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Posts Tagged ‘coefficient of friction

Walking barefoot: The advantages for all and the kids

Note: Re-edit of “Why kids should go barefoot more (and probably adults, too) March 5, 2016″

Lauren KnightFebruary 29, 2016

During an unseasonably warm day this past winter, my husband and I walked with our three boys to the playground down the street from our house.

The sunshine was toasty and the boys were quick to take advantage of it.

As soon as we arrived, all three of our little boys immediately shed the light jackets they had been wearing, along with their shoes and socks, and took off, small bare feet pounding and bouncing on the playground’s rubberized soft surface.

They ran fast, climbed easily, using their feet to wrap around the poles they scaled, clearly delighted. 

It wasn’t long before a few other children at the playground caught on and attempted to remove their shoes and socks.

“NO!” one mother shouted, “Do not remove your shoes and socks,” she told her son.

When he whined and asked her why not, she simply stated, “We always keep our shoes on outside.

This was nothing new. We have, for years, been the odd family out at the playground, the ones who play chase, balance on a slackline nearby, and practice handstands shoeless, sometimes all five of us at the same time.

On one occasion, a parent would not let his son take off his shoes when we invited him to come onto our slackline — not only did the slackline end up covered in mud, but the little boy gave up quickly — he was unable to keep his balance with his shoes on.

Another time, a father chastised me to his child for allowing my children to go shoeless, implying that I was endangering them somehow.

The judgements don’t bother me: I am secure in my parenting choices and have made them purposefully and fully-informed, but it did make me wonder why so many parents of young children forbid them from taking off their shoes outdoors.

I decided to research the myths and benefits of going barefoot, and what I found out may surprise you.

Two common reasons parents give for not allowing their children to go barefoot outside include fear of injury to the foot, and fear of picking up some unsavory disease or illness through their feet.

Unless you are in the city where there is broken glass everywhere, the likelihood of injuring one’s foot is minimal, especially on a soft rubber surface where it is easy to see and avoid stepping on objects.

Both children and adults who go barefoot frequently also have a heightened sense of their surroundings and can easily spot a sharp object they need to avoid.

Children’s feet also toughen up the more they go barefoot, leading to more natural protection.

As far as picking up an illness or disease from going barefoot, our skin is designed to keep pathogens out, and you are far more likely to spread or contract an illness through your hands (think public doorknobs, sinks, keyboards, and handrails) where germs are most plentiful.

(Unless the skin is injured, the skin is the best protective envelope. The problem is that it is difficult to check the skin before the kids remove their shoes.)

Also, children are much more likely to put their hands, not their feet, in their mouths and touch their faces and eyes, where disease or illness most commonly enters the body.

Parasites are not likely to be transmitted through the foot in a developed country. (In Non-developed countries, they go barefoot anywhere and they develop a thick skin)

Since the advent of modern plumbing, hookworm is much less common, especially in non-tropical regions that experience cold winters.

A child is much more likely to contract a mosquito- or tick-borne illness than a parasite these days.

In fact, shoes actually create an opportunity for illness by trapping bacteria and fungus (along with the heat and moisture) establishing an ideal environment for the growth of icky things like athlete’s foot and toe fungus.

Kevin Geary, parenting guru, teacher, and author of Revolutionary Parent, a site dedicated to raising physically and psychologically healthy kids, argues that shoes are actually quite bad for children.

Shoes destroy feet, preventing proper toe spread, which interferes with the foot’s ability to function properly, and prevent proper movement development, which can make children be more susceptible to foot and lower leg injury.

The benefits of going barefoot are plentiful.

1. One major benefit of allowing a child to go barefoot is that it strengthens the feet and lower legs, making the body more agile and less prone to injury.

2. It enhances proprioception, the sense of the relative position of neighboring parts of the body and strength of effort being employed in movement. Going barefoot helps a child develop body awareness.

