Categorized | Health

One Small Step for Man…Proprioceptive Deception

Posted on 12 December 2012

Most of us during the course of the day seldom watch where we put our feet when we are out and about. Instead, we rely on our innate sense of balance and the neural-muscular connection between the brain and feet. It’s as if our body is on auto-pilot. For example, when you’re carrying a cup of coffee back to your desk, careful that you don’t spill any liquid on your clothes or computer keyboard, you really aren’t paying all that much attention to your feet. This type of “silent communication” is often called proprioception, and enables walkers and runners to travel long distances without staring down at their feet or shoes. Just imagine running a full marathon focusing solely on each foot strike!

But the powers of  proprioception can be thrown out of whack by the slightest anomaly such as a protruding root on the trail or uneven seam in the office carpet. The end-result can be a stumble or even a fall.

Earlier this year, New York City filmmaker Dean Peterson set up his camera at Brooklyn’s 36th Street subway stop, where one of the steps was slightly higher than the others. How much higher? Just a half-inch higher than the others. Yet that half inch caused no end of tripping and stumbling by people walking up to street level. (Subway stairway design guidelines call for risers to be a minimum of 6 inches and a maximum of 7 inches.) The mischief-making step has since been repaired.

We asked Dr. Phil Maffetone to watch the subway-stairway viral video and comment on what he observed– and what it means for those with “unhealthy feet.”  — NRC

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Proprioceptive Deception

by Dr. Phil Maffetone

This  video is an example of “proprioceptive deception.” The communication between the foot and the brain is fooled, or even impaired, resulting in not knowing when a slight deviation occurs in walking stairs—in this case, a relatively minor increase in the height of one step.

Stair steps are supposed to be very similar in height, with local building codes dictating specific measurements. In this case, New York City mandates the difference between steps should not exceed three-eighths of an inch. That’s because climbing stairs, and descending them, can raise the risk of falls when a height discrepancy is too great. A half-inch higher step is clearly too much for most people, especially after having just walked up a number of stairs that don’t have such a deviation.

Part of the problem is in the brain. We have taught it, through past experiences of climbing stairs, to expect each step to be almost the same. So when one is a half-inch higher than the previous ones, exceeding the brain’s expectation, many of us will stumble.

Ascending stairs is different than hiking up a rugged trail with a similar incline. In this case, your brain expects each step to be a uniquely different height, and it helps the body compensate in at least two ways. One is through visual senses, which involves looking at where you’re walking. A certain deviation, between one step and the next, if large enough, would be seen. The minor deviation on the subway staircase was probably not visually noticeable.

Another way the brain compensates is through information received from each foot as it makes contact with the ground. It does this all the time when you are on your feet. Nerve endings, especially those in your toes and the bottoms of the feet, immediately sense the ground with each step, sending very specific details of what it feels—hardness and softness, levelness, slippery or secure, etc.—to specific parts of the brain. This information reaches an area called the cerebellum in the back of the head as well as  the mid-brain. These locations evaluate what the feet have felt, an assessment is made regarding balance and the risk of falling, and this information is then sent to the motor cortex—in the top-middle of the brain. Here it’s decided which muscles throughout the body to contract and move for the most appropriate body response to the odd step.

All this occurs in much less than one second. The outcome can be easily seen in the video: when people begin to stumble on the higher step, with seemingly erratic, but really well organized movements of flaring arms, bending backs and tilting heads, they quickly “catch” themselves thereby preventing a fall to the ground. Those with better foot-brain function have minimal hesitation, while those with ineffective function stumble more.

No doubt, the camera caught some individuals who did not have any problem with the higher step, and these were edited out. Or, the numbers of people in New York with poor functioning feet are very high (most of those in the video appeared to be wearing bad shoes). Those with better communication between foot and brain also appeared to be more fit individuals, who would have quicker reaction times.

The most common reason for reduced foot function is wearing shoes. The thicker the soles, higher the heels, and the more support systems in the shoe, and those that don’t fit well, the worse it can be for your feet. These are bad shoes. (Conditions such as diabetes, heart disease, and other illness that impair circulation are associated with deterioration of the tiny nerves in the feet rendering them dysfunctional. This leads to poor foot-brain communication and can significantly impair balance even walking stairs that are uniformly built.)

Those with healthy feet and who don’t regularly wear bad shoes are usually better aware of very slight differences in step heights. Walking or running on an uneven trail would usually be easy to do without stumbling.

Try this simple exercise at home—carefully. In your bare feet, walk up and down your stairs and using only your foot-brain sensation try to feel which steps are higher or lower than others. Carpet, like thick and soft supported shoes, will distort your ability to do this. If your feet are not healthy, it will be impossible to feel the height differences. (Of course, there may not be any significant changes from one step to the other, but like the subway steps, many builders and inspectors are not as careful as they should be). Once you think you feel any changes in height, get a ruler and measure the steps to see how well your feet and brain are aware of these subtle differences.

Had a group of more fit people, who were also barefoot, took part in the same subway stairs video, there would no doubt be far less people stumbling on that slightly higher step.

 

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3 Responses to “One Small Step for Man…Proprioceptive Deception”

  1. Sue Kenney says:

    Love his article. I was at a party tonight and talked to some people about this very topic. I didn’t have the scientific words or backup you have, but I basically told them exactly what you’ve written here because of my own personal experiences. For the last year and a half I have been reprogramming my brain/sensory nerve endings in my feet to react differently as I’ve been barefoot most of the time and walk/run in the forest. Thankyou for sharing what you know.

  2. Joseph McKay (Dr) says:

    I have to disagree with Dr Maffetone. Rather than proprioception alone, this whole exercise relates to learning and assumptions made from visual information as well as proprioception. They learnt , from seeing, that the stairs were there and then made the assumption that the steps were all of equal height. ANd there are many other fctors involved, including, alertness, health of joints cephalad to the foot blah blah.

    eg If you blindfolded shoed or bare foot individuals they would both most likely trip on the first step unless they were getting the proprioceptive information via a cane held in the hand. Proprioceptive impulses are relayed to the brain during the step and height could not be determiined untill afer the foot ahs been planted on the offending step. And it not only relies on the proprioceptors opf the foot but also of the entire leg and spine.

    This is not to say that I disagree with Dr Maffetones statements regarding footware and more accurate proprioceptive impulse in bare feet. It stands to reason.

    • MarkC says:

      Joseph,

      Agree that we would trip with or without shoes in this setting….but likely more w the shoes. would be an interesting experiment to try. in midevil times the dungeons had similar uneven steps to make it more difficult for prisoners to escape.
      thanks as always Phil for a thought provoking piece.

      Mark


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