Hip flexor function at 90 degrees of flexion

[Greg Lehman]

Hi,

I just wanted to test the strength of an idea of mine against the fire of this board. As preface, this question has nothing to do with pain only functional anatomy.

Shirley Sahrmann and other strength coaches/physios inspired by her have argued that at 90 degrees of hip flexion only the Psoas and Iliacus are capable of creating a hip flexor moment. The rationale is that the TFL, Sartorius and Rectus Femoris do not have a moment arm at this angle because their distal insertion is now below their proximal insertion.

I have never been able to visualize this idea and don't find it biological plausible. It spurred me to write a blog post here:

http://thebodymechanic.ca/2012/04/23...common-belief/

Why I think this is significant because the theory spawns a test for the psoas/iliacus that is supposedly effective in finding dysfunction in those muscles (people go on to argue how this leads to pain but lets just avoid that for now). I find that this test and the ideas behind complicate hip function in a way that is not necessary. This again allows some therapists to look like they have some special knowledge and those that do not follow this path may thus be judged uninformed and lacking. I see this occasionally (ok, more than occasionally) and I don't particularly appreciate it.

Thanks and please let me know if I'm wrong,

Greg

[gollygosh]

Greg, I tend to view the tests to differentiate hip flexors as less than necessary. Bodies don't move in isolated patterns. If these means I can't test a muscle with precision then so be it.

Geralyn

[Milehigh]

Okay,

I may have differing opinions than others at SS....but I do think you gain a lot of information by hypothesizing which tendencies a body has for movement. I do believe there is no single movement, position or posture that is pathological. However, when a pattern of movement is so stereotypical that it excludes other possible movement responses then the body has poverty of choice to solve movement related problems. That is why novel movements are so important because they educate the CNS/movement system that there are other possible choices, combinations and sequences of muscles and joint configurations. Therefore, looking at someones general pattern of movement, detecting a stereotypical response can be an avenue for directing a specific novel movement rather than just any random movement.

I also know that you cannot isolate muscles. However, positionally you can use proportionally a greater amount of one muscle than another.

I am of the opinion that if you rotationally bias the hip you can alter this proportional muscular usage. Therefore in a sagital plane hip flexion if you flex the hip with internal rotation you will use the TFL, if you do it with external rotation you will use psoas + adductors, mid-line is probably a combination of both but greater proportion of RF. There are plenty of studies of other body parts showing that a change of rotation will generate differentiate EMG firing patterns of muscles. I am not aware of any of the hip. Partly because the psoas is a terribly invasive muscle to study.

I watch people move, I see people rotate and flex and extend in sterotypical ways. I use combinations of cueing (tactile and verbal), education and very, very, very specific exercise to give the pt. more solutions to solving movement problems. Often not because one movement pattern was "bad" but they just did not know how to move any other way. I believe rotation is a very powerful selector of proportional use of a muscle for a given pattern of movement.

The complexity of muscles should never be reduced to simple 2D lines and any biomechanist who does this ignores individual variation. I am not sure you can even pin down an exact attachment site of the TFL as it attaches to the entire fascia, of the leg. Therefore any therapist or clinican whom builds an entire PT theory on some very limited bio mechanical information is therefore going to be greatly limited.


Eric

[Greg Lehman]

Eric,

First thing, I hate you for where you live. I'm ridiculously envious.

Second, I love you for your first paragraph. I will be stealing and morphing your words for years.

Last, I agree with your final synopsis. But when you write

I am of the opinion that if you rotationally bias the hip you can alter this proportional muscular usage. Therefore in a sagital plane hip flexion if you flex the hip with internal rotation you will use the TFL, if you do it with external rotation you will use psoas + adductors, mid-line is probably a combination of both but greater proportion of RF. There are plenty of studies of other body parts showing that a change of rotation will generate differentiate EMG firing patterns of muscles. I am not aware of any of the hip. Partly because the psoas is a terribly invasive muscle to study.

I pretty much disagree with this but don't want to make a big deal about it because I want to focus on the 90 degree of hip flexion theory. However, to substantiate my massive blast (but kind) against your idea I would stress that we can't put a lot of weight into changes in EMG amplitude. I spent a decade using this as a primary outcome measure for my research and know how limited it is. For example, if you flex the hip with IR your TFL will shorten and you will get a greater amount of EMG. This does not mean that it is contributing a greater amount of force just that we have recorded greater amounts of EMG. So many factors influence how much EMG you measure under two electrodes. Small movements, changes in fat distribution that occur with movement, skin folding with movement etc, all influence muscle EMG amplitude and it is not a good surrogate for force. So, while changing the hip IR might change the line of pull of the TFL it might also change all the other factors that influence EMG amplitude. Its tough to tease out the differences. Hence,the rationale for the post.

I am in agreement with the TFL having a broad insertion but I think that this would strengthen my argument that its moment arm is still in existence with flexion greater than 90 degrees.

Anyways, thanks for the input. There is a lot to discuss biomechanically but probably none of it helps a patient get better as your post illustrated perfectly.

BTW, I went to your website from my comment section and it did not appear to be working. Under construction?

