Hip flexors do not initiate hip flexon.

We have been saying it in writing and podcasts for years, the hip flexors are limb swing phase PERPETUATORS, not initiators of hip flexion.
It is the elastic response discussed below and the changing of the pelvis obliquity (from posterior positioning to anterior) via the abdominal wall acting on the pelvis-hip interval in conjunction with the stance phase hip musculature that drives hip flexion.
The next time you go after the psoas as a culprit in your meanderings for solutions, because that is what is all over the internet, think bigger, smarter, deeper.

"These experiments also showed that the trailing leg is brought forward during the swing phase without activity in the flexor muscles about the hip joint. This was verified by the absence of EMG activity in the iliacus muscle measured by intramuscular wire electrodes. Instead the strong ligaments restricting hip joint extension are stretched during the first half of the swing phase thereby storing elastic energy, which is released during the last half of the stance phase and accelerating the leg into the swing phase. This is considered an important energy conserving feature of human walking."

Dan Med J. 2014 Apr;61(4):B4823.
Contributions to the understanding of gait control.
Simonsen EB1.

#thegaitguys, #hip, #hipflexors, #pelvismechanics, #swingphase, #gait, #gaitanalysis, #gaitproblems

The hip flexors do not cause initial hip flexion.

The hip flexors are not responsible for pulling/flexing the swing leg forward in gait or running. The psoas is a mere swing phase perpetuator, not an initiator.
For about 2 decades we have been saying in our lectures, posts and podcasts that it is the reduction of the obliquity of the pelvis during gait from various other tissues and biomechanical events that causes leg swing, meaning the trail leg is brought forward in swing largely by the abdominal muscle linkage to the pelvis (and other loaded tissues) that is responsible for forward swing of the leg. It is not the hip flexor group that does this hip flexion action. Thus it could be considered foolish to train the hip flexors to be the primary swing drivers. Here is another supporting piece of research.

"These experiments also showed that the trailing leg is brought forward during the swing phase without activity in the flexor muscles about the hip joint. This was verified by the absence of EMG activity in the iliacus muscle measured by intramuscular wire electrodes. Instead the strong ligaments restricting hip joint extension are stretched during the first half of the swing phase thereby storing elastic energy, which is released during the last half of the stance phase and accelerating the leg into the swing phase. This is considered an important energy conserving feature of human walking. "

Dan Med J. 2014 Apr;61(4):B4823.
Contributions to the understanding of gait control.
Simonsen EB1.

https://www.ncbi.nlm.nih.gov/pubmed/24814597?fbclid=IwAR3yZQLb2Z0X1LZSVp2hOFLCt3wefsPt4iWEGveswn7-aGaou5OdDqmj4lA

What do the hip flexors have to do with the knee extensors ?


"It is not about your test, it is what your client displays in your test that matters. They will try to find a way. The load has to go somewhere, and they will find a place to put it, they always do. Finding out how your client cheats, compensates, recruits and fails is the value of the assessment."

This is just a small example of how I approach a client through small assessment window.
As best as I am able, knowing the absolute limitations of a supine examinations translation to vertical loading, I will approach a client's ability to stabilize in all 3 planes of movement. Today, i will micro-dissect a thought process.

The straight leg resistance test (SLR):
just a few incomplete thoughts on a SAGITTAL perspective (so as to avoid writing a book).
I will do it looking at **pelvis posture (anterior, posterior, oblique), lumbar spine posture (incr/decr lordosis), if they can keep their knee locked in a position, does the pelvis rotate, do they want to deviate into internal or external rotation at the hip, do they plantar or dorsiflex their ankle or toes. Lots to see here in how a client will recruit, and this is just a small snapshot of things they might do. Yes, head position, arm position were left out , again, to avoid a longer post today.
I will add consistent (as best as possible) resistance in the SLR test , with full locked knee, at hip 30, 45 and then full straight leg SLR (at the client's hamstring tension limit), then again at 45 degree knee lock with partial hip flexion, 90 degree hip and knee. I am changing loading vectors frequently to see if their is a directional loading failure. I am looking for their ability to provide ample resistance, and how they might cheat (see above).
But here is how my mind works through the test on the most basic level, which will give me insight on the above cheats** the client may employ.
* In the MOST SIMPLEST thought of the assessment, can they EFFECTIVELY stabilize the pelvis to the lumbar spine, can they stabilize the femur into the pelvis, can they stabilize the tibia onto the femur? It is how they choose to engage the system that matters, and that might be partly why their "Screen" shows up shoddy and may be a window into their pain.
The question is, if they fail, where are they failing and what tissues are overburdened or over protecting ? Where is the load, and where NOT is the load, going ?

