Biomechanics

NEW INSIGHTS INTO THE BIOMECHANICS OF WALKING AND STEPS IN THE SKI TURN

Comments made by S.S. Komissarov in his paper, Dynamics of carving runs in alpine skiing. The centrifugal pendulum in conjunction with a critical examination of the biomechanics of the walking cycle and subjective on-snow experiments I did last ski seaon has given me insights into the mechanism that enables fluid dynamic skiing with directional control.

A telling statement by Komissarov is that in the fast skiing typical of FIS WC racers’ rhythmic carving turns are still possible but balanced carving turns are no longer possible. Komissarov further states that during rhythmic carving turns a skier is never in balance. I would modify this statement to posit that during rhythmic carving turns a skier is only in what can be described as a state of dynamic balance wherein neurobiomechanical processes effect tight control over variances in the orientation of the transverse plane of the base of the edged outside ski as it pertains to the alignment of the vector of opposing applied and reaction forces for a few milliseconds.

These insights explain why static balance exercises done on one foot, lateral side to side jumps where a subject lands and balances on one foot and even one ski turn exercises don’t equate with the dynamic mechanism responsible for the fluid movement of dynamic skiers.

A critical examination of the walking (aka gait) cycle raised issues that as far as I know may never have been explored. These issues have potential implications for the role of steering in the alignment of the pendulum vector of COM with the transverse aspect of the outside ski as it pertains to the edge angle in carving and the stiffening of the outside foot and leg that enables powerful carving forces to applied to the outside ski that when released act can act as catapult mechanism to propel the skier into the next turn.

Pelvic rotation appears to be a key component in the dynamic processes of both walking and skiing.

In my next post I will start to explain how I believe pelvic rotation in walking relates to pelvic rotation in a ski turn and what the differences are.

 

IS DYNAMIC SKIING A FORM OF WALKING?

The text below is from a sub page I put up on the home page in 2014 in which I posited that elite skiers use the same hard-wired processes as walking.

It was only recently after I connected pelvic alignment with the ball of the outside foot of a turn achieved by steering the foot into position with COM to create an alignment with the fall or gravity line did I finally put the last piece of the puzzle in place.


As bipeds, we propel our bodies forward by moving from one fascially tensioned base of support with foot to core sequencing on one foot to another fascially tensioned base of support with foot to core sequencing.

Dynamic skiing uses the same basic pattern. In skiing, we need to establish a fascially tensioned base of support with foot to core sequencing on one foot in order to be able to move with precision to another fascially tensioned base of support with foot to core sequencing on another foot. As far back as the 70’s, the famous French ski technician, Patrick Russell, said that the key to effective skiing is to ‘move from ski to ski’. What Russell was really alluding to is the process of alternating single limb support.

Ever since alpine skiing became formally established, it has been known that the best skiers move from the outside ski of one turn to the outside ski of the next turn. Although this may sound simple enough, the key to being able to effectively move from ski to ski (foot to foot) is the ability to establish a fascially tensioned base of support with foot to core sequencing one one foot and then use it to move the body or Centre of Mass to the new outside foot (current uphill ski) of the next turn. Good skiers do this so seamlessly that turns seem to have no beginning or end. The turns just flow together. When viewed in the context of stance and swing phases, the resemblance to walking becomes apparent

How to make skiing as intuitive as walking is what this blog is about. I devoted an entire series of patents to this subject commencing with US Patent No. 5,265,350 and associated international patents on the elements of a minimal ski boot necessary to accommodate the process of establishing a fascially tensioned base of support with foot to core sequencing on one foot and transitioning seamlessly back and forth between bipedal and monopedal stances.

The ability to balance multi-plane torques on the outside leg of a turn is, and continues to be, the secret of the worlds’ best skiers including Toni Sailor, Nancy Greene Raine, Pirmin Zubriggen and, today, Mikaela Shiffrin, Lindsey Vonn and Ted Ligety to name but a few.