Greg

[mrupe82]

"Shirley Sahrmann and other strength coaches/physios inspired by her have argued that at 90 degrees of hip flexion only the Psoas and Iliacus are capable of creating a hip flexor moment."

I know you don't want to hear this but, who cares?

Their argument may be grounded by the rectus femoris attachment at the AIIS. From a purely flexion argument and line of force, it no longer has a distance from the fulcrum rendering it obsolete.

From a physics standpoint, any muscular attachment that has a distance from the fulcrum will create a moment of force, even if it is minimal. In the end it's splitting hairs, not clinically relevant, has not improved outcomes and allows for physical therapists to sound smarter they need be while making money on the weekends. I wish Shirley would grasp hold of her PhD in neurobiology and back off the biomechanics. I think the profession would benefit much more.

[Greg Lehman]

Matthew,

You are making a point for me about why it is important.

If i am right i want people to forget about this type of thinking. I want athletes to train hip flexor strength not because some invalid tests says it is weak but because that is a movement they should do. For people in pain, i want them to move and not to think about their oh so terribly dysfunctional psoas.

I know this can seem academic but i think it is the start of the wedge. Questioning the buomechanical model with biomechanics can lead to an openess to other ideas of explaining phenomenon (e.g. A neurofriendly approach).

Anyways, any data suggesting that i am wrong. As far as i know the aiis is still superior to the axis of rotation.

Greg

[Milehigh]

However, to substantiate my massive blast (but kind) against your idea I would stress that we can't put a lot of weight into changes in EMG amplitude. I spent a decade using this as a primary outcome measure for my research and know how limited it is. For example, if you flex the hip with IR your TFL will shorten and you will get a greater amount of EMG. This does not mean that it is contributing a greater amount of force just that we have recorded greater amounts of EMG. So many factors influence how much EMG you measure under two electrodes. Small movements, changes in fat distribution that occur with movement, skin folding with movement etc, all influence muscle EMG amplitude and it is not a good surrogate for force. So, while changing the hip IR might change the line of pull of the TFL it might also change all the other factors that influence EMG amplitude. Its tough to tease out the differences. Hence,the rationale for the post.

I agree 100% EMG and force are not well correlated. However, my point was more theoretical. If you change the rotational aspect of a joint and have the distal segment of the bone move through the same straight in this case the hip. You will use, and fire a different combination of muscle patterns and thus proportionally this will be different than before.


There is probably no way to measure in vivo forces accurately, esp to compare the relative contribution of the psoas versus the illiacus and therefore biomechanics inevitably relies on computer modeling which is relatively quite limited. Total force output will always be a contribution of many muscles and the greater total force required you will get overflow recruitment of opposing muscle groups to stabilize vectors of force away from the main vector of force generation.

I agree this is a very complicated issue.

I disagree with Matthew on its importance. Lets just not go building an entire treatment rationale on it.

Thanks for the kind words regarding my previous statement. I appreciate the crispness of your thought in your blog. There is a place for biomechanics we just have to understand its limits. I think this the prob with many pseudo theories that claim biomechanical rationale. Is that people whom come up with them don't actually know or appreciate the limits of biomechanics.

Eric

[CDano]

Since we do a lot of deep hip flexion in yoga I've has a lot of personal experience with this.

Long before I knew anything about Sahrmann I'd come to a similar conclusion from observing carefully how I got into a very deep forward bend and what was going on with my students.

At the end range of movement the RF and TFL do need to relax to get one deeply tucked in against the legs. I've also seen many students with ASIS pains and they would often have some issue with the coordinating the movement to deep hip flexion and were trying to use RF and TF from start to finish. This lessened their ROM and eventually could lead to a pain situation.

To say TFL and RF stop contributing at 90 degrees might be a bit much, but there is certainly, from my experience a good deal of coordination that one can produce throughout the entire hip girdle to create deep hip flexion.

[Randy Dixon]

Eric,

Did you know your website is in Latin? And they said they don't practice witchcraft here. What other reason could it be?

[amacs]

Off at a tangent perhaps Greg but given your focus on running athletes is hip flexor strength really that important?


regards
ANdy

[Milehigh]

What you don't read latin. Yeah I am still in development with my website. I am prob 2 mo from completion of the basic architecture of it. Some things get bogged down when you do it yourself.

Cdano, I think you have a great observation there. Is what your talking about with yoga a position where your pushing the body into the hip using the ground as a lever point aka pigeon pose. Or something else like it without the extreme end of ER?

I think a concentric pattern versus an actively relaxed one with passive movement would have drastically different firing patterns as you observed and even agonist contraction of a muscle may limit motion via the compression and translation it may produce @ the joints.

Eric

[Greg Lehman]

Hi ANdy,

You asked

Off at a tangent perhaps Greg but given your focus on running athletes is hip flexor strength really that important?

Absolutely, I say. Probably the most important. There being a few reasons:

1. Running is more pulling than pushing. Halfway through the gait cycle the extensors of the stance limb shut off...this is called the extensor paradox.

2. Recovery of the stance leg (the start of the swing phase) is preceded by strong hip flexor contractions. it is this hip flexor contraction and subsequent contraction that causes the knee to flex. Thus we don't even have to flex our knees actively they happen passively.

