Do you know SQUAT? Have you seen SQUAT? Have patients/clients that LIKE to squat? Seen a foot that looks like this? Can you say REARFOOT VALGUS?

 "Significant changes in lower limb kinematics may be observed during bilateral squatting when rearfoot alignment is altered. Shoe pitch alone may significantly reduce peak pronation during squatting in this population, but additional reductions were not observed in the subtalar neutral position. Further research investigating the effects of footwear and the subtalar neutral position in populations with lower limb pathology is required."
 
So, what does this study tell us?

when rearfoot aliment changes, so do the kinematics (duh)
the surface (tilted into varus or inversion) or shoes (which are medially posted) can make or break the man (or women) when it comes to "peak" pronation (we knew that already; confirmation is always nice)
inverting the rearfoot can change ankle dorsiflexion (read "ankle rocker"); inverting the rearfoot seems to reduce it
inverting the rearfoot can change knee flexion; inverting the rearfoot seems to increase knee flexion
inverting the rearfoot can change hip abduction (and thus knee valgus); reducing it

Learn about the gait kinematics and clinical findings associated with this foot type, along with video clip examples and always entertaining discussion with us tomorrow night on onlinece.com: Biomechanics 308: Focus on the Rear Foot.  5PST, 6MST, 7 CST, 8EST

Power V, Clifford AM. The Effects of Rearfoot Position on Lower Limb Kinematics during Bilateral Squatting in Asymptomatic Individuals with a Pronated Foot Type. J Hum Kinet. 2012 Mar;31:5-15. doi: 10.2478/v10078-012-0001-0. Epub 2012 Apr 3.

#rearfootvalgus #squat #foottype

2012 Mar;31:5-15. doi: 10.2478/v10078-012-0001-0. Epub 2012 Apr 3.

The Effects of Rearfoot Position on Lower Limb Kinematics during Bilateral Squatting in Asymptomatic Individuals with a Pronated Foot Type.

Power V1, Clifford AM.

Author information

Abstract

Clinicians frequently assess movement performance during a bilateral squat to observe the biomechanical effects of foot orthotic prescription. However, the effects of rearfoot position on bilateral squat kinematics have not been established objectively to date. This study aims to investigate these effects in a population of healthy adults with a pronated foot type. Ten healthy participants with a pronated foot type bilaterally (defined as a navicular drop >9mm) performed three squats in each of three conditions: barefoot, standing on 10mm shoe pitch platforms and standing on the platforms with foam wedges supporting the rearfoot in subtalar neutral. Kinematic data was recorded using a 3D motion analysis system. Between-conditions changes in peak joint angles attained were analysed. Peak ankle dorsiflexion (p=0.0005) and hip abduction (p=0.024) were significantly reduced, while peak knee varus (p=0.028) and flexion (p=0.0005) were significantly increased during squatting in the subtalar neutral position compared to barefoot. Peak subtalar pronation decreased by 5.33° (SD 4.52°) when squatting on the platforms compared to barefoot (p=0.006), but no additional significant effects were noted in subtalar neutral. Significant changes in lower limb kinematics may be observed during bilateral squatting when rearfoot alignment is altered. Shoe pitch alone may significantly reduce peak pronation during squatting in this population, but additional reductions were not observed in the subtalar neutral position. Further research investigating the effects of footwear and the subtalar neutral position in populations with lower limb pathology is required.

Who Rules -- The glutes or the quads? Well, it is complicated.

We have often talked about how important it is to be able to achieve terminal hip extension for an athlete, and arguably for everyone. This means one must have strength of the glutes into that terminal range so one can actually achieve the range of motion and access it functionally. If one does not, then extension movements may occur in the lumbar spine via some anterior pelvic tilt. However, one must not dismiss that upright posture needs sufficient quadriceps strength as well -- meaning, hip extension and knee extension get us to an upright posture and make locomotion possible. If we make the hip flexors or quadriceps tight, due to weakness of the lower abdominals or glutes,  we get anterior pelvic posturing and less hip extension (these are admittedly very rough principles, we all know it is far more complex that this).  What I am saying is that there is an interaction amongst groups of muscles, functional patterns of engagement, recruitment and whatnot. 

