Sports Science posts

THE MECHANICS OF PLATFORM ANGLE: PART 1

In order to engage in an interactive productive dialog on issues pertaining to ski technique and related equipment a frame of reference based on validated, non-negotiable principles of physics, mechanics and (neuro)biomechanics as well as a schedule of defined reference terms such as exists in the sciences of mechanics, anatomy and physics is essential. Defined technical reference terms help ensure all participants in a discussion are on the same page.

I decided to start the new direction of The Skier’s Manifesto with a critical examination of the mechanics of platform angle starting with a schedule of the technical terms associated with platform angle and their definitions. Additional technical terms and their definitions will added in future posts according to the content of the discussion. The intent at this point is to start with a basic discussion of forces applied to a rigid body and/or surface (in this case, the surface of the snow) and then expand the scope of the discussion in future posts. Agreement on terms and definitions is important. So please comment if you feel one or more the following terms are inappropriate or inaccurate or should be expanded and/or refined.

Technical Terms associated with Platform Angle

  • Platform Angle: the angle of the transverse aspect of the body of the ski underfoot with the surface of the snow.
  • Edge Angle: the angle of the edge of the ski in relation to the plane of the transverse aspect of the body of the ski adjacent the edge.
  • Force: an unopposed interaction that will change the motion of an object. A force has both magnitude and direction, making it a vector quantity.
  • Force Vector: the magnitude and direction of a force.
  • Applied Force: a force applied to a rigid body or surface.
  • Reaction Force: a force that opposes a force applied to a rigid body or surface.
  • Normal Force: a force acting perpendicular to a rigid body or surface that is resisting a force applied to it.
  • Angular Force: a force applied to a rigid body or surface that is not normal (perpendicular) to the rigid body or surface to which the force is applied.
  • Angle of Attack: the angle an angular force forms with the rigid body or surface to which it is applied to.
  • Resultant Force: also known as Net Force, is a single force associated with torque obtained by combining a system of forces and torques acting on a rigid body.

Technical discussions of the forces associated with the angle of the platform with the snow typically show opposing resultant and ground reaction forces implying a state of balance of the forces acting on platform created by the outside ski underfoot.

Schematic diagrams showing forces acting on the platform created by the body of the ski underfoot often show two opposing forces in alignment with each other acting close to or at the axis point created the inside edge of the outside ski. Or diagrams may simply show opposing forces aligned with each other implying the existence of a state of equilibrium.

In my next post I will discuss whether the above force diagrams accurately reflect a state of equilibrium of the forces acting on the platform of the outside ski. Please join the conversation.

WHAT DOES HIRSCHER HAVE IN COMMON WITH BRIGNONE, WORLEY AND SHIFFRIN?

The short answer to this question is that the 4 racers share a stance with the muscles of the biokinetic chain in isometric contraction during what I term the Load Phase of a turn sequence and the ability to use the elastic recoil energy created during the Load Phase for acceleration.

One of the key visual cues of an isometric stance is an extended outside leg with small angles at the knee and ankle and a forward position of the pelvis. Another key visual cue is high hands with arms reaching forward as if the racer is trying to reach forward and hug a large barrel.

The screen shot below is of Marcel Hirscher in the December 16, 2018 Alta Bada GS that he won by 2.53 seconds.

The screen shot below is of Tessa Worley in the 2018-19 Soelden GS.

Reductionist Anatomy

A longer answer to the question posed by the title of this post, one that I will expand on in future posts, is that Hirscher, Brignone, Worely and Shiffrin are examples of the application of the principles of an emerging paradigm that is challenging the fundamental way in which muscular anatomy has long perceived muscles as separate systems with specific functions. In the new paradigm that has arisen out of recent discoveries muscles function in conjunction with the myofascial network as a wholly integrated system; one that responds and adapts to the stresses imposed on it. Since these discoveries are almost ten years old the odds are that the dominant technique of Hirscher, Brignone, Worely and Shiffrin is not by chance.