A REVIEW OF GAIT CYCLE AND ITS PARAMETERS – Ashutosh Kharb1, Vipin Saini2 , Y.K Jain3, Surender Dhiman4 – https://ijcem.org/papers72011/72011_14.pdf

Dynamic loading of the plantar aponeurosis in walking – Erdemir A1, Hamel AJ, Fauth AR, Piazza SJ, Sharkey NA. – https://www.ncbi.nlm.nih.gov/pubmed/14996881

Active regulation of longitudinal arch compression and recoil during walking and running – Luke A. Kelly, Glen Lichtwark, and Andrew G. Cresswell – https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4277100/

The Foots Arch and the Energetics of Human Locomotion – Sarah M. Stearne, Kirsty A. McDonald, Jacqueline A. Alderson, Ian North, Charles E. Oxnard & Jonas Rubenson – http://www.nature.com/articles/srep19403

Shoes alter the spring-like function of the human foot during running – Kelly LA1, Lichtwark GA2, Farris DJ2, Cresswell A2. – J R Soc Interface. 2016 Jun;13(119). pii: 20160174. doi: 10.1098/rsif.2016.0174. – https://www.ncbi.nlm.nih.gov/pubmed/27307512

The Science of the Human Lever: Internal Fascial Architecture of the Forefoot with Dr. Emily Splichal – https://www.youtube.com/watch?v=_35cQCoXp9U

 

 

 

 

THE FUTURE OF THE SKI BOOT – PART 1

SHOEspiracy, a new feet-first documentary by barefoot/minimal shoe maker Vivobarefoot (1.) provided me with insights on the factors behind the unproven theory on which the design and modification of the rigid plastic ski boot is based that supporting and immobilizing the foot of a skier in neutral places it in the strongest position for skiing.

The intent of SHOEspiracy is to shed light on what amounts to a  ‘Shoe-shaped’ Public Health Scandal’.

There is a 20 billion pair a year, silent public health scandal a’foot and it’s shoe shaped!

It’s astonishing to us that the vast majority of shoes produced each year are actually bad for people’s feet—and the wearers are none the wiser.

VIVOBAREFOOT co-founder Galahad Clark

According to the documentary SHOEspiracy is intended to inspire viewers to reconnect with their feet and create a drive within the multi-billion-dollar footwear industry to establish a template for healthy shoes, healthy feet and natural movement. Most people are blissfully unaware of the problems footwear can and does cause and assume that what they put on their feet is benign.

I commend Galahad and Asher Clark and Vivobarefoot for taking the initiative to educate consumers on the problems shoes can and do cause and to establish a template for shoes that respect and accommodate the physiologic requirements of the user.

From Function to Fashion

At one time all humans were barefoot. This changed about 40,000 years ago when humans began to wrap animal skins around their feet to protect them against damage from the elements.  From crude beginnings as nondescript forms of protection, footwear evolved into a fashion entity; one that changed the shape and appearance of the foot, often radically, to render it more aesthetically pleasing. Heels first appeared in horsemen’s shoes as a device to help keep the rider’s feet in the stirrups.

As the evolution progressed shoes became corrective and lifestyle devices in addition to fashion accessories. In the footwear fashion era people have historically worn shoes that deformed their feet, the Chinese Lotus shoe  being an extreme example. But since a degree of deformation does not typically result in a noticeable impact on low-key locomotion the negative impact of restrictive footwear has generally flown under the radar unnoticed.  Adverse effects due to footwear such as joint and muscle pains and impaired balance are usually attributed to other factors.

Young feet are especially malleable. Their shape can be molded by footwear often resulting in permanent deformity as mine were when as a child my feet were put in orthopedically correct, supportive footwear to help them develop properly. The recent photos below show the state of my feet after more than 5 years of wearing exclusively minimal shoes, doing exercises like the short foot and using NABOSO insoles. Although they have become much stronger and healthier, it is doubtful whether the damage done when I was a child can ever be undone.

