What do pigs and humans have in common?

“The majority of in vitro research has examined repeated axial loading with the spine in a neutral position from which observed herniations are extremely rare.”

 

This means that loading much weight onto your shoulders doesn’t appear to affect the disc negatively, aside from compressing it. Picture the people doing strongman, powerlifting, Olympic weightlifting or Crossfit. All of these sports are safe regardless of how much weight is being used, as long as technique remains good, while under the weight.

 

“The most consistent development of disc herniation with repeated loading conditions was achieved by Gordon et al. In vitro human lumbar motion segments were flexed from a neutral posture to 7 degrees of flexion with a small axial twist motion. All 14 of the motion segments examined failed with herniations of the Intervertebral disc (either nuclear protrusion or extrusion) with an average of 40,000 loading cycles to failure. It appears that load, motion, degenerative condition, and repetition require further investigation as prerequisites to disc herniation.”

 

Stu is one of the great gurus of back pain. He states in his papers that he does not endorse a specific number of flexion cycles to create a herniation. This is individual for each person. Also of note is that the above experiment is not done on a live person, but on a cadaver. This means that there is little compensatory motion that can occur, which may occur in real life. For example, there is one paper (don’t have it currently, but I will find it for later) that postulates that the posterior longitudinal ligament (a strong ligament on the back of the spine) may be a protective mechanism for back pain, which would then work to prevent a disc herniation by absorbing some of the flexion load. It’s just an idea though and is no more right or wrong than the number of loading cycles found in the above quote.

 

“The cervical spines of 26 porcine specimens were obtained immediately following death. Pig cervical spines have been shown to be the section closest to human lumbar spines for anatomical and biomechanical characteristics.”

 

The authors make is sound so humane that they waited until the pigs died, but then went on to say that the mean age was 6 months. They died for science. What is most important though is that this study was performed on pig spines! The results can be correlated to humans, but again this will not be precise because the subjects aren’t real live humans.

 

“The remains of any soft tissue and discs were dissected from the cranial and caudal endplates.”

 

The muscles were removed. The muscles, tendons and ligaments provide active and passive support to the joint. Without this support, we are only looking at how the spine joint moves in a vacuum. This again makes it hard to take the results of this study and apply them to humans. We can though take the idea of the study and generalize it to another spine.

“Herniation occurred with modest levels of compression and flexion/extension movements but with a high number of motion cycles. Specimens tested in the lowest compressive force group had nuclei that were intact after 86,400 flexion cycles…All herniations that were created during testing occurred in the posterior or posterior-lateral areas of the annulus.”

 

The first thing to take from this is that the spinal segment is strong. It can withstand over 80,000 cycles of flexion/extension, without resting, and some were able to withstand the force without significant anatomical changes. All herniations were posterior or posterior lateral. This is consistent with what we see in the clinic. Very rarely is there an anterior herniation, but in real life there is also a very strong ligament on the anterior portion of the spine, which would impede a herniation in this direction.

 

“…highly repetitive flexion/extension motions and modest flexion/extension moments, even with relatively low magnitude compression joint forces, consistently resulted in Intervertebral disc herniations. Larger axial compressive force resulted in more frequent and more severe disc injuries…there is no doubt that disc herniation is a cumulative process that can result with modest forces if sufficient flexion/extension cycles are applied.”

 

This is a mouthful. Let’s start by saying that if you spend a lot of time in a flexed (slouched posture position), this may lead to a posterior disc herniation. It’s kind of like the straw that broke the camel’s back. It may not happen the first time, but the more often one spends in flexion the more that the nucleus (the pudding substance inside the disc) will travel towards the border of the disc (annulus). This article doesn’t state what happens to the disc when we rest and stop spending time in a flexed position. For instance, what is not stated is that if we flexion for an entire day, but then move in the opposite direction (extension), do we then counteract the effects of flexion? This article doesn’t say this, but one would have to infer if we could create a herniation that we can reduce a herniation with movement. More to come in future posts.

 

“While there may be a tendency to identify an event that ‘caused’ an intervertebral disc herniation, this work together with our other experiments have led us to form the opinion that this is only a culminating event and that the real cause had already occurred.”