In previous posts, I described a stance based on isometric contraction as the SR Stance. SR is an abbreviation for the Stretch Reflex. Technically, a better term for the stretch reflex is the stretch-shorten cycle

The reason I chose SR for the name of the stance is that isometric contraction and the stretch reflex are not part of the narrative of ski technique. I discuss the three forms of muscle contraction in my post I-C-E: SR (2.) which I have recently updated.

The reason a ski stance based on isometric contraction provides a huge competitive advantage has to do with recent finding discussed in a 2009 article (1.) in which ultrasound imaging that allowed for quantitative assessment of the mechanisms for elastic energy storage and return at the ankle joint during human walking found that the Achilles tendon stores elastic energy as the mid stance phase progresses until the energy peaks in late midstance and is released to produce a rapid recoil with very high peak power output. The researchers named this the Catapult Mechanism (3.).

An important feature of the ankle ‘catapult mechanism’ is that the stretch and recoil of the Achilles tendon allows muscle fibers to remain nearly isometric producing high forces with very little mechanical work. In the isometric state, muscles expend much less metabolic energy to produce force when compared to muscles shortening in concentric (positive work) contractions.

Recent research has also found that during explosive movements, the contractile elements of a muscle remain in an isometric state to increase tension in the non-contractile components in an effort to produce higher levels of force. The enhanced stiffness from the contractile component can help the connective tissue rapidly store mechanical energy during the lengthening (recoil) phase delivering greater power output during the shortening phase. (4.), (5.)

What all this means is that the power advantage seen in racers like Hirscher, Brignone, Worely and Shiffrin results from an integrated system. But the human body can only function as an integrated system under conditions which allow multi-plane movement, something conventional ski boots intentionally interfere with.

In my next post I will start from what I see as the fundamental element of a ski stance based on isometric contraction and progress upward from there.


  1. It Pays to Have a Spring in Your Step – 2009 Gregory S. Sawicki1, Cara L. Lewis2, and Daniel P. Ferris2 – 1. Department of Ecology and Evolutionary Biology, Brown University, Providence, RI; and 2. School of Kinesiology, University of Michigan, Ann Arbor, MI
  2. https://wp.me/p3vZhu-1wT
  3. Fascial Fitness: Fascia oriented training for bodywork and movement therapies – Divo G. Muller, Robert Schleip 
  4. Cutting Edge: Training the Fascial Network (Part 1) by Pete McCall M.S.
  5. Cutting Edge: Training the Fascial Network (Part 2) by Pete McCall M.S.

 

LEARN THE SR STANCE IN 3 EASY STEPS

This post was originally published on October 23, 2016. I have revised the post to clarify that the SR Stance applies to the load phase of a turn that occurs in what is commonly referred to as the bottom of a turn and that the joint angles of the SR Stance are configured by the major muscles in isometric contraction. When external forces cause the muscles to lengthen or stretch this will trigger the myotatic or stretch reflex. Because the myotactic reflex is a spinal reflex it is activated in 1 to 2 thousandths of a second. As such, it is both rapid and powerful.


The SR Stance configures some of the most powerful muscles in the body in a state of isometric contraction so that the powerful myotactic stretch reflex can maintain the angles of the ankle, knee, and hip and keep the CoM of a skier in balance on their outside ski in the most powerful position in the load phase of a turn.

The SR Stance is best learned outside the ski boot in an environment where the feet and legs are free from any influences. One of the benefits of learning an SR Stance outside the ski boot is that, once learned, it provides a reference against which to assess whether a ski boot supports the functional parameters of the skier. If it doesn’t, the SR Stance can be used as a reference to guide equipment modification and establish when and if it meets the functional requirements of the skier.

The SR Stance tensions the pelvis from below and above; below from the balls of the feet through the PA-soleus-gastrocnemius-hamstring muscles to the pelvis and above from the shoulders-latissimus dorsi-trapezius muscles to the pelvis.

