Interesting discussion but that regarding facilitating movements without much if any (sorry, didn’t read entire thread) discussion regarding the accrual of the final output we seek to create and something I believe that is ultimately defined as ski to surface interaction outcome. While perhaps the best evidence of which is the tracks a skier will leave in the snow, that is not a very applicable visual aid for instruction yet, helpful to think about in terms of goal setting. Otherwise, we are instructing skiers to follow a map that has no destination. We are telling people how things should look rather than how things should respond. A very popular absence is often in regards to discussion around minimizing inside tip lead. Why is it important to keep both skis under your mass in fully carved turns? That is because we are trying to equally tip both skis which means equal bending, equal carving and equal tracking of both skis. With too much inside tip lead, we cannot pressure the inside ski. That is fine if your technique is to pressure and use only one ski (outside) at a time, a technique that is dated for the purposes of modern advanced carved turns. But, without a modicum of inside pressure, we have little control of what that inside ski is actually doing and in the case of no pressure, that means it is doing nothing but being a useless appendage that must be “reactivated” with each turn which is more sequential and less fluid. It also makes the BoS less quick and laterally mobile which is a limitation to the properties of separation we would seek to achieve in this type of turn.
Imagine for a moment only the mechanical input and output of the ski alone. Do we actually know how we would prefer to tip, pressure and coordinate a pair of skis? If your skis were magic and skied alone with nothing on them and you wanted to cast a spell on them with specific instructions for executing high performance dynamically carved turns, what would you specifically ask those skis to do? Do you want them to tip equally so they can bend equally so they can track equally? Do you want the fore to aft pressure migration equal but dominant to the outside? Do you want them lined up under you with little inside tip lead? Do you want a fluid pressure distribution through the skis from turn to turn? What is it you are specifically asking of the ski as a carving tool?
Now, let’s say you know exactly what you want from the ski, have cast the spell on them and off they go doing exactly what you instructed all by themselves and they make those beautifully round and dynamic arcs leaving the tracks we see forming under the skiers we seek to emulate. However, you are told one day that you will have to mount bindings and ride on top of these magically carving skis over which you will be able to exhibit no control. How is your body going to accommodate these movements of the ski? What are you going to do as the soles of your feet are forced to follow the radical tipping angles of both skis? What would you be planning on doing to stay on top of those skis so you do not end up being dragged to the bottom of the hill like a rag doll? How are you going to survive? Are you going to manage the relationship between your CoM and BoS in order to stay on top? What would that look like? Are you going to jump up and down, do a hula dance or moonwalk?
Now, imagining further along, let's hang your CoM on a long and winding coat rack that runs straight through the center line of your magically turning skis. What is your body doing to accommodate the differences between the upper path of the CoM and the lower path of the BoS? Is it going to flex, extend, rotate, incline and angulate the relationship between the CoM and BoS? Do you have the mobility to effectuate this accommodation of movement? Do you have to force these movements with muscular intervention (interference) or do you allow them to happen on their own accord? Will your musculoskeletal system accommodate these two externally forced paths or will it just break up and tear apart?
Luckily for us, our biomechanics were built for this kinetic path of movement required for accommodating the path differential of the CoM and BoS of an alpine skier. As a matter of fact, it is that specific kinetic path of movement allowed by our very particular human biomechanics that has invented these two paths taken over a pair of skis. It is the concept of skiing that developed out of these peculiar human elements of biomechanics. Especially in light of today’s contemporary technical freeskiing and the extreme mobility demonstrated between the CoM and BoS through the spine in large and small carved turns has likely reached its evolutionary limits (barring some unlikely new sort of ski design).
As we all know, due to the resulting complexities of melding physics, biomechanics and engineering in the conceptual discussion of ski technique, there are multitudes of ways to skin this cat. One of those ways is the “ski as a carving tool” concept. In this light, we base technique solely on the ski to snow interaction outcome we seek and as definitively represented by the tracks we leave in the snow. The ski is the carving tool and the terrain is what is being carved. Take a hand saw for instance: We all know how to use one. We all know that the goal is to be able to cut a piece of wood as accurately, quickly and effortlessly as possible. Between our wrists, elbows, shoulders and spine, the kinetic path used for sawing wood, we execute movements of flexion, extension, rotation, inclination and angulation as slight as some may be. We know that we use these movements and their adjustments to find a certain saw to wood interaction outcome that we feel with each pass of the saw. It is this interaction outcome we use to identify the change in movements we need. If we extend too aggressively, the blades slows to a crawl. If we flex too much, the blade will speed up but cut very little wood as a result. If we misalign the blade, things squeak to a stop. We will incline the blade over the cutting path to shorten or lengthen the cutting surface area when our cutting output does not meet our expectations. We will angulate and rotate our spine to find the most comfortable and effective path for our body and saw to do its job. Perhaps not quite as large and complex as the kinetic path we use for skiing but somewhat representative of the scope and outcome.
Now, I do like this description of “force-couple” which aligns with the idea that good skiing is a practice in managing a network tension (from opposing forces) throughout the entire kinetic chain and turn cycle. The biomechanical characteristics of the human musculoskeletal system offers a path of movement that relies both on closed chain stability and open chain mobility. Two stabilizing factors offered by our chain of movement is that we can never achieve more inside tipping or inside pull back beyond that of the position of the outside foot/shin. This is the main concept behind the benefits of inside tip lead whereby the outside follows. These are two small “walls” of stability that can be pushed against with a tension that will not be over applied. Typically a mechanical term, force coupling, as I understand it biomechanically, is when two muscles, tendons or ligaments provide opposing forces on either side of a joint whether for the above mentioned stability or mobility. I refer to this as that network of tension which further defines our kinetic path of movement that we use to find our way from one movement to the next.
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) and the skiing of many other mere mortals that the tendency is to end up with too much inside tip (foot, knee, hip) lead, and consequent twisting of the hip toward the outside of the turn, hip dump, losing connection with the outside ski, falling inside and skidding.
