balance

NABOSO PROPRIOCEPTIVE STIMULATION INSOLES

For several weeks, I have been testing the first-ever small nerve plantar proprioceptive stimulation insole technology called NABOSO, which means “barefoot” in Czech. The surface science technology was invented by Dr. Emily Splichal and is being marketed by her in conjunction with NABOSO yoga mats and floor tiles.

Introducing Naboso Insoles by Naboso Barefoot Technology. Get ready to experience what it truly means to move from the ground up with the first-ever small nerve proprioceptive insole to hit the footwear industry.

The skin on the bottom of the foot contains thousands of (small nerve) proprioceptors, which are sensitive to different stimuli including texture, vibration, skin stretch, deep pressure and light touch. When stimulated these proprioceptors play an important role in how we maintain upright stance, activate our postural muscles and dynamically control impact forces. – Dr. Emily Splichal

http://nabosotechnology.com/about

Dr. Emily Splichal goes on to state:

The skin on the bottom of the foot plays a critical role in balance, posture, motor control and human locomotion. All footwear – including minimal footwear – to some degree blocks the necessary stimulation of these plantar proprioceptors. The result is a delay in the nervous system which can contribute to joint pain, compensations, loss of balance and inefficient movement patterns.

Naboso Insoles are backed by surface science and texture research – and have been shown to not only improve balance but also positively impact gait patterns, ankle proprioception and force production in athletes.

Dr. Splichal stresses that:

This (NABOSO insole) is an insole providing proprioceptive and neuromuscular stimulation – it is not an orthotic providing biomechanical control.

http://nabosotechnology.com/naboso-insoles/

The principle proprioceptive neural activity associated with balance responses occurs across the plantar plane. It is strongest in the 1st MPJ (big toe joint) and big toe.

Dr. Splichal cites studies that found that textured insoles increased the activity of receptors in the plantar surface of the feet with a significant, immediate effect seen in the outcome measures of static (weight bearing) and dynamic (weight symmetry index, strength symmetry) in balance tests  as well as in gait symmetry (single support and swing phases). Thus, the proprioceptive stimulation benefit of textured insoles is carried over into footwear without textured insoles. I have noticed a significant improvement in  plantar proprioceptive sensitivity when barefoot or when my feet are not bearing weight. It is as if my feet have been put to sleep by a local anesthetic which has worn off.

Dr. Splichal’s information on NABOSO states that for the first time ever it is now possible to bring the power of barefoot science and plantar proprioceptive stimulation to all footwear – regardless of support, cushion or heel toe drop.

Assuming a NABOSO is trimmed, if necessary, to fit a shoe, there will be a positive effect on plantar proprioceptive stimulation. But my experience to date has been that the plantar proprioceptive stimulation will be much more pronounced in a minimal, zero drop shoe with adequate width for fascial forefoot tensioning and correct alignment of the big toe. I have experienced the best results with NABOSO in the Xero Prio shoe with the Lems Primal 2 and a Vivobarefoot model, close seconds.

The photo below shows the Xero Prio (blue-grey) with the Lems Primal 2 (black).

Both shoes have thin soles with low resiliency (the material compresses very little). The soles are also very flexible, an important quality. The sole wearing qualities of the Xero are excellent. The Xero Prio has become my all around minimal shoe. I use it for cycling on my mountain bike fit with large flat platform pedals.

The photo below is of the NABOSO insole for my left shoe.

Initially, NABOSO insoles are perceived, but not uncomfortable. After a time, shoes feel strange without them.

Over several weeks, I have done many tests of different shoes and insoles where I compare cushioned, standard insoles to NABOSO and different shoes with and without NABOSO as well as one-on-one comparisons with different shoes on each foot. After an initial walk in period, if I remove a NABOSO insole from one of my Xero Prios, it feels as if sole of the foot with the Xero without the NABOSO is signicantly less sensitive.

The most significant aspect of trying NABOSO insoles in different shoes is that it immediately becomes apparent just how bad some shoes are. The more cushioning, the narrower the fit and the greater the heel to toe elevation of the sole, the worse the shoe feels. For example, when I compared the Xero Prio with zero drop to a Nike Free with a 5 mm drop, I immediately sensed a pronounced negative effect on my posture and muscles of my legs, especially my glutes.

A Game Changer?

