SR Stance

THE MECHANICS OF BALANCE ON THE OUTSIDE SKI: PRESS AND POINT THE BIG TOE

A widespread perception appears to exist within the skiing community is that the ability to hold a ski on edge by using the leg to exert force against the side of the stiff shaft of a ski boot and staying upright and not falling, equates with good balance. This ingrained perception presents a challenge in terms of communicating how the world’s best skiers create a platform under the body of the outside ski that they can stand and balance on using the same processes that we all use to stand and balance on a hard, flat level surface.

Last ski season, I developed simple cue to help skiers find the right mechanics and biomechanics as the new outside ski goes flat between edge change and then rolls into the turn on its new inside edge.  At ski flat, if a skier has the right stance, they should feel strong pressure under the ball and the big toe. As the skier extends and inclines into the new turn, the outside leg should be rotated into the turn to point the big toe in the direction of the turn. Hence the cue, press and point the big toe.  This pressure under the ball of the foot and big toe should be maintained through the turn phase until it is released by the transfer or weight to the inside (uphill) ski at the start of the transition to the inside. The strong pressure under the ball of the foot and the force that presses the big toe down flat is passively created by a strong stance, not conscious effort.

The Reverse Windlass

The pressure under the big toe is created by what is called the Reverse Windlass Mechanism. This naturally happens in the late phase of stance when walking barefoot. But wearing shoes with raised heels and cushioned insoles makes it impossible for the Reverse Windlass to function. When the Reverse Windlass is lost, it must be re-acquired by being barefoot as much as possible and walking, running and training in zero drop, thin soled minimal shoes. In some cases, people have to learn to walk naturally by rehearsing the action.

There is an excellent YouTube video by Teodoro Vazquez on Blog del Runner  called Windlass Mechanism and Running Biomechanics – https://youtu.be/y_8SrufgmDk. Vazquez describes the 3 phases of the windlass mechanism, Active (Activo), Reverse (Inverso)  and Passive (Pasivo). Although the video is directed at running, the primary concepts have direct application to skiing and ski technique. The reverse windlass is activated by the weight as shown in the graphic below from Vazquez’s YouTube video.
 This tensions the arch of the foot and presses the big toe down.
As the shank angle increases, the soleus muscle goes into isometric contraction and arrests further shank movement. The results in a heel to forefoot rocker action that dramatically increases the down force under the ball of the foot and the big toe. What I call the Spinal Reflex or SR Stance maximizes the down forces.

It is important that when the big toe (aka Hallux) is pressed down flat, the ball of the foot and big toe feel like one. When the big toe is pressed down properly, you should feel your glutes tighten. The leg you are standing on should be straight and the knee pointed straight ahead.

An important muscle in the Reverse Windlass is the Flexor Hallucis Longis or FHL. When the soleus goes into isometric contraction, the FHL is tensioned. This stabilizes the foot and knee by rotating them away from the center line of the body.

Things that prevent the Reverse Windlass

1. A condition called Hallux (big toe) Valgus
2. Narrow shoes and especially shoes with a pointed toe box.
3. Ski boots, especially ski boot liners.
4. Shoes with elevated heels, cushioning and toe spring (toes raised up). Note: A small amount of ramp angle is necessary for the SR Stance.
5. Footbeds and Insoles.
In my next post, I will discuss fixes to enable and/or restore the Reverse Windlass.

THE MECHANICS OF BALANCE ON THE OUTSIDE SKI: FIRST STEP

In this post, I am going to begin the first of what I expect to be a series of posts on the Two Step Process to Balance on the Outside Ski.

Prelude

Before I start, I am going to caution the reader that they should not expect that the ability to learn and engage the processes responsible for balance on the outside ski to be easy to understand or quick to learn.  Many obstacles stand in the way of the ability to balance on the outside ski. As Benno Nigg’s experiments in the early ’90s at the Human Performance Laboratory at the University of Calgary demonstrated, the human body is highly adaptable. If a person puts their feet in footwear that prevents natural barefoot function, the body will find a best case work around compromise.