3. Comparing elites from even very good runners we say greater hip flexion during the swing phase and often less extension.

4. The quads act as brakes rather than "pusher offers". Calf flexors are still important though when it comes to increasing speed.

5. Faster sprinters have larger hip flexors than less fast sprinters

Here are a few links from my site to waste 15 minutes on:

http://thebodymechanic.ca/2010/12/20...nsight-part-2/

http://thebodymechanic.ca/2010/12/20...soas-part-one/

http://thebodymechanic.ca/2011/02/02...he-hamstrings/

[Jackson]

Originally Posted by Greg Lehman

If i am right i want people to forget about this type of thinking. I want athletes to train hip flexor strength not because some invalid tests says it is weak but because that is a movement they should do. For people in pain, i want them to move and not to think about their oh so terribly dysfunctional psoas.

Greg

Greg,

I agree with the last sentence. Can you expound on the sentence I've bolded?

Nick Nordtvedt

[John W]

I know this can seem academic but i think it is the start of the wedge. Questioning the buomechanical model with biomechanics can lead to an openess to other ideas of explaining phenomenon (e.g. A neurofriendly approach).

This is precisely what Jason Silvernail, Supreme Rule of the Universe (or something like that), did in his recently published research study on knee joint mobilization.

It's a very smart approach, but certainly not the only way to traverse the chasm.

[Greg Lehman]

Hi Nick,

You wanted me to expound upon this:

I want athletes to train hip flexor strength not because some invalid tests says it is weak but because that is a movement they should do.

For runners I want them to train everything regardless of what an assessment says. Say, you believe in movement pattern tests (e.g. Janda's stuff) and the athlete performs beautifully. I would still advocate doing all of the exercises/movements that you might choose if the test was considered "poor". The "corrective exercises" are still good in building capacity, tolerance or performance and are I believe are beneficial regardless of what an assessment tells. So what if the assessment says you are already good...you can be better or your train the movement because the assessment does not tell us enough about the reason for doing the exercises. The assessment does not tell the entirety of the movement experience. Just some snippet of function that someone thinks is important.

Specifically, in respect to hip flexors, Hip flexors and all associated muscles and nervous system commands are used in running and I therefore advocate that they build the capacity of these muscles, movements and neuromuscular engine. Not in anyone position but in all positions. Lets train the whole potential of your joints and nervous system.

All movement is good (I really believe that, have felt it for decades but have struggled against conventional beliefs on "form", injury and performance). I have a bias to believing that strength training improves running performance. Whether it prevents injury is another topic but I tend to believe that it may help some individuals as well, regardless,I think increasing hip flexor movement is good in and of itself for a happy body

I've linked to a few blog posts in a previous post about what I see as the importance of hip flexion for runners and athletes.

Does this help? Or where you looking for me to address something else? Thanks for the opportunity to think about this...it helps me understand my thought process and rationale as well.

Greg

Greg

[John W]

I have a bias to believing that strength training improves running performance.

I think that's a pretty safe "bias". Jakalski, you out there?

[amacs]

Hi Greg

interesting area, some initial responses

1. Running is more pulling than pushing. Halfway through the gait cycle the extensors of the stance limb shut off...this is called the extensor paradox.

I am not sure that the extensor paradox actually demonstrates that pulling is more important. Are you writing off the mass spring model?

2. Recovery of the stance leg (the start of the swing phase) is preceded by strong hip flexor contractions. it is this hip flexor contraction and subsequent contraction that causes the knee to flex. Thus we don't even have to flex our knees actively they happen passively.

No issue that hip flexors fire just their importance which relates to the next point

3. Comparing elites from even very good runners we say greater hip flexion during the swing phase and often less extension.

We do but I am not sure that it follows that is due to psoas/iliacus flexor complex. We also see longer stride lengths but that isn't due to "taking" longer strides rather increased GRF.

4. The quads act as brakes rather than "pusher offers". Calf flexors are still important though when it comes to increasing speed.

In what direction are they breaking - and more importantly why?

5. Faster sprinters have larger hip flexors than less fast sprinters

I think if we looked at sprinters we would find most of their muscles were larger, the difficulty is proving what that means.

Here are a few links from my site to waste 15 minutes on:

http://thebodymechanic.ca/2010/12/20...nsight-part-2/

http://thebodymechanic.ca/2010/12/20...soas-part-one/

[url]http://thebodymechanic.ca/2011/02/02/running-biomechanics-the-knee-is-not-flexed-by-the-hamstrings/

I don't think that is a waste although it did take more than 15 minutes!


Where is Ken!!!

regards

ANdy

[Greg Lehman]

Hi ANdy,

1. I wrote a little loosely if it looks like I wrote off the spring mass model. My statements can be tempered. It is a theory that the forward leg swing may help with opposite leg extension. You are write that the extensor paradox does not prove that hip drive is important. I will review some of the joint moment data and get back to you. A recent paper by Hamner and another by Schaeche is edifying here. As well as the work from Ralph Mann in the eighties who has greatly influenced me.