Prior to NABOSO, footwear companies could make shoes that have a negative affect on posture, balance and gait because it could be argued that the benefits of protecting the soles of the feet from mechanical damage outweigh any negative effects on balance and increased susceptibility to falls and injury. But the criteria for product liability is that a product must minimize, but not necessarily eliminate, the risk of injury to the consumer. Studies of textured insoles and even thin, low resilency soled footwear have shown dramatic improvements in balance and gait while reducing the risk of falls and potential injury. The inescapable conclusion is that footwear that reduces balance and the efficiency of gait while increasing the risk of falls and potential injury fails to meet this standard. This raises the question, “Will product liability litigation in footwear be the “next shoe to drop?””

NABOSO in  Ski Boots?

I have not yet had an opportunity to test NABOSO ski boots. But 2 racers I am working with are using NABOSO in zero drop minimal shoes. Stay tuned.

 

THE MECHANICS OF BALANCE ON THE OUTSIDE SKI

In the next series of posts, I am going to focus on the single most important, but least understood, aspect of skiing; skier balance, in particular, the ability to balance perfectly on the outside ski. Given its univerally recognized importance in the ski culture, it is both perplexing and disconcerting that little attention appears to be given to the study and analysis of the mechanics associated with balance on the outside ski.

For decades, the worlds greatest skiers, including Patrick Russell and Marc Giardelli, have stressed the importance of standing on the downhill (outside) ski. Giardelli said that once you can balance perfectly on the outside ski, everything else follows. The ability to stand on the outside ski and balance perfectly on it, implies the same mechanics of balance we engage in when we balance perfectly on one leg when we take a step to move forward in locomotion. Balancing perfectly on one leg requires a stable surface under the entire plantar aspect of the foot to provide a source of GRF. The reason why the ankle-foot complex has a triplanar joint system is so the tripod-like structure of the foot can seek stable ground. This is the classic text book definition of one-footed or monopedal balance and the standard for studies on balance performed on one foot.

The problem is that there is no ground or any form of stable GRF under the outside foot of a turn when the ski is on its inside edge other than the GRF acting along the portion of the edge in contact with the snow surface and a small portion of the base of the ski adjacent the edge. If elite skiers such as Russell and Giardelli really can stand on their outside ski and balance perfectly on it the question is where is the source of GRF coming from that acts to support weight of the body expressed on the plantar foot?

By 1990, I had an explanation in a hypothesis I had articulated. According to my hypothesis, elite skiers extend GRF acting along the portion of the inside edge of their outside ski from the snow to the base of the ski by rotating their outside leg and foot into the turn. This action causes the base of the ski on the outboard side of the inside edge to pivot upward about the portion of inside edge underfoot with sufficient force to support the weight of the body. The Birdcage studies done in 1991 were designed to find out if my hypothesis were right.

Balance on the outside ski is a Two-Step process

Having seen great skiers like Nancy Greene Raine and Toni Sailor ski with ease on pistes that would be difficult, if not impossible, for most skiers to hold an edge on, I was convinced that some skiers really could balance perfectly on their outside ski when it was on its inside edge, the same way that every skier could easily balance on one ski when the base of the ski was fully supported on a firm, stable surface.

I set out to try and figure out how this was possible. It took me about 10 years between 1980 and 1990, to formulate a hypothesis that explained the mechanics. Once I had an explanation, I understood why no one else had been able to figure it out.

Balancing on the outside ski does not adhere to the text book descriptions of single leg balance where a stable source of GRF under the plantar foot is assumed. The ability to stand on the outside ski when on its inside edge and balance perfectly on it, is a Two-Step Process. The key is that the Second Step is dependent on the First Step.  The First Step makes the Second Step possible. Without getting the First Step right within a very short window of opportunity, the Second Step is not possible.

Since my hypothesis predicted that sequence and timing is the critical, it was quite simple to prove my hypothesis with strategically placed strain gauges mounted in the Birdcage on discrete force plates positioned opposite the predicted force transfer points of the foot. The critical nature of the sequence was easily confirmed by preventing the First Step from occurring.

In my next post, I will discuss the Two Steps of the balance process and provide examples using screen shots and video clips from recent World Cup races showing the sequence in a turn where racers such as Mikaela Shiffrin make the two steps to balance on the outside ski.

