Gait and the lower visual field.

Gait and the eyes. We forget about the eyes. If you have vision issues, your gait may change.
Gaze during adaptive gait involving obstacle crossing is typically directed two or more steps ahead where as visual information of the “in the moment” swinging lower-limb and its relative position during the task is available in the lower visual field. This study determined exactly when visual information is utilised to control/update lead-limb swing trajectory during obstacle negotiation.
In this study, when the lower visual field was blocked out the foot-placement distance and toe-clearance became significantly increased, suggesting the brain overcorrecting for safety. A logical assumption. “These findings suggest that lower visual field input is typically used in an online manner to control/update final foot-placement, and that without such control, uncertainty regarding foot placement causes toe-clearance to be increased.”

http://www.ncbi.nlm.nih.gov/pubmed/22424759

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

Your gait and peripheral vision: Part 2. There is more to it than what you do/don’t see.

Written by Dr. Shawn Allen

Yesterday we did a blog post on the loss of peripheral vision from drooping eye lids leading to the necessity (not vanity based) of a minor surgical procedure called a blepharoplasty.  Here was that blog post (link), it had some important research based points you need to know.

Vision is typically the predominant sensory system used for guiding locomotion. Online visual control is critical for adjusting lower limb trajectory and ensuring proper foot placement, including optimal limb/foot crossing velocity, optimal trail-foot horizontal distance and lead-toe clearance. Research suggests that peripheral visual cues play a large role in this online gait control. 1

We have discussed many of these issues, the conscious and subconscious importance of vision on human gait, in many of our blog posts over time.  Namely, blog posts on dual-tasking attention, negotiating stairs, and even in tandem walking holding hands. These all require a degree of peripheral vision function otherwise gait problems, including falls, rise on the risk list.

According to Timmis and Buckley (2), “although gaze during adaptive gait involving obstacle crossing is typically directed two or more steps ahead, visual information of the swinging lower-limb and its relative position in the environment (termed visual exproprioception) is available in the lower visual field (lvf).”  Their study determined exactly when lvf exproprioceptive information is utilized to control/update lead-limb swing trajectory during obstacle negotiation. 

Their study determined that “when (the) lower visual field (lvf) was occluded, foot-placement distance and toe-clearance became significantly increased; which is consistent with previous work that likewise used continuous lvf occlusion”. Their findings suggest that “ lvf (exproprioceptive) input is typically used in an online manner to control/update final foot-placement, and that without such control, uncertainty regarding foot placement causes toe-clearance to be increased. Also that lvf input is not normally exploited in an online manner to update toe-clearance during crossing: which is contrary to what previous research has suggested.” 2

Elliot and Buckley (3) showed the importance of peripheral visual cues in the control of minimum-foot-clearance during overground locomotion. In their study, 

From their abstract: “eleven subjects walked at their natural speed whilst wearing goggles providing four different visual conditions: upper occlusion, lower occlusion, circumferential-peripheral occlusion and full vision. Results showed that under circumferential-peripheral occlusion, subjects were more cautious and increased minimum-foot-clearance and decreased walking speed and step length. The minimum-foot-clearance increase can be interpreted as a motor control strategy aiming to safely clear the ground when online visual exproprioceptive cues from the body are not available. The lack of minimum-foot-clearance increase in lower occlusion suggests that the view of a clear pathway from beyond two steps combined with visual exproprioception and optic flow in the upper field were adequate to guide gait. A suggested accompanying safety strategy of reducing the amount of variability of minimum-foot-clearance under circumferential-peripheral occlusion conditions was not found, likely due to the lack of online visual exproprioceptive cues provided by the peripheral visual field for fine-tuning foot trajectory.”

These appear to be important studies on the effects of vision and peripheral vision and proprioceptive cues.  How we move our bodies depends much on visual cues, the ones we know we see, and the ones we are unaware that we “see”. Take this to the next level, imagine how the blind must adapt to gait without these cues. That is gait topic we will save for another time.

So, the gait analysis you are doing with your runners, your athletes, your clients takes into consideration their vision right ? Hmmmm, some how we just know that many gait gurus just sat back in their chairs and let out a long exhale. We go even more rogue in podcast 95 when we discuss head tilt and the vestibular system, we know that one is almost always overlooked. Another long exhale we presume.

Shawn Allen … .  one of the gait guys

References:

1. Exerc Sport Sci Rev. 2008 Jul;36(3):145-51. doi: 10.1097/JES.0b013e31817bff72.Role of peripheral visual cues in online visual guidance of locomotion. Marigold DS1.

2.Gait Posture. 2012 May;36(1):160-2. doi: 10.1016/j.gaitpost.2012.02.008. Epub 2012 Mar 17.Obstacle crossing during locomotion: visual exproprioceptive information is used in an online mode to update foot placement before the obstacle but not swing trajectory over it.Timmis MA1, Buckley JG.

3. Gait Posture. 2009 Oct;30(3):370-4. doi: 10.1016/j.gaitpost.2009.06.011. Epub 2009 Jul 22.Peripheral visual cues affect minimum-foot-clearance during overground locomotion.Graci V1, Elliott DB, Buckley JG.