This is what happens to skiers when they put their feet in ski boots. As the Polish study showed, over time, the body will adapt. But adaptation always comes at a price.  Some skiers may adapt to constraints of a ski boot to the point where they are considered expert skiers by the prevailing standards. But they typically reach a point where they can no longer advance. Given same ability, the least compromised skiers become the best.

The problem faced by skiers who wish to learn balance on their outside ski (foot) is that the ingrained motor patterns their brain has created as a work around to address the limitations caused by their ski boots can be exceedingly difficult to erase. A skier will typically make some progress only to have their brain revert to motor patterns that have worked in the past when it senses danger. When this happens, the odds are great that even the most athletically gifted skier may have to relearn skiing to some extent. I have seen many graphic examples of this pattern over the past several years in skiers and racers I have worked with.

WARNING: The Mechanics of Balance on the Outside Ski is Not Simple

About the simplest way I can describe the mechanics is that the First Step involves a heel to 1st MPJ rocker loading mechanism while and the Second Step involves an intertia-driven turntable, over-centre mechanism. The mechanics is unified sequence of events. The reason I have broken it two steps is to make it easy to understand the critical nature of the first part of the sequence.

More than 25 years ago, I tried to make the First Step simple and easy to understand with the model I fabricated shown in the photo below and that graphic illustration that follows that shows how the Achilles tendon tensions the Plantar Aponeurosis (aka the Plantar Fascia) and enables foot to pelvic core sequencing. Note the annotation in graphic to Late Stance and (SR) Ski Stance Zone.

In my demonsrations, I  would drop the model on a table from a height of a few inches.  The rotation of the leg of the model would be quickly arrested by simulated isometric contraction of the Achiles. The model and the demonstration failed to garner attention or interest because the importance of the forefoot to foot function was not on the radar screen. Instead, the focus was on the hindfoot and addressing the known looseness of the forefoot associated with the mid stance phase of gait. A late stance phase was not yet part of the gait cycle narrative. The importance of late stance and fascial tensioning of the forefoot to foot function and foot to core sequencing has only recently been recognized.

sr-tripod-demo

Plantar Apo Dynamics

First Step

The First Step is to tension the biokinetic chain that extends from the MPJs of the foot to the pelvis. The timing of this event, which is critical, will be discussed in a later post.

The key move is the loading of the outside foot. This should happen in the top of the turn as the fall line is approached. This is the point where a skier should become the tallest in relation to the snow. At the end of a turn (in the bottom) is where a skier should be lowest.

It is not possible to replicate the loading move except when skiing because of the dynamic nature of the 3-dimensional forces associated with ski maneuvers. But the forefoot loading move that creates fascial tension the forefoot is essentially the same move we make when we move forward on the stance foot in walking in preparation to take a step. Once the foot has adapted to the ground, forward rotation of the shank (ankle flexion) is arrested by isometric contraction of the calf muscle. At this point, further forward movement of the torso occurs through knee extension in what amounts to a heel to ball of the foot rocker mechanism; i.e. a forward and downward action that applies force to the ground to prime the energy return foot spring in preparation to propel the body forward.
One way to get a feel for this mechanism is to stand sideways across the bottom of a stair and place one foot on the first tread about a whole foot length ahead of the foot on the floor. The knee of the leg on the floor should have slight bend so the calf muscle is in isometric contraction (SR Stance). The angle of the shank of the foot on the tread should be a little less than 90 degrees in terms of dorsiflexion. From this base position, the torso is projected forward in order to achieve a position of balance over the foot on the first tread. This is roughly what the loading move should feel like in skiing that is made as the fall line is approached. Once a feel for this has been acquired I can discuss how this integrates with rotation of the leg.
It is important to not have the ankle flexed for the above exercise because the ski boot limits ankle flexion. At the start of the transition at the end of a turn, the weight will be under the heel of the inside (uphill) foot. It is also important that the calf muscle of the foot on the stair tread go into isometric contraction so that further forward movement of the torso occurs through knee extension.
In a ski turn, the forefoot loading move is one of a quick heel to 1st MPJ forward rocker knee extension pulse that loads the ball of the foot (1st MPJ). Loading of the 1st MPJ (ball of the foot) is caused by forward movement of the torso (CoM), not plantarflexion. This loading move is made in the top of a turn as the fall line (aka rise line) is approached. The window in which to make this move is narrow and the time required  to complete the move, brief.
If you watch video of Shiffrin slowed to 0.25 normal speed or step the video in frame-by-frame, you will clearly see her make this loading pulse which usually involves a lifting of the fore-body of the old outside ski due to swing leg reaction force.
In my next post, I will discuss Step Two.