 

This quote says it best and I will leave it at that.

 

Thanks for reading. If you would like to learn more about a topic, feel free to ask a question on here or at my Facebook page @movementthinker. I love reading research and if I can read something that may help you specifically then it is more functional than just reading stuff that I enjoy.

 

Callaghan JP, McGill SM. Intervertebral disc herniation: studies on a porcine model exposed to highly repetitive flexion/extension motion with compression force. Clinical Biomechanics. 2001;16:28-37.

 

link to article

To slouch or not to slouch?

“Epidemiologic studies have shown that individuals in occupations that involve prolonged periods of sitting experience a high incidence of low-back pain”

I don’t think that this surprises anyone, but as we continue to advance with technology, the jobs that require mostly standing are going away. Put the data into today’s terms. How many of us had cable t.v when we were kids? How many of us had tablets and laptops as kids? I didn’t and was more active because of it. My daughter would be extremely content to watch Curious George on the tablet all day instead of playing. This sedentary nature is hard to break and usually results in crying until she realizes that we are actually going to play. This research demonstrating sitting as a correlation to back pain needs to be looked at seriously, as our society is sitting more on average, at least in my opinion.

“When changing from a standing to a sitting posture…an increased load on the spine as measured by Intervertebral disc pressures.”

The study that this is from is the landmark study for measuring disc pressure. Alf Nacchemson’s study on disc pressures was the first of its kind and mostly likely will never be reproduced again. The subjects in the study allowed a needle inserted into the disc in order to read the pressure. Picture a pressure gauge for a tire and how it measures how much air pressure is in the tire. Now picture the same thing, but with a needle at the end, measuring the pressure in your disc. This is no good. In order to do this, the disc itself needs to be punctured. This is why the study will not be reproduced. No review board would ever approve a study in which the participants have an increased risk of injury…just for the sake of measuring.

“…anular failure and gradual disc prolapse following fatigue loading of lumbar discs wedged in flexion…sitting for 1 hour results in significant changes in the mechanical properties of the lumbar Intervertebral disc…Wilder et al propose that lumbar disc herniations can be a direct mechanical consequence of prolonged sitting.”

Anyone out there just adjust his/her sitting posture?

There is a lot of research demonstrating that sitting is bad for you. This can’t be argued. There is a newer article that states that sitting for one hour, while watching t.v., can take up to 22 minutes off of your life. In the phrase of the show that we are currently watching on Hulu…”YOU ARE THE BIGGEST LOSER!”

“…studies have shown that subjects with or without back pain are more comfortable sitting with a lumbar support in a LP (lordotic position) compared to a KP (kyphotic position).”

If you sit up really tall and elevate your chest, your low back will make a hollowed position…this is called lordosis. When you bend forward, your low back will make an arched position (think the overly slouched position) and this is called kyphosis. Previous studies demonstrated that the slouched position was less favorable than a more upright position…ARE YOU KIDDING ME?! Who doesn’t like holding a good slouched position for hours on end?

“McKenzie describes a ‘centralization’ phenomenon whereby certain lumbar movements and positions result in a change in the distribution of referred symptoms from a distal to a more central location”

OKAY…THIS IS HUGE. I have written about centralization in the past, here, here, here, here, and here, but I’ll cover it again…just for you. If you have pain that started in the back and then moved location, specifically into one of the legs…this is no good. If you have back and leg pain that moves from the leg into the back…this is good. This is the basics of centralization. It’s called a phenomenon because we don’t know exactly why it happens, but there is a high correlation between centralization and a disc lesion (such as a herniation), which can also be found here.

“…Donelson et al reported that 76 patients (87%) demonstrated centralization. Further, all individuals exhibiting this phenomenon did so following extension rather than flexion movements”

Let’s start with this study may be a little biased, but that doesn’t negate the information in the study…it just has to be looked at through a lens that takes this into account. This article is co-written by the man, the myth, and the legend Robin McKenzie. I hold this man in high regard, as do many therapists that practice in the orthopedic setting. He was voted the most influential PT of the last century and that is a title that takes a lifetime of hard work, educating others and helping the public at large. Here’s a quick video of the legend… watch Robin treat a patient.   With that said, it was still written by an author that has something to gain from a positive outcome by using lumbar rolls. He has his namesake rolls, so we can expect a good outcome from using the rolls prior to even reading the article. It’s still good information that a person can learn from though.