The graphic below shows the Achilles Tendon junction with the PA at the heel bone.

pa-ac

The graphic below shows the 3 major muscles of the leg associated with the SR stance.

3-muscles

The Soleus (left image in the above graphic) extends from the back of the heel bone (see previous graphic) to a point just below the knee. It acts in concentric contraction (shortening) to extend or plantarflex the ankle. In EC-SR, the Soleus is under tension in stretch in isometric contraction.

The Soleus is one two muscles that make up the Triceps Surae.

The Gastrocnemius (center image in the above graphic) extends from the back of the heel bone  to a point just above the knee. It acts in concentric contraction (shortening) to flex the knee. In EC-SR, it is under tension in isometric contraction to oppose extension of the knee.

The Hamstrings (right image in the black rectangle in the above graphic) extends from a point just below the knee to the pelvic girdle. It acts in concentric contraction (shortening) to flex the knee. In EC-SR, it is under tension in isometric contraction to oppose extension of the knee.

A number of smaller muscles associated with the SR that will be discussed in future posts.

The graphic below depicts the 3 steps to learning an SR Stance.

er-steps

  1. The first step is to set up a static preload on the shank (shin) of the leg by tensioning the soleus muscle to the point where it goes into isometric contraction and arrests ankle dorsiflexion.

The static preload occurs when the tension in the soleus muscle of the leg simultaneously peaks with the tension in the sheet-like ligament called the plantar aponeurosis (PA). The PA supports the vault of the arch of the foot. The soleus is an extension of the PA. This was discussed in my post ZEPPA-DELTA ANGLE AND THE STRETCH REFLEX.

  • While barefoot, stand erect on a hard, flat, level surface as shown in the left hand figure in the graphics above and below. The weight should be felt more under the heels than under the forefoot.
  • Relax the major muscles in the back of the legs (mainly the hamstrings) and allow the hips to drop and the knees to move forward as shown in the right hand figure in the graphics above (1.) and below.
  • As the knees move forward and the hips drop towards the floor the ankle joint will dorsiflex and the angle the shank forms with the floor and the angle of the knee, will both increase until a point is reached where the shank stops moving forward on its own. Movement of the shank will probably be arrested at a point where a plumb line extending downward from the knee cap ends up slightly ahead of the foot. This is the static preload shank angle. It is the point where the soleus and quadriceps muscles go into isometric contraction.

static-preload

2. From the static preload shank angle, while keeping the spine straight, bend forward slightly at the waist. The angles of the shank (ankles) and knees will decrease as the pelvis moves up and back and the CoM moves forward towards the balls of the feet. This will cause the muscles of the thigh to shift from the Quadriceps to the Hamstrings. Bending at the waist tilts the pelvis forward. As the pelvis tilts forward, it tensions the Hamstrings and Gastrocnemius causing the knee and ankle to extend to a point where extension is arrested by the muscles going into isometric contraction. Tension in the Hamstrings and Gastrocnemius extends the lever arm acting to compress the vault of the arches of the feet from the top of the shank to the pelvis thus increasing the pressure on the balls of the feet through Achilles-PA load transfer.

3. From the position in 2., round the back and shoulders as you bend forward from the waist.

Shldrs-back

Make sure the core is activated and tightened as you round the back and shoulders. Pull the shoulders forward and towards each other as the back is rounded so as to form a bow with the shoulder girdle. Looking down from above, the arms should look like they are hugging a large barrel.

Repeat steps 1 through 3. Pay close attention to the changes in the sensations in your body as you work through each step. If you bounce up and down lightly in the position in Step 3., the angles of the joints in your stance should return to the static preload position between bounces.

With the ski boot and Zeppa-Delta ramp angles configured to enable an SR stance, your ski boots will work for you and with you instead of the other way around.

In my next post, I will go into greater detail on how rounding the shoulders and holding the arms in the correct position optimally activates the muscles associated with the SR stance.