One must clearly realize how much knee and hip motions are coupled and work with and off of eachother.  If we bend over in a squatting type motion, we are in hip flexion and knee flexion. When we stand, hip and knee extension. These guys play off of eachother.  One must consider these issues when movements are more advanced and loading and loading rates are magnified, such as in squatting type lifting.  

A few weeks ago Bret Contreras in conjunction with Strength and Conditioning Research put out an article by Yamashita , yes, a 1988 article.  "EMG activities in mono- and bi-articular thigh muscles in combined hip and knee extension."  What this article looked at was what happened during isolated hip extension and isolated knee extension, and more importantly, what happened to the forces when both joints loaded simultaneously, paired in generating extension at the hip and knee, as in a squat. 

This article suggested that when hip and knee extension forces are generated in conjunction, the knee extensors are more activated than if the same force was generated in isolation. What this seemed to suggest is that during the extension phase of a squat, it is easy for the quad thigh muscles (rectus femoris, vastus medialis in this study) to to try and rule the movement, from an activation perspective -- the hip extensors (g. max and semimembranosus) take second seat.  We have talked many times about the dangers of this principle when we frequently say "the glutes should be in charge of the hip, not the quads, when the quads try to apply dominant control of the hip motion, trouble may ensue." Admittedly, this may not be entirely true and it is very loosely stated, but the principle has some sound value when it is approached from how we intend it to be heard, that many athletes do not have sufficient glute strength, hip extension range of motion, and poor control of pelvic neutral. So, they dump into the quads because as we see here in this study, they are very appropriately positioned to help synergistically drive the positioning for, and activity of, hip extension motor pattern production. Is this why we see small buttocks and large quadriceps in distance runners, and the opposite in sprinters ?  We think so, but we need to dive deeper into the research to prove or disprove it, but the principles seem to make sense.
This is why I like to initially drive my glute and hip extension work with my clients in a more knee flexed position, such as supine bridges.  I cannot say it better than Bret Contreras did when he reviewed this article,  

"So exercises that involve less knee extension (glute bridges, hip thrusts, deadlifts, pull throughs and back extensions) will tend to produce much greater hip muscle activation than those that involve more knee extension (squats, lunges, and leg presses), although there are always other factors involved of course!".  

If you are not following Bret's and Strength & Conditioning Research's work, you are missing out, They are thorough and insightful, they do their homework, learn from them.
We clearly need to dive into some newer research on this topic, we will see if we can squeeze out the time. 

- Dr. Shawn Allen, the other "gait guy"

Here is an embedded code for the beautiful slide that accompanied Strength and Conditioning Research's summary of the study. If you cannot find it above in this post, goto their Facebook page and scroll to Sept 22nd, 2016. You will find it beautifully laid out there.  Beautiful job S&CR!

<iframe src="https://www.facebook.com/plugins/post.php?href=https%3A%2F%2Fwww.facebook.com%2FStrengthandConditioningResearch%2Fposts%2F982124818565207%3A0&width=500" width="500" height="731" style="border:none;overflow:hidden" scrolling="no" frameborder="0" allowTransparency="true"></iframe>

Yamashita  1988. Eur J Appl Physiol Occup Physiol. 1988;58(3):274-7. EMG activities in mono- and bi-articular thigh muscles in combined hip and knee extension.
https://www.ncbi.nlm.nih.gov/pubmed/3220066
 

Podcast 112: Strengthening the foot's arch

Interested in our stuff ? Want to buy some of our lectures or our National Shoe Fit program? Click here (thegaitguys.com or thegaitguys.tumblr.com) and you will come to our websites. In the tabs, you will find tabs for STORE, SEMINARS, BOOK etc. We also lecture every 3rd Wednesday of the month on onlineCE.com. We have an extensive catalogued library of our courses there, you can take them any time for a nominal fee (~$20).
 

Show links:
http://traffic.libsyn.com/thegaitguys/pod_112f.mp3
http://traffic.libsyn.com/thegaitguys/pod_112f.mp3
* and on iTunes, Soundcloud, and just about every other podcast harbor site, just google "the gait guys podcast", you will find us.
 

Show notes:

Job security, become so good and so unique that Ai cant replace your skills as a doctor
http://www.techinsider.io/age-of-ems-machines-will-take-over-all-jobs-2016-8

How prosthetics are working now, and will in the future
and why you should be scared
http://thenextweb.com/insider/2016/08/04/researches-think-we-may-have-to-protect-our-brains-from-hackers-in-a-few-years/

Open talk about how coordination is the first strength changes someone notes. It comes before true strength is achieved. It is neurologic, and its can feel decievingly safe, but it is a lie.