Ah yes…extension. This means bending backwards such as this video by Yoav Suprun a MDT instructor.

“Excluded from the study were patients with:

  1. Medically diagnosed stenosis, spondylolisthesis or recent fractures;
  2. Neurologic motor deficit:
  3. Surgical intervention for the present episode;
  4. Apophyseal joint or epidural injections administered within the previous 4 weeks;

6….

  1. Obvious deformity of acute list or lateral shift or lumbar kyphosis;
  2. Symptoms of hysteria or anxiety neurosis”

This is important to note that the authors are trying to subcategorize patients that are most likely to benefit from using a lumbar roll with sitting. Not all patients will respond well to extension. Patients with stenosis may not respond to extension. This is not true for all, but is the long standing myth taught in PT school. Patients that come in looking crooked or bent over probably shouldn’t be in this study either. I like the last one though…these authors were trying to think of every patient that may not benefit from a lumbar roll in order to rule out using the rolls on everyone.

“The first 70 patients to present within each of the categories were randomly assigned to either a KP or LP group. Whenever required to sit, the KP group were instructed to do so with their back in a supported but flexed posture. Conversely, the LP group were instructed to sit with their back in a supported but lordotic position.”

This is a decent amount of people in the group so it should give some valuable information. One group had to sit slouched and the other group has to sit upright.

“During their first visit to the clinic, patients were seated on the standard chair and immediately given the questionnaire to complete. They were then seated in their assigned posture for 10 minutes, and the questionnaire was readministered.”

This is actually a pretty good way to test the intervention or “treatment”. A test performed before the treatment and immediately after the intervention is the best way to minimize the number of variables looked at during the second testing. For instance, if I give you an anatomy test and tell you to take the same test after studying and watching t.v and sleeping, it’s hard to say which of the three changed the score on the second test. We can assume studying, but it’s not certain. If all you do is study or sleep or watch t.v., then we can narrow down what would’ve caused a change in score.

“Before leaving the clinic, patients were instructed as to the position they were to adopt, whenever seated, over the next 24-48 hours”

This is the part in which the “scientific rigor” of the study will break down. Over the course of 48 hours, there are so many possibilities of making a pain better or worse and the sitting posture is but one variable. Any outcomes taken after this point waters down the results.

Prior to the interventions, there were no differences between the groups with regards to pain location, leg pain or back pain intensity.

“…while there was a 21% decrease in BPI (back pain intensity) for the LP group, there was a corresponding 14.5% increase in pain for the KP group…reduction in leg pain for the LP group after only 10 minutes of sitting…the very marked reduction in leg pain (56%) for the LP group contrasts with no significant change in pain for the KP group”

There were a greater percentage of patients that responded well to sitting with a more upright posture than those that sat slouched and some of those that slouched actually got worse over time. The advice that out moms gave to stand up tall appears to hold true for some folks.

“…adoption of a LP resulted in 48% of these patients having pain that centralized above the knee after only 10 minutes of sitting…10% for the KP group…24% of the KP group’s pain peripheralized below the knee at POST-TEST 3 compared to 6% for the LP group.”

The first thing to take from this is that an upright posture is not for everyone, in that 6% of those that sat upright actually got worse. Getting worse means that the symptoms that you have from your back actually gets worse into the leg, calf or foot. Now, 48% got better in that the leg pain reduced within 10 minutes. What this means for the patient is that sitting taller is worth a shot if you have pain that radiates into your leg. If you get worse from sitting up tall…stop. It’s really that simple to start with. A lumbar roll could be a useful device to get you to sit more upright. This could be homemade such as a rolled up towel, a purse or a forearm by putting your arm behind your back at about the belly button area.

EXCERPTS TAKEN FROM:

 

Williams HM, Hawley JA, McKenzie RA, van Wijmen PM. A Comparison of the Effects of Two Sitting Postures on Back and Referred Pain. Spine. 1991;16(10):1185-1191.