3. Skin of feet have a much better resistance, or coefficient of friction, to slippery paths

4. Geary explains that the nerves in our feet are sensitive (the sole of your foot has over 200,000 nerve endings– one of the highest concentrations in the entire body) for this very reason the nerves make us safer, more careful, and better able to adapt to the ground beneath us.

5. When barefoot, we are better able to climb, cut, pivot, balance, and adjust rapidly when the ground shifts beneath us, as it does when we walk on uneven terrain, or anything besides concrete and pavement.

6. Dr. Kacie Flegal, who specializes in pediatrics, wrote about optimal brain and nervous system development of babies and toddlers, stating that being barefoot benefits a young child tremendously. “One of the simplest ways to motivate proprioceptive and vestibular development is to let our babies be barefoot as much as possible.”

7. Flegal goes on to say, “Another benefit to keeping babies barefoot is the encouragement of presence of mind and conscious awareness. As the little pads of babies’ feet feel, move, and balance on the surface that they are exploring, the information sent to the brain from tactile, proprioceptive, and vestibular pathways quiet, or inhibit, other extraneous sensory input. This creates focus and awareness of walking and moving through space; babies get more tuned in to their surroundings.”

8. Another benefit of going barefoot is that it encourages a natural, healthy gait.

9. Adam Sternberg wrote about the topic for New York Magazine in 2008 and cited studies that reveal the damage shoes are doing to our feet; in particular, that we humans had far healthier feet prior to the advent of shoes.

Sternberg further reported that despite these findings, people are still not actively encouraged to go barefoot outdoors.

Podiatrist Dr. William A. Rossi said it all when he wrote,

“It took 4 million years to develop our unique human foot and our consequent distinctive form of gait… in only a few thousand years, and with one carelessly designed instrument, our shoes, we have warped the pure anatomical form of human gait, obstructing its engineering efficiency, afflicting it with strains and stresses and denying it its natural grace of form and ease of movement head to foot.”

10. And finally, going barefoot is a joy to the senses, especially to young children who experience all the newness of the tactile world around them.

Think of the relaxing feeling of walking on soft warm sand at the beach, the refreshing feeling of cool dewy grass in the early morning of a summer day, the feeling of slippery wet mud squishing between toes in the garden, the feeling of the rough bark of a climbing tree, the surprise at the splash of a puddle underfoot.

All of these sensations are available when we allow our children to experience a bit of shoe-free time. Perhaps you should join us and kick off those shoes at the playground and in the backyard.

Enjoy your feet and what they were made for.

Lauren Knight is a frequent contributor to On Parenting. She blogs at Crumb Bums.

 

Why kids should go barefoot more (and probably adults, too)

During an unseasonably warm day this past winter, my husband and I walked with our three boys to the playground down the street from our house.

The sunshine was toasty and the boys were quick to take advantage of it. As soon as we arrived, all three of our little boys immediately shed the light jackets they had been wearing, along with their shoes and socks, and took off, small bare feet pounding and bouncing on the playground’s rubberized soft surface.

They ran fast, climbed easily, using their feet to wrap around the poles they scaled, clearly delighted. It wasn’t long before a few other children at the playground caught on and attempted to remove their shoes and socks.

Lauren Knight. February 29, 2016

“NO!” one mother shouted, “Do not remove your shoes and socks,” she told her son.

When he whined and asked her why not, she simply stated, “We always keep our shoes on outside.”

This was nothing new; we have, for years, been the odd family out at the playground, the ones who play chase, balance on a slackline nearby, and practice handstands shoeless, sometimes all five of us at the same time.

On one occasion, a parent would not let his son take off his shoes when we invited him to come onto our slackline — not only did the slackline end up covered in mud, but the little boy gave up quickly — he was unable to keep his balance with his shoes on.

