

It's helpful for entertaining academic debates.

I am curious about the correlation between orthotic success in reducing symptoms and ankle joint sagittal plane plantar flexion power. I think an increase in plantar flexion power is what they are seeing with their force measurements.

Eric

 

Thanks for that Eric,
its got me thinking about some of the stuff Craig has said in realtion to patellofemoral pain syndrome There seems to be 2 sides on the debate.

1 strenghten gluteal
2 use of orthosis
there is evidence for both having positive results but not better with using both treatments plans at the same time.
So the question becomes why ? ( well it was for me)

I came up with this maybe the cause of the patellofemoral pain syndrome be seen from 2 different views or effects on the knee Q angle and all the other causes such as muscle inbalance etc.

1 femoral torsion and angle of trochanter

2 Tibial Torsion.

This could be away to determine which treatment plan is more likely to succeed.

ie if the femoral bone is the cause then an orthosis is less likely to succed, due to the poor joint coupling that you discussed in the knee joint.

and therefore vice versa

Tibial Torsion cause then increase in gleutal strenghth less likely to succeed.

 

Simon,

Sounds about right to me. So the ankle joint plantarflexors are proximal to the ankle joint but their attachment is distal to it. So the muscles are the motors that drive the system up in opposition to the forces of gravity, and they are proximal to the axis. But they must attach distal to the axis to create a plantarflexion moment at the ankle joint that is capable of lifting the heels off of the floor. If we severed the attachment (i.e. achilles tendon) then firing of the plantarflexors would not produce an ankle joint plantarflexion moment.

Lowering back down is accomplished by the eccentric contraction of the plantarflexors. But what if the individual passed out at the top of this maneuver and in theory, no more muscle action had occurred. The person would probably still experience dorsiflexion of the ankle joint but it would occur in a rapid manner in the process of the individual collapsing to the ground. This would occur without eccentric contraction but it couldn’t be initiated without the previous phase.

Here is another analogy. A car dives up and down hills. What drives the car, the engine or the wheels? The car can start out going downhill with the benefit of gravity. But unless the engine is turned on, it can’t start to move on a flat surface or start out going uphill. It is a dependent system. I can start the engine but unless the drive shaft is connected, the car can’t move in spite of the power of the engine. So the engine doesn’t drive the car in and of itself, but it does provide the power in the same way that muscle power in the leg helps drive motion at the ankle and the stj.

STJ pronation is often a decelerating function (i.e. reducing the influence of gravity) while stj supination is typically an accelerating function (overcoming the influence of gravity). I can drive my car up the hill and then coast down. I can even apply my brakes on the way down. But I can’t do this unless my car is first set in motion by the power of the engine. This was the purpose of my analogy using the ankle joint. Thanks for your contribution to my effort to make my point.

Respectfully,
Jeff

 

Jeff:

In your example, the power flow is from the leg to the foot (i.e. positive power flow) for ankle joint plantarflexion since the increase in internal ankle joint plantarflexion moment from the gastrocnemius-soleus complex undergoing increased contractile activity is greater than the external ankle joint dorsiflexion moment from ground reaction force (GRF) acting on the plantar forefoot anterior to the ankle joint axis.

When the ankle is stable, with no angular velocity, either in relaxed bipedal stance or at the peak of the plantarflexed ankle position (i.e. at the peak of "tip-toe standing"), there is no power flow since there is no ankle joint motion. The equation for power is P = M x w, where P = power, M= moment of force and w = angular velocity of joint. Therefore, if the joint is static, with no angular velocity, then there can be no power or power flow.

When the ankle is dorsiflexing from the "tip-toe standing" position to the relaxed bipedal stance position the power flow is from the foot to the leg (i.e. negative power flow) since the external ankle joint dorsiflexion moment from GRF acting anterior to the ankle joint axis is greater than the internal ankle joint plantarflexion moment from gastrocnemius-soleus complex contractile activity.

Therefore, for example, if there is no rotational movement measured in the calcaneus when the subtalar joint (STJ) is maximally pronated, then there is no joint power and there can neither a negative nor a positive power flow. One can begin to see, using such examples, how there may quite significant magnitudes of opposing moments acting with the foot and lower extremity during weightbearing activities (e.g. increased interosseous compression force within the sinus tarsi due to medially deviated STJ axis), but since the joint is in rotational equilibrium with the angular velocity of the joint = 0, there would be no joint power measured no measurable power flow. Therefore, we can begin to see the serious limitations with using the concept of power flow to determine how foot orthoses "work" or determine how pathological mechanically-based conditions occur in the human foot and lower extremity. Obviously, the authors and reviewers of the Bellchamber and Van Den Bogert paper did not appreciate such serious limitations in using this type of mechanical analysis to speculate on whether foot orthoses can be "successful" at treating such conditions as patellofemoral syndrome.

When I get more time, I will provide further clarification.

 

I spoke to one of the folks in the Foot and Ankle Research Team (FART ), The bone pin folks based in Sweden. Which most on here recognise as C Nester is involved in.



He thought that the paper below from 2008 p 96 shows the graph of timing which might add to some of the discussion. He also said it´s not as clear as people think when it comes to what drives what. Which is clear from the discussions so far.

 

That's an acronym they can't of fully thought through beforehand surely...

 

No the opposite I think they though long and hard about it.

 

Temporal couplings between rearfoot–shank complex and hip joint during walking
Thales R. Souza, Rafael Z. Pinto, Renato G. Trede, Renata N. Kirkwood and Sérgio T.
Clinical Biomechanics (Article in Press)

 

This is one of those age old questions that could remain unanswered - just like:

"Which came first - the chicken or the egg?"
or
"Who would win in a fight between Bruce Lee and Jason Bateman's fictional character in Teen Wolf Too?"

After much pondering and procrastination, I can't help but feel the answer lies somewhere in the following rousing song:

"Hamilton - Thou art highest of them all
We, your loyal subjects - Are listening for your call
Proud are we of your emblem - Of your columns straight and...
White! White!
So let's get in the ring, boys - And FIGHT FIGHT FIGHT!"

 

Bob you maybe correct about the chicken or the egg, I was just waiting in hope that Ian can post up the full text when it is available to have a read.

ps Bruce lee

 

I understand your point, but Jason Bateman's fictional character from Teen Wolf Too is a werewolf! He could somersault into a boxing ring and knock an ordinary human out with one punch!

Now, I've seen Bruce Lee's one inch punch, but he could never make his eyes go a bit red and talk in a scary deep voice to get what he wanted! My money is on Jason Bateman's fictional character from Teen Wolf Too. At first I thought it may be a close contest, but on reflection, it'd be over in seconds - with Jason Bateman's fictional character from Teen Wolf Too the victor!

 

It looks once more like a classic case of understanding the STJ axis in its entireity for one to be able to understand the true nature and workings of the foot, hope i wont sound like a nutter to my colleagues who are always playing catch up!!!!

 

Podiatrists you are nutters really, after reading all this stuff now thats my professional diagnosis......"if you put a 10 degrees valgus wedge and the tibia rotates it means the foot has moved the tibia???? cummon guys!! what happened to the wegde and the GRF?

 

That's great, until you put a varus wedge under the heel and the rearfoot eversion increases etc.. just like here: Orthotic control of rear foot and lower limb motion during running in participants with chronic Achilles tendon injury.
Donoghue OA, Harrison AJ, Laxton P, Jones RK.
Sports Biomech. 2008 May;7(2):194-205