Foot Strengthening ?
https://drjohnrusin.com/advanced-strength-training-for-feet/

http://www.jospt.org/doi/abs/10.2519/jospt.2016.6482?platform=hootsuite&

Impaired Foot Plantar Flexor Muscle Performance in Individuals With Plantar Heel Pain and Association With Foot Orthosis Use

Tags:
foot arch, foot intrinsics, short foot, yoga toes, gastrocnemius, soleus, heel pain, hammer toes, correct toes, foot exercises, thegaitguys, squatting, gait, gait analysis, gait assessment,  orthotics, prosthetics
 

The Circle of Durability.

The article below for some reason inspired today's soft rant. I hope you feel this is worth your time. 
Yesterday I talked about arch height and ankle mortise dorsiflexion and how we can obtain more global dorsiflexion range through some pronation, loosely meaning, some arch compression/drop and splaying apart of the tripod legs of the foot. Global arch flexibility is a piece of that puzzle.  This action of arch compression/drop/tripod splay moves the tibia forward in the sagittal plane and this is global dorsiflexion. Let me be clear however, a reduced ankle mortise dorsiflexion range of sagittal motion which is met by more arch height reduction/prontation/tripod splay, is still dorsiflexion however it is less sagittal dorsiflexion and a little more adduction and medial drift. This can bring the knee into the medial plane and it does promote more internal spin of the limb, this can be a problem.  None the less, it is still global dorsiflexion. It is something we see at the bottom of a squat, we see it because to get there most of us do not have all that dorsiflexion at the mortise. It is not abnormal, the question is, "is it safe for you? Can you do it repeatedly, safely?" It is where we go when we need more sagittal motion, but it may not be ideal, and is often what creates functional pathology. We see it all the time, someone says in an email, "I have plenty of ankle dorsiflexion, that is not my issue".  Do you have plenty? Is it not really your problem? This is fine tuning stuff, it takes a skillful eye and assessment hand. It takes experience to see the whole picture. You cannot get this full 4k experience and understanding from a 2 dimensional youtube video. This arch compression and pronation is normal to occur, it should occur, it must occur. But, how much is too much, for you ? I like to explain it this way, 

"there is a point at which sound, economical, durable, biomechanics becomes a liability. And, at that point where the liabilities begin is in fact where we begin to skirt the edges of that durable skilled movement. Where we begin juggling our liabilities is where the risks begin to mount and begin to whittle away or trump our S.E.S.P (skill, endurance, strength, power). This is where injury often occurs, at that intersection where the gas tank of our S.E.S.P. begins to run low and our liabilities begin to run high." 

Sidebar: 
I have explained this concept many times before when talking about the cross over gait. Moving towards a narrower step width is fine if you have the durability to be there. The question is, how long are you going to be there ? A cross over gait tendency is more economical but you begin to risk liabilities toward injury if that durability becomes challenged. As a runner you must know where your safe zone exists and know how much durability you have at those fringes of your movement. It is when you are there too long, too often, or too much that you empty that durability gas tank which then increases your liabilities towards injury. This is why I give high volume and strength work once a problem is solved, to make sure that they can keep that circle of durability high. It is when we stop keeping our gas tanks large and full that we run on fumes and our risks increase. You might be able to run economically for 5 miles with a narrow step width cross over style running gait. But, can you do it safely at 10 miles ? How about 15?  Is it any wonder why people get injured as they fatigue their safe motor patterns ?  If they have worked hard to keep that circle of durability large (S.E.S.P.) they are bound to be safer and less injured. Injuries occur because we exit our circle of durability, its gas tank has run too low, liabilities now trump economy and durability.

- Dr. Shawn Allen, the gait guys

http://www.japmaonline.org/doi/abs/10.7547/8750-7315-2016.1.Song
 

Eliminating the fake out of ample ankle rocker through foot pronation in the squat and similar movements:  How low can you go ? 

This is a simple video with a simple concept. 