Another time, a father chastised me to his child for allowing my children to go shoeless, implying that I was endangering them somehow. The judgements don’t bother me; I am secure in my parenting choices and have made them purposefully and fully-informed, but it did make me wonder why so many parents of young children forbid them from taking off their shoes outdoors.

I decided to research the myths and benefits of going barefoot, and what I found out may surprise you.

Two common reasons parents give for not allowing their children to go barefoot outside include fear of injury to the foot, and fear of picking up some unsavory disease or illness through their feet.

Unless you are in the city where there is broken glass everywhere, the likelihood of injuring one’s foot is minimal, especially on a soft rubber surface where it is easy to see and avoid stepping on objects.

Both children and adults who go barefoot frequently also have a heightened sense of their surroundings and can easily spot a sharp object they need to avoid.

Children’s feet also toughen up the more they go barefoot, leading to more natural protection.

As far as picking up an illness or disease from going barefoot, our skin is designed to keep pathogens out, and you are far more likely to spread or contract an illness through your hands (think public doorknobs, sinks, keyboards, and hand rails) where germs are most plentiful.

(Unless the skin is injured)

Also, children are much more likely to put their hands, not their feet, in their mouths and touch their faces and eyes, where disease or illness most commonly enters the body.

Parasites are not likely to be transmitted through the foot in a developed country. (In Non-developed countries, they go barefoot anywhere)

Since the advent of modern plumbing, hookworm is much less common, especially in non-tropical regions that experience cold winters. A child is much more likely to contract a mosquito- or tick-borne illness than a parasite these days.

In fact, shoes actually create an opportunity for illness by trapping bacteria and fungus (along with the darkness, heat, and moisture) and holding them against your feet, establishing an ideal environment for the growth of icky things like athlete’s foot and toe fungus.

Kevin Geary, parenting guru, teacher, and author of Revolutionary Parent, a site dedicated to raising physically and psychologically healthy kids, argues that shoes are actually quite bad for children.

Shoes destroy feet, preventing proper toe spread, which interferes with the foot’s ability to function properly, and prevent proper movement development, which can make children be more susceptible to foot and lower leg injury.

The benefits of going barefoot, however, are plentiful.

1. One major benefit of allowing a child to go barefoot is that it strengthens the feet and lower legs, making the body more agile and less prone to injury.

2. It enhances proprioception, the sense of the relative position of neighboring parts of the body and strength of effort being employed in movement. In other words, going barefoot helps a child develop body awareness.

(3. Skin of feet have a much better resistance, or coefficient of friction, to slippery paths)

Geary explains that the nerves in our feet are sensitive (the sole of your foot has over 200,000 nerve endings– one of the highest concentrations in the entire body) for this very reason; they make us safer, more careful, and better able to adapt to the ground beneath us.

4. When barefoot, we are better able to climb, cut, pivot, balance, and adjust rapidly when the ground shifts beneath us, as it does when we walk on uneven terrain, or anything besides concrete and pavement.

5. Dr. Kacie Flegal, who specializes in pediatrics, wrote about optimal brain and nervous system development of babies and toddlers, stating that being barefoot benefits a young child tremendously. “One of the simplest ways to motivate proprioceptive and vestibular development is to let our babies be barefoot as much as possible.”

6. She goes on to say, “Another benefit to keeping babies barefoot is the encouragement of presence of mind and conscious awareness. As the little pads of babies’ feet feel, move, and balance on the surface that they are exploring, the information sent to the brain from tactile, proprioceptive, and vestibular pathways quiet, or inhibit, other extraneous sensory input. This creates focus and awareness of walking and moving through space; babies get more tuned in to their surroundings.”

7. Another benefit of going barefoot is that it encourages a natural, healthy gait.

8. Adam Sternberg wrote about the topic for New York Magazine in 2008 and cited studies that reveal the damage shoes are doing to our feet; in particular, that we humans had far healthier feet prior to the advent of shoes.

Sternberg further reported that despite these findings, people are still not actively encouraged to go barefoot outdoors.