 

 

WHY YOUNG TALENTED SKI RACERS FAIL AND EVENTUALLY QUIT RACING

The impetus for the subject of this post came from interest in my post FEATURE POST: MIKAELA SHIFFRIN: THE POWER OF SHEAR FORCE and an article (1) in the  February 14, 2017 edition of Ski Racing by sports psychologist, Dr. Jim Taylor.

Taylor’s article is aimed at U14 and younger ski racers. He points out that this is the age where the foundations are laid which often determine how well a racer does and especially how long they will remain in ski racing. Taylor cites statistics that show that qualifying for Topolino or Whistler Cup (international competitions for 13-15 year olds) isn’t highly predictive of success even five years later. Specifically, only 25% of those who qualified for those race series later earned a spot on the USST. Moreover, 35% were off the elite ski racing radar within four years; some before their 18th birthday. The problem, that is the focus of Taylor’s article, is that parents enter what he calls the “too” zone, where the parents of kids, who are 11 years old or younger, have become “too” important to the parents who have become “too” invested in how their kids do (or don’t do).

The question I have is what events preceded parents getting to the “too” zone? I have seen more than one situation where a child who started ski racing at a very young age and who would be considered a child ski racing prodigy, had a promising career unravel soon after they reached their teens. Why? What, changes happened that could have caused this tectonic shift?

Let’s go back to beginning when the racer first showed promise. Many racers demonstrate prowess when they are only 4 or 5 years old. Often, one or both parents are elite skiers. One of both may have raced. So their child has an excellent role model. As a result, the child quickly becomes comfortable following one of their parents down the ski hill. But there are also some important factors in their favour when a child is young;

  • They are light weight.
  • They are short in stature.
  • Their muscles and skeleton are not yet fully developed.
  • Their feet are small.

A significant factor is that young racers often learn to ski in their mother’s ski boots or boots that would be considered too big for their feet if they were older. The implications? Young racers acquire a kinesthetic sense of how to stand in their boots in what I call the SR Stance (3 to 10). As a consequence, they learn to utilize the mycostatic reflex balance response.

The authors of the Polish study on skier balance (2) note that three types of postural reactions to the loss of the body’s balance can be observed.

  1. The first reaction is the mycostatic stretch reflex, which appears in response to changes in the position of the ankle joints, and is recorded in the triceps surae muscles. This is the earliest mechanism, which increases the activity of the muscles surrounding the joint that is subject to destabilisation. The reflex caused by a mycostatic stretch reflex causes its contraction, which then results in the stiffening of the surrounding joints as a response to the stimulus that has disturbed the balance. For example, changes in the angle of the joints of the lower limbs are followed by a reflexive (fascial) tensioning of the adjacent muscles. The subsequent release of the reaction prevents an excessive mobility of the joints and stabilises the posture once again.
  2. The next reflex in the process of balancing is the balance-correcting response, which appears in response to a strongly destabilising stimulus. This reaction has a multi-muscle range, and occurs almost simultaneously in the muscles of the lower limbs, torso and neck, while the mechanisms that initiate the reaction are centrally coordinated.
  3. The last of the three types of muscular reactions is the balance-stabilising response. In a situation of a sudden loss of balance, a stretch reflex first occurs and then is followed by a balance correcting response, which prevents a fall.

I call these responses green (1), orange (2) and red (3).

As young racers enter their teens, a number of significant changes have occurred.

  1. They are much heavier.
  2. They have grown in height
  3. Their muscles and skeleton are more developed.
  4. Their feet have grown larger and are more defined.

It is about this time in what is appearing to be a child’s promising racing career, that parents turn to the experts in a well intended effort to maximize their child’s chances of success. One of the key things parents often do is to get race boots for their child and have them customized with footbeds, form-fit liners and increasingly, heat molded shells. The process typically involves race fit which is downsizing ski boots to the smallest possible shell that the feet can be squeezed into. Custom footbeds or orthotics are integral to race fit because they prevent the foot from spreading and elongating; they prevent the fascial tensioning that enables the mycostatic reflex associated with ultra high speed spinal reflex balance response (11).

No longer able to use the mycostatic reflex (Green = Normal) balance response, the CNS shifts to Level 2 (Orange = Caution) or even Level 3 (Red = DANGER).

