Stretch Reflex

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.

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, aimed at U14 and younger ski racers, 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 the 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 was considered to be a child ski racing prodigy, had a promising racing career unravel soon after reaching their teens. Why? What, changes happened that could have caused such a tectonic shift?

Let’s go back to beginning when a 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 and one or both may have raced. In such a situation a young racer would have had an excellent role model that would have helped them  become comfortable by following one or both of their parents down the ski hill. But there are also other important factors in a young racer’s favour:

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

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 (stretch relfex) Stance (3. to 10.). As a consequence, they acquire dynamic stability that provides superior edge and ski control while enabling the myotatic stretch reflex balance response.

The authors of a Polish study on skier balance (2.) cite three types of postural reactions to external forces that disturb equilibrium and can cause the body to lose balance can be observed.

  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).

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 what is called race fit wherein ski boots are downsized to the smallest possible shell that the feet can be squeezed into. Custom footbeds or orthotics are considered an essential integral component of race fit because they prevent the foot from spreading and elongating. But this actually interferes with or even prevents the fascial tensioning process that enables dynamic stability and the myotatic reflex associated with the ultra high speed spinal reflex balance response (11).

No longer able to use the myotatic 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 of the CNS at the expense of speed. Racers start losing ground to lesser racers. Not understanding the cause, parents and coaches can 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. Defeated by their boots, the child eventually quits ski racing and takes up 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

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

A READER ASKS ABOUT STATIC PRELOAD AND SR STANCE

I apologize for the delay in taking the static preload issue to the next level; application to stance. There are a number of associated issues that I need to generate graphics and animations for. In the meantime a reader asked the following questions:

“1) Am I understanding “static preload” they way you want us thinking of it? That is “static preload” is the basic optimal stance for skiing.”

COMMENT: The static preload sets up the initial angle of the shank. It provides the foundation on which to build an SR stance. A number of factors, but especially excessive Zeppa-Delta Ramp Angle and arch supports, can prevent the setting up of the static preload. It is important to understand that the static preload is established by a reflex action. It happens as a result of relaxing the hamstrings-gastrocnemius muscles and allowing the weight of the body (CoM) to stretch them.

“This stance would be then modified to accommodate the forces and demands place on the skier’s body by speed, terrain, turn shape etc. In other words, the body once it has learned this optimal stance(s) it will then use the stretch reflex to maintain optimal balance in the Coronal or frontal (for aft) and Sagittal (left right) planes regardless of terrain etc. It is this vital sensitivity element that allows as skier’s brain to actually control the edge/snow interface to effortlessly locomote on skis.”

COMMENT: The stance is configured from the static preload that configures the triceps surae (soleus-gastrocnemius) in isometric contraction. Every day when you start skiing, you need to perform what amounts to a pre ski SR check. I will explain how to do this in a future post.

“2) There is a caveat of course; the boot must be mechanically able to permit the optimal stance(s), or “static preload”. ”

COMMENT: The structures of the boot must enable the 3-dimensional global articulations of the joints of the foot associated with the optimal stance characterized by the posterior chain of muscles (soleus-gastrocnemius-hamstrings) in isometric contraction.

“3) You are suggesting that the “static preload” be a learned experienced in bare feet so that the skier’s neurologic system will recognize the sensation both in skiing and boot fitting. Modern ski boots make both more difficult.”

COMMENTS: Yes and yes. I will explain why soon.

 

I-C-E: SR

These letters are not some sort of secret code. They are abbreviations for Isotonic, Concentric and Eccentric and Isometric.

  • Isotonic is a muscular contraction in which the length of the muscle changes
  • Concentric is an isotonic contraction where the length of the muscle shortens
  • Eccentric is an isotonic contraction where the length of the muscle lengthens
  • Isometric is when a muscle contracts but does not change length

Tonus is state of light muscle contraction. When there is no weight on a leg (i.e. – the foot is off the ground as it is in the swing phase of gait), there is no tonic activity.