The left hand photo shows my feet with forefoot minimally weighted. The right hand photo shows my feet weighted. Note the difference in the robustness of the big toe of my left foot compared to the big toe of my right foot. I believe this at least partially explains why I am able to stand and balance with superior stability on my left foot compared to my right foot.

The photos below serve to graphically illustrate why I gave up road biking several years ago and now ride a touring bike with large flat platform pedals and minimal shoes fit with NABOSO insoles. As my feet became stronger and more functional I was no longer willing to abuse them with constrictive footwear.

The Jogging/Ski Boot Connection

About 50 years ago a new type of shoe appeared; one that would revolutionize the footwear market. The Sports Shoe was created in response to the running boom of the 1970’s. When I took up running on the cusp of the running boom, runners of the day ran in flats made for tennis or basketball. These were plain canvas shoes with no heel toe drop or special features.

Jogging, published in 1967 by Nike cofounder, William J. Bowerman, served as a catalyst for the running boom that emerged in the 1970s and with it the development of jogging and other sports footwear including plastic ski boots. At the time that he wrote Jogging Bowerman was working with elite runners looking for ways to improve their performance. His book was preceded by the introduction of the first Lange ski boot in 1962 followed by a racing model in 1965.

People who took up jogging who hadn’t run before started having problems with their Achilles tendon and calf muscles because their everyday shoes had heels. After consulting with doctors Bowerman made a decision to raise the heel of his jogging shoes by 1/2” (12 mm) to accommodate people who wore dress shoes. This feature was for the general public, not the athlete. Bowerman recognized that the sports footwear industry needed to create a consumer product that could be worn without causing discomfort. In an attempt to address problems caused by raising the heel the sports shoe industry responded by adding counters, arch supports and other features; in effect adding band aids in an effort to correct problems caused by raising the heel.

When the Nike Waffle Trainer was marketed as a shoe designed specifically for jogging the idea of sport specific shoes initially made sense to me. But even though I had been running with a heel strike technique in flats I experienced problems right away with ankle and knee shock at heel strike in my Nike Waffle Trainers. In comparing the Nike shoe to my canvas flats it became obvious to me that the flared heel was adversely altering the mechanics of heel strike. Trimming away the outer (lateral) and rear aspects of the flared heel reduced the shock of impact at heel strike.  I suspected that other aspects of the shoe were also adversely affecting my running mechanics. This incident caused me to question whether the design of sport specific shoes was supported by science.

When I started looking for answers I found out that it had been known for decades that footwear can negatively impact the physiologic function of the user. But the issue of the effect of footwear on athletic performance came into sharp focus in 1989 with the publication of the medical textbook, The Shoe in Sport (published German in 1987 as Der Schu im Sport). The Shoe in Sport brought together the collective expertise of 44 international authorities on orthopedics and biomechanics to focus their attention on the SHOE PROBLEM in the context of problems shoes can cause for athletes that compromise performance and contribute to injury. The Shoe in Sport focusses on the medical and orthopedic criteria of sports shoes in offering guidelines for the design of shoes for specific athletic activities including skiing and ice skating. The efforts of the Shoe in Sport was supported by the Orthopedic/Traumatologic Society.

In the Introduction to the Shoe in Sport, Dr. med. B. Segesser and Prof. Dr. med. W, Pforringer note that the buyers of athletic shoes are always looking for the ideal shoe. In their search for the ideal shoe they encounter a bewildering variety of options and are largely dependent for information on the more or less aggressive sales pitches directed at athletes from every angle.

Segesser and Pforrineger go on to state that the findings in the textbook should enable the interested reader to distinguish between hucksterism and humbug on the one side and scientifically sound improvements in the athletic shoe on the other. The Shoe in Sport makes it abundantly clear that it is not a question of if the structures of footwear will affect the physiologic function of the user but a question of how they will affect the physiologic function of the user and especially whether the footwear will compromise athletic performance and/or contribute to injury. The Shoe in Sport studies the biomechanical, medical and technical aspects of the shoe problem as it exists in various fields of athletic endeavour.