What happens next? The young racer starts to become intimidated by courses and conditions they were previously comfortable with. When this happens, their brain senses imminent danger of serious injury or worse and resorts to what I call the Survival Technique. Survival becomes the priority at the expense of speed. Racers start losing ground to other racers. Not understanding the cause, parents and coaches start pushing the child in an effort to get results. The more the child tries, the worse things get. When this happens, frustration sets in. Eventually, the child no longer wants to race. Defeeted by their boots, the child eventually and takes up soccer or some other sport.

Unfortunately, this story is all “too” common. This is also one of the “toos”.


  1. What Young Ski Racers Need – http://www.drjimtaylor.com/4.0/young-ski-racers-need-dont-need/
  2. Influence of a nine-day alpine ski training programme on the postural stability of people with different levels of skills  (April 2016, Biomedical Human Kinetics (DOI: 10.1515/bhk-2016-0004) – Michał Staniszewski, Przemysław Zybko and  Ida Wiszomirska,  Józef Piłsudski University, Warsaw, Poland.
  3. THE SR STANCE: SURFACE EFFECTS,
  4. THE SR STANCE AND TOTAL BODY CORE INTEGRATION
  5. SR STANCE: ROUNDING THE BACK AND SHOULDERS
  6. THE SR STANCE: AFFECT OF JOINT ANGLES ON COM
  7. LEARN THE SR STANCE IN 3 EASY STEPS
  8. SR: ACHILLES-ARCH TENSION
  9. SR STANCE BASICS: ECCENTRIC MUSCLE POWER AND THE STRETCH REFLEX
  10. I-C-E: SR
  11. INNATE FLOW BALANCE

NEW STUDY: HOW SKI BOOTS AFFECT BALANCE

Thomas’ comments on the effect of the reptilian brain on stance created a perfect segue to discuss a recent paper on the effect of ski boots on skier balance.

Influence of a nine-day alpine ski training programme on the postural stability of people with different levels of skills  (April 2016, Biomedical Human Kinetics (DOI: 10.1515/bhk-2016-0004) – Michał Staniszewski, Przemysław Zybko and  Ida Wiszomirska,  Józef Piłsudski University, Warsaw, Poland.

The subject paper is an important source of information for any party with a serious interest in the mechanics, biomechanics and physics of skiing, especially academics and researchers.

https://www.degruyter.com/downloadpdf/j/bhk.2016.8.issue-1/bhk-2016-0004/bhk-2016-0004.xml

The aim of the study, which recognised that balance is one of the key elements that determine the effectiveness of the ride in alpine skiing, was to determine to what extent a few days of skiing activities and the level of technical skills affected the skiers’ level of postural stability; i.e. balance. While recognizing the importance of balance in alpine skiing, the authors commented:

Publications on issues related to the biomechanics of a descent, with particular emphasis on the balance parameters, are rare in the literature on alpine skiing.

Authors of a 2014 study, Changes in the Balance Performance of Polish Recreational Skiers after Seven Days of Alpine Skiing – Beata Wojtyczek, Małgorzata Pasławska, Christian Raschner, similarly commented:

Our results were in agreement with the scarce information available regarding balance changes during or after a ski training camp.

The conclusion of the subject study is that skiing had a positive effect on postural stability. But the authors qualified this conclusion as valid only in measurement conditions that were similar to those in which this stability was practiced, i.e. in measurements involving ski boots and in the trials where the participants stood on one lower limb (monopedal stance) and mainly in the beginners. In the trials done with ski boots on both feet (bipedal stance), balance was worse than when the subjects were barefoot.

The fact that the improvment occured mainly in beginners provides a vital clue.

 The restriction of mobility within the ankle joint significantly influenced the training-induced changes in the postural stability of both beginner and advanced alpine skiers.

Wearing Ski Boots Weakens Balance 

Wearing ski boots for a few hours can lead to a weakening of the muscles that operate within the ankle joint. This works as though one joint was excluded from the locomotive function.

Dudek et al.  demonstrated that the stabilising function in the process of maintaining balance was significantly weakened after an injury to the ankle joint which excluded it from locomotion for some time. Also, according to Caplan et al. [3], the muscle groups that determine strength and are responsible for the function of stability in the ankle joint are very sensitive to changes caused by immobilisation. They found that immediately after immobilising the ankle joint for a week, the balance parameters were 50% lower than before the immobilisation.

