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

“those with chronic neck pain demonstrated a narrower step width, a shorter step length and slower gait speed during walking with the head movements and at maximum speed” –  Uthaikhup et al. study:

Head movement and Gait Parameters:

By now you should have a good grasp of the global impact of gait and how it presents and translates in everything we do. It is how we move through this world, and everything we do, and everything that has happened to us, impacts our gait. And, our gait impacts things in turn, from our mental state to how we think and act.  

By now, if you have been with us here on The Gait Guys long enough, you know that with the tremendous proprioceptive impact of the system from the cervical spine, that neck pain can influence sensorimotor function and thus motor function. However, little is known about the effects of head movement and walking speed on gait characteristics in patients with neck pain.

From the Uthaikhup et al. study:

Patient sample:  20 women aged between 18 and 59 years with chronic neck pain (>3 months) and 20 healthy controls of similar age, weight and height

Indexes used: Neck Disability Index and Visual Analogue Pain Scale.

“The experiment consisted of two walking sessions. The first session included walking with head straight, head up-down, and head turns from side to side. The second session included walking at comfortable and maximum speeds. Each trial was performed twice. Gait parameters measured using GAITRite walkway system were step length, stride length, step time, stride time, step width, cadence and gait speed.”

According to this study, the clients with chronic neck pain showed several changes in how they implemented their gait. They displayed step width narrowing, a reduction in step length and speed of gait, and even an overall reduction in gait speed when neck movements were induced or encouraged or when there was pain..

As Uthaikhup et al. summarized, “The results suggest that patients with chronic neck pain have gait disturbances. This supports the notion that assessment of gait should be addressed in patients with persistent neck pain.”

You have to know your gait norms to understand abnormals. We have written about other parameters that affect gait speed, step length and width here on the blog. Here is one more parameter for you to store in your noggin. It is all connected. So, when you goto your gait analysis guru, ask them if they are going to clinically assess your painful neck as part of the gait analysis (be prepared for the “deer in the headlights” look).

Dr. Shawn Allen, one of the gait guys

Reference:

Man Ther. 2014 Apr;19(2):137-41. doi: 10.1016/j.math.2013.09.004. Epub 2013 Sep 27.The effects of head movement and walking speed on gait parameters in patients with chronic neck pain. Uthaikhup S, Sunkarat S, Khamsaen K, Meeyan K, Treleaven J.

Does slowing gait increase gait stability ?

As this study suggests, it has been difficult to find studies that establish a clear connection between gait stability and gait speed. One can easily assume that slowing down increases stability, we do it on slippery surfaces, we do it when a joint is painful, even the elderly do it naturally everyday. Walking speed, step length, step frequency, step width, local dynamic stability , and margins of stability were measured in this study below. It was found that the subjects did not change walking speed in response to the balance perturbations rather they made shorter, faster, and wider steps with increasing perturbation intensity. They became locally less stable in response to the perturbations but increased their margins of stability in medio-lateral and backward direction. 

So what did they conclude ?  Here are their words,“In conclusion, not a lower walking speed, but a combination of decreased step length and increased step frequency and step width seems to be the strategy of choice to cope with medio-lateral balance perturbations, which increases Margins of Stability (MoS) and thus decreases the risk of falling.”

It is my assumption, and this just seems logical, that if the perturbations were to continue constantly, that one would slow the gait speed to reduce the need for these shorter, faster and wider steps. 

Dr. Shawn Allen

http://www.ncbi.nlm.nih.gov/pubmed/22464635

Gait Posture. 2012 Jun;36(2):260-4. doi: 10.1016/j.gaitpost.2012.03.005. Epub 2012 Mar 29.Speeding up or slowing down?: Gait adaptations to preserve gait stability in response to balance perturbations.Hak L1, Houdijk H, Steenbrink F, Mert A, van der Wurff P, Beek PJ, van Dieën JH.

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.

Texting and Walking.  Your gait will change when you are texting on your phone.
You are going to want to put away your cell phone after you read this, or at least hide your parent’s phones.
*(the video link attached here has likely been blocked by ABC News, you should see a forwarded link to their youtube feed. If not, here it is

So you think you are a multi-tasker do you ?  Do you know how much cerebral cortex real estate is necessary to walk or drive and text ? Just try texting while walking for 5 seconds in an unfamiliar environment and see what happens.  Dual tasking is difficult especially when one task is cognitive and the other is spacial and motor. At some point something has to give, especially if you are on the edge of tapping out the executive function centers in the brain because of early disease or age related mental decline.  This has never been more prevalent than in the elderly and the number of mounting studies proving that dual attention tasks lead to a dramatic increase in age related fall injuries.  If you look into the literature the fall rate increases from anywhere from 11 to 50%, these are strong numbers correlating falls and dual attention tasking in the elderly.  Certainly the numbers are worse in the frail and gait challenged and fewer in healthier elderly folks, but the correlation seems to be strong particularly when there are even early signs of frontal cortex demise. We have talked about this on several recent podcasts (check out podcasts 80-85) and this has been rooted even further from one of our neurology mentors, Dr. Ted Carrick.  