"It is not about your test, it is what your client displays in your test that matters. They will try to find a way. The load has to go somewhere, and they will find a place to put it, they always do. Finding out how your client cheats, compensates, recruits and fails is the value of the assessment. This is how you need to be thinking when you perform many of the mostly useless orthopedic tests in the textbooks.

This is key,
a SLR screen will not show you any of this, it will just show you their range of motion, nothing more, not how they did it, what parts worked harder than other parts, and which parts are weak, injured or inhibited, for example. It is not what a client does, it is how they go about it that has the most value to you in helping them.

Today's article below is what spurred my rant today. It gives light that most already know, that everything is connected. And perhaps we can translate it into deeper thoughts for our clients, namely, what part is not doing its job, and where are they not connecting the parts, and where are they putting the loads ?

From the Ema study:
"Our findings indicate that hip flexion training results in substantial neuromuscular adaptations during knee extensions similar to those induced by knee extension training."-Ema et al.

We need a stable and strong core-spine-pelvis connection to display powerful knee extension, and, we need a stable and strong femur-pelvis connection as well. So, where is your client doing more or less of the work, and is it related to their hip, low back or knee pain? Or are they tossing it into the ankle perhaps? This is the beauty of the game we all play every day, if we are actually paying attention.

Now, remember my discussion last week about "adding strength to dysfunction" ? Where is your client going to put the load?, the answer, where they can/able. And that doesn't exactly mean where they should be putting it. Mindless prescription of corrective exercises is a real problem in my opinion.

Shawn Allen, the other gait guy.

#gait, #gaitproblems, #gaitanalysis, #correctiveexercises, #running, #hipflexors, #kneeextension, #SLR, #corestrength, #thegaitguys

Scand J Med Sci Sports. 2018 Mar;28(3):947-960. doi: 10.1111/sms.13008. Epub 2017 Nov 22.
Neuromuscular adaptations induced by adjacent joint training.
Ema R1,2, Saito I3, Akagi R1,3.

Swing matters, too.

 

 

We speak often about the 3 foot rockers, with particular attention often to ankle rocker (ankle mortise). But one must not forget about the rear and forefoot rockers, they have their important place as well.
But, we all too often only think of these parameters when the foot is on the ground.  The truth is, the swing limb is very important as well. How we swing, how the foot prepares for initial contact is also critical. 

Last week Ivo wrote about toe walkers, a topic we have written about several times previously on our blog "The Gait Guys". 

In this study, the researchers were appearing to look at plantarflexion posturing of the foot-ankle complex. the noted that"unilateral restricted ankle motion influenced kinematics mainly in the swing phase" as we proposed. Again, swing phase is just as critical as the stance phase of gait.  One might recall our mnemonic, "when the foot is on the ground, the glutes are in charge, and when the foot is in the air, the abdominals are in charge". This admittedly is a very loose statement, but it has its place to begin the dialogue. Meaning, there is more to it.  Yes, the hip flexors are key, but they have to be active on a precursor, sufficient control of the pelvis, via the abdominals in part.  To this point, the researchers noted that, "hip and knee peak flexion in the swing phase were increased on the restricted side". Meaning, that to clear a plantarflexed foot-ankle complex, one might have to accentuate flexion elsewhere.  No rocket science here. This is the "foot drop" strategy most of us are all to familiar with. People with foot drop have an inability to dorsiflex the ankle to clear the ground in swing, thus, to avoid tripping, one has to flex the limb higher up the chain, perhaps even hike the pelvis with the opposite leg hip abductors (plus a little frontal plane lean perhaps). This article however discusses restrictions, and not what we just discussed, loss of function. 

Furthermore, "Walking with unilateral restricted ankle motion had a negative effect on walking velocity, cadence, step time, and step length."

Gait Posture. 2015 Mar;41(3):835-40. 
Immediate effects of unilateral restricted ankle motion on gait kinematics in healthy subjects.  Romkes J1, Schweizer K2.
 

https://www.ncbi.nlm.nih.gov/pubmed/25800648

The glutes are in fact great internal hip rotators, too. Open your mind.