In summary, it can be stated that the restriction on the  mobility within the ankle joints had a significant (detrimental) impact on the training-induced changes in postural stability while the participants were standing on two feet, in both beginner and advanced alpine skiers. However, in the trials where the participants stood on one lower limb, balance improved mainly in the beginners.

The most plausible explanation of this effect is that the biomechanics of the human limbs and the human torso depend on the cooperative actions of various groups of muscle.

A number of researchers have stated that, in addition to endurance and strength components, coordination and sensorimotor performance are of the utmost importance in alpine skiing.

The apparent paradox of the improvement seen in the balance of beginners on one limb when in ski boots is explained by the fact that the ski boot acts as a balance stabilizing frame as shown in Figure 58 show below from my US Patent No. 5,265,350.

fig-58

In monopedal stance, inversion-eversion oscillation of the subtalar joint occurs about the tuberosity of the calcaneus (heel bone) as shown Figure 58B. Stabilizing the ankle joint within the confines of the rigid shell of ski boot effectively doubles the proximate width of the tuberosity of the calcaneus while the shaft acts as a steadying cage.

Clues to the Real Balance Issue, Torque

Scott et al. [22] demonstrated that during ski turns, the angular changes in the knee and hip joints can reach 50°, while in the ankle joint the oscillation is only a few degrees.

The authors of the paper, Flexural behavior of ski boots under realistic loads – The concept of an improved test method (Michael Knye*, Timo Grill, Veit Senner) commented:

Usually boots with high flex indices (stiff boots) are used by more experienced and skilled skiers whereas for beginners softer boots are recommended.

Coincidentally experienced skiers tend to keep a constant lower leg posture using boots with varying stiffness.

Isometric Contraction – The SR Stance

Three types of postural reactions to the loss of the body’s balance can be observed. The first reaction is the myotatic stretch reflex, which appears in response to changes in the position of the ankle joints, and is recorded in the triceps surae muscles. This is the earliest mechanism, which increases the activity of the muscles surrounding the joint that is subject to destabilisation. The reflex caused by a myotatic stretch causes its contraction, which then results in the stiffening of the surrounding joints as a response to the stimulus that has disturbed the balance. 

The observations of the authors are confirming that experienced skiers have learned a stance that places the calf muscles in isometric contraction;  an SR Stance.

The authors of the subject paper further commented:

In this situation, a torque is created between the force of gravity and the force of the reaction of the snow on the skis, which results in a descent in a curve and a loss of balance.

There are actually 3 torques that affect balance. Two of the torques are coupled through the subtalar joint as shown by the bridged rotations of Lateral-Medial Axial Rotation/Inversion-Eversion in the graphic below.

3-degrees-of-freedom-r1

 

It is the outset of force applied to the outside foot through load transfer from the pelvis offset to the ground reaction force acting along the entire length of the inside edge in contact with the snow, that creates a torque that inverts the base of the ski and the foot. The torque is translated through the subtalar joint to vertical lateral axial rotation of the tibia. While the translation is somewhat restricted by confines of the shaft of the ski boot, the moment of force is not significantly diminshed,

Both sets of torques must be balanced across the ski equipment/snow interface. The question is which torque must be balanced first? Once again, the authors of the subject paper provide a clue.

This is the earliest mechanism, which increases the activity of the muscles surrounding the joint that is subject to destabilisation.

In my next post, I will describe the mechanism by which the remaining (coupled) torque is balanced.

 

 

THOMAS’ THOUGHTS ON THE REPETILIAN BRAIN AND ITS EFFECT ON SKIER STANCE AND MOVEMENT

 

I started this blog with the objective of stimulating critical thinking on issues of skiing that would result in an intelligent, interactive dialogue. It appears as if this is beginning to happen as expressed in the critical thinking by Thomas in his comments on recent posts.

Thomas’ comments follow below with emphasis added in the form of underlined and bolded text by me.


This quote from W Hauser, P. Schaff, caught my eye.

“Many alpine skiers have insufficient mobility in their knees and ankle. The range of motion, particularly in the ankles, is much too small. This results in a static, stiff run. It does not correspond at all to the ideal of a wide range of mobility in the area of the knee and ankle, which was proposed and taught during early alpine ski lessons. Even the best diadactic (patronizing) methodology is not always successful in imparting to the student the full range of motion. The lack of proper technique seem so often is not due to a lack of ability, but to an unsatisfactory functional configuration of the shaft in so many ski boots. This is particularly true in models designed for children, adolescent and women.”