Podiatrist Dr. William A. Rossi said it all when he wrote, “It took 4 million years to develop our unique human foot and our consequent distinctive form of gait… in only a few thousand years, and with one carelessly designed instrument, our shoes, we have warped the pure anatomical form of human gait, obstructing its engineering efficiency, afflicting it with strains and stresses and denying it its natural grace of form and ease of movement head to foot.”

And finally, going barefoot is a joy to the senses, especially to young children who experience all the newness of the tactile world around them.

Think of the relaxing feeling of walking on soft warm sand at the beach, the refreshing feeling of cool dewy grass in the early morning of a summer day, the feeling of slippery wet mud squishing between toes in the garden, the feeling of the rough bark of a climbing tree, the surprise at the splash of a puddle underfoot.

All of these sensations are available when we allow our children to experience a bit of shoe-free time. Perhaps you should join us and kick off those shoes at the playground and in the back yard. Enjoy your feet and what they were made for.

Lauren Knight is a frequent contributor to On Parenting. She blogs at Crumb Bums.

How the dog pack Homo Erectus became weak and brutal? Keep running properly

I listened to the talk of Christopher McDougall on TEDx at a regular meeting in Awkar (Lebanon).

McDougall claims that Homo Erectus survived for 2 million years without any weapons, in an environment of carnivorous animals far more equipped genetically to chasing and killing prays.

Mankind is at a disfavor in all aspects of sensory capabilities, speed, and killing means than most animals.  So how did this specie managed to survive for so many years?

Christopher McDougall claims that Homo Erectus went hunting, all of them, as a tribe, men, adults, women, children, and even babies.

One factor that Homo Erectus outdid the performance of other animals is that he could cool-off while running, and thus, as other animals needed to stop to refresh, our dog pack of homos kept running and wearing out his chase to a stop, encircled, and then killed at leisure.

I am wondering:  How the homo erectus killed the pray?

They must have used some kinds of weapons like a heavy stick or stones.

How they managed to skin the pray?  They must have used some kinds of knives.

Do you believe ancient homo erectus ate the meat with the fur? Did they have more performing teeth mechanism or different finger nail shapes?  Or these lucubration are beside the topic?

(I have seen documentaries of African hunters chasing antelopes for 8 straight hours and forcing the victim to kneel down and say: “Okay, I outran you, I did my best to avoid you and blend in the environment.  You win. Please, kill me quickly.”

They were three Africans specialized in these long chases; they were naked and carried spears; most probably a few of them carried a sort of knife.

The documentary didn’t show what portion of the antelope they carried back to the community:  The antelope must be far heavier than the three hunters combined. The documentary failed to mention how the hunters returned, walking or running, and how long the return trip lasted. And how they carried the meat…

Are these pieces of intelligence beside the subject matter?

It is amazing the kinds of skills these hunters must have acquired to achieving this feat.  Does anyone believe that if he is equipped with modern technologies like GPS locators, compasses, and…he can find his way back after 8 hours of running in the jungle?

McDougall said that there is a tribe in Mexico that survived the Spanish Conquistadors’ holocaust by keeping on the run as a tribe since the year 1600.

his tribe emulated the hunting strategy of the Homo Erectus to survive all these years.  I bet this tribe learned to fabricate weapons so that they don’t have to run 8 hours every-time they need to feed.

I don’t know from where McDougal gathered his statistics that the members of this tribes never experienced feet, leg, or back injuries from running.  Is that too beside the point?

A regular attendee, William, has been experimenting with McDougall suggestions; not the hunting part, but the running methods.

William hand-made his flat thin sandals (as the one used by the Mexican tribe) and has been running with his dog Misha.  William said that he suffered from his knees before wearing the special sandals.  To double check that the former sneakers were the culprit, he wore his regular running shoes and the pains in his knees returned.  That is not all.