THE 2018 SOELDEN GS: A LITMUS TEST OF DYNAMIC STABILITY – WILD CARD RESULTS

I found the wild card result in the skate tests discussed in my last post shocking but not unexpected. I had known for decades that ski boots can dramatically impact user performance. But until the skate tests I had no way of confirming my subjective observations, which could be summarily dismissed as nothing more than my opinion. The results of the skate test provided convincing support for my long held assertion that testing the effect of ski boots on the user with a set of realistic performance metrics is absolutely essential.

In the graph below of Peak Force all 5 competitive skaters improved in the NS.

Skater number four went from the skater with lowest Peak Force to the skater with the highest Peak Force. But skater number one, who had the fourth highest Peak Force in their OS, hardly saw any improvement in the NS whereas skater number four realized over a 100% increase in Peak Force!But the real shocker was in Impulse Force. As expected, results varied. But the Impulse Force of skater number one actually decreased slightly in the NS!Without a standardized, validated test protocol there is no way of knowing how their ski boots affected the performance of the competitors in the Soelden GS or any race for that matter. Guessing should not be acceptable.

THE 2018 SOELDEN GS: A LITMUS TEST OF DYNAMIC STABILITY

Challenging  course conditions, especially in GS, are the litmus test of dynamic stability. The 2018 World Cup GS at Soelden had challenging conditions in spades.

The ability to rapidly achieve dynamic stability across the inside edge of the outside ski is key to moving the Center of Force forward to the point where the biokinetic chain of the outside leg attains sufficient tension to enable the stretch reflex. The stretch reflex (SR) can then modulate pertubations due to asperities in snow surface and terrain with ankle strategies. The principle muscle in ankle balance synergies is the soleus. Dynamic stability enables a racer to float between turns, accelerate under gravity then land on line and load the outside ski. A racer with good dynamic stability is on and off the edges in milliseconds and back into the float phase. Like a skilled gymnast elite skiers and racers can choose their line and stick their landing. Tessa Worely excelled at this in the 2018 Soelden GS.

Tell Tale Signs of Dynamic Stability

Key indicators of dynamic stability are a quiet upper body and the speed at which a racer achieves their line and crosses over into the new turn with their upper body. It’s like watching a flat rock thrown low skipping off water; fly-skip-fly-skip.

In my post, WHY YOUNG TALENTED SKI RACERS FAIL AND EVENTUALLY QUIT RACING (1.), I discuss the 3 levels of balance:

  1. 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 a joint that is subject to destabilization. Spinal  reflex triggered by the myotatic stretch reflex response causes the muscle to contract resulting 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 adjacent muscles. The subsequent release of the reaction prevents 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 is evoked in response to a strongly destabilising stimulus. This reactive response 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 reaction is the balance-stabilising response. In a situation of a sudden loss of balance, a myotatic stretch reflex first occurs and is then is followed by a balance correcting response, which prevents or attempts to prevent a fall.

I call these balance responses Green (postural reaction 1), Orange (postural reaction 2) and Red (postural reaction 3).

If a racer is no able to use the myotatic reflex (Green = Normal) balance response, the CNS shifts to Level 2 (Orange = Caution) or even Level 3 (Red = DANGER).

Level 1 balance is characterized by a stable, well-controlled upper body (aka quiet upper body) with well controlled and directed positions of the arms.

When the myotatic (stretch) reflex is compromised by restriction of the ankle flexion range required to tension the soleus the balance system will shift to level 2 or level 3 depending on the degree of interference. As the degree of interference with required range of ankle flexion increases the degree of reflexive balance will progress from small, rapid, reactive arm movements to gross reactive arm movements that eventually include gross movements of the torso.

The authors of the Polish skier balance study cited in my post state that ski boots exclude the ankle joint complex from the process of maintaining the stability of the body. However, I don’t believe this is the case with all skiers and especially all racers as evidenced by Soelden video of Tessa Worley, Federica Brignone and Michaela Shiffrin. In my next post I will discuss what I look for in analyzing that suggests dynamic stability and especially a lack of dynamic stability and the indications of compromise and the potential cause.