  • I would take a rather contrary view here and say the problem comes not from the boot design but a lack of technique. That is not because I disagree with Herr. Schaff.
  • The modern skiing didactic does not really teach the hard, strong, or tensioned arch which if I understand it correctly is only induced when a certain forward range of shank motion and COM is achieved.
  • This in turn sets up a chain reaction through the legs into the torso. Without this the skier can not attempt optimal form(s) or balance.
  • The arch concept is not widely taught or understood. Therefore there is not a demand for footwear that meets the basic requirements for optimal skiing.
  • Without this basic understanding it will be a matter of chance whether ski enthusiasts purchase or even know to adjust boots for full range of shank motion.
  • A key part of teaching stance technique has to become adjusting boot cuff for adequate shank range of motion. When I suggested to a student lessening cuff buckles, he reflexively tightened them. Ouch.
  • Once the body finds (if boots permit it) the strong arch, our neurology gravitates to your SR stance and presto all kinds of problems just go away including the back seat.

Rather disconcerting it all has to be reprogrammed after lunch.

This brings me back to a general question of safety with respect to equipment. Not is the equipment safe? But (is it) safe in terms of how the brain perceives safety (balance) and makes purchase decisions.

For example in skiing on one 190 cm ski and one 90 cm snowblade I notice that the 190 allows me to be way back without negative consequence. I had to really learn to keep balance on the strong arch of the 90cm snowblade. In a hockey stop the 90 snowblade flew out from under me up into the air! I remained upright because of the other ski’s long tail and the hard stop of the other boot. My reptilian (spinal reflex) brain reaction to the short snowblade was it was unstable and therefore dangerous.

The conclusion is when my brain tells me I am safe, I will want to ski all day long in really bad form with boots/skies designed to compensate for, well, bad technique. Therefore, neither would I likely ask other people to try the strong arch, SR, optimal range of motion cuffs, 90cm skies nor purchase lessons or equipment of like kind.

No one I ski with is willing to try the 90/long ski combo or the pair of 90s. My guess is because of their emotional reaction to imagining loss of stability; their brains will NOT permit them to even try.

These equipment usage and purchase decisions are occurring below the level of perception, consciousness. They are logical in terms of the reptilian brain’s safety hard wiring. I’m guessing this was the motivation for the student above to tighten (not loosen) boots because his brain equated more rigidity with security = safety.

If we want to ski better read this blog don’t listen to your reptilian brain anymore. Except when the speed and accuracy of these emotional reactions saves your life!

 

THE SR STANCE: SURFACE EFFECTS

A good segue to continuing my discussion of the SR Stance is to provide a tool that will enable the assessment of the effect of different surface densities and textures and footwear, orthotics and generic insoles on the small nerve proprioceptors in the plantar foot.

Most people assume that cushioning under the plantar foot is a good thing; that it provides comfort and helps protect the foot from shocks. Who needs footbeds? Everyone. It’s only common sense. Everyone knows the foot is weak. It needs support. Except, that none of this is true.

“With thousands of plantar receptors, the foot is also a proprioceptive-rich structure, containing thousands of small nerves that are sensitive to every subtle movement we make. Our ability to walk, run or jump is all initiated through stimulation of these nerves on the bottom of the foot (aka the plantar foot).

“Because of the smaller diameter these plantar nerves are able to send signals faster to the Central Nervous System, creating faster response times”.

– Barefoot Strong by Dr. Emily Splichal

“80% of our plantar proprioceptors are sensitive to vibration”    – Nigg et al

“With small nerve receptors sensitive to stimuli such as texture, vibration, pressure and skin stretch, the skin on the bottom of the foot is unique when compared to the skin on the top of the foot or the lower leg.

“As soon as we put on socks, orthotics  or shoes we block these highly sensitive small nerves on the bottom of the foot.”

– Barefoot Strong by Dr. Emily Splichal

What Dr. Splichal says is true of any form of arch support. Ski boots are arguably the worst form of footwear for blocking the highly sensitive small nerves on the bottom of the foot.

As Dr. Splichal explains, the power of neuromuscular activation that enables precise balance and movement originates from the ground and moves upward through the plantar foot.