When we are standing erect on a flat, level, hard, stable surface in the ideal anatomic plumb alignment position, the degree of muscle effort required to maintain an upright posture is minimal and tonus is light. But skiing involves maintaining balance in a dynamic physical environment characterized by constantly changing 3-dimensional forces made more complex by asperities (variations in the snow surface) and undulations in terrain. This places enormous demands on the balance system. Maintaining balance in such a challenging enviroment, requires minimal latency (time for the balance system to respond) and maximal refex corrective action.

Despite the importance of eccentric contraction in balance in skiing, suprising little, if any, recognition or consideration is given to the type of muscle action associated with a movement such as knee angulation, let alone any consideration of the effect on skier balance and the physiologic processes that protect against injury. I could not find the words concentric or eccentric listed in the Index to LeMasters’s Ultimate Skiing even though he refers to specific muscles in his description of knee angulation. An online search for ‘stretch reflex alpine skiing’, garnered only one hit (I will discuss the results in a future post). There doesn’t even appear to be universal agreement among the various authorities on what constitutes balance in skiing let alone any discussion of how the balance process works. Balance seems to be whatever the authorities declare it to be.

In order to understand how to build a strong stance based on the SR, one has to possess at least a basic knowledge of muscle actions, the role of EC in postural responses and how the static preload enables the SR.

The postural responses that maintain an upright posture are mediated by muscles in eccentric contraction; primarily the soleus-gastrocnemius-hamstring chain. What is seldom mentioned is that postural muscle action relies on reaction force resulting from compression loading of the plantar ligament that supports vault of the 3 arches of the foot. Compression of the arches sets up tension in the plantar ligament that creates shear force driven reaction force for EC-SR contraction.

In my next post, I will explain how this works. For now, the graphic below shows a simple model of the foot that I made in 1992 to illustrate how a static preload is set up.

In the LH graphic, the model is suspended in the air (unweighted). So there is no load on the base and no tension in the arches.  The black arrows show the reaction forces. The blue lines show tensile forces. The red arrows show the action force arising from muscle contraction. The plumb bob, representing CoM, is pulling from the front ends of the two struts (balls of the foot) to the top of the Tibia where it acts vertically over the arches of the model of the foot.

Think about how this works.

sr-tripod-demo

 

ZEPPA-DELTA ANGLE AND THE STRETCH REFLEX

Never heard of the Stretch Reflex (SR)? You’re probably not alone. Even though the SR was the central focus of the research I did in 1991 with the Birdcage, I have yet to encounter anyone in skiing who knows what it is, let alone how it can function to assist skier balance by maintaining the major joint angles associated with a strong stance. The SR is what enables the world’s best skiers to ski with precision and with a fraction of the effort of lesser skiers.

After Nancy Greene Raine began supporting my work in 1978 and I started to work with world class racers and coaches I began to hear the comment that skiers like the legendary Toni Sailor or Nancy Green Raine ‘knew how to stand on their skis’. This implied that the reason other skiers could not ski like the Toni Sailors and Nancy Green Raines of the world was that they didn’t know how to stand on their skis. I found this puzzling. If it were that simple (it wasn’t and still isn’t), why hadn’t someone figured out how Sailor and Raine stood on their skis and started teaching the rest of the skiers how to stand the same way?

It was also about 1978 that the story began to take root within the ranks of the ski industry that ‘the foot functions best in skiing when it’s joints are completely immobilized in the ski boot’. The holy grail of skiing, a perfect fit of the ski boot that precisely mirrors the shape of a skier’s foot, emerged soon after. In this paradigm, if tight was good, tighter was better.

Aside from the obvious contradiction (the foot functions best when it is rendered dysfunctional?), it was a good story. On the surface, it made sense to most skiers, myself included, right up until I watched Nancy Green Raine undo all the buckles on her boots and ski better than any other skier on the hill. In observing and speaking with numerous elite skiers, a consistent pattern began to emerge; they all skied with their boots relatively loose compared to the boots of the average skier or racer; a stark contradiction to the ‘tighter is better’ story. A tight fit/loose fit paradox existed. This caused me to start to question the official position on boot fit.