* Caveat: To avoid rants and concept trolling, am blurring lines and concepts here today, to convey a principle. Do not get to tied up in specifics, it is the principle I want to attempt to drive home.  What you see in this video is clearly more lunge/knee forward flexion rather than hip hinge movement. However, keep in mind, that this motion does occur at the bottom of many movements, including the squat. 

You can achieve or borrow what “appears” to be more ankle dorsiflexion, a term we also loosely refer to as ankle rocker, through the foot, foot pronation to be precise. Do not mistaken this extra forward tibial progression range as ankle rocker mobility however. When you need that extra few degrees of ankle dorsiflexion deep in your squat, or similar activities, you can get it through your foot. Often the problem is that you do not think that is where it is coming from, you might just think you have great ankle mobility.  Many deep squatters are borrowing those last few degrees of the depth of the squat from the foot. This is not a problem, until it is a problem.  Watch the video above.  Why ? Because when the foot pronates and begins to collapse (hopefully a controlled collapse/pronation) the knee follows. Forcing the knees outward in a squat like some suggest is a bandaid, but I assure you, the problem is still sitting on the table. 

Go do a body weight squat with the toes up like in this video. Toes up raises the arch from wind up of the windlass and increased activity of the toe extensors and some assistance from the tibialis anterior and some other associated “helper” muscles.  When the arch is going up, it cannot go down. So, you raise your toes and do your squat. This will give you a better, cleaner representation of how much mobility in your squat/lunge/etc is from ankle dorsiflexion, knee flexion and  hip flexion. You can cheat and get some from the foot. The foot can be prostituted to magnify the global range, and like I said, this is not a problem until it IS a problem.   We know that uncontrolled and unprotected increases in foot pronation can cause a plethora of problems like plantar tissue strain, tibialis posterior insufficiency and tendonopathies, achilles issues, compression at the dorsum of the cuneiform bones (dorsal foot pain) to name a few. This dialogue however is not the purpose of this blog post today. You can read more about these clinical entities, proper foot tripod skills and windlass mechanics on other blog posts on this site. 

Today, we just wanted to bring this little “honesty” check to your awareness. Has been a staple in my clinic for over a decade, to help me see where limitations are and to show folks how they can cheat so much through the foot. Go ahead, try it yourself, see how much you use your foot to squat further if you have end range mobility issues in the hips, knees or ankles.  The foot is happy to give up the goat, it just doesn’t know the repercussions until they show up. 

So, lift your toes, do a full squat. Go as low as you can with good form with the toes up.  Then, at the bottom of the squat or the bottom of  your clean mobility, suddenly drop your toes and let the arch follow if it must. Here is the moment of truth, at that moment the toes go down, feel what happens to the foot, ankle, tibial spin, knee positioning, pelvis posture changes. Careful, these are subtle. You may find you are using foot pronation more that you should, more than is safe.  Now try this, bottom out your cleanest squat as you regularly would, and at the bottom, raise your toes and try to reposition the foot arch and talus height. In other words, reposture your foot tripod, see how difficult this is if you can do it at all. Perhaps you will find your toe extensors are too weak to even get there.  This is how we cheat and borrow. We should not make it a habit, it should be used when we need it, but it should not be a staple of your squatting diet, it should not be a regular event where you prostitute sound biomechanics.  Unless you wish to pay for it in some way.  What should happen is that you should be able to bring your toes down and not let the arch follow, but that is a skill most have not developed. It is a staple move in your clients’ movement diets.

Does all this mean you should squat with your toes up ? No, but it may serve you well in awareness, evaluation, and looking for potholes and power leaks. At the very least, give it some thought and consideration. You may see some smiles and have some lightbulb moments between you and your athletes and clients. 

Plan on blocking this foot pronation range with an orthotic ? How dare you ! At least try to do it through reteaching this and the tripod skill first. Give your a client a chance to improve rather than a bandaid to cope. 

Dr. Shawn Allen, one of the gait guys

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.”

Podcast 95: Head tilt while squatting or running.

We have a strong show for you today. Ankle instability from a neurologic perspective, shoe wear, head tilt and the neurologic and functional complications… we also talk about Efferent Copy and motor learning.