A number of leading footwear company executives have often said to me over the years that they know science and agree with the philosophy behind the benefits of barefoot shoes, but that consumers aren’t ready. – Galahad Clark

Clark’s statement seems to suggest that little has changed since the publication of The Shoe in Sport in 1987 and the subsequent publication of Nigg’s Biomechanics of Sports Shoes in 2010. One reason may be the difficultly in conducting objective studies that lead to definitive conclusions pertaining to effects on the user of specific features of footwear.

After I learned of the research done by Benno Nigg at the Human Performance Laboratory at the University of Calgary that found that anything appended to the human foot compromises physiologic function I set out to develop a minimal constraint device for rigid soled footwear such as hockey skates, ski boots, cycling shoes and the like that would create a functional environment equivalent to barefoot. Activities that employ rigid soled footwear are much easier to conduct in vitro and in vivo studies than other activities. The objective of the device I wanted to develop was to enable the study of the effects of interfering with the action of discrete joints or joint systems of test subjects by controlling variables against a standard reference. In 1991, I succeeded in developing such a device in a corroborative effort with a biomedical engineer. The device can be constructed at minimal cost and readily fit with instrumentation to capture performance data.

When I wrote my US patent 5,265,350 at the beginning of 1992 I described the research device in impeccable detail with the intent and hope that others would construct the device and conduct studies with it. Under the terms of a patent, research may be conducted using a technology for which patents are pending or granted without infringing. This meant that research vehicle could have been constructed and studies commenced as soon as my patent application was published.

The graphic below shows the Birdcage research device on the left and Figure 1 from US patent 5,265,350 published on  February 22, 1993 on the right.

Form follows Function

The designation of the research device as Figure 1 in the patent is symbolic of the priority I give to function and science over other considerations.

The design and development strategies used by David MacPhail are very holistic in nature, placing the human system as the central and most critical component in the biomechanical system. His intent is to maximize human performance and efficiency, while foremost preserving the well-being and safety of the users and minimizing biomechanical compromises.  Alex Sochaniwskyj, P. Eng.

In US 5,265,350 and subsequent patents granted to me I disclosed a series of accessories for use with the research device. I designed these  to enable the effect on the user of factors such as the position of key mechanical points of the foot in relation to the mechanical points of a snow ski appended to it to be studied. To the best of my knowledge the minimal constraint research device and accessories has yet to be constructed and employed by other parties.

…………. to be continued.


  1.  https://www.shoespiracy.tv

FOOTBEDS: THE UNKNOWN COST OF SUPPORTING THE ARCH OF A SKIER’S FOOT

Two recent studies (1.), (2.) question the merits of supporting the arch of a skier’s foot and especially any claims made that supporting the arch in neutral is the strongest position for skiing. 

It is well established in the scientific literature that the plantar aponeurosis (aka plantar fascia or PA) is one of the major arch-supporting structures of the human foot.  A positive correlation between Achilles tendon loading (ATF) and plantar fascia tension (PAF) has been reported. A study (3.) found that plantar aponeurosis forces (PAF) gradually increased during mid stance and peaked in late mid stance. The study found a good correlation between plantar aponeurosis tension (APF) and Achilles tendon force (ATF). The study concluded:

The plantar aponeurosis transmits large forces between the hindfoot and forefoot during the (mid) stance  phase of gait. The varying pattern of plantar aponeurosis force (PAF) and its relationship to Achilles tendon force (ATF) demonstrates the importance of analyzing the function of the plantar aponeurosis throughout the stance phase of the gait cycle rather than in a static standing position. – (my emphasis added in bold)

I discussed this in my post TRANSITIONING TO A HIGHER LEVEL OF SKIER PERFORMANCE.

The graphic below from Kevin Kirby’s Foot and Lower Extremity Biomechanics II:  Precision Intricast Newsletters, 1997-2002 illustrates how the position of COM in relation to the foot tensions the GS (gastroc-Soleus) compressing the arch which tensions the plantar aponeurosis ligament. I have added arrows to indicate PA strain Force F and Shear Force as well as Arch Compression Force.