We do but I am not sure that it follows that is due to psoas/iliacus flexor complex. We also see longer stride lengths but that isn't due to "taking" longer strides rather increased GRF.

I see what you are saying. Greater hip flexion is because of greater speed which is due to a greater push off not necessarily because of any special contribution from the swing psoas (i.e. the greater hip angle just naturally follows from a longer stride). Again, looking at the joint moment and power data I need to do. In the study I was thinking of there wasn't longer strides in the more elite group running at the same speed. They actually had a higher cadence with a greater hip flexion angle. I am at work without the reference but I can post it.

in what direction are the quads braking

Not sure I follow. I believe that they are involved during the initial phase of foot strike. This is based on the work of both Hamner and that of Schaeche (I will post these as well) who I believe both concluded the similar functional roles of the quads. Essentially, the EMG of the quads does not increase with increasing speed and I believe that the knee extension moment does not increase with increasing speed during the push off phase.

Anyways, can anyone rule out that or in that the Psoas and Iliacus are the only hip flexors greater than 90. We should start a running biomechanics thread and I can post my articles in the sounds of silence. This is a great and edifying diversion. Thanks for keeping me on my toes ANdy et al.

greg

[Jackson]

Thanks, Greg. This is what I wanted to understand better.

Nick

[amacs]

Thanks for the reply Greg

Not sure I follow. I believe that they are involved during the initial phase of foot strike. This is based on the work of both Hamner and that of Schaeche (I will post these as well) who I believe both concluded the similar functional roles of the quads. Essentially, the EMG of the quads does not increase with increasing speed and I believe that the knee extension moment does not increase with increasing speed during the push off phase

I wasn't quite sure what you meant by braking here, did you mean a force applied in the opposite or a tangent of it to the direction of travel or did you mean braking as in decelerating the downward momentum of the mass at foot strike. I think it could be postulated that the braking moment may be necessary in order to generate and appropriate GRF to induce fwd leg swing of the trailing leg. THe current emphasis in reducing braking forces by some coaches may actually I suspect be working against the runner.

If I recall correctly extension angle diminishes with increasing speed which would fit with increasing active "stiffness" of the system methinks.

As for the above 90degree discussion for my money it isn't a great test that if investigated rigorously would reveal the usual results of highly varied mechanics which are solved differently by different individuals and even in different ways by the same individual at different times. On that note your glute/hamstring paper did you test ppl more than once and on different occasions?

regards

ANdy

[Ken Jakalski]

I'll chime in here quickly. It's the biggest meet of my season tomorrow (our 45th annual Carlin Nalley Invitational), and the I'm still having to host two other big meets in the next three weeks. But I'm retiring after thirty-seven years at the end of this month!

On the hip flexor front. Before my visit to the Harvard locomotion lab in 2001, I had believed I was onto something regarding the importance of hip flexor strength for sprinters. In fact, I was a big proponent of weighted thigh trainers desgined by the late Leigh Kolka. In fact, I was asked by Leigh to come up with some corroborative reasearch to support this eveidence. There was always something to be found, but that material did not reflect what we've learned about high speed running in the past ten years.

You can see the attention this focus on hip flexors received in the surrounding newspapers. I certainly got some good press. However, what I learned about what occurs in high speed running, first at the Harvard's Concord Field Station and later at Rice University, really changed my thinking--and pointed out how little I really knew about the mechanics of running after twenty-five years as a coach.

For example, here was the view of the locomotion guys after I thought I had made a compelling argument:

"This [my approach] is typical of the conceptual paradigm that most human and applied biomechanists bring to these issues. In my opinion, they begin with a mistaken assumption - that is, that running fast requires forward propulsion. Once a runner is up to speed, this is simply not true- the net requirement for forward propulsion is zero if a runner's speed does not change. Any change in speed is fully accounted for by the interaction between the foot and the ground (ignoring wind resistance which is significant for elite sprinters biut nonetheless largely secondary.

What propels the body forward is horizontal kinetic energy that is already present, the extensor muscles essentially impart this to the runner by applying force in a backward direction against the ground as the runner accelerates. After the 1st 10-20 meters, the runner bounces along the ground in a manner analogous to a super ball or skipping stone.

In the latter analogies, the only acceleration occurs when the hand imparts the velocity to the ball during the throw, and the ball bounces along, simply maintaining it's speed - no propulsion whatsoever after leaving the hand but bouncing forward at whatever speed."



"This focus on hip flexors makes little sense even apart from the above consideration. There is very little muscle there, a small fraction of the mass vs. the hip extensors, and indwelling electrodes indicate these muscles do not even fire during moderate speed running. They do fire at high speeds but this has little to nothing to do with providing propulsion."

[Milehigh]

Should we differentiate between phases of running. Because as Ken pointed out there are drastically different muscle patterns involved with different types of running.

If we have a look at the 100m
1. Drive phase
2. Transition - from drive to upright
3. The rest of the race (i.e. running)
4. Final drive

I am guessing the length of the race has a big impact on the proportional impact of the above mentioned four phases. If you are a short distance sprinter then your drive phase proportionally is going to be drastically more influential on the outcome than the 1500m

I would make the argument that hip turnover and therefore hip flexor acceleration is tremendously important @ the the drive phase, when the sprinter is trying to strike the balance between the most forward lean possible and foot turnover. I am not sure if there is a study that looks at this.