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.

Take this simple test. 

Want to be faster? Better incorporate some proprioceptive training into your plan. It is the 1st part of our mantra: Skill, Endurance, and Strength (in that order). Proprioceptive training appears to be more important that strength or endurance training from an injury rehabilitation perspective as well part of an injury prevention program

 What is proprioception? It is body position awareness; ie: knowing what your limbs are doing without having to look at them.

Take this simple test:

  • Stand in a doorway with your shoes off. Keep your arms up at your sides so that you can brace yourself in case you start to fall. Lift your toes slightly so that only your foot tripod remains on the ground (ie the base of the big toe, the base of the little toe and the center of the heel.). Are you able to balance without difficulty? Good, all 3 systems (vision, vestibular and proprioceptive) are go.
  • Now close your eyes, taking away vision from the 3 systems that keep us upright in the gravitational plane. Are you able to balance for 30 seconds? If so, your vestibular and proprioceptive systems are intact.
  • Now open your eyes and look up at the ceiling. Provided you can balance without falling, now close your eyes. Extending your neck 60 degrees just took out the lateral semicircular canals of the vestibular system (see here for more info). Are you still able to balance for 30 seconds? If so, congrats; your proprioceptive system (the receptors in the joints, ligaments and muscles) is working great. If not, looks like you have some work to do. You can begin with exercises we use every day by clicking here.

Proprioception should be the 1st part of any training and/or rehabilitation program. If you don’t have a good framework to hang the rest of your training on, then you are asking for trouble. 

The Gait Guys. Your proprioceptive mentors. We want you to succeed!

Mirror Neurons: We are gonna piss off ALOT of people today with this post.  

How closely do your kids watch you? If you are a guy, how closely did you study the sporting greats like Michael Jordan, Joe Thiesman, Magic Johnson, Nolan Ryan, Carl Lewis, etc ? And ladies, who did you mirror yourself after?  When we are young we idolize, mimic and mirror that which we are surrounded by or that which we aspire to.  Every kid in my neighborhood had a Kareem Addul Jabar Sky-hook.  Heck, why not ?!

When it comes to gait, we model there too. In our practice we have seen, enough times to know it is not coincidence, a father walk into the office and his son have the same limp and swagger.  Kids pay attention, they just don’t model our 4 letter words.  Actions speak loudly and imitation is a strong method of learning and communication.

Humans have always observed other humans.  Observation, modeling and imitation are a form of survival.  If we want to socially understand, interact and survive we have to understand the actions of others and learn to assimilate, interact and react to others. Mirror neurons and the mirror-neuron mechanism are fundamentally human and necessary to complete these tasks of social interaction.

To this end, it is imperative to understand the gait cycle, both the walking and running cycles. The observer must know the normal cycles in order to identify the abnormal components of someone’s gait cycle. Once this can be identified one must know how to determine the cause of what is observed and know how to remedy the cause of the abnormality, not the remedy of the observed abnormality.  And just as importantly, the observer must help the client see and feel the pathologic pattern, correlate the causitive factor and help model a cleaner motor pattern. We find it very helpful to be able to mimic the client’s pathology to help them see and recognize it outside of their own body and then help them better feel their pathology (which is often an epiphany to them), model a remedy, and help them remedy the problem fitting the new pattern into a new non-pathologic gait pattern.  Once a client sees their problem, recognizes it, feels it in their own gait, feels the cleaner remedied pattern then they can cycle in a new neurologic pattern.  Then the clock begins to tick, and a new pattern will develop in 10+ weeks once a new myelinated pattern is engrained with conscious practice.  

* But one thing is clear, if you do not identify the source or cause of the abnormal gait pattern first (with remedy to follow), and you skip this critical diagnostic first step, deciding to go directly into showing your client how they SHOULD walk or run then you merely have helped them to develop a new gait cycle on top of the faulty old gait pattern which was a compensatory strategy to begin with around the underlying neuromechanical pathology (ie. immobility, hypermobility, instability, weakness etc). Whew ! That was mouthful.

Go for the root level of the problem, forget about the grass level appearance of the problem. Dig deep, don’t be a shallow digger. Be part of the solution, not part of the problem.  Think about all of this the next time you goto a running clinic that is teaching what is supposed to be “better form”. First of all, better form for whom ? The elite running? The upper quartile athlete?  The mean? The median? Or, the first timer amateur ?  Telling people how running should look and feel, rather than looking for the cause as to why someone runs less than optimally is a big mistake.  The body doesn’t decide to run poorly and inefficiently, it chooses to do so because some of the parts are either twisted (ie. osseous torsions), there are remnants of old injuries unresolved completely, they are in the wrong shoes for their foot type, they have physical limitations from underlying weakness (which then predicate the development of tightness or altered patterns to compensate) or lack of body awareness. Think about all this the next time you start to ponder form running clinics and treadmill gait analysis at your local store or therapists office.

Examine your client, test their motor patterns, test their muscle strength, find the cause of that gimpy gait or running technique.