The graphic below also from Kevin Kirby’s Foot and Lower Extremity Biomechanics II:  Precision Intricast Newsletters, 1997-2002 illustrates how the anterior (forward) advance of CoM in relation to the foot decreases rear foot loading (GRF-RF) and increases fore foot loading (GRF-FF). I have added a red dashed vertical line and a red triangle to show the approximate location of what would be what I term the tipping or pivot point where the foot would rock rearward and forward with a corresponding shift in CoM.

The two recent studies I referred to (1.), (2.) that question the merits of supporting the arch of a skier’s foot were actually done with subjects walking and running on flat and inclined surfaces. But the effect on arch compression is applicable to the effect of arch supports used in ski boots.

New Balance Minimus road MR00 shoes were provided to all participants to wear for testing (approx. weight 180 grams, zero heel-toe drop, no medial arch support and a uniform EVA midsole). Pockets filled with lead weights were affixed to the laces of both shoes in order to standardize foot weight across all shoe and insole conditions. The minimal shoe was chosen as a control condition in order to standardize non-insole effects as much as possible.

Two separate custom insoles were designed for each participant and fabricated by orthotic laboratory. The first insole was designed to restrict arch compression near-maximally compared to that during shod (barefoot) running (Full Arch Insole; FAI). The second insole was designed to restrict compression by approximately 50% during stance (Half Arch Insole; HAI). TO qualify for the study participants could not wear orthotics on a regular basis.

The study found:

The insert restricted maximum arch compression by approximately 70% when compared to unrestricted shod running and consequentially resulted in lower strain values throughout the entire stance phase. It should be noted that the PLF length only surpasses the estimated resting length between ~25%-80% of the stance phase in the insert condition (Fig 3). The negative strain values should be regarded as a slack PLF length, not as the PLF shortening beyond the resting length. 

The graphic below from the paper The Foot’s Arch and the Energetics of Human Locomotion shows the maximum arch compression of subjects shod barefoot (Shoe-only), with the Half Insole that restricted arch compression to 50% of the maximum amount and with the Full Insole that maximally restricted arch compression. The Full Insole is typical of insoles used to support the arch of a skiers’ foot.

 

The insoles had no effect on the metabolic cost of walking despite restricting ~80% of arch compression. 

In a personal communication with Sarah Stearne she advised me that the study didn’t measure muscle EMG activation with and without the insole but they did know that the ankle performed less positive (-8%) and negative (-10%) mechanical work when the insole was worn and that the ankle peak dorsiflexion moment was reduced (-7%). Based on the ankle moment and Achilles tendon moment arm data they calculated that there was ~6% less force in the Achilles tendon when the insole was worn.

Whilst several studies have acknowledged the elastic energy storage potential of the PLF, this ligament is primarily regarded for its role in providing integrity to the bony arch structure, and in supplying the rigidity required for the foot to function as a lever during propulsion (or skiing, my comment) 

This study confirms what I experienced in 1973 after I had full support custom orthotics made by a well known sports podiatrist. The orthotics felt comfortable standing on them and even walking. I experienced some discomfort when attempting to run with the orthotics in my jogging shoes. But when I tried skiing with them in my ski boots I felt as if my foot were floating on the top of the orthotic with little or no sensation of any force under my first MPJ.

Based on the results of two cited studies I believe there is no basis to assume that supporting the arch of a skier’s feet will have positive benefits or is without adverse consequences without first conducting comparative studies using standardized controlls (no insole, flat boot board) and established scientific protocols.


