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.
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.
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.