*Video Gait demo: The couple in the hats, are they in phase or out of phase?

*Video Gait demo: The couple in the hats, are they in phase or out of phase?
Have you ever wondered why people who walk together quickly synchronize their gaits ?

The synchronization between walking partners is more complex than it seems on the surface. There are two types of synchronization, in-phase (both person’s right foot move forward at the same time) and out-of-phase synchronization (where the right foot moves forward with the partners left foot). You can see in the video above that the couple has subconsciously fallen into an Out-of-Phase synchronization.

There are multiple factors and communication mechanisms occurring. There are auditory mechanisms in play such as the sound of the other persons foot fall. There are even visual mechanisms through peripherally seeing your partners arm swing and foot fall which encourages the imitation synchronization. However, the strongest in-phase synchrony occurred in the presence of tactile feedback meaning hand holding or embracing each others waist from behind, which couples often do when walking more slowly, seem to create a stronger synchrony. When this tactile component is engaged between two walkers it is plausible that the upper and lower limbs move more freely when paired up, particularly with arm swing.
Read on, there is more to it here in an post we did awhile back. . . . link below

https://thegaitguys.tumblr.com/post/29333686230/have-you-ever-wondered-why-people-who-walk

https://youtu.be/05XtMtap3Yg

Have you ever wondered why people who walk together quickly synchronize their gaits ?

From healthy heart cells that synchronize to a single beat, to women in school dormitories or work places who synchronize their menstrual cycles, to fireflies who begin blinking in synchrony when they all perch in the same tree synchronization is something that is abundant in nature.  It is no wonder that we find synchronicity in one of our most primitive and frequent motor patterns, walking together with someone shows the same synchronicity phenomenon.

Hold the hand of your favorite person and go for a walk. Within a few strides your gaits will synchronize. Is it because it is easier ? Is it because when synchronized the arm swings will match thus making it easier and more effortless to hold hands ?  Does the same effect occur if you are not holding hands ? Studies have concluded that although it does not happen all of the time, they found it occurs in almost 50% of the walking trials even among couples who do not usually walk together. This is far too high a percentage to not make it a statistically significant finding.

The synchronization between walking partners is more complex than it seems on the surface.  There are two types of synchronization, in-phase (both person’s right foot move forward at the same time) and out-of-phase synchronization (where the right foot moves forward with the partners left foot).  You can see in the video above that the couple has subconsciously fallen into an Out-of-Phase synchronization, then after the tide splash that throws them off within just a few steps they fall right back into Out-of-Phase synchronization and hold it in that state.  There are multiple factors and communication mechanisms occurring. There are auditory mechanisms in play such as the sound of the other persons foot fall.  There are even visual mechanisms through peripherally seeing your partners arm swing and foot fall which encourages the imitation synchronization. However, the strongest in-phase synchrony occurred in the presence of tactile feedback meaning hand holding or embracing each others waist from behind, which couples often do when walking more slowly, seem to create a stronger synchrony.  When this tactile component is engaged between two walkers it is plausible that the upper and lower limbs move more freely when paired up, particularly with arm swing.

What is thought to happen is that one partner dominates the lead in the gait, just as in dancing, one person is the leader and the other is the follower. The lead partner’s lower limbs determine the movement of their arms, which in turn when holding hands, sets the arm movement pattern in the partner then determining the leg swing and stance phases. Thus, synchrony is achieved. 

However, it is important to note that many of the studies were clear to mention that even in non-tactile cases, many of the gaits of two people walking together are synchronized. This was likely due to the visual and auditory parameters however height, leg length cadence etc could also play into those successful non-tactile synchrony cases.

These are interesting findings at 50% because it is very unlikely that any two people are of the same height, leg length, cadence, stride and step length.  These are all parameters that are likely to change the likelihood of gait synchrony.  Zivotofsky found that “even in the absence of visual or auditory communication, couples also frequently walked in synchrony while 180 degrees out-of-phase, likely using different feedback mechanisms”. The studies below discuss many issues of this synchrony but it is perhaps most significant in clinical rehabilitation cases or in early or moderately advanced movement impairment disorders and diseases these findings may partially explain how patients can enhance their gait function when they walk with a partner or therapist.  It is in these movement impairment syndromes and diseases where the central processing and Central Pattern Generators (CPG’s) are diseased leaving them with the need for other cues such as those discussed here today, auditory, visual and tactile. 

You may have read our previous blog articles on arm swing and how intimately they are anti-phasically (opposite) paired with lower limb swing.  But today’s blog post article took limb swing to another level.  Stay tuned for more on arm and leg swing in human movement.  If you wish to read our other works on arm and leg swing and their deeper effects on gait, go to our blog www.thegaitguys.tumblr.com and enter the words “arm swing” into the SEARCH box.

Shawn and Ivo…….. taking gait far beyond what you learned about it in school.
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References used:

J Neuroengineering Rehabil. 2007; 4: 28. The sensory feedback mechanisms enabling couples to walk synchronously. An initial investigation.  Ari Z Zivotofsky and Jeffrey M Hausdorff  Published online 2007 August 8. doi:  10.1186/1743-0003-4-28

Hum Mov Sci. 2012 Jun 22. [Epub ahead of print] Modality-specific communication enabling gait synchronization during over-ground side-by-side walking. Zivotofsky AZ, Gruendlinger L, Hausdorff JM.Gonda Brain Research Center, Bar-Ilan University, Ramat-Gan 52900, Israel.