If you break down the activity in most "organized" sports I would guess that patterns of acceleration between 5 and 10m are the most critical and then decreasing importance after that.

While those patterns probably are not exactly the same as the drive phase of 100m sprinter. I am sure they have more in common than the cruzing muscle pattern of 1500M runner.

Ken congrats on retiring sounds like you have put together quite the career.

[Milehigh]

btw,

I have always thought one of the best ways to train hip flexor turnover is to sprint up hill on a loose surface--Walter Payton style. You can't push off because you will go nowhere.

[Greg Lehman]

This post is getting fun. As I read it again it looks like a set myself up as a strawman. I love hip flexion during running and think it is important but I don't think it is everything and Ken's post certainly illustrate this.

As for running being about pulling and not just pushing (I think I said more pulling but this is debatable and I should be chastised) I also view the Glut Max as "pulling" the hip back to neutral when the hip is flexed.

However, I will admit I am caught up on this pulling despite two great researchers not supporting my ideas within email exchanges.

Below are two very helpful email exchanges I had last year with two very impressive researchers. I won't name as I never asked permission to quote them. This is what the first wrote me more than a year ago:

Hi Greg,
Thanks for your email and positive comments.
Regarding your specific question........hamstrings EMG activity is virtually silent at toe and early swing, so from such data it would appear that the rapid knee flexion that occurs during early swing is not "actively" produced by the hamstrings. Rather it would seem that the knee flexion occurs largely as a by-product of rapidly pulling the thigh upwards into hip flexion. This is precisely the point in the stride cycle where we predict peak loads to occur onto the rectus femoris. This is because at this time the RF is reach peak muscle-tendon length and there is a large amount of power being generated at the hip (which the RF would contribute to) whilst at the same time there is a large amount of power being absorbed at the knee (i.e. the knee extensors (RF/quads) are working eccentrically to 'control' the rapid knee flexion that occurs during early swing).

So.....rapid knee flexion during early swing is not actively produced by the hamstrings but rather is a by product of rapidly flexing the hip. Inverse dynamics estimates that the knee extensors at this time work eccentrically to absorb energy about the knee joint and thus 'control/decelerate' this rapid knee flexion motion

I then asked

Based on the idea of the extensor paradox (emg silence in the extensors in late stance) and your kinetic findings is it also appropriate to describe ruinning and increasing ones speed to be more a function of "pulling" (I.e. We pull the hip forward and this contributes to toe off and we pull the hip back toward the ground at late swing) rather than "pushing" (ie. Positive work by the plantar flexors and quads).
I have quietly taught running patients for years this idea, I think based on Cavanaughs and Mann's work but I've never been fully confident in it with out a power analysis dumbed down for me

.

And he wrote:

Hi Greg,
Just some further thoughts....
Increasing running speed is brought about by two inter-related strategies:
(a) we can use our muscles to push on the ground harder (ie increase stride length) and/or
(b) we can push on the ground more frequently (ie increase stride frequency)
As speed increases froma slow jog, we tend to increase stride length initially, but toward top end speeds of running our ability to push on the ground harder becomes limited, so we then start to become more reliant on pushing on the ground more frequently.
I strongly encourage you to read the 2 attached papers by Weyand et al. very carefully. These are very well designed studies and will be of great benefit in helping you understand both mechanisms for increasing running speed as well as the factors which likely limit top speed.

All in all, it seems that what ultimately limits top speed is an inability for the stand phase extensor muscles (namely the calf muscles) to push on the ground harder. They have the capacity to do so, but because contact times become so reduced at max speed, the calf muscles run out of time to produce their maximal forces.

Have a read and see what you think.

And here is what I wrote to a gait researcher around the same time:

I read your recent paper in the Journal of Biomechanics (Muscle contributions to propulsion and support during running) and was wondering if you could dumb it down a little for me. Could you provide some insight/explanation into the idea that running propulsion occurs more from "pulling" (e.g. the hip flexors of the swinging leg) rather than "pushing off" during terminal stance. I noticed that you addressed this with calf musculature in your discussion but I did not see much comment about hip flexion. I have read authors (Mann and I think Cavanaugh, separately) explain the "extensor paradox" at mid to late stance as being due to swinging leg's hip flexion moment essentially "pulling" the contralateral leg into extension.

On an unrelated note since you have obviously have a great understanding of Dr. Delp's model could provide any comment on the idea that the only hip flexors that can create a flexion moment with the hip above 90 degrees are the psoas and iliacus. I work in the sport injury field and this is a test that is commonly advised to test the strength of the psoas with the preceding rationale.