  1. The Foot’s Arch and the Energetics of Human Locomotion – Sarah M. Stearne1, Kirsty A. McDonald1, Jacqueline A. Alderson1, Ian North2, Charles E. Oxnard3 & Jonas Rubenson1,4 – (January 19, 2016)
  2. The Role of Arch Compression and Metatarsophalangeal Joint Dynamics in Modulating Plantar Fascia Strain in Running – Kirsty A. McDonald1, Sarah M. Stearne1, Jacqueline A. Alderson1, Ian North2, Neville J. Pires1, Jonas Rubenson1,3* – (April 7, 2016)
  3. Dynamic loading of the plantar aponeurosis in walking – Erdemir A, Hamel AJ, Fauth AR, Piazza SJ, Sharkey NA

THE FIRST SKI BOOT PROTOTYPE BASED ON THE BIRDCAGE

In going through archived files for the MACPOD Ski Boot Project I found a photo of the first injection molded ski boot prototype based on the principles of the Birdcage.

The photo below is of the Birdcage research vehicle that was used to validate my hypothesis that explained the mechanism by which elite skiers establish dynamic stability of the platform under the outside foot of a turn by balancing torques in two planes across the inside edge. This mechanism extends GRF acting along the running surface of the edge out under the platform for the skier to stand and balance on.

The photo below is of the Logan Chassis (aka The Convincer) that was developed in conjunction with the first injection molded ski boot prototype based on the principles of the Birdcage.

The photo below is of the first injection molded ski boot prototype. It was called the MACPOD boot. The design and format were very good. But the stiffness of the plastics, which were stiffer than used in conventional ski boots, was many orders too low on the scale of shore hardness. A subsequent effort called the Rise boot suffered from the same problem. It was a lack of suitable materials and manufacturing technologies that eventually sealed the fate of the MACPOD ski boot project.

NABOSO: FEEL THE FORCE

To Dr. Emily Splichal

In recognition of Dr. Emily Splichal’s contribution to my knowledge and through the knowledge gleaned from the use or her pioneering NABOSO surface science technology I am dedicating this post to her as my teacher, mentor and inspiration. Thank you Dr. Splichal.


In this post I am going to discuss how NABOSO surface science technology gave me the feedback mechanism to confirm the optimal ramp angle I needed to transition to a higher level of skier performance.

Optimal Ramp Angles starts with Stance Training

My transition started with refinements to my stance that came from incorporating Dr. Splichal’s principles of foot-to-core sequencing (that connects the feet with the pelvic core) and body fascial tensioning (that unifies the body). Prior to these changes my stance is what I would now define as good but not optimal. The huge improvement resulting from the refinements served as the impetus for a series of posts on the sequencing process required to assume a fascially tensioned stance with foot to core sequencing. I called this the SR Stance. The reason I chose this name was to draw reader attention to the stance posts by making the stance seem innovative, but not intimidating.

KIS is the Stance Kiss of Death

In reviewing material on ski technique, a skier’s stance is described as anything from an athletic stance, a relaxed stance, a ready stance, a balanced stance, a centered stance or a whatever feels good stance. A focus on selling skiing as easy with the KIS principle (Keep It Simple) has resulted in stance being perceived as less than critical to good technique. This leaves most skiers with the impression that a ski stance should feel similar to a relaxed upright stance on two feet with weight equally distributed between both feet and the heels and forefoot of each foot. This is interpreted by skiers as meaning they are balanced or in balance. So it follows that in actual skiing there should be even ‘pressure’ everywhere with no sensation of pressure on any specific area of the foot.

If I ask a typical skier to stand on a ramped surface and assume their ski stance they will find the sweet spot where their weight feels evenly distributed and identify it with their ski stance regardless of the  angle of the surface

So the first challenge to transitioning to a higher level of skier peformance is accepting that a strong ski stance must be learned and consistently rehearsed by doing drills as I do every time I go skiing. It’s like pre-flight check. NABOSO provide the conscious and subconscious CNS feedback that tells me when I am cleared for take off.

The NABOSO Effect

In my post NABOSO PROPRIOCEPTIVE STIMULATION INSOLES, I stated that 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. The fast acting small FA II nerves in this area are activated by pressure and skin stretch both of which occur in the late phase of Mid Stance. Optimal ramp angle is critical because it maximizes both pressure and skin stretch thereby potentiating the sensory input required to initiate controlled movement.