Even his sandals eventually hurt his knees and back for his 10 km run.  Thus, William experimented with the running posture and discovered that an erect posture, the groin forward, relying on the buttocks muscles, and managed to eliminate the leg and back pains.

William calls this posture “Fucking the dog posture”.  Obviously, this image is misleading, since you cannot fuck anything in this posture, not even an inflated man-made doll, but the male attendees nodded their head in agreement, simply because it is the “virtual posture” they like to  dream of.

Experiment in physics have demonstrated that bare feet have better coefficient of friction than any manufactured shoes, running or climbing shoes.  The bare foot opposes better resistance to slippery roads. Actually, African hunters go bare feet; maybe a few of them fabricate appropriate footwear from their hunting experience.

Maybe mankind evolved to run and run.

It is not organizing marathons or participating in marathons that will reverse the sedentary life-style of mankind.  When have you decided to go to work on foot?

Can cycling be another alternative to running?  Are we evolving into Homo Cyclist?

Instead of relying on buttock muscles, what other muscles we might rely on?

Note 1: Christopher McDougall said that, two decades ago, women were discouraged from running Marathons by disseminating the false information that the uterus will fall off and women will no longer be able to bear babies.  In  a few marathons, you see women breast feeding while running!

Note 2:  I suggest to design shoes by elevating the insole and having the outside sole thicker than the ball of the shoe so that the ball of the foot does not hit the ground first. That is my trademark design.

Article 35

 “Efficiency of the human body structure”

This article is an on going project to summarize a few capabilities and limitations of man. While the most sophisticated intelligent machines invented by man may contain up to ten thousand elements, the human machine is constituted of up to a million trillion of cells, up to a thousand trillions of neurons in the central nervous system, about a couple hundred bones, and as many organs, muscles, tendons and ligaments.

In the previous article #33 we discussed a graph in a story style and discovered that a human barefoot in texture, shape, and toes has a higher coefficient of friction than many man-made shoes that allow easier traction to move forward for less energy expenditure. We also expanded our story to observe that the structure of the bones and major muscles attached to limbs for movements as lever systems provide higher speed and range of movements at the expense of exorbitant muscular efforts.

A most important knowledge for designing interfaces is a thorough recognition of the capabilities and limitations of the five senses.  One of the assignment involves comparing the various senses within two dozens categories such as: anatomy, physiology, receptor organs, stimulus, sources of energy, wave forms, reaction time, detectable wavelengths and frequencies, practical detection thresholds of signals, muscles, physical pressure, infections and inflammations, disorders and dysfunctions, assessment, diagnostic procedures, corrective measures, effects of age, and safety and risk.

Human dynamic efforts for doing mechanical work is at best 30% efficient because most of the efforts are converted to maintaining static positions in order to preserve stability and equilibrium for all the other concomitant stabilizing joints, bones and muscles.  For example, the stooping position consumes 60% of the efforts for having a work done, in addition to the extremely high moment effected on the edges of the lower back intervertebrae discs.  Static postures constrict the blood vessels and fresh blood is no longer carrying the necessary nutrients to sustain any effort for long duration and heart rate increases dramatically; lactic acid accumulates in the cells and fatigue ensues until the body rests in order to break down that acid.

Human energy efficiency is even worse because most of the energy expended is converted into heat.  Not only physical exercises generate heat but, except for glucose or sugar, most of the nutrients have to undergo chemical transformations to break down the compounds into useful and ready sources of energy, thus generating more heat.  Consequently, heat is produced even when sleeping when the body cells are regenerated. Internal heat could be a blessing in cold environments but a worst case scenario in a hot atmosphere because the cooling mechanism in human is solely confined to sweating off the heat accumulated in the blood stream.  Heat is a source of blessing when we are sick with microbes and bacteria because the latter is killed when the internal body temperature rises above normal.

 “How to tell long and good stories from human factors graphs?”