A. Link to our server:
http://traffic.libsyn.com/thegaitguys/pod_95final.mp3

Direct Download:  http://thegaitguys.libsyn.com/pod-95

-Other Gait Guys stuff
B. iTunes link:
https://itunes.apple.com/us/podcast/the-gait-guys-podcast/id559864138
C. Gait Guys online /download store (National Shoe Fit Certification & more !)
http://store.payloadz.com/results/results.aspx?m=80204
D. other web based Gait Guys lectures:
Monthly lectures at : www.onlinece.com type in Dr. Waerlop or Dr. Allen, ”Biomechanics”

-Our Book: Pedographs and Gait Analysis and Clinical Case Studies
Electronic copies available here:

-Amazon/Kindle:
http://www.amazon.com/Pedographs-Gait-Analysis-Clinical-Studies-ebook/dp/B00AC18M3E

-Barnes and Noble / Nook Reader:
http://www.barnesandnoble.com/w/pedographs-and-gait-analysis-ivo-waerlop-and-shawn-allen/1112754833?ean=9781466953895

https://itunes.apple.com/us/book/pedographs-and-gait-analysis/id554516085?mt=11

-Hardcopy available from our publisher:
http://bookstore.trafford.com/Products/SKU-000155825/Pedographs-and-Gait-Analysis.aspx

Show notes:

Human exoskeletons: The Ekso
http://www.thedailybeast.com/articles/2015/08/03/the-mechanical-exoskeleton-shaping-the-future-of-health-care.html

Ankle muscle strength influence on muscle activation during dynamic and static ankle training modalities
http://www.tandfonline.com/doi/abs/10.1080/02640414.2015.1072640?rfr_id=ori%3Arid%3Acrossref.org&url_ver=Z39.88-2003&rfr_dat=cr_pub%3Dpubmed&#.VcYWR-1VhBc

Chronic ankle instability:

http://tmblr.co/ZrRYjx1akudcm

http://tmblr.co/ZrRYjx1ah6ThV

http://thegaitguys.tumblr.com/post/68785250796/just-because-a-muscle-tests-weak-doesnt-mean-it
http://thegaitguys.tumblr.com/post/117109093439/last-week-we-ran-an-archived-piece-named-just

the future of footwear and orthotics ?
http://lermagazine.com/special-section/conference-coverage/the-future-of-footwear-and-orthoses-is-here-now-what

squats- head posture-gait vision-gravity
http://thegaitguys.tumblr.com/search/vision

Music: brain rhythm
http://www.kurzweilai.net/the-brains-got-rhythm

Tom Purvis hits some strong points in this video about squatting, hip hinges, ankle dorsiflexion, and movement as a whole.  * Keep in mind, this is all sagittal plane stuff….. it gets far more complicated when there are lateral (frontal) plane or rotational (axial) considerations ….. these are the “knees out” dialogues and debates you have read over and over on the web in the last year.

Dr. Shawn Allen

addendum:

Food for thought after posting today’s Tom Purvis squat video.

Could this study below translate into the statement/question: 

“attempting to achieve sufficient dorsiflexion through the combined ‘foot pronation-ankle dorsiflexion’ mechanism, as opposed to just dorsiflexion from the ankle mortise joint alone, may change the dynamics of the entire limb…. in this case, hip flexion range observation. Is this because when dorsiflexion is cheated via foot pronation, instead of just ankle dorsiflexion, there is more internal tibia/femoral spin than would normally occur from just sagittal ankle hinging which can in turn impair terminal hip flexion range via impingement type action ? I think so. It would be cool to see what would have happened in the study had the pronating clients been shown my foot tripod restoration exercise (it’s on youtube).   -Dr. Allen

here is some new research on this point, for what it is worth.  It keeps the mind thinking though.

J Phys Ther Sci.  2015 Jan;27(1):285-7. doi: 10.1589/jpts.27.285. Epub 2015 Jan 9.The kinematics of the lower leg in the sagittal plane during downward squatting in persons with pronated feet.  Lee,Koh da,  Kim 

Abstract

[Purpose] This study aimed to examine changes in lower extremity kinematics in the sagittal plane during downward squatting by subjects with pronated feet. [Subjects and Methods] This study selected 10 subjects each with normal and pronated feet using a navicular drop test. The subjects performed downward squatting, in which the knee joints flex 90° in a standing position. We recorded the angles of the hip, knee, and ankle joint in the sagittal plane through motion analysis. For the analysis, the squatting phase was divided into phase 1 (initial squat), phase 2 (middle squat), and phase 3 (terminal squat) according to the timing of downward squatting. [Results] In the pronated foot group comparison with the normal group, thehip joint flexion angle decreased significantly in phases 2 and 3. The dorsiflexion angle of the ankle joint increased significantly in phase 3. The flexion angle of the knee joint did not differ between groups in any of the phases. [Conclusion] The pronated foot group utilized a different squat movement strategy from that of the normal foot group in the sagittal plane.