In the meantime, here’s something to think about.

Early in my boot modification career I came to the conclusion that some skiers, especially racers, were born with the right shape of feet and legs (2.) and this explained why they could ski in ski boots right out of the box with minimal or no modifications better than the majority of skiers even after extensive boot modifications. In a recent series of posts I discussed the results of the 2012 skate study that I modified hockey skates for; the NS (New Skates – Blue bars in the graphics below). The modifications I made were based on ski boot modifications that had resulted in dramatic improvement in performance and race results. Although I optimistically predicted improvements in performance metrics of at least 10% (110%) based on my experience with World Cup skiers, I knew that there was the possibility of a wild card competitive skater who was already close to their maximum performance in their OS (Own Skates – Red bars in the graphics below). If this were the case the skater would realize minimal improvement from the New Skates.

My previous posts only included the results for four competitive skaters. There were actually five competitive skaters in the study. Skater number 1 was the wild card. Look what happened to the results when the wild card skater was added.Look carefully at the graph of the Impulse Force below. Compare Skater number one’s Impulse Force results with the Peak Force results in the preceding graph.This raises the question: Do Tessa Worely, Federica Brignone, Mikaela Shiffrin and other top World Cup racers have the right shape of feet and legs or do they have the right modifications made to their ski boots.


  1. (https://skimoves.me/2017/02/15/why-young-talented-ski-racers-fail-and-eventually-quit-racing/)
  2. THE IDEAL SKIER’S FOOT AND LEG – https://wp.me/p3vZhu-qf

 

 

 

WHY TRYING TO COPY HIRSCHER AND SHIFFRIN’S MOVES DOESN’T WORK – PART 4

A central premise in skiing, especially in ski teaching and coaching, is that skiers and racers can learn to ski like the best by observing and copying them. Hence, articles and videos that talk in nebulous terms about good balance, an athletic stance, pressure control, steering, edging, extension, separation etc. as elements that, when blended together, will enable skiers and racers to ski like the Hirschers and Shiffrins of the world. If a racer who has undergone training in the system is not competitive or worse, suddenly becomes uncompetitive, the racer is typically blamed for not being strong enough or not pushing themselves hard enough or not taking enough risk or some other factor. In the end, the responsibility for lacklustre performance is conveniently assigned to the racer.

Ski boots are rarely considered a factor. So long as the boots are comfortable that is the only thing that matters. To suggest otherwise is to blame the equipment. This flies in the face of my experience. But until the skate study (1.) I had no reliable way of measuring and thus comparing performance.

The two pressure studies done in 1998 by the University of Ottawa with elite ski instructors provided an opportunity to compare the results of the studies to those of the 2012 skate study that I modified skates for. This study was also done by the University of Ottawa. Of the three studies:

  • One 1998 skier pressure study used three highly skilled ski instructors (CSIA level IV)
  • One 1998 skier pressure study used six internationally certified Canadian ski instructors.
  • The 2012 skate study used five competitive skaters.

The 1998 study with the six internationally certified Canadian ski instructors provided Peak Force data that I could use to compare to the Peak Force data obtained from the 2012 skate study.

As I pointed out in my previous posts, skating and skiing are similar in that they both depend on the ability of the participant’s neuromotor system to create a foundation of dynamic stability across the skate blade or the inside edge of the outside ski prior to being able to effectively apply force to the ice blade or ski edge. The existence of dynamic stability across the skate blade or inside edge of the outside ski enables the neuromotor system to regulate fore-aft stability in what is typically referred to as skater or skier balance.

Peak Force

Peak Force is the highest force applied in an Impulse Force

In the skate study skaters performed forward skating sprint starts in each skate (OS and NS) for a total of 6 trials each. As would be expected with competitive skaters Dynamic Stability as represented by Peak Force was very close among the skaters in their Own Skates as shown in the graphic below.