Article #33, (Feb. 28, 2006)

If we concentrate on a graph we might generate a long story that span many disciplines and furnish us with a wealth of information and knowledge that pages of words barely can convey. A graph might open the gate for dozen of questions that are the foundation of scientific, experimental, and critical thinking.

Suppose that we are comparing the efficiency in energy consumption between walking bare feet or wearing shoes that weight 1.3 Kg.  Considering the walking speed as the other independent variable, along with the type and weight of shoes, we observe that the curves show that we are consuming less energy at low speed, then both curves decreasing to a minimum consumption of 0.2 KJ/Nm and intersecting at around 80 meter/min and then increasing as walking speed increases.

This graph is telling us that casual walking consumes less energy per unit walking effort than fast walking and that, at a cut off speed of 80 meter/min, the energy consumption is equal for both foot wares.  Some people might jump to the conclusion that this cut-off speed can be generalized to all foot wears, but more experiments are necessarily needed to verify this initial hypothesis.

Another piece of information is that after the cut-off speed, it is more economical in energy to walk barefoot. Basically, this graph is saying that the more weight you add to your lower limbs the more energy you should expect to spend, a fact that is not an earth shattering observation.

Biomechanics tells us that the structure of our body is not geared toward saving on our muscular effort, but to increasing our range and speed of movements.  Most of our muscles are connected to the bones of our limbs and their respective joints in manners they have to exert great effort and many fold the weight of our body members to overcome any of our limb’s mass.

Usually, the tendons of our muscles are inserted to the limb bones, close to the joints, and thus the muscles have to exert a huge effort to overcome the moment of the bone and flesh weight in order to effect a movement. Any extra mass to our limbs will tax our muscles to produce many folds the additional weight.

There is a caveat however; if you wrapped a weight of 1.3 kg around your ankles and walked bare feet you would consume more energy than without the added weight, but the curve would be parallel to the previous curve and not increasing more steepily than walking with shoes weighting 1.3 Kg.  Consequently, the variation in the behavior of the graphs result from a combination of added weight and lesser static coefficient of friction exerted by the shoes on the walking surface than the bare foot..

Thus, what this graph does not mention is the static coefficient of friction between the footwear and the ground, and which is the most important variable and in this case, can concatenate many independent and control variables such as the materials of the footwear and the type of ground into a unique independent variable of coefficient of friction.

The higher the coefficient of friction the easier it is to move and progress and thus walking faster for the same amount of effort invested.  It is not that important to generate muscle force if the reaction force on the surface cannot be produced to move a person in the right direction.  For example, it is extremely difficult to move on slippery surfaces no matter how much muscular effort we generate.  Apparently, the shape and skin texture of our foot provide a better and more efficient coefficient of friction than most foot wears.

However, the most important fact of this simple experiment is showing us the behavior of the curves and offering additional hypotheses for other studies.

What this graph is not telling us is the best story of all, and which can excite the mind into further investigation. For example, what kind of earth materials are we walking on; sands, asphalt, rough terrains, slippery roads or grassy fields?  Does the sample of bare feet walkers include aboriginals used in walking bare feet, city dwellers, and people from the province?  Does the sample includes groups of  people according to the softness of their feet skins or the size of feet?

May be the shape of the curves are the same for females as well, but it would be curious to find out the magnitude of variations compared to males.  It is clear that a simple and lousy graph delved us into the problems of experimentation and raised enough questions to attend to various fields of knowledge.

In the final analysis, the question is how relevant is this experiment practically?  How far can a modern man walk bare feet?  Does any economy in energy compensate for the ache, pain and injuries suffered by walking bare feet?  Would athletes be allowed to compete bare feet if it is proven to increase performance and break new records?  Does anyone care of walking barefoot in order to save a few kilo Joules?

The theme of this article is that you can venture into many fields of knowledge, just by focusing your attention on graphs and tables and permitting your mind to navigate into uncharted waters through queries and critical thinking.

 


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