And he wrote back

OK, here's my attempt at a simpler explanation of running propulsion and support... From the measured ground reaction forces during the running gait cycle, it is clear that in early-to-mid stance (approx the first 50% of the stance phase) the body mass center is accelerating backward (i.e., "braking"), and then in mid-to-late stance (the remaining 50% of stance) the mass center is accelerating forward (i.e., "propulsion). Our paper showed that for a single subject at a single speed (~ 4m/s), the quadriceps muscle group was the main contributor to braking and support during early-to-mid stance, while the ankle plantarflexors (i.e., gastrocnemius and soleus) were the main contributor to propulsion and support during mid-to-late stance (up to toe-off). Our results showed that muscles or inertial effects of the contralateral limb made insignificant contributions to braking, propulsion, or support of the mass center .


You mentioned that previous researchers suggested that the swinging forward of the contralateral leg provided forward propulsion, yet our results suggested quite the opposite. Could you point me to the study that concludes this?


However, we have not fully examined the contributions to hip, knee, and ankle accelerations for running (in other words, we have not addressed the question, "Does the contralateral limb contribute to knee extension?") I have actually just completed data collection for a study including 20 subjects running at multiple speeds where I hope to address this question and others about joint accelerations. But this has been examined for walking by others in my lab, and those results show the contralateral leg muscles do contribute to knee extension during double support (Fox, MD, Delp, SL, J Biomech, 2010; Fig 3), and the contribution increases with speed. They also show that the uniarticular ankle plantarflexors (e.g., soleus) also contribute to knee extension (Fig 4), due to dynamic coupling (or in other words, since bones are connected muscles spanning the ankle can cause an acceleration at the knee). These results suggest that multiple muscles have the potential to extend the knee in late stance during walking and running, and I hypothesize that people use a combination of these muscles (i.e., vasti, plantarflexors, and contralateral leg muscles) to achieve knee extension in running, too. Thus, in my opinion there is no "extensor paradox", or that's the wrong way to frame the problem, but instead we need to tease apart which combination of muscles are contributing to knee extension. And as I mentioned, I am hoping to do this in my current study.

As you can see from the last exchange I still held out hope to the importance of hip flexor motion in "driving" the body forward. I don't think it has been resolved.

I wonder what Ralph Mann says nowadays. His work is what really influenced me.

I will try to give a better post with some Moment data in the near future. Super busy tonight.

Greg

[PatrickL]

Hi Eric,

I use combinations of cueing (tactile and verbal), education and very, very, very specific exercise to give the pt. more solutions to solving movement problems.

Just curious about the specificity of exercise facilitation/education. I'm picturing you, for example, guiding the movement of a joint through range with a novel degree of rotation. I've been playing around with increasing solutions to movement problems by creating self selecting novelty using obstacles/diffrent surfaces/various agility drills etc. Do you see one approach as more valuable than a another? Perhaps the former leads into the latter as the rehab progresses?

[amacs]

Hi Ken

thanks for the input, much appreciated.


Greg

I note that at one point one fo your respondents said this,

results showed that muscles or inertial effects of the contralateral limb made insignificant contributions to braking, propulsion, or support of the mass center

at face value that would seem to deny my earlier suggestion about braking affording a GRF to accelerate the contralateral limb fwd. However I am still wondering about that - must go see if I can find much although my library access is limited these days .

Good to see someone in the biomech community using inverse dynamics what we do need though is someone looking at the non-linear dynamic aspect of movement and well - here be crocodiles!

Thinking along those lines is the hip flexor test really valid at all - it is in supine, gravity is at 90deg, the body will solve for stability and movement differently than it will in standing, spinal extension is necessarily reduced altering force moments, same applies to the glute/hamstring test. We do know that strength testing should be position specific etc etc.

fun thread

regards

ANdy

[Diane]

I can't help but consider that lot of the brainpower devoted to running the legs, at a spinal cord level, came for free from having evolved as quadrupeds. I suspect it takes a lot of inhibition from cortex to enable bipedal gait, reroute motor control to independent arm/hand movement.
Not sure what the implications are for lower limbs, other than the motor output to them evolved with legs that were flexed at the hip and abs that were slung ventrally to support breathing while running away from lions, or toward prey if you were a lion. And elastic recoil in tendons, however long or short, wherever located, always a good thing for short term power boosts..

[Greg Lehman]

Hi ANdy,

You quoted this in an email exchange I had

results showed that muscles or inertial effects of the contralateral limb made insignificant contributions to braking, propulsion, or support of the mass center

What was odd about this statement was that the graphs and even the discussion talked about contralateral leg swing and the increasing moment that occurred with increasing speed during running.

[IMG]file:///C:/Users/Greg/AppData/Local/Temp/msohtml1/01/clip_image002.gif[/IMG]

Fig. 1 Sagittal-plane torques developed about the hip (top panels), knee (middle panels) and
ankle (bottom panels) joints across the full stride cycle for the left lower limb (left foot-strike to
left foot-strike) for the four discrete running speeds. Data represent the group mean (solid black
line) ± one standard deviation (grey shading). The running speeds of 3.50 m/s, 5.02 m/s and 6.97
m/s contain data for 8 subjects, whereas the running speed of 8.97 m/s contains data for 7
subjects. The dashed vertical line indicates the average time (% stride cycle) of toe-off for each
speed condition. LFS: Left foot-strike; LTO: Left toe-off; Ext: Extension; Flex; Flexion



I hope the above graph came through. I can't get into detail today but hope to put together a better synopsis of a few papers in the next few days. I think the question has been answered but in a few different studies.