But when the highest and lowest Peak Forces of the competitive skaters were compared to the highest and lowest Peak Force of the internationally certified Canadian ski instructors the difference was much greater; approximately 125% for the skaters and 300% for the ski instructors. The researchers noted this significant variance and suggested equipment could have been a factor. But that aspect was not investigated.

Peak Force Improvement

It would seem logical to assign sole responsibility for such marked differences to inferior muscle strength or improper training. Muscle strength and training are definitely important factors. But their contribution to overall performance is dependent on the ability of a competitor to create dynamic stability and quickly acquire a position from which they can effectively apply force to a skate blade or edges of a ski. These factors, in turn, are dependent on a functional environment in the footwear for the physiogic function of the lower limb.

As shown in the graphic below, when the same skaters switched from their Own Skates (OS) to the skates I prepared (NS) there was an immediate and statistically significant improvement in mean Peak Force of approximately 190%. Even more significant is the fact that the Peak Force of skater number 4 (the lowest of the four skaters) increased by approximately 252% changing the skater’s ranking from #4 to #1.

Impulse Force Improvement

An Impulse Force is a high force of short duration that causes a change in momentum.

When the skaters switched from their Own Skates (OS) to the New Skates (NS) there was an immediate mean increase in Impulse Force of approximately 216% as shown in the graphic below. Even more significant, the Impulse Force of skater number 4 (the lowest of the four skaters in their Own Skates) increased by approximately 276% raising skater number 4 to almost the same level as skater number 3. Meanwhile, an increase in Impulse Force of approximately 224% raised skater number 2 to almost the same level as skater number 1. In other words, the New Skate was literally a game changer that resulted in a leveler playing field for the four competitive skaters.

Center of Force (CoF) Variance: Where Races are Really Won

The most significant effect of the New Skate (NS) was on what is called Center of Force (CoF) Variance. Center of Force Variance is the amount of forward movement of the Center of Force within a fixed unit of time to the position on a skate blade or ski edge where force can effectively be applied.

The graphic below shows the Center of Force Variance of the four competitive skaters in their own skates (OS).

The graphic below shows the Center of Force Variance of the four competitive skaters in their Own Skates (OS) compared to the Center of Force Variance in the new skates (NS). When the skaters switched from their Own Skates (OS) to the New Skates (NS) there was an immediate mean increase in CoF Variance of approximately 172% as shown in the graphic below. Skater number 4 experienced the largest increase in CoF Variance (approximately 241%) that changed the ranking from #3 to #1.

An increase in the variance of CoF results in increased control during the stance phase of forward skating.

The graphic below shows what would happen if only skater number four were provided with New Skates (NS) while the other 3 competitive skaters continued to use their Own Skates (OS). Think of the red dashed line at 1.20 as the finish line of the CoF Variance race. It should obvious who will win and who will have the advantage at every turn.

The Score for Skater Four

Skater number four experienced the following improvements in the New Skates (NS) over their Own Skates (OS)

  • Peak Force – 252%
  • Impulse – 276%
  • CoF Variance – 241%
  • Mean improvement – 256%

The improvement in the three metrics was immediate and, based on my experience with skiers and racers, probably immediately reversible simply by having the competitive skaters revert to their Own Skate (OS) format.

Few forms of athletics place as high demands on the footwear used in their performance as alpine skiing. It (the ski boot) functions as a connecting link between the binding and the body and performs a series of difficult complex tasks. (2.)

To paraphrase Dr. Emily Splichal:

A skier is only as strong as they are dynamically stable.

In my next post, I will discuss the implications of the skate study and associated performance technology and metrics for the future of skiing, especially ski racing.