Recently in the Journal of Applied Biomechanics, Parr and associated took 30 young able bodied healthy individuals with experience texting on cellular phones. The study used an 11-camera optical motion capture system on a 8m obstacle-free floor. 
The study showed a reduction in gait velocity in addition to significant changes in spatial and temporal parameters, notably, step width, while the double support phase of the gait cycle increased.  Furthermore, and equally disturbing, toe clearance decreased but luckily step length and cadence decreased. 
Thus, it appears that the attention draining texting task generally forced the brain to slow the gait, reduce step length while improving stability via increasing step width and double support phase of gait, keep in mind that these are young healthy experienced individuals with no early cognitive challenges.  This is not the case in aging adults, or in adults with factors that have either challenged gait stability (degrees of impaired balance, vision, vestibular, proprioception etc) or challenged frontal cortex function where that functionality of the brain is already nearing its tipping point for adequate function.  Sadly, these are all factors in the aging adult and they are why falls are increased and riskier for the elderly. Essentially, what the studies are showing is that dual tasking creates a distraction that can amplify any sensory-motor challenges in the system.  Mind you, there are studies that show that if the dual task is remedial such as talking while walking the effects are more muted, however in those who are at the tipping point capacity of mental executive function, mere talking (cognitive linguistic engagement), can also tip the system into deciding whether to focus on the gait or the talk but not both adequately.  Something will have to give in these folks, safe competent dual tasking is beyond the ability of their system. 
As we have eluded to here, there are many factors and variables that can challenge the system. Visual challenges such as low light vision problems or depth perception challenges can act similarly on the system to dual tasking attempts and thus magnify fall risk. What about sensory challenges from a spinal stenosis or peripheral neuropathy such as in advancing diabetes?  Balance and vestibular challenges, let alone factors such as unfamiliar environments (perhaps magnified by vision challenges) as precursors are a foregone conclusion to increase fall risk in anyone let alone the elderly.
By this point in this article it should be a given that texting while doing anything else is a dual tasking brain challenge that could lead to a fall, an embarrassing spill into the public pool or into a fountain at the mall let alone driving off a cliff or into a crowd of people.  But are all of these unfortunate people showing signs of frontal cortex/executive function impairment? Perhaps not, especially if they are healthy.  One has to keep in mind that texting is a high demanding cognitive attention task, even though we think nothing of it as a healthy adult. Think about it, one has to engage a separate screen other than the environment they are trying to walk through. Additionally, one has to think about what they are trying to text, engage a seperate motor program to type, then there is spelling, choosing text recipients, sending the message, watching and listening for a response, and the list goes on meanwhile the person is still trying to run the gait subprograms.  We take it for granted but texting is highly engaging and adding walking can tip the system into a challenge or failure if we are in a crowd, unfamiliar environment, low light etc.  
So if you have ever wondered why elderly people trip and fall in even the most benign environments, it is likely a compounded result of challenges to situation and spatial awareness and working memory with many possible factor challenges. Again, things like poor lighting, vision limitations, unfamiliar environment, vestibular limitations, numbness in the feet, talking or even if they are simply carrying the afternoon tea to the sun room these things all are dual tasking and some require higher demands from the executive function brain centers.   Any factor(s) which tax the already-reducing executive function centers in the elderly subtract from the most basic elements required for upright posture and gait.  If dual-tasking can impair healthy young individuals, the elderly are a forgone conclusion to have magnified risks.  
There can be a plus to all of this however. If the goal were to only reduce falls and fall risks in the elderly, an astute clinician can work this to their favor and do gait challenges and retraining in the office environment while safely stacking dual task challenges to expand and restore some executive function capabilities.  We are never too old to learn and lay down improved motor and cognitive patterns. So, use this information to your advantage to improve function instead of delivering it as a dark cloud to hang over your clients, whether they are elderly or neurologically challenged. 
In summary, put down the darn phone, trust us, that text can wait.  Rather, enjoy the sunshine, the smiling faces, the trees.  If you are driving or walking, dump the phone and pay attention to traffic and your environment. Stop and wave to a friend. Teach your kids about this texting problem, they are likely already oblivious to many risks in the world, and this one likely hasn’t crossed their mind either. At the very least, help the elderly lady or man cross the street. By now you should understand all that they are consciously and subconsciously trying to calculate to negotiate the street crossing. Their declining executive function is often a mental feat all on its own, but having to actually add the physical act of walking (which is likely already showing aspects of age related biomechanical decline) might just be their tipping point leading to a fall.  So offer your arm, a warm smile, and think everything of it, because someday it will be you at that street corner with sweaty palms and great fear.
 