Podcast 74: Cross Fit: More on Squatting and Hip Torsions, Part 2

Lots of great hip, squatting and biomechanics in this weeks show !

*Show sponsor: www.newbalancechicago.com

A. Link to our server: 

http://traffic.libsyn.com/thegaitguys/pod_75.f_74.mp3

Direct Download: 

http://thegaitguys.libsyn.com/podcast-74

B. iTunes link:

https://itunes.apple.com/us/podcast/the-gait-guys-podcast/id559864138

C. Gait Guys online /download store (National Shoe Fit Certification and more !) :

http://store.payloadz.com/results/results.aspx?m=80204

D. other web based Gait Guys lectures:

www.onlinece.com   type in Dr. Waerlop or Dr. Allen,  ”Biomechanics”

______________

Today’s Show notes:

Diving deeper into crossfit’s squatting, lunges, leg press.

 Walking in sync makes enemies seem less scary

https://www.sciencenews.org/blog/science-ticker/walking-sync-makes-enemies-seem-less-scary

 

http://thegaitguys.tumblr.com/post/23671468080/external-tibial-torion-a-video-showing-the

 

The Next Big Thing In Sports Data: Predicting (And Avoiding) Injuries

http://m.fastcompany.com/3034655/healthware/the-next-big-thing-in-sports-data-predicting-and-avoiding-injuries

“LER editor’s pick: Hip internal and external rotation are associated with shoulder mechanics in collegiate baseball pitchers. http://ow.ly/zULpO”

Michael August 27 at 7:49pm I’m curious to hear some thoughts on this, too. I listened to the podcast and read the blog post by the Gait Guys. I’ve coached CrossFit since 2009 and have owned my own affiliate for the last three years and follow Starrett closely. The cue “knees out” originated in powerlifting and the purpose is to keep people from ending up compensating with a valgus knee position during a squat, which is the most common compensation. Also, CrossFit did a special “Offline Episode” with Starrett, Kilgore, Russel Berger (he represented CrossFit) and two other coaches in which the sole topic was the “knees out” cue. It’s very illuminating for this topic. One interesting thing is that CrossFit does not tell people who go through the level 1 to tell others as a law, knees out. It’s merely a cue to fix a common compensation.

Podcast 73: Cross Fit and Squatting. Knees out ?

Podcast 73: Femoral and Tibial Torsions and Squatting: Know your Squatting Truths and Myths

*Show sponsor: www.newbalancechicago.com

Lems Shoes.  www.lemsshoes.comMention GAIT15 at check out for a 15% discount through August 31st, 2014.

A. Link to our server: http://traffic.libsyn.com/thegaitguys/pod_74f.mp3

Direct Download: 

http://thegaitguys.libsyn.com/podcast-73-cross-fit-squatting-knees-b. out

iTunes link:

https://itunes.apple.com/us/podcast/the-gait-guys-podcast/id559864138

C. Gait Guys online /download store (National Shoe Fit Certification and more !) :

http://store.payloadz.com/results/results.aspx?m=80204

D. other web based Gait Guys lectures:

www.onlinece.com   type in Dr. Waerlop or Dr. Allen,  ”Biomechanics”

______________

Today’s Show notes:

1. Bioengineers create functional 3D brain-like tissue   http://www.nih.gov/news/health/aug2014/nibib-11.htm

2.  A Novel Shear Reduction Insole Effect on the Thermal Response to Walking Stress, Balance, and Gait

http://dst.sagepub.com/content/early/2014/08/07/1932296814546528.abstract

 

3.  Hi Shawn and Ivo, There is a lively debate in the Crossfit community about “knees out” during squatting. I have attached a blog post. It might be a good blog post or podcast segment. 

http://dsstrength.com/2013/11/11/supple-leopards-vs-the-world-my-take-on-the-knees-out-debate/

 