An easy way to impart an appreciation of how the stability, density and texture of surfaces under the plantar foot or structures such as insoles, orthotics, ski boots, liners or any form of footwear, affect stance, balance and movement patterns is by doing a series exercises on one foot starting barefoot on a hard level, stable surface, then adding different materials between the plantar foot and the supporting surface and assessing their effect on balance.

Dr. Splichal demonstrates a series of exercises in her EBFA YouTube Fitness group called Best Surfaces for Barefoot Training – https://youtu.be/gvJjIi3h1Bs

There are some issues with the quality of this particular video, especially as it ends and the volume increases dramatically. So use caution, especially if you are wearing earbuds or headphones. This issue aside, Dr. Splichal’s demonstration is spot on.

Reference Surface

The reference surface for establishing a baseline should be solid, stable, level and uniform. Texture is important. The worst surfaces for small nerve stimulation are smooth and glass like. Through experimentation, I have found that the best surface in my home is the concrete floor in the mechanical room which is coated with an epoxy paint with fine sand imbedded in it. The worst surface is the smooth laminate in the main living area. Tile in the entry hall with a slight texture is somewhere in between.

The photo below shows textured surface concrete on the left, smooth laminate on the right.

textures

Balancing on One Foot

Although balancing on one foot in a process of alternating single limb support is our basic mode of locomotion, most people seldom engage in prolonged balance on one foot. In order to ensure accurate assessment of surface effect, the move from balance on two feet to balance on one foot should be rehearsed. In my patents, I refer to these two states as bipedal and monopedal support.

Start by standing relaxed on both feet in an upright stance. Start moving the pelvis towards one foot. The movement of the pelvis should be in an arc that is sideways and forward as if the side of the pelvis on the support leg is moving diagonally towards the little toe.

As the pelvis moves forward, relax the ankle and allow the weight (pressure) to move to the ball of the foot. Keep a small bend in the knee as Dr. Splichal advises in her video.

Move back to balancing on two feet. Then repeat the balance exercise on the other side.

Repeat the exercise until you can quickly find stable balance on each foot and maintain it with minimal effort for at least 20 seconds. This may take time if the muscles that are being recruited are weak and/or unbalanced.

When you are comfortable balancing on either foot, try the exercise on different stable, hard surfaces and compare the effect of the different surface textures on balance.

You may want to try the same exercise on carpet if it is available.

A Word about Pronation

A campaign of misinformation has created a widespread perception that any amount of pronation is unnatural, even dangerous and should be prevented with a supportive insole or orthotic. Some experts have taken the position that a small amount of pronation is desirable but that it should be restricted to a specific amount controlled by an orthotic.

In a future post, I will expand on my earlier discussions of the 3 foot types. While it is correct that both pronation and supination are abnormal, the context of abnormal is in bipedal stance. From a perspective of basic trigonometry, the leg must adduct (move towards center of the body) about 6 to 7 degrees in order for the foot to be positioned under the centre of gravity. The foot must rotate an equivalent 6 to 7 degrees about its long axis in order for its tripod points to become compliant with the supporting surface.  STJ joint coupling produces an equivalent amount of internal rotation of the tibia about its vertical axis. Eversion/internal rotation is called pronation.

The absurdity of what amounts to an all out war on pronation should become apparent from viewing the stick man figure below from my patents.

FIG 23A - 23BSystematic efforts aimed at immobilizing the joints of the foot and leg in the ski boot, usually in neutral STJ, prevent skiers from assuming a balanced (read: pronated) position on the outside foot and ski ski thus ensuring the existence of an unbalanced moment of inversion/external rotation force. In addition, studies have shown that restraining the ankle in a tightly fitting ski boot increases laxity of the knee under closed chain whole leg rotation by approximately 30% over lesser forms of ankle constraint.

In my next post, I will discuss a series of exercises for assessing the effect of the components of the ski boot, including different liner components and interventions that support the arch of the foot.


Dr Emily Splichal is a Podiatrist and Human Movement Specialist.

She is the Founder of the Evidence Based Fitness Academy (EBFA) and Creator of the Barefoot Training Specialist, Barefoot Rehab Specialist and Bare Workout Certifications for health and wellness professionals.

Her book, Barefoot Strong is available in print and ebook formats.

http://evidencebasedfitnessacademy.com/faculty.html