  1. A Novel Protocol for Assessing Skating Performance in Ice Hockey – Kendall M, Zanetti K, & Hoshizaki TB – School of Human Kinetics, University of Ottawa. Ottawa, Canada
  2. Ski-Specific Injuries and Overload Problems – Orthopedic Design of the Ski Boot –  Dr. med. H.W. Bar, Orthopedics-Sportsmedicine, member of GOTS, Murnau, West Germany

WHY TRYING TO COPY HIRSCHER AND SHIFFRIN’S MOVES DOESN’T WORK – PART 2

In previous posts I discussed the two studies (1, 2) done by the University of Ottawa in 1998 that analyzed pressure under the feet of elite alpine ski instructors

The pressure data from the study that used 6 elite alpine ski instructors found maximal (peak) force ranged from a high of 1454 Newtons to a low of 522 Newtons. The graph below compares the peak force seen in pressure data captured from the 4 competitive skaters in their own skates from my last post to the highest and lowest peak force seen in pressure data captured from the 6 elite alpine ski instructors used in the 1998 University of Ottawa study.

In consideration of the fact that the researchers commented that force-time histories revealed that forces of up to 3 times body weight can be attained during high performance recreational skiing it is interesting that the peak force of one of the 6 elite alpine ski instructors in the study was less than the lowest peak force of one of the 4 competitive skaters in the 2012 University of Ottawa study while the highest peak force of one of the 6 elite alpine ski instructors in the 1998 study was almost twice the highest peak force of one of the 4 competitive skaters in the 2012 University of Ottawa study.

A significant challenge in attempting to conduct foot pressure studies with alpine skiers is the variability of the slope and environmental and piste conditions. Test conditions and variables, especially ice, can be tightly controlled in the conditioned environment of an indoor skating rink.

Although the studies did not provide pressure data that compared peak and average pressures for different ski instructors, the peak forces from one study reached up to 30 newtons per square centimetre.

In the spring of 2012 I was asked to modify a number of pairs of the same brand and model of a hockey skate for use in a study that would compare metrics derived from pressure data captured from a competitive skater’s own skates to the same metrics from data acquired  from skates I had modified. I saw this as an opportunity to document the effect of modifications made to hockey skates based on the principles of neurobiomechanics described in my patents and this blog. When I speculated that the metrics derived from the pressure data might show improvements as high as 10% (i.e. 110%) I was told that the study was unlikely to result in more than a single digit improvement of approximately 2% or 3%.

I modified the pairs of skates in the shop in the garage of my home near Vancouver. The modifications were general in nature and made without the benefit of data on the feet of the test subjects. No modifications were made after I shipped the hockey skates to the University of Ottawa. I was not involved in the design of the study protocol or the actual study. I was hopeful that the study would produce meaningful results because it would have implications that could be extrapolated to alpine skiing.

The graph below shows the highest peak force in Newtons recorded for each of the 4 competitive skaters in their own hockey skates (blue = OS) and in the hockey skates that I modified (red = NS). The improvement was immediate with little or no run in period in which to adapt. The percentage improvement for each skater is shown at the top of each bar.

The mean (i.e. average) improvement was approximately 190%. The only factor that improvements of this magnitude could be attributed to is improved dynamic stability resulting from an improved functional environment in the skate for the foot and leg of the user.

……. to be continued in Part 3.


  1.  ANALYSIS OF THE DISTRIBUTION OF PRESSURES UNDER THE FEET OF ELITE ALPINE SKI INSTRUCTORS – Dany Lafontaine, M.Sc.1,2,3, Mario Lamontagne, Ph.D., Daniel Dupuis, M.Sc.1,2, Binta Diallo, B.Sc.: Faculty of Health Sciences1, School of Human Kinetics, Department of Cellular and Molecular Medicine, Anatomy program, University of Ottawa, Ottawa, Ontario, Canada.
  2. ANALYSIS OF THE DISTRIBUTION OF PRESSURE UNDER THE FEET OF ELITE ALPINE SKI INSTRUCTORS – Dany Lafontaine, Mario Lamontagne, Daniel Dupuis, Binta Diallo, University of Ottawa, Ottawa, Ontario, Canada