4. Shoe Finder ?

http://www.runnersworld.com/shoe-finder/shoe-advisor?cid=socSG_20140817_29829646

 

5.  Michael wrote: “I know this is too broad a topic for facebook, but I was wondering what your general recommendation would be for someone with flat feet and exaggerated, constant over-pronation. I’ve tried strengthening my calves and ankles, but have seen no noticeable reduction in the automatic "rolling in” of my feet whenever walking or standing. I can consciously correct the over-pronation, of course, but as soon as I stop tensing my arch muscle, everything flops back down.“

Lombard's Paradox: A unique look at the cooperation of the quadriceps and hamstrings

Lombard’s Paradox

 In searching our personal archives for neat stuff we came across an oldie but a goodie. We posted this one on the blog for the first time in July 2011 so it was time to revisit it here on the blogs “Rerun Fridays”. This is one to certainly make your head spin. We do not even know where this came from and how much was our original material and how much was someone  else’s.  If you can find the reference we would love to give it credit.  We do now that we added some stuff to this but we don’t even know what parts were ours !  Regardless, there is a brain twister here worth juggling in your heads.  Lets start with this thought……..

When you are sitting the rectus femoris (a quad muscle) is “theoretically” shortened because the hip is in flexion. It crosses the bent knee in the front at it blends with the patellar tendon, thus it is “theoretically” lengthened at the knee.  When we stand up, the hip extends and the knee extends, making the R. Femoris “theoretically” lengthen at the hip and shorten at the knee.  This, it bodes the question…….did the R. Femoris even change length at all ? And the hamstrings kind of go through the same phenomenon. It is part of the  uniqueness of “two joint” muscles.   Now, onto Lombard’s paradox with more in depth thought on this topic.

Warren Plimpton Lombard (1855-1939) sought to explain why the quadriceps and hamstring muscles contracted simultaneously during the sit-to-stand motion.  He noted that the rectus femoris and the hamstrings are antagonistic, and this coactivation is known as Lombard’s paradox.

The paradox is classically explained by noting the relative moment arms of the hamstrings and rectus femoris at either the hip or the knee, and their effects on the magnitude of the moments produced by either muscle group at each of the two joints.

By virtue of the fact that muscles cannot develop different amounts of force in their different parts, the paradox develops.  The hamstrings cannot selectively extend the hip without imparting an equal force at the knee. Thus, the only way for hip extension and knee extension to occur simultaneously in the act of standing (or eccentrically in the act of sitting) is for the net moment to be an extensor moment at both the hip and knee joints. Lombard suggested three necessary conditions for such paradoxical co-contraction:

• the lever arm of the muscle must be greater at its extensor end
• a two-joint muscle must exist with opposite function
• the muscle must have sufficient leverage so as to use the passive tendon properties of the other muscle

In 1989, Felix Zajac & co-workers pointed out that the role of muscles, particularly two-joint muscles, was much more complex than has traditionally been assumed. For example, in certain situations, the gastrocnemius could act as a knee extensor. It is clear now that the direction in which a joint is accelerated depends on the dynamic state of all body segments, making it difficult to predict the effect of an individual muscle contraction without extensive and accurate biomechanical models (Zajac et al, 2003).

 In fact, back to the gastrocnemius another 2+ joint muscle (crosses knee, mortise and subtalar joints), we all typically think of it as a “push off” muscle.  It causes the heel to rise and accelerates push off in gait and running. But, when the foot is fixed on the ground the insertion is more stable and thus the contraction, because the origin is above the posterior joint line, can pull the femoral condyles into a posterior shear vector. It thus, like the hamstrings, needs to be adequately trained in a ACL or post-operative ACL, deficient knee to help reduce the anterior shear of normal joint loading. It is vital to note, that when ankle rocker is less than 90  degrees (less than 90 degrees of ankle dorsiflexion is available), knee hyperextension is a viable strategy to progress forward in the sagittal plane.  But in this scenarios, the posterior shear capabilites of the gastrocnemius are brought to the front of the line as a frequent strategy.  And not a good one for the menisci we should mention.

Andrews J G (1982)  On the relationship between resultant joint torques and muscular activity  Med Sci Sports Exerc  14: 361-367.

Andrews J G (1985)  A general method for determining the functional role of a muscle  J Biomech Eng  107: 348-353.