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.

The big breakthrough for me came after I started using NABOSO insoles in shoes with different heel raises (drops). It turned out that I had the highest perception of  pressure under the ball of my foot in late mid stance phase with shoes with zero ramp (drop). When I put NABOSO insoles in my ski boots to test them I could hardly perceive any pressure under the ball of my outside foot during skiing no matter how I adjusted my stance or the tensions in my boot closures. This told me that my ramp angle of almost 3 degrees was far too great. As soon as I reduced the angle to 1.2 degrees (which is what I tested best at on my dynamic ramp angle device) it is no exaggeration to state the the whole world changed. But the transition effect didn’t kick into high gear until this ski season after my brain had time to delete a lot of the bad programming from the old ramp angle.

NABOSO 1.0 on the left. NABOSO 1.5 on the right. I use 1.5 in my ski boots. I purchase the large size and trim to fit.

Tentative Conclusions

  • A system that provides continuous subconscious sensory input to the CNS with the ability to consciously sense sensory input during drills in executive mode is important.
  • Stance training should be incorporated into racer training programs at an early stage and optimal stance ramp angle identified and implemented.
  • Once optimal ramp angle has been implemented the boot should be set up to the skier’s functional specification which I will discuss in future posts.
  • Stance ramp angle should be retested on a periodic basis to confirm the requirements have not changed.
  • Adjustments should be made as soon as possible after the end of a competitive season and no further changes made during the subsequent competitive season.

In my next post I will discuss Dr. Splichal’s protocol for using NABOSO insoles and matts in training.


Disclosure

I am not involved in any form of business association or affiliation or any have business interest or investment with Dr. Splichal/NABOSO/EBFA. Nor do I receive any form of compensation from the sale of NABOSO. Prior to marketing her NABOSO insoles Dr. Splichal provided me with a small sample of NABOSO material at her cost to cut insoles from for testing.

 

 

THE ULTIMATE LOOSE FOOT TEST OF METAL

The human foot is a masterpiece of engineering and a work of art.

                                                                                                                  Leonardo da Vinci

Despite what da Vinci said, skiers seem to have an inherent distrust in the structural capacity and integrity of the human foot.

In skiing demonstrations with ski boot prototypes based on the Birdcage it didn’t matter how hard I tried to explain to testers how the dorsal loading system worked and how little force was needed to secure their foot, it didn’t stop them from attempting to crush their foot by tightening down the dorsal plate until their noses bled. They were so conditioned by the persistent, ‘the tighter the boot, the better the ski control’ message that they just didn’t want to believe how little force it takes to activate the auto stiffening mechanism of the longitudinal arch (FIT VS. FUNCTION) and retain the foot in solid contact with the base of the boot.

In order to try and convince testers how little force was required to make their foot dynamically rigid one of our team members had a device we called the Logan Chassis designed and fabricated. The photo below is of the Logan Chassis aka The Convincer.

If it’s not obvious from the photo  the Logan Chassis was very heavy. The components were milled from solid blocks of aluminum. The heel counter and a few other components are missing. But the photo should give you a good enough idea. This thing was a tank. This device was not intended for skiing. It was a pre-ski boot skiing test conditioner.

To demonstrate how little force it takes to make the foot so rigid it is like steel I would get the test subject to put their foot in the Logan Chassis. Then I would try to get them to adjust the knob on the screw to the point where it applied firm but gentle pressure on the dorsum of their foot making sure there was no discomfort. Then I would ask them to stand up and lift the foot in Logan Chassis off the floor and tell me what they felt. They were shocked. Hell, I was shocked when I tried this.

The Logan Chassis feels incredibly light and the foot feels glued to the base with no sensation of pressure or discomfort. It defies logic. But I doubt I would have to convince da Vinci.

The truth is whatever people are willing to believe.

The problem is that most skiers have been convinced to believe that tight is not just right, tight is might.