I recently got a message from a colleague questioning as to how in the world, that when the hip is in flexion, the glutes and piriformis become internal rotators.  This is again another example of lack of functional anatomy knowledge.  It took me awhile to find a picture to help explain this, but I finally found one reasonable to do so. Many readers who are stuck on this concept are just too stuck on the anatomy as presented in the image to the right, neutral stance-like.  This article today will be all about internal and external moment arms, here, this lecture will help a little, it is on glute medius internal moment arms in stance phase however, so there is little carry over but it will at least get you understanding moment arms more clearly. 

We tend to just think of the glute max as a hip stabilizer and extensor, for the most part. It also decelerates flexion in terminal swing.  The glute medius is mostly thought of as a lateral hip stabilizer and abductor, either of the femur (open chain) or of the pelvis in stance position (closed chain), meaning zero degrees or neutral plus or minus the trivial degrees of engaged hip flexion and extension used in normal gait.

No one I know consciously trains the glutes as an internal rotator, but there are many actions where we need this function, such as in crawling and many high functioning activities such as martial arts grappling and kicking for example. Gymnasts should also know that the glutes are powerful internal hip rotators.  If you are doing quadruped crawling work you also need to know this as your client approaches 90 degrees of hip flexion. No one ever seems to check this critical gluteal function, at least I see it missed all the time from my referring doctors and therapists for unresolving hip pain cases. Patients with hip pain, anterior, lateral or posterior, with lack of internal hip rotation need the glutes checked just as much as the other known internal hip rotators we all seem to know (though some still do not understand how powerful the vastus lateralis is as an internal rotator, but again, those are folks who just have not spend the time in a mental 3D space looking at functional anatomy. I live mentally in that 3D space all day long when working with patients, you should too.) Let me be more clear, the anterior bundle, the iliac bundle of the glute max, is an internal rotator in flexion, the sacral and coccyxgeal divisions are not, they are external hip rotators in flexion. The gluteus medius and minimus are internal hip rotators closing in on 90 degrees hip flexion.  Hence, you must be able to tease out these divisions in your muscle testing, one cannot just test the glutes as external rotators or extensors, you are doing a really sloppy job if that is all you are doing. Nor should someone just train the glutes as hip stabilizers, external hip rotators and extensors (which is probably 90% of the trainers and coaches out there I might assume?). IF one knows the origin and insertions (see the blue and green arrows) and moves those points towards each other in a fashion of concentric contraction (purple arrows) one should be able to easily see that this will orient the femur to spin into internal rotation in the acetabulum (follow the arc of the black arrows). The same goes for eccentric contractions, it is the same game.  If you are doing DNS and crawling work, you should know this stuff cold gang. When you close chain the hip in sitting, or are moving from tall kneeling into flexed kneeling chops, performing high knees in sprint training,  or especially in crawling and climbing type actions, you must understand the mechanisms of internal rotation creation and stabilization -- if the glutes are not present and trained and useful in flexion, you are missing a chunk of something big. Amongst many other things, your client must be capable, stable, strong and skilled in moving from supine to quadruped all in one turning-over motion to teach how to stabilize the hip in the quadruped action and then progress into crawling.  This is a reflexive action learned in the early motor developmental phase of locomotion.  So take your client back through this motor pattern if they have some of the hip problems with internal rotation, it is a small piece of the gluteal puzzle.

I am sure this will show up in someone's seminar at some point, hopefully it is in many already, it has always been in my lectures when going down the rabbit hole of all things glutes. And to be fair, I haven't been to seminars in years as I get too frustrated, so this concept may be everywhere for all I know (lets hope).  But that is something I have to get over, I am sure I still have much to learn.  

To give credit where credit is due, which we always insist upon here at The Gait Guys, this was refreshed in my mind by Greg Lehman in a Facebook post forwarded to me by the inquiring doctor.   Link here  and from the article that spurred him to discuss it, an old article I read long ago just after completing my residency, the article is by Delp et al.  It is worth your time.  Thanks Greg for bringing this back into the dialogue, it is critical base knowledge everyone should already know. 

Variation of rotation moment arms with hip flexion.  Scott L. Delp,*, William E. Hess, David S. Hungerford, Lynne C. Jones  J. of Biomechanics 32, (1999)

-Dr. Shawn Allen, the other Gait Guy

Why can’t I squat.