 

Link to article

 

 

 

 

 

Barefoot influence on arch height

Barefoot influence on arch height

 

“Our aims were to establish the prevalence of flat foot in a population of schoolchildren in rural India and to determine whether this prevalence varied between shod and unshod children”

 

First, it is hard to translate this research over to an American population. Just because it is the prevalence in India, doesn’t mean that it will be the prevalence in other countries. Until I have other research though…this is all I have to work with.

 

Unshod means not wearing shoes. Therefore, shod means wearing shoes.

 

“…2300 children between the ages of four and 13…static footprints of both feet were obtained from all 2300 children”

 

This encompasses a large age span from the time prior to arch formation to post arch formation. I remember learning in school that the arch starts to take shape around the age of 8, but this may just be a tradition that has carried through the ages of PT students. Anyway, this is a large sample size to look at.

 

“The footprints were classified as normal, high-arched or flat. Some form of footwear was worn by 1555 children and 745 never used shoes.”

 

It’s still hard to believe that there were this many children that hadn’t used shoes. The children in the study were between the ages of 4 and 13. We sometimes take for granted all of the “needs” that we have here in the states. Anyway, here is a link to give an idea of what the arches would look like on a static footprint. One way to think of it is to get your foot wet and go walk on a wood floor or deck. You would have an imprint of your foot as follows: picture of arch height.

 

“…1551 were considered to have normal arches in both feet, 595 had a high arch in one or both feet and 154 had unilateral or bilateral flat foot. The prevalence of flat foot progressively decreased with increasing age.”

 

This last statement is what is taught in PT school. There are so many facts that are taught in PT school, but we don’t learn the research behind the facts. A majority of children go on to develop normal arch height. There needs to be a further breakdown of the children that go on to develop an “abnormal arch height”.

 

“There was a significantly higher prevalence in children who wore shoes (8.6%) than among the unshod (2.8%)”

 

There is a large difference between the two populations of children, but we also have to consider the small sample size of 154 children. I would love to see this study take it one step further and search for all children in a larger radius with flat feet and see if the same types of prevalence rates are present. If this is the case, then we can start to make some assumptions regarding footwear affecting arch height. There are so many other variables that are not accounted for that could also play a role in arch formation, so this study has to be taken with a grain of salt. It does though make a statement that kids wearing shoes may not develop a normal arch compared to those not wearing shoes. It literally states: “…shoe-wearing predisposes to flat foot”.

 

“It seems that closed-toe shoes inhibit the development of the arch of the foot more than do slippers or sandals. This may because intrinsic muscle activity is necessary to keep slippers from falling off.”

 

This is a good theory, but would have to be proven. As a PT, we tend to recommend against sandal or flip flops because of the same reason: we have to work differently to keep the shoes from falling off. There is something called the windlass mechanism that can be altered when wearing shoes that can easily fall off. Again, more research is needed in order to figure out which party is right.

 

Excerpts taken from:

 

Rao UD, Joseph B. The Influence of Footwear On the Prevalence Of Flat Foot. J Bone Joint Surg [Br]. 1992;74-B:525-527.

 

Link to article

 

 

 

 

OPEN MOUTH…INSERT (BARE)FOOT

Open mouth…insert (bare)foot

 

  1. “Around one in three older people falls each year with one third of over 65s and half of of over 80s falling each year.”

 

Falling sucks. People get hurt when they fall. Most older adults can’t withstand the impact of a fall and get seriously hurt. There is research demonstrating that people older than 80 that sustain a fractured hip have a higher prevalence of death. One way that we can keep people from dying is to keep people from hitting the floor. There are many ways to do this and the article below will emphasize how footwear plays a role.

 

  1. “The shoe features which have been shown to influence balance performance include heel height, heel collar height, and sole thickness and hardness.”

 

I am going to take the low hanging fruit first. The density of the foam that is on the bottom of the shoe will play a role in how a person balances. Think about standing on a bed and how unstable it is. Now, think about standing on a waterbed…a little more unstable. The less stable the bottom of the shoe the decreased stability you will have when on your feet. There were shoes at one time that were advertised to “improve your balance”, needless to say it didn’t work out so well. When we place more cushioning under our feet, we lose a little of our stability because we are decreasing the role that one of our three senses, proprioception, systems have in maintaining balance.