Shawn and Ivo, The Gait Guys…….. likely pissing off a whole lot of people today with science, logic and neuro-mechanical principles. And, not intentionally pissing folks off, just suspecting that a bunch of people just had a light bulb moment and are pissed at the messenger.

Another video link:   http://youtu.be/6s1ON7ZZQxQ   Family Performance by Warren & Kristi Boyce – Glenn Richard Boyce & Kayleigh Andrews @ 3rd Surabaya International Dancesport Championship 2013 (8th June 2013)

Reference Links:

http://www.ncbi.nlm.nih.gov/pubmed/15217330

http://www.ncbi.nlm.nih.gov/pubmed/19129788

Do you bank your head into the turns when you run corners ? You had better !

From time to time we get asked, why have you guys focused so intently on gait ?  Our answer is always the same. It is the most frequently engaged motor pattern that the body does other than breathing. Without the ability to walk our health declines on many levels.  And, because gait impacts every aspect of the human organism when it comes to locomotion.  All too often gait is thought of as what the feet are doing. We see this as evidenced by how many shoe stores still just do a foot treadmill video analysis, but thankfully, many stores have gotten the message from somewhere that the rest of the body is vital to the assessment as well. However,  how many of you are capturing the  head on your gait analysis ?  The head is where the software exists. Balance, visual, many proprioceptive centers, auditory and the processing of these and more are all located north of all of the other body parts.  

We have done many previous blog posts on the visual and auditory centers and how they impact gait.  You can goto our blog and type these into our SEARCH box and read more about these topics however today we wanted to share with you an article that is a few years older to show that there are many predictive gait parameters that are pre-calculated and have a huge determining effect and outcome on one’s gait. 

Anticipatory head movements during turns, whether running on a banked track, taking tight turns on your local road, trail running on the side of slopes or even when biking and trail riding, all occur in order to gather advance visual information about the trajectory and potential obstacles.  Below is an abstract that pretty much speaks for itself and you should read it. In the study they investigate the relationship between head and trunk movements during ambulation.  They discuss how the head makes its calculated turn prior to the trunk turning, setting up the body for a proper negotiation of the banking of the turn thus gathering “visual information about the trajectory and potential obstacles”. 

If you are truly a gait geek, you should get a little warm and fuzzy about this. And if you do not, well, you might still be a gait geek if you think a bit further about this and understand that cervical spine stability and mobility can negatively or positively affect the outcome.  It just goes to prove once again, if you are going to address someones gait, you better have a clinical examination as part of their gait assessment if you want to truly find out where their impairment exists, and hides. If you depend solely on video, you are most likely giving advice on missing information, this we pretty much promise you. For example, we recall a younger lady from a few years ago, a patient of ours, who was left with unilateral deafness from a vaccine complication (MMR vaccine). She would always have her better ear turned more forward to gain an auditory edge to her hearing loss on the opposite side (we all do the same thing when we are talking to someone in a loud place). What we noticed, and what she was unaware of, what that this impaired her arm swing bilaterally making the one side swing more and the other less (which was a huge clue into her shoulder problem that she was seeing us for).  This in turn, because they are neurologically connected by reflexive locomotion patterns, impaired swing and stance phases of her gait on both sides.  It just goes to prove our point earlier, and to further make the point that, you cannot impact symmetry in one place and not expect that the body will not compensate for that asymmetry elsewhere. It is all connected … . you know the song.

If you are a gait geek, you can see the entire picture of the human organism clearer than many others.  

Enjoy the whole abstract below for the great details by Sreenivasa et al.

* Shawn and Ivo …….. not your average wild and crazy guys……unless there is a gait topic to talk about.

Exp Brain Res. 2008 Nov;191(3):313-20. doi: 10.1007/s00221-008-1525-3. Epub 2008 Aug 8.

Walking along curved paths of different angles: the relationship between head and trunk turning.

Sreenivasa MN, Frissen I, Souman JL, Ernst MO.

Source

Max Planck Institute for Biological Cybernetics, Spemannstrasse 41, 72076 Tübingen, Germany.

Abstract

Walking along a curved path requires coordinated motor actions of the entire body. Here, we investigate the relationship between head and trunk movements during walking. Previous studies have found that the head systematically turns into turns before the trunk does. This has been found to occur at a constant distance rather than at a constant time before a turn. We tested whether this anticipatory head behavior is spatially invariant for turns of different angles. Head and trunk positions and orientations were measured while participants walked around obstacles in 45 degrees, 90 degrees, 135 degrees or 180 degrees turns. The radius of the turns was either imposed or left free. We found that the head started to turn into the direction of the turn at a constant distance before the obstacle (approximately 1.1 m) for turn angles up to 135 degrees . During turns, the head was consistently oriented more into the direction of the turn than the trunk. This difference increased for larger turning angles and reached its maximum later in the turn for larger turns. Walking speeds decreased monotonically for increasing turn angles. Imposing fixed turn radii only affected the point at which the trunk started to turn into a turn. Our results support the view that anticipatory head movements during turns occur in order to gather advance visual information about the trajectory and potential obstacles.