By 1989, I had hypothesized that the SR was the ‘secret’ of the world’s best skiers. If I were right, these skiers weren’t flexing the shaft of their boots to put pressure on the front of the ski. They were flexing their ankles to set up the static preload that enables the SR. I had concluded that it wasn’t so much that elite skiers knew how to stand on their skis, but more a case that they were able to stand on their skis in a way that enabled them to use the SR. It seemed probable to me that these skiers had acquired a feel for the SR when they were first learning to ski. Once the feel was acquired, they were able to select boots and adjust them as required to enable the SR. The majority of skiers never acquire a feel for the SR when they first start to ski because the design and structure of their ski boots prevents this. If they don’t learn the feel of the SR early in skiing, the odds are great that they never will acquire it. If my hypothesis were correct, then the entire ski industry had gotten it wrong. The Birdcage experiments validated my hypothesis.

When Steve Podborski asked me to try and invent a new ski boot that did the same thing for all skiers as the in-boot technology I invented in 1980 did for him, I needed confirm my hypothesis that the structures of ski boots were preventing the majority of skiers from using the SR. This was especially important because preiminent safety experts had raised red flags in the Shoe in Sport (published in 1987) about the lack of sound principles in the design of the plastic ski boot. They had specifically flagged the shaft of the boot.

“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.”

  • Sports Medical Criteria of the Alpine Ski Boot – W Hauser P. Schaff, Technical Surveillance Association, Munich, West Germany

A principle objective of my research in 1991 was to valid my hypothesis that structures of the ski boot prevent the overwhelming majority of skiers from being able to use the SR.

As far as I know, I am the first to describe how to set up the static preload that primes the SR and how to configure a ski boot so it accommodates and supports the SR. In the application of the SR to skiing, it is a powerful balance mediator and a PROTECTIVE mechanism.

The science behind the SR is complex. The best and perhaps simplest way to appreciate it is to acquire a feel for it by going through a static preload exercise barefoot on a hard, flat surface and then applying the acquired feel in progressive stages while standing in ski boots. This aspect involves correcting or removing any factors that prevent attaining the static preload. The process starts by learning how to set up a static preload on the shank-angle dorsiflexion angle.

  • In barefeet, stand erect on a hard, flat, level surface as show in the left hand figure in the graphic below.
  • Relax the major muscles in the back of the leg (mainly the hamstrings) and allow the knees to move forward as shown in the right hand figure.
  • As the knees move forward, the hips will drop down towards the floor. The ankle joint will dorsiflex and the angle of the shank with the floor and the angle of the knee will increase until a point is reached where the shank stops moving forward on its own.
  • As the knees are moving forward, bend slighly forward at the waist. The angles of the shank (ankles) and knees will decrease as the pelvis moves back and up and the back rounds. If you bounce up and down lightly, your stance will return to the static preload position.

static-preload

  • Move forward in the hips until you feel good pressure under the balls of your feet. Feel the whole system tighten up. You have set up a static preload on the shank of the leg. This is the foundation to build an SR stance on.

Try doing this in your everyday footwear. A number of factors  can prevent the setting up of the static preload that enables the SR. The ZeppaDelta Ramp Angle in ski equipment is a big factor as is drop in shoes. Over more than a few degrees of ramp angle, it is not possible for the SR to engage.

If you try the preceding exercise in your everyday shoes and the shoes have significant drop (toe lower than the heel), it is probably not possible to set up a static preload on your shank. Instead of stopping, the shank will keep going until it reaches the physiogical limits of ankle dorsiflexion.

In my next post, I will describe how to build an eccentric muscle contraction (EC) tensioned stance from the static preload shank angle.