Bobbert MF, van Soest AJ (2000) Two-joint muscles offer the solution - but what was the problem? Motor Control 4: 48-52 & 97-116.

Gregor, R.J., Cavanagh, P.R., & LaFortune, M. (1985). Knee flexor moments during propulsion in cycling—a creative solution to Lombard’s Paradox. Journal of Biomechanics, 18, 307-16 .

Ingen-Schenau GJv (1989) From rotation to translation: constraints on multi-joint movement and the unique action of bi-articular muscles. Hum. Mov. Sci. 8:301-37.

Lombard, W.P., & Abbott, F.M. (1907). The mechanical effects produced by the contraction of individual muscles of the thigh of the frog. American Journal of Physiology, 20, 1-60.

Mansour J M & Pereira J M (1987)  Quantitative functional anatomy of the lower limb with application to human gait  J Biomech  20: 51-58.

Park S, Krebs DE, Mann RW (1999) Hip muscle co-contraction: evidence from concurrent in vivo pressure measurement and force estimation. Gait & Posture 10: 211-222.

Rasch, P.J., & Burke, R.K. (1978). Kinesiology and applied anatomy. (6th ed.). Philadelphia: Lea & Febiger.

Visser JJ, Hoogkamer JE, Bobbert MF & Huijing PA (1990) Length and Moment Arm of Human Leg Muscles as a Function of Knee and Hip Angles. Eur. J Appl Physiol 61: 453-460.

Zajac FE & Gordon MF (1989) Determining muscle’s force and action in multi-articular movement  Exerc Sport Sci Revs  17: 187-230.

Zajac FE, Neptune RR, Kautz SA (2003) Biomechanics and muscle coordination of human walking - Part II: Lessons from
dynamical simulations and clinical implications, Gait & Posure 17 (1): 1-17.

Stop Doing Kegels: Real Pelvic Floor Advice For Women (and Men)

This web article just came out today and we felt it was important to share. 

Nicole Crawford did a nice job with the article (LINK) and you need to read it.  The pelvic floor is a complicated place. There needs to be balanced muscular contraction and there has to be neutral pelvis and lumbar spine.  We have to agree with her comment:

A Kegel attempts to strengthen the pelvic floor, but it really only continues to pull the sacrum inward promoting even more weakness, and more PF (pelvic floor) gripping. The muscles that balance out the anterior pull on the sacrum are the glutes. A lack of glutes (having no butt) is what makes this group so much more susceptible to pelvic floor disorder (PFD). Zero lumbar curvature (missing the little curve at the small of the back) is the most telling sign that the pelvic floor is beginning to weaken. An easier way to say this is: Weak glutes + too many Kegels = PFD.

 There are too many people who have a shallow lumbar spine lordotic curve. These folks often hold the pelvis as neutrally as they can by keeping a constant squeeze of the glutes to “push” the pelvis “tipped up or levelled up” in the front when in fact the lower abdominals should “hold” them up in the front, to a notable degree.  It is easier for many to push the pelvis up with the glutes particularly when so many individuals are lacking in the abdominal compartment. 

We have so many of our patients learn the “potty squat” where the buttock is pushed backwards in a proper squatting technique.  We do this to reteach gluteal work, hamstring length in an environment of proper abdominal bracing. IT takes time to get the technique down, but it is worth it.  And, Crawford’s article gives it even more validity with its effect on the sacral posturing and impairing pelvic floor tension.

There is much good information in this article by Crawford.  It is worth everyone’s read. If you have been here with us on The Gait Guys for awhile you will know that we hold the mighty glutes on a high pedestal.  They are absolute key in gait and many folks do not use them properly.  After a few rough weeks practicing going gradually deeper as tissue length and strength is earned many of our patients have an epiphany of how little they were using their glutes, and how poorly they squat and how weak they were in the lower limbs.  Even our elderly patients in their 70s and 80s benefit from early shallow potty squat progressions.  We just put a chair behind them in case they fall back. It is never shocking to see what a few weeks of propper “potty-ing” will do to a person.  Do them alot, and do them often.

Good potty-ing to ya’ll.

Shawn and Ivo………Kings of our own Potty Thrones

Here is Crawford’s article link once again.

http://breakingmuscle.com/womens-fitness/stop-doing-kegels-real-pelvic-floor-advice-women-and-men