Shawn and Ivo, “the gait guys”
References :
1. Eur J Neurol. 2009 Jul;16(7):786-95. doi: 10.1111/j.1468-1331.2009.02612.x. Epub 2009 Mar 31.
Stops walking when talking: a predictor of falls in older adults?Beauchet O1Annweiler CDubost VAllali GKressig RWBridenbaugh SBerrut GAssal FHerrmann FR.
2. J Appl Biomech. 2014 Dec;30(6):685-8. doi: 10.1123/jab.2014-0017. Epub 2014 Jul 9. Cellular Phone Texting Impairs Gait in Able-bodied Young Adults. Parr ND1, Hass CJTillman MD.
3. Gait Posture. 2014 Aug 20. pii: S0966-6362(14)00671-7. doi: 10.1016/j.gaitpost.2014.08.007. [Epub ahead of print]  Texting and walking: effects of environmental setting and task prioritization on dual task interference in healthy young adults. Plumer, Apple, Dowd, Keith.
4. Gait Posture. 2012 Apr;35(4):688-90. doi: 10.1016/j.gaitpost.2011.12.005. Epub 2012 Jan 5.  Cell Phones change the way we walk.  Lamberg, Muratori
5. Int J Speech Lang Pathol. 2010 Oct;12(5):455-9. doi: 10.3109/17549507.2010.486446.  Talking while walking: Cognitive loading and injurious falls in Parkinson;s disease. LaPointe LL1, Stierwalt JAMaitland CG.

 

Human gait is cyclical. For the most part, when one limb is engaged on the ground (stance phase), the other is in swing phase. Before we continue, you should recall that there is a brief double limb support phase in walking gait, that which is absent in running gait. Also, we wish to remind you of our time hammered principle that when the foot is on the ground the glutes are heavily in charge, and when the foot is in the air, the abdominals are heavily in charge.  

For us to move cleanly and efficiently one would assume that the best way to do that would be to ensure that the lower 2 limbs are capable of doing the exact same things, with the same timing, same skill, same endurance and same strength. This goes for the upper 2 limbs as well, and then of course the synchronizing of the 4 in a cohesive effort. For this clean seamless motor function to occur, one must assume that there would be no injuries that had left a remnant mark on one limb thus encouraging a necessary compensation pattern in that limb (and one that would then have to be negotiated with the opposite limb as well as the contralateral upper or lower limb).  For example, when right ankle rocker (dorsiflexion) is impaired, early heel departure will occur and hip extension will be limited. An alteration in right glute function will most likely follow.  One could theorize that the left step length (the length of measure from right heel strike through to left heel strike) would thus be shortened. This would cause a premature load onto the left limb, and could very well force the left frontal plane to be more engaged than is desirable. This could lead to left core and hip frontal plane weakness and compensation patterns to be generated (ie. right arm abduction. One can see all of these components in the photo above, and in this case here). It could also lead to a pelvic distortion pattern which would further throw off the anti-phasic nature of symmetrical and efficient gait.  To complicate the cyclical scenario, the time usually used to move sagittally will be partially used to move into, and back out of, the left frontal plane. This will necessitate some abbreviations in the left stance phase timely mechanical events. Some biomechanical events will have to be abbreviated or sped through and then the right limb will have to adapt to those changes. These are simple gait problems we have talked about over and over again here on the gait guys blog. (Search “arm swing” on our blog and you will find 45 articles around this topic.) These compensation patterns will include expressed weaknesses in various parts of the human frame as part of the pattern, and merely fixing those weaknesses does not address the right ankle rocker problem. Fixing said weaknesses merely encourages the brain to possibly continue to perpetuate necessary tightnesses in other muscles and engrain the compensations (challenges to mobility and stability) further or more complexly.  It is easy to find something weak, it takes a sharp brain to find the sometimes silent sparking event. Are you able to find the problem in this never ending loop of compensations and find a way to unwrinkle the system one logical piece at a time, or will you just chose to strengthen the wrinkled system and hope that the new strength on top of the compensations is adequate for you our your client ? One should not be forever sentenced to daily or weekly rehabilitative sessions/ homework to negate and alleviate symptoms, this is a far more durable machine than that. Fix the problem.