Greg

[amacs]

Hi Greg

no graph just the graph description

ANdy

[Greg Lehman]

Http://www.flickr.com/photos/77990604@N07/7000707530/


Snap,

I have to copy the picture from a pdf and then import it into Adobe Illustrator to create a JPEG. Is there any other way to do this to get it into a post. I tried to cut and paste.

Hoping this works. It seems to work as a link above not as a picture within the post. I will look into this

[toddhargrove]

Greg,

Interesting topic.

I've always been interested in why most strength training programs for athletic development seem to neglect the hip flexors.

Here's a thread on Lyle McDonald's forum where I posted this question (as Seattleite):

http://forums.lylemcdonald.com/showthread.php?t=9362

As you can see, I didn't learn much, but I still find the question interesting.

Any thoughts?

[Randy Dixon]

Originally Posted by Diane

I can't help but consider that lot of the brainpower devoted to running the legs, at a spinal cord level, came for free from having evolved as quadrupeds. I suspect it takes a lot of inhibition from cortex to enable bipedal gait, reroute motor control to independent arm/hand movement.
Not sure what the implications are for lower limbs, other than the motor output to them evolved with legs that were flexed at the hip and abs that were slung ventrally to support breathing while running away from lions, or toward prey if you were a lion. And elastic recoil in tendons, however long or short, wherever located, always a good thing for short term power boosts..

Diane,

I'm not going to get involved in the fine details of running mechanics with people who know more about it than me, but I have coached and been coached in many different sports and came up with a truism that goes, You spend the first few months learning which muscles to use for your sport, you spend the rest of your career trying to learn which muscles NOT to use.

I think you are saying pretty much the same thing happens at the neurological level. I think we all know that most motor control output is inhibitory, it doesn't hurt to keep in mind why that is.

[amacs]

Originally Posted by Greg Lehman

http://www.flickr.com/photos/77990604@N07/7000707530/

Snap,

I have to copy the picture from a pdf and then import it into Adobe Illustrator to create a JPEG. Is there any other way to do this to get it into a post. I tried to cut and paste.




Hoping this works. It seems to work as a link but not as a picture within the post. I will look into this

'fraid not Greg

[Ken Jakalski]

Hi Diane!

I can't help but consider that lot of the brainpower devoted to running the legs, at a spinal cord level, came for free from having evolved as quadrupeds. I suspect it takes a lot of inhibition from cortex to enable bipedal gait, reroute motor control to independent arm/hand movement.

This is an excellent point.

Some of the things I picked up at the Harvard lab:

"The emphasis on motor control I feel is considerably overdone. Consider whether the fastest runners (cheetahs, antelope, quarter horses) need to have running technique taught to them in a conventional humanmotor control sense. The nervous systems of these runners do everything necesary, and this with an appreciably greater need in some respects for fine coordination vs. human runners."

And with the Derby yesterday...

"Imagine a race horse trying to claw and concentrate on negative vertical velocity."

It seems as if the more the leading researchers explore the specifics of high speed human locomotion, the more minimalist they are in their thinking.

"Horses hit the ground running. Must they first be taught running mechanics on the drop from their mother's womb"?

The older I get, the more I coach...like Barrett works with patients in pain.

Laissez faire coaching and therapy...but many would consider it "LAZY" faire.

I don't care anymore. I've been where they are now.

They're not getting it.

[Barrett Dorko]

Thanks Ken.

I think my last blog post about becoming increasingly minimal fits this attitude perfectly.

[amacs]

"The emphasis on motor control I feel is considerably overdone. Consider whether the fastest runners (cheetahs, antelope, quarter horses) need to have running technique taught to them in a conventional humanmotor control sense. The nervous systems of these runners do everything necesary, and this with an appreciably greater need in some respects for fine coordination vs. human runners."

Interesting Ken!

I am not sure many of those guys really either do or know motor control, they use a fairly 2D perspective of biomechanics and wrap it in the language of motor control without actually grasping what motor control is or does.

I find most love the concept of motor programs but none or very few go anywhere near the concepts of inverse dynamics and the vastly more complex but satisfying (to me) theories found int eh action systems/ecological approaches. Perhaps thats because such approaches are a lot less amenable to pat answers and so often deliver what appear to me mundane answers which you are harder to make a living out of.

Pendular systems will do what pendular systems do, you can only alter the output so far and you do that by changing the input parameters not the output.

regards

ANdy

[Milehigh]

Just curious about the specificity of exercise facilitation/education. I'm picturing you, for example, guiding the movement of a joint through range with a novel degree of rotation. I've been playing around with increasing solutions to movement problems by creating self selecting novelty using obstacles/diffrent surfaces/various agility drills etc. Do you see one approach as more valuable than a another? Perhaps the former leads into the latter as the rehab progresses?

Patrick that is a very intuitive response, requiring some novel thought.

I think there are a variety of ways to approach novelty in movement.

