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:
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-Other Gait Guys stuff
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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:

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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

Forefoot Varus Anyone?Forefoot varus appears to move the center of gravity medially while walking. Nothing earthshaking here, but nice to see the support of the literature.“The most medial CoP of the row and CoP% detected increased medial CoP …

Forefoot Varus Anyone?

Forefoot varus appears to move the center of gravity medially while walking. Nothing earthshaking here, but nice to see the support of the literature.

“The most medial CoP of the row and CoP% detected increased medial CoP deviation in FV ≥ 8°, and may be applied to other clinical conditions where rearfoot angle and CoP of the array after initial heel contact cannot detect significant differences.”

We will be talking about foot types this week on onlinece.com; Wednesday 8 EST, 7 CST, 6MST, 5 PST Biomechanics 314. Hope to see you there!

J Formos Med Assoc. 2015 May 5. pii: S0929-6646(15)00132-1. doi: 10.1016/j.jfma.2015.03.004. [Epub ahead of print]
Analysis of medial deviation of center of pressure after initial heel contact in forefoot varus.

picture from: http://forums.teamestrogen.com/showthread.php?t=46901

Ankle muscle spindles play a significant role in the control of posture and balance during the swing phase of locomotion

 
                                                                                                              
“The results provide strong evidence that the primary endings of ankle muscle spindles play a significant role in the control of posture and balance during the swing phase of locomotion by providing information describing the movement of the body’s COM with respect to the support foot. Our results also provide supporting evidence for the proposal that there are context-dependent changes in muscle spindle sensitivity during human locomotion."                                                                                    

  • This study tells us what we already know: The muscles surrounding the ankle, especially of the leg you are standing on (the "stance” phase leg) provide important information to the central nervous system about both that leg AND the leg not on the ground (The “swing” phase leg).  Remember the central integration of things like the Crossed Extensor Response we have talked about in prior podcasts ?
  • The implications are that if you have an ankle injury, this mechanism can be altered, resulting in loss of balance (or proprioception) as well as opening you up to greater (or additional) injury.
  • The other implication is that the whole ball of wax is “situationally dependent”; meaning plastic and adaptable. Pretty cool !
The Gait Guys. Bringing you the latest and greatest, each and every post.
                                                                                       
                                                                                                                
 SOURCE:
Exp Brain Res. 2002 Mar;143(1):24-34. Epub 2001 Dec 18.

The effects of human ankle muscle vibration on posture and balance during adaptive locomotion.

Source

Gait and Posture Laboratory, Department of Kinesiology, University of Waterloo, Ontario N2L 3G1, Canada.

Abstract

This study investigated the contribution of ankle muscle proprioception to the control of dynamic stability and lower limb kinematics during adaptive locomotion, by using mechanical vibration to alter the muscle spindle output of individuals’ stance limbs. It was hypothesised that muscle length information from the ankle of the stance limb provides information describing location as well as acceleration of the centre of mass (COM) with respect to the support foot during the swing phase of locomotion. Our prediction, based on this hypothesis was that ankle muscle vibration would cause changes to the position and acceleration of the COM and/or compensatory postural responses. Vibrators were attached to both the stance limb ankle plantarflexors (at the Achilles tendon) and the opposing dorsiflexor muscle group (over tibialis anterior). Participants were required to walk along a 9-m travel path and step over any obstacles placed in their way. There were three task conditions: (1) an obstacle (15 cm in height) was positioned at the midpoint of the walkway prior to the start of the trial, (2) the same obstacle was triggered to appear unexpectedly one step in front of the participant at the walkway midpoint and (3) the subjects’ walking path remained clear. The participants’ starting position was manipulated so that the first step over the obstacle (when present) was always performed with their right leg. For each obstacle condition participants experienced the following vibration conditions: no vibration, vibration of the left leg calf muscles or vibration of the anterior compartment muscles of the lower left leg. Vibration began one step before the obstacle at left leg heel contact and continued for 1 s. Vibrating the ankle muscles of the stance limb during the step over an obstacle resulted in significant changes to COM behaviour [measured as displacement, acceleration and position with respect to the centre of pressure (COP)] in both the medial/lateral (M/L) and anterior/posterior planes. There were also significant task-specific changes in stepping behaviour associated with COM control (measured as peak M/L acceleration, M/L foot displacement and COP position under the stance foot during the step over the obstacle). The results provide strong evidence that the primary endings of ankle muscle spindles play a significant role in the control of posture and balance during the swing phase of locomotion by providing information describing the movement of the body’s COM with respect to the support foot. Our results also provide supporting evidence for the proposal that there are context-dependent changes in muscle spindle sensitivity during human locomotion.