Now, lets add another wrinkle to the system.  What if there were problems before any injuries ?  Meaning, what if there were problems during the timely maturation and suppression of the primitive reflexes ? Or problems in the timely appearance or maturation of postural reflexes? A problem in these areas may very well result in a central or peripheral nervous system malfunction and a representation of such in one’s movement and gait.  That is a larger discussion for another time.

There is a reason that in our practices we often assess and treat contralateral upper and lower limbs as well as to address remnants from old injuries whether they are symptomatic or not. This is a really tough puzzle and game you are playing. For example, when there is insufficient hip internal rotation unilaterally you can regain some of the loss through increased foot pronation unilaterally, but at a consequence to both the local and global pictures.  Remember, most of the time you are trying to walk in a straight line from A to B and if the parts are not symmetrical you have many options to compensate. It is not as simple as telling your athlete to swing one arm more, or to stop pulling it across their body; they need to do those things, it is called a “compensation”. It is often not as simple as finding an impaired Rolling Pattern and driving it back to symmetry, in doing so, you may have just added strength and skill to a compensation.  Merely addressing things locally can be a crime.  If you are seeing an arm swing change, you would be foolish not to look at the opposite lower limb and foot at the very least, and of course assess spinal rotation, lateral flexion and hinging as well as core mobility and stability.  For your neuro nerds, remember the receptors from the central spine and core fire into the midline vermis of the cerebellum (one of the oldest parts of our brain, called the paleo cerebellum); and these pathways, along with other cerebellar efferents, fire our axial extensor muscles that keep us upright in the gravitational plane and provide balance or homeostasis.  So, those need assessed and addressed as well.  

Or, if this is too much thinking for you, … you can just train harder and get stronger . .  . in all your compensation patterns, after all, it is easier than figuring out why and how that right ankle started the whole mess, if in fact that is even the first piece of the puzzle.

Welcome to the matrix.

shawn and ivo, the gait guys

The power to bend bones.

What have we here? Hmmm. This little girl was brought in by her mother because of intermittent knee pain and “collapsing” of the knees while walking, for no apparent reason.

The ankle dorsi flexion (or ankle rocker; see last 2 pictures; we are fully dorsiflexing the ankles)  needs to occur somewhere, how about the knees? Or in this case, the tibia. Wow!

You are looking at a 4 year year with a condition called genu (and tibial) recurvatum. Genu recurvatum is operationally defined as knee hyperextension greater than 5 degrees. The knee is hyperextended, and in this case, the tibia is literally “bent backward”. Look at the 2 pictures of her tibia.

Generally speaking, the tibial plateau usually has a slight posterior inclination (as it does in this case; look carefully at the 1st picture) causing the knee to flex slightly when standing. Sometimes, if it is parallel with the ground and the center of gravity is forward of the knees, the knee will hyperextend (or in this case, the tibia will bend) to compensate.

In this particular case, the tibia has compensated more, rather than the knee itself. The knee joint is stable and there is no ligamentous laxity as of yet. She does not have a neurological disorder, neuromuscular disease or connective tissue disorder. She has congenitally tight calves.

As you can imagine, her step length is abbreviated and ankle rocker is impaired.

So what did we tell her Mom?

  • keep her barefoot as much as possible (incidentally, she loves to be barefoot most of the time, gee, go figure!)
  • have her walk on her heels (she’s a kid, make a game of it)
  • showed her how to do calf stretches
  • balance on 1 leg with her eyes open and closed
  • keep her out of backless shoes (like the clogs she came in with)
  • keep her out of flip flops and sandals where she would have to “scrunch” her toes to keep them on.
  • follow back in 3 months to reassess

There you have it. Next time you don’t think Wolff’s (or Davis’s) law* is real, think about this case. Want to know more? Consider taking our National Shoe Fit Program, available by clicking here.

The Gait Guys. Making you gait IQ higher with each post.

*Wolff’s law: Bone will be deposited in areas of stress and removed in areas of strain. or put another way: bone in a healthy person or animal will adapt to the loads under which it is placed

Davis’s law: soft tissue will adapt to the loads that are placed on it