1) Specific movement instructions (verbal or visual demonstration). i..e move your leg this way. Which is a way that I have identified/hypothesized as a therapist that is outside the patient's normal repertoire.

2) Design environmental conditions which demand specific adaptations. In a training sense sprinting up hill on loose surfaces could be one example for encouraging hip turnover.

3) Encourage self exploration of a movement. I.e. a general agreement with the patient for movement exploration and then very general commands are given for a given activity.

In truth most of my practice involves all three of the above techniques in some combination or form. Depending on what the person is responding to and the type of learning style the patient presents I change my technique as I monitor their response in real-time.

I think the most important aspect of all the above techniques is to encourage the 'patients engagement of their own senses with movement. Sometimes they may need some direction depending on the level of their kinesthetic/interoceptive senses.

At first I will use tactile cues to help facilitate some of this sensorimotor integration. However, I try to get people into feeling themselves so they are not as reliant on myself either with their own hands.

A simple example may be a quad set for a post op knee. I try to really engage people in sensing their quad contraction. Touch it, feel it, see it etc. Most people are given a route quad contraction but have no idea how to sense it.

Additionally, in terms of prescribing movements the techniques 1 and 2 require less time, are more directed and IMO encourage slightly less interaction. The third technique is superior but usually takes more time, patience and interception to implement. Not always easy for patients or all contexts of PT/training.

Eric

[Greg Lehman]

Trying to insert the Moment graphs of running at increasing speeds. I believe I have finally done it

hip-flexion-moment-graphs.jpg


Fig. 1 Sagittal-plane torques developed about the hip (top panels), knee (middle panels) and
ankle (bottom panels) joints across the full stride cycle for the left lower limb (left foot-strike to
left foot-strike) for the four discrete running speeds. Data represent the group mean (solid black
line) ± one standard deviation (grey shading). The running speeds of 3.50 m/s, 5.02 m/s and 6.97
m/s contain data for 8 subjects, whereas the running speed of 8.97 m/s contains data for 7
subjects. The dashed vertical line indicates the average time (% stride cycle) of toe-off for each
speed condition. LFS: Left foot-strike; LTO: Left toe-off; Ext: Extension; Flex; Flexion

[advantage1]

MIlehigh:

Love the Payton example. By training uphill he reported the feeling of running downhill as he ran through opponents.

[smith]

From what I've read; I think training the hip flexors has a big upside. Not do to biomechanics though. There're part of the axial skeleton and as such are controlled by the more primitive brain, the ventral medial system. There're more conducive to training and building up neuro reflex's then say the biceps. They'll also act as a strong base for power production.

[Diane]

Originally Posted by smith

From what I've read; I think training the hip flexors has a big upside. Not do to biomechanics though. There're part of the axial skeleton and as such are controlled by the more primitive brain, the ventral medial system. There're more conducive to training and building up neuro reflex's then say the biceps. They'll also act as a strong base for power production.

Excuse me, but I disagree.
They are part of the appendicular skeleton.
They are innervated by ventral motor roots. My understanding is that anything innervated by dorsal motor roots (i.e., paraspinals only) constitutes part of the axial skeleton.

[amacs]

This is an interesting perspective or line of thought Mr Smith, I note Diane's disagreement at a neural level, I do wonder how practically such a focus would be worked out in the terms of running. Or are you thinking outside that?

Regards
ANdy

[smith]

My thinking is it would work with running too Andy. One theory on the pelvis is that during sport it rotates tilt anteriorly. If one could train it reflexively not to do this, subconsiously, it would free up the lateral system for tactical stuff, leg kick etc.

University of Wisc.'s coursebook on neuroantomy states that, "the ventromedial system is not well suited for discreet control of a few muscles but rather for control of groups of muscles involved in posture and balance." Ha ha, lots of debate.

On another note. Seems tadpoles are partial to SC and DNM too. Google science daily tadpoles and locomotion

www.sciencedaily.com/releases/2012/05/120516115980.htm

[Milehigh]

Did that last post make sense to anyone?

[smith]

Did you read the article on tadpole and locomotion Eric?

Researchers said, " by touching skin on the the head of the tadpole and applying cellular neurophysiology techniques, the scientists identified nerve cells that detect touch on the skin. Also, "these findings address the longstanding question of how locomotion is initiated following sesory stimulation." Sure sounds like SC and DNM to me.

Researchers also mention evolutionary interest. There sure is. Seems like SC and DNM is conserved through hundreds of millions of years of evolution.

[Milehigh]

Your link goes to the general science daily page, so no I could not find it.

From my understanding simple contact and DNM are used for individuals with pain. If pain is inhibiting normal gait. Yes, I would think these techniques could be used.

While touch and contextual stimulus are important in the development of normal sensorimotor function of gait and running in the infant. I don't think the aforementioned interventions are necessary for a healthy baby in an average environment to develop either.

We are discussing optimization of running and its analysis, and not specific infant or evolutionary development. Nor do I think Barrett or Diane use these treatments on healthy individuals to improve performance. Perhaps I am wrong? Therefore your comments seem to be more of a sidebar and slightly confusing to me.

I would like to read the specific tadpole article it does seem interesting though. So if you find it DM me.

Eric