 

 

 

 

 

 

 

 

 

 

 

TRANSITIONING THE SR STANCE TO THE SKI BOOT

In this post, I will describe the sequence of events required to successfully transition the SR Stance learned barefoot out of the ski boot, into the ski boot.

Learning and rehearsing the SR Stance in bare feet on the same hard, flat surface provides a kinesthetic sense or reference with which to assess the effect of external influences. By following a specific sequence of events, the effects of individual components such as boot board (zeppa) surface and ramp angle, clearances of the foot to the inner shell wall, footbeds and liners can be identified.

A preliminary step is to measure the boot board (zeppa) and binding (delta) ramp angles. Although the effect of ramp angle on stance and skier balance should be studied in a laboratory setting and in actual ski maneuvers, through subjective assessment in working with skiers and racers, I have arrived at a range of 2.5 to 2.7 degrees of total ramp angle (zeppa + delta) that supports the SR Stance. A combination of approximately 0.2 degrees of delta in combination with 2.3 to 2.5 degrees of zeppa seems to give the best results. The window of the total ramp angle that supports an SR Stance appears to be narrow and falls off rapidly on either end of the range.

Steps to Transition the SR Stance to the ski boot

  1. In bare feet, learn and rehearse the SR Stance as described in my posts on the subject on 2 feet until the SR Stance is familiar. Try and maintain the spacing of your feet every time you rehearse the SR Stance.
  2. In bare feet, learn and rehearse the SR Stance as described in the posts on the subject on 1 foot until is familiar.
  3. Add a ramp board with the same combined zeppa + delta ramp angle as your ski boots and skis and repeat exercises 1 and 2.
  4. Try the same exercises above while wearing your ski socks. You might be surprised.
  5. Repeat the exercises 1, 2 and 3 with the insoles or footbeds (if you are using them) from your ski boots in place under your feet.
  6. Repeat exercises 1, 2 and 3 while standing in the liners from your ski boots with no insoles in them. Check for areas of tightness. Are your toes crunched up? Do the liners feel too short? Can you sense significant pressure around the ankle bones or on your Achilles? If yes to any of the preceding, flag the liner as a potential problem in terms of the ability to assume the SR Stance in your ski boots.
  7. Repeat the above exercise while standing in the liners with the insoles or footbeds (if you are using them) in place under your feet. If you feel significant pressure under the arches of your feet, flag the liner as a potential problem in terms the ability to assume the SR Stance in your ski boots.
  8. With your ski boots spaced approximately the same distance apart as your feet in exercises 1. and 3., stand in the ski boot shells (no liners). Try and assume the SR Stance. Check the shell wall for interference with structures of your feet such as ankle bones, width across the balls of your feet and the alignment of your big toe. The big toe should be able to sit straight, in its natural alignment.
  9. If there are no issues with the shell, insert the liners and repeat the above exercise.

If you have made it this far with no significant issues, congratulations. You are among the world’s elite skiers, the top guns, the best of the best. But the odds are overwhelming that most who try the above sequence of exercises will have identified more than one issue that prevented them from conforming to the SR Stance barefoot reference.

In my next post, I will discuss the types of modifications typically needed to remove the impediments to the SR Stance identified in the above series of exercises.


See posts on the SR STANCE under the drop down menu under the heading INDEX OF POSTS on the Home page.