Client presents to you:
On the exam table they have plenty of ankle dorsiflexion range of motion (ROM), full knee flexion ROM, full hip flexion ROM.
You then ask them to perform all 3 together in the form of a squat. The result is that they cannot even squat past parallel thighs. They have used a mere portion of the ranges which they showed plentiful on the exam table. Why ?

Possibilities: The exam showed passive movements, not active loading. Perhaps lack of Skill (unfamiliarity of the skill), lack of coordination (lack of knowing how to put the pieces together), lack of balance and body mass space awareness (ie. where do i put my parts so i do not fall over), lack of hip, knee, pelvis-core stability, etc.

“Just because you have it, doesn’t mean you own it. Nor does it necessarily mean you know how to use it or have the right to push the limits if you have never been there before.”

Ivo and i have a bunch of screens we use to glean information as we move down through the examination tree. Here is one i like to use, it is quick and easy and allows you to check something functionally and quickly while a client turns over. It is a very VERY small piece of a larger puzzle, but it is knowing what to look for and then what to test to verify. You might not have noticed this clients limitations in a passive supine joint assessment, but often when you load them up, mobility and stability challenges start to blossom into something different. If you are thinking, “possible loss of right knee flexion or left hip flexion” you are on the right track, with *caveat. There is more to it, but it is a start.  Hope to see you on www.onlinece.com next week for our new course, “thinking through functional pathologic biomechanics”.  
* Caveat: The lack of joint flexion range doesn’t necessarily mean they need more flexion, it means their flexion mobility is lost and that might mean they need more stability there or elsewhere for the flexion to present. This is the challenge a screen provides, it doesn’t tell you what’s wrong, it tells you if they can or cannot do the screen. If they cannot, it’s your job to find out why, but giving this particular client flexion work (range or strength work) would have led to a quick demise in their status. Quite often a joint displaying less mobility displays such because it has insufficient stability (from lack of skill, endurance, strength, proprioceptive etc) , but this is not a hard and firm rule. It’s your commission to find out the functional limitation(s) that are leading to these deficits and challenges.

Psoas, iliacus. . . .  hip flexors ?

How many times have you heard us say, “hip flexion in the swing phase of gait is not driven by the hip flexors. In swing phase, the psoas and iliacus complex is not a hip flexor initiator, it is a hip flexion perpetuator/” ?
More evidence … . .
“These experiments also showed that the trailing leg is brought forward during the swing phase without activity in the flexor muscles about the hip joint. This was verified by the absence of EMG activity in the iliacus muscle measured by intramuscular wire electrodes. Instead the strong ligaments restricting hip joint extension are stretched during the first half of the swing phase thereby storing elastic energy, which is released during the last half of the stance phase and accelerating the leg into the swing phase. This is considered an important energy conserving feature of human walking. ”

http://www.ncbi.nlm.nih.gov/pubmed/24814597

Foot Clearance: We don't think about it until we are face down in the mud, and we have all been there.