Arm and leg swing gait quiz. Today I combine concepts from my previous quizes ! This one may really put you to the test. 

Two women walking on a sloped beach. They are arm in arm.

Take the principles I have taught you on slope walking, functional leg length differentials to level the pelvis, and arm swing to answer the question.

Here is the question: Are these two more likely to walk “in phase or out of phase”? 

* Do not mistaken the question for anti-phasic or phasic. These are two different concepts. If you are out of the loop on these 4 terms, just search the blog for them. Then come back here to answer this brain thumper.

Make for your case in your head and then scroll down to hear my reasoning for my answer.

This is an EXTREMELY difficult mind bender of a question. You will need to understand the concepts of 2 prior blog posts to even get to the starting line of the solution.  These are the questions I will often pose to myself so that I force the mental gymnastics of gait biomechanics, and quicken my “gait mind” so that I can leave room for processing unique factors in someone’s individual gait. If you have to take time to process the basics, you are gonna run out of time during a consultation and your client will notice you scratching your head. This is a maturation process, you must put in the work that Ivo and I have, if you want to solve the really tough cases. Simple cases are a break, a vacation if you will, they are welcome during a clinic day, but it is the tough cases that make you stretch that truly fulfill your day.  When you are in the clinic, you have to think fast, efficiently and effectively. Recently I had a powerlifter drive from out of state to see me. His case problems were unresolved for many years.  The treating clinician was on the right page, doing a great job actually, but there were so many issues going on that it was hard to see the root of the problem so the case was just being more “managed” than solved. His case was much like this one, all of the findings and factors were related but because I had seen this hodge podge of complaints before (right foot, right knee, left hip, low back, pelvis distortion and a classic Olympic lift compensation fail) so I knew quickly how to piece it all together into a logical solution and find the single spot to focus the therapy, at the root of the problem. My point is that I had done the hard “head scratching” work long ago, so I readily was able to dismiss the distractors and recognize this beast for what it was.  

Back to the two ladies beach walking, I am basing things on a simple assumption that on most beaches the slope gently levels out at the water line, and that the sand several feet up the beach from the water is on a steeper incline, simple tide erosion principles.  Thus, the woman higher up on the beach will be on a steeper slope, this means more beach side leg knee flexion which means less hip extension, meaning a shorter right step length.  This will impair left arm swing, likely shortening it. Less right hip extension will be met by less left arm extension (posterior arm swing behind the body). This often leads to left arm cross over, arm adduction. 

Here is where things get squirrelly. The lady lower on the beach is on a slightly more gentle slope but her issues are the same just muted slightly. So her right beach side leg is in less flexion at the knee and hip, so hip extension is greater and step length will be longer (relative to her friend higher up on the beach). However, she (ocean side lady) is being led by the impaired arm swing, as discussed above, of the lady on the beach side.  That is, if in fact she is being led or if she is the leader. Oy ! There is the brain bender !  

One must consider who is the more corrupting force. In this case, the more corrupting forces will likely trump out the cleaner forces. The ocean side lady is clearly going to have a “more normal” gait with more normal arm and leg swing and step lengths, quite simply the slope she must negotiate is less so there is less corrupting forces on her. The lady on the beach side is having to accomodate more to her greater slope. The lady up the beach is working harder to keep her pelvis level, her eyes and vestiular apparati on the horizon, her differing step lengths from pulling her off from a straight line course, to keep her from falling over (the steeper the slope, the greater the balance challenge to fight from falling into the beach or falling down the slope. Laws of physics say that things roll down hill, so she is fighting this battle while trying to walk a straight line down a sloped beach, with a friends arm in tow).

So, with all that said, one could logically assume that the gal up the beach is definitely working harder, she has greater differing arm and leg swings from side to side, different step lengths, greater struggles with staying up on the slope when gravity wants her to move down the slope, she has more left arm flexion and adduction to help pair with the struggling and perpetual right hip flexion (and loss of right hip extension), she will have to demonstrate more spinal stiffness to deal with these limb girdle torsional differences side to side and a host of other issues I have outlined in these prior “beach walking” quiz posts. Clearly beach side lady is working harder. Thus, just to maintain her gait posturing up on the slope, she will have to dominate the gait. If she gives in to the signals of her ocean side gal, she will have to soften her slope work strategies and she will move down the slope to easier ground. 

Now, back to the question: Are these two more likely to walk “in phase or out of phase”? 