Running, Einstein, Gravitational Push and Space. What do they have in common ?

WAIT !  Don’t watch the video just yet !  Read this first paragraph first !

Yes, you read it right. Gravitational PUSH.  Did your physics teachers mislead you ?  There is no such thing as Gravitational “Pull”.  Actually it is most accurate to say atmospheric push. Gravity does not pull us to the ground, space (as in the atmosphere) is pushing down on us. Space and time are curved and adjustable, Einstein proved this. You must be saying, “Oh Gait Guys, you are going way too deep now !”.  No, we are not. And you need to know this if you run or walk. It is simple. Your 5th grader will understand this and so should you !   Watch the video for a very nice explanation of what we are going to discuss today, atmospheric PUSH, start at the 3:30 mark for support for our point today.  If you choose not to watch this video today, it is your loss.  You will be depriving yourself of some of the most important information and logic there has ever existed in science. There is a big difference between pull and push.  Ask anyone who has had a car breakdown and had to push it off the road. Ask any weightlifter as well.

What does this have to do with running, walking and gait ?

Well, it is pretty simple.  This is yet another reason why posture is dependent upon the extensors such as the gluteals, the quadriceps, the cervical spine extensors, the thoracolumbar paraspinals, the abdominals etc.  These muscles must be strong enough to resist the push of Space down upon our bodies. Think of it this way, what muscles would have to work harder and be more isometrically and eccentrically strong and endurance trained if you had to carry a 100 pound person on your shoulders all day ?  It is much the same as if you were carrying a bunch of extra winter fat on your body. You will need more of these extensors otherwise you will begin to break down into compensations. 

With the natural motion of pronation during impact loading we need to dampen the internal spin of the hip, femur and tibia to resists the pronatory forces from space pushing down on us. 

So, our neuromuscular system has evolved to resist this push, and that job lies largely with the antigravity extensor muscles, which keep us upright. The elderly eventually begin to lose this battle as they weaken and posturally decompose. These muscles are powered by a special part of our our brain, largely the cerebellum, assisted by the vestibular apparatus (inner ear). Remember that there are 3 systems that keep us upright; vision, the vestibular system and the proprioceptive system. The interplay of these 3 systems is what Newton was trying to figure out and Einstein was eluding to.

This is one of the reasons orthotics (for the long term) often, but not always of course,  do not make sense.  Space pushing down on us and thus space pushing our body mass down onto our tri-arched foot (what we have come to understand as gravitational pull, which is technically misspeaking of the facts) is a large part what creates the pronation; with the musculature of the lower kinetic chain assisting in slowing it.  Slapping an orthotic under the foot to resist this force is not a permanent solution; it is often a temporary fix to a long term problem. This returns us to the hypothesis of today’s post, gravitational pull or Space push. Which is smarter, pushing up against the downward pressure of Space push (orthotic) or finding a better way of using the body’s anatomy to pull up against it ?  Which makes us stronger and a better human and athlete ? Finding better skill, endurance and strength (there it is again, S. E. S.) in the anti-gravitational muscles if you will, such as the toe extensors, tibialis anterior and posterior and foot intrinsics as well as those muscles above that are not dampening internal spin (medial quads, gluteals, lower abdominals)  is the answer if you really want to fix it.  Often times, a stability shoe is much the same as the orthotic; it provides dampening and slows pronation, or “resists” the push of gravity. It can sometimes be helpful in the short term; creating mechanics that you do not have; but is seldom good for the long term (though in some cases they are necessary, we are not negating their occasional beneficial use). We just ask that you, or at least your orthotist,  use your/their brain when making that decision.

As we always say, there are so few people who truly understand the neuro-ortho-biomechanics of the human parts going into the shoe that we get  all caught up in the shoe as the solution.  The solution is S. E. S.  , if you still  have the anatomy to get there.

Shawn and Ivo ………. two Uber geeks today.  They are the kind of guys who keep neurology and physics textbooks beside the toliet rather than Sports Illustrated Swimsuit issues.  Hey, we try to keep it simple. We like to pick the low hanging fruit just like everyone else. But it is the higher hanging fruit that are often the gems.  Sure, space pushing down on us all can make it hard to get up that high to the good stuff…….but it is worth it when you get there.  Thanks for tagging along on this journey. If you are a regular reader,  reconsider your bathroom reading material if you haven’t already !