How many times have you tripped over something so small and insignificant you can barely believe it ? We have all tripped over a small elevation in a cracked sidewalk or a curled up rug corner.  But sometimes we look back and there is no evidence of a culprit, not even a Hobbit or an elf.  How can this happen ?
Minimum foot clearance (MFC) is defined as the minimum vertical distance between the lowest point of the foot of the swing leg and the walking surface during the swing phase of the gait cycle. In other simpler words, the minimum height all parts of the foot need to clear the ground to progress through the swing phase of the limb without contacting the ground. One could justify that getting as close to this minimal amount without catching the foot is most mechanically advantageous.  But, how close to vulnerability are you willing to get ? And as you age, do you even want to enter the danger zone ? Obviously, insufficient clearance is linked to tripping and falling, which is most concerning in the elderly. 
Trips or falls from insufficient foot clearance can be related to insufficient hallux and toe(s) dorsiflexion (extension), ankle dorsiflexion, knee flexion and/or hip flexion, failure to maintain ipsilateral pelvis neutral ( anterior/posterior pelvis posture shifting), even insufficient hip hike generated by the contralateral hip abductors, namely the gluteus medius in most people’s minds. It can also be from an obvious failed concerted effort of all of the above. Note that some of these biomechanical events are sagittal and some are frontal plane.  However, do not ever forget that the swing leg is moving through the axial plane, supported in part by the abdominal wall, starting from a posteriorly obliqued pelvis at swing initiation into an anteriorly obliqued position at terminal swing. We would be remiss as well if we did not ask the reader to consider the “inverted pendulum theory” effect of controlling the dynamically moving torso over the fixed stance phase leg (yes, we could have said “core stability” but that is so flippantly used these days that many lose appreciation for really what is happening dynamically in human locomotion).  If each component is even slightly insufficient, a summation can lead to failed foot clearance.  This is why a total body examination is necessary, every time, and its why the exclusive use of video gait analysis alone will fail every time in finding the culprit(s). 
When we examine people we all tend to look for biomechanical issues unless one grasps the greater global picture of how the body must work as a whole. When one trips we first tend to look for an external source as the cause such as a turned up rug or an object, but there are plentiful internal causes as well. For example, we have this blog post on people tripping on subway stairs.  In this case, there was a change in the perceptual height of the stairs because of a subconscious, learned and engaged sensory-motor behavior of prior steps upward.  However, do not discount direct, peripheral and lower fields of view vision changes or challenges when it comes to trips and falls. Do not forget to consider vestibular components, illumination and gait speed variables as well.  Even the most subtle change in the environment (transitions from tile to carpet, transitions from treadmill to ground walking etc) can cause a trip or fall if it is subtle enough to avoid detection, especially if one is skirting the edge of MFC (minimal foot clearance) already. And, remember this, gait has components of both anticipatory and reactive adjustments, any sensory-motor adaptive changes that impair the speed, calculation and timely integration of these adjustments can change gait behaviors. Sometimes even perceived fall or trip risk in a client can easily slip them into a shorter step/stride length to encourage less single leg stance phase and more double support phase gait. This occurs often in the elderly. This can be met with a reduced minimal foot clearance by design which in itself can increase risk, especially at the moment of transition from a larger step length to a shorter one. Understanding all age-related and non-age related effects on lower limb trajectory variables as described above and only help the clinician become more competent in gait analysis of your client and in understanding the critical variables that are challenging them. 
Many studies indicate that variability and consistency in a motor pattern such as those necessary for foot clearance are huge keys for predictable patterns and injury prevention, and in this case a predictor for trips and falls.  Barrett’s study concluded that “greater MFC variability was observed in older compared to younger adults and older fallers compared to older non-fallers in the majority of studies. Greater MFC variability may contribute to increased risk of trips and associated falls in older compared to young adults and older fallers compared to older non-fallers.”
Once again we outline our mission, to enlighten everyone into the complexities of gait and how gait is all encompassing.  There are so many variables to gait, many of which will never be noted, detected or reflected on a gait analysis and a camera.  Don’t be a minimalist when it comes to evaluating your client’s gait, simply using a treadmill, a camera and some elaborate computer software are not often going to cut the mustard when it really counts.  A knowledgeable and engaged brain are arguably your best gait analysis tools.  
Remember, what you see in someone’s gait is not their problem, it is their adaptive strategy(s).  That is all you are seeing on your camera and computer screen, compensations, not the source of the problem(s).
Shawn and Ivo
the gait guys

References (some of them): 

1. Gait Posture. 2010 Oct;32(4):429-35. doi: 10.1016/j.gaitpost.2010.07.010. Epub 2010 Aug 7.

A systematic review of the effect of ageing and falls history on minimum foot clearance characteristics during level walking. Barrett RS1, Mills PM, Begg RK.

2. Gait Posture. 2007 Feb;25(2):191-8. Epub 2006 May 4. Minimum foot clearance during walking: strategies for the minimisation of trip-related falls. Begg R1, Best R, Dell’Oro L, Taylor S.

3. Clin Biomech (Bristol, Avon). 2011 Nov;26(9):962-8. doi: 10.1016/j.clinbiomech.2011.05.013. Epub 2011 Jun 29. Ageing and limb dominance effects on foot-ground clearance during treadmill and overground walking. Nagano H1, Begg RK, Sparrow WA, Taylor S.

4. Acta Bioeng Biomech. 2014;16(1):3-9. Differences in gait pattern between the elderly and the young during level walking under low illumination. Choi JS, Kang DW, Shin YH, Tack GR.