Who truly knows is the answer ! However, we know beach lady is working harder and must continue to do so to stay up on the slope, so her left arm will remain dominant and the ocean side gal will have to accommodate to a very jerky yet cyclically synchronous gait. To walk linked together they will have to find some rhythm. Walking slower will be easier for them to find a harmoniously rhythm. However, one could make the case that “out of phase” gait will be easier (mental image to help you, if they tie ocean side lady’s right ankle to beach side ladies left ankle you will create “out of phase” gait. Thus, the ocean side lady will not mirror her beach side friend. Thus, when beach lady has right leg in extension, ocean side lady will have her left leg in extension. Why? Well, the left arm swing , their point of union, is the trouble zone. With beach side lady having the left arm in more flexion and adduction, the ocean side lady has to accommodate and meet that troubling arm swing. This means her right leg will be in extension at the same time beach side lady has her left leg in extension. This will be more accommodative work for ocean side lady, but she will just have to go with it. Failure to do so will pull her friend down off the beach and making life harder for her friend.

So there you have it. The person up the slope is working harder to stay here, the person down the slope is working harder to accommodate to a gait that their  lower slope is not requiring. Thus, they are both working hard, but for different reasons. But the winner, the dictator, is the one with the greater slope risk. And thus, she will dictate an “out of phase” gait of her ocean side partner, if they are to still walk embraced. 

How did you do ? Can you make a case for “in phase” as the solution ? I can, but I think that “out of phase” is more likely, for the above reasons.

Thanks for playing  this tough one. Congratulations to you if you followed things smoothly. IF you did not, go back and play the mental game again, I think these are important fundamentals everyone should have if you are doing gait work.

Dr. Shawn Allen

Dr. Allen’s Quiz question of the week. See if you can get this one.

Reference point is the Girl in the middle, big sister. Choose all that apply. Note: there is something deeper than the obvious going on here, it doesn’t make sense. Can you see it ? 

a. she (big sister) is out of phase with her little sister 

b. she is in phase with her little sister

c. she is out of phase with her little brother

d. she is in phase with her little brother

e.  A and C

f.  B and C

g. B and D

h. A and D

i. AC~DC rules

Yes, Answer  “i” is always right.

otherwise the answer is … . scroll down

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F. she is in phase with her sister to her left and out of phase with her brother (at least if you are referencing her leg swing).  With her little sister, left feet are both forward in swing at the same time.

However, there is something deeper and requires some true critical thinking. IF you got the answer correct, congratulations. IF you did not, type in “in phase gait” or “arm swing” into the blog search engine and you will be able to read more about “in phase” and “out of phase” gaits.  

Now, look at the picture again. If she is “in phase” with her little sister to the left big sister should technically have her left arm in anterior/forward swing to meet little sister’s right arm swing. But, big sister’s left foot is forward, which technically means her left arm swing should be posterior to match her normal Anti-phasic gait.  But this does not pair with little sister. Can you see that this is a conflict in synchrony ? 

In phase and phasic are not the same thing, nor are out of phase and anti-phasic. Search our blog for these differences.  

Obviously you should glean by now that “In and out of phase” gait refers to the leg swing. Whereas, phasic and anti phasic gait refers to the synchrony of the upper and lower limbs in an individual.  The lower limb spinal cord motor neuron pools are more dominant than the upper arm pools (except in climbing, which is why I spent so much time last week talking about climbing and crawling here on the blog). Thus the lower legs often run the protocols and thus why arm swing changes should not be primarily or initially coached or amended in an athlete, they are very adaptive and accommodating.  The legs need to run the show, we need our arms free to be able to carry things while walking or running (water bottle, babies, spears, rifle, brief case etc) without disrupting the normal leg swing gait mechanics.  

Big sister is “out of phase” with her brother when it comes to the legs, but their arm swings are matching in phase so that there is no conflict. When people walk “out of phase” their arm swings will always match. Thus, it would seem that this is the more harmonious way to walk with a partner. 

So how are they all walking together ? Certainly not in harmony.

Obviously the little sister is not in sync with big sister. She is much shorter, and thus her step length is going to be different and that is the likely answer. She will have to pick up cadence to keep up and that will mean much of the time she will not synchronize with her big sister. As I mentioned in a prior post on these topics, often the larger or more dominant person’s arm swing will dictate the arm swing pattern of the other partner, and this will in turn, dictate how the lower limbs synchronize to the dominant partner. It would make sense that perfect harmony would bring about “out of phase” leg swing, but it does not always occur. Why? There are many reasons I discussed here today, things like differing arm and leg lengths and step lengths come to mind.

* There is one more option, none of them are in anti-phasic gait. Maybe they all have back pain :) Back pain patients tend to shift towards phasic gait to reduce spinal torsion and shear. If they all are anti-phasic then arm and leg swing matter very little in terms of full limb swing propulsive gait. This is quite possible as well, perhaps this is just a still photo representing a very slow strolling gait and thus little need for anti phasic gaits from all 3 of them. 

Neat points if you are a true gait nerd. Did you catch it ? A picture is worth a thousand words.

Hope this little quiz helped you to put some pieces together.

One more thing, here is a clinical pearl. By walking hand in hand with someone, you can help a person learn arm swing and leg swing and how to create a clean cadence, the normal anti-phasic gait, and learn how to dual task as well as add audible, visual and tactile queues to one’s gait. It is a great tool for helping neurologic gait pathologies, post stroke gait training and helping someone who has joint replacements or back pain regain normal anti-phasic gait traits where gait has become phasic and apropulsive. 

Dr. Shawn Allen