 

When we increase the height of the heel, a few things happen. First, we place more weight over the front of the foot and decrease the weight bearing over the back of the foot. This changes the base of support during walking, as the person will have an earlier heel off (when the heel leaves the ground) and a quicker heel strike. This is one reason, in my opinion, that a person wearing heels doesn’t take a large stride. Doing so would impair the balance because the base of support would be very narrow during portions of the gait cycle.

 

Another thing that happens when a person adds a heel is that the person becomes a little taller. There is a good t.v. episode about this on Seinfeld. Raising your height will make balancing a little more difficulty because the center of gravity has gone a little higher. Think of it this way, when you are on an unstable surface, what’s the easiest way to keep your balance…squat slightly to lower your base of support. This is why wrestlers are so well balanced during the match because the squat down when they are being pushed and pulled.

 

The heel collar height is a little harder for me to rationalize. The higher the collar, the less mobility the ankle will have. The lower the collar, the less external stability will be provided to the ankle. I could make a case for both.

 

“Lord and Bashford evaluated balance in 30 older women when barefoot, wearing low heeled walking shoes, wearing high-heeled shoes and wearing their own shoes. The worst balance performance was seen when subjects wore high heels.”

Is this surprising? I included the quote because the author’s name was Lord…just kidding. Story time:

 

I tell all of my patients that I would not have them do anything that I either haven’t done or am willing to try. I had a patient once whose main goal was to be able to walk in heels. Needless to say, she called me out on the carpet for trying to teach how to walk in high heels based on book knowledge and not on actual experience. She went out and bought me a pair of heels. I wore the heels the entire treatment session. I got some catcalls from coworkers during the session. The best part of the story is the following. After the session I through the heels in the back seat of the car. That night I gave my wife’s mom a ride in the car. She looked into the back seat and must have seen the heels. She didn’t mention anything in the car…possibly because she mostly speaks polish and didn’t want to start a conversation that she wouldn’t be able to understand, but she told my wife when I got home. BOY DID I GET AN EARFUL! After I explained myself and it is still a funny story that I get to live to tell.

 

“The aim of this study was to examine the effects of usual footwear (versus going barefoot) on balance in frail older women attending a geriatric day hospital”

 

Remember what I said about the different portions of the shoe? If a person is barefoot, the center of gravity is lower, there is no cushion and there is decreased ankle stability. Two of the three may favor barefoot walking. I thought for sure that barefoot would be the answer…Read more to see how wrong I was.

 

“Berg Balance Scale was used to assess balance…under two conditions in this study: shoes on and shoes off. The order of testing with shoes on and off was counterbalanced so that 50% of patients were tested ‘shoes on’ first and 50% ‘shoes off’ first so as to avoid an order effect when testing”

 

First, you can see my report on the Berg Balance Scale from many years ago. I’m sure that the research has changed slightly, but the basics will still hold true. It’s important that the authors of the study changed the order of performing the testing for different patients in order to get a good idea of how patients perform. For instance, in high school no one liked the dreaded POP QUIZ! But when the teacher did a review for a test and gave a “wink wink”, you knew that the question would show up on the test. This is the same concept. If the participant already knows what’s on the test (seeing as they do the test twice), we would expect the second score to be slightly, is not significantly, elevated from the first score.

 

“One hundred elderly females were assessed with a mean age of 82…most were living in the community, required a mobility aid and had had a fall in the previous year.”

 

This is good information. A study can only be generalized to the population that the study was performed. For instance, the results of this study can not be generalized to a barefoot running group or a military group. It sounds obvious, but you’d be surprised how many “professionals” read an abstract (summary) of an article and start applying the “research” immediately in practice.

 

“There was a significant improvement in the mean BBS score of 2.5 when shoes were on”

 

I was wrong. I expected barefoot to win hands-down. This is because I have read a lot of research on barefoot walking and running. I came in biased and was WRONG! There I said it…mark this date. Moving on. Come back next week when I have a better chance of being right again.

 

Horgan NF, Crehan F, Bartlett E. The effects of usual footwear on balance amongst elderly women attending a day hospital. Age and Ageing. 2009;38:62-67.

 

 

Link to article