Another great thread from mike m. Markop’s and Chris V’s brief discussion on steering and separation got me thinking.
Unfortunately, terminology for ski technique has no reigning authority with which to precisely classify what we are trying to say. Sometimes we settle for what is most popular. Sometimes we go with the source we think has the most authority. Perhaps we will choose what best fits our overall understanding or model at the time. Sometimes we have to take from the established sciences of physics, engineering and biomechanics. Perhaps a publication, a video, a lesson, a website or an enlightening conversation. Sometimes, to cut through the veneer of dev program branding language and get down to the brass tax, we have to take the closest definition from Merriam Webster and re-apply it to the context of ski technique as Bob Barnes does with his definition of steering. Bob Barnes encyclopedia of skiing? Good descriptions of many technical terms that I would agree with. Sometimes we take from all those sources to settle on what we feel works best. The result? Almost anything in an online forum. It may even cause hesitancy in contributing from those who are very knowledgeable being fully aware that there will be disagreements no matter what is said or claimed. The following is how I understand the term “steering” and associated concepts.
The term steering is a word that commonly gets used loosely as there are three usages of the word in the context of ski technique. For the term “steering angle”, steering refers to the direction of the ski in reference to the direction of the CoM. Then there is “rotary steering” which refers to the change of the direction of the ski by twisting (skidding) and rotating it from the feet or the ski’s “center”. Then there is the least recognized form of the word in a carving context whereby steering is controlling the direction of the ski through tipping only. “Tip steering”? The more the ski tips, the more it bends; the more it bends, the more it changes direction. One constant in all three definitions is a reference to the direction of the ski (BoS). However, “pivoting” is not a constant among all the definitions of steering and, thus, only a method of steering. The steering angle is equally relevant/present regardless of carve/skid status. While, for some, the term steering may only represent a pivoting action, I would respond that the preponderance of evidence suggests otherwise.
Then there is an even more obscure term, even too obscure for Barnes expansive glossary, that is the ski’s “attack angle” which (for some) refers to the angle between the direction of the ski and the direction of the fall line which is very similar in effect to the steering angle in terms of overlapping attributes. The term “attack angle” has been used to mean “steering angle” by some. Because the angle of attack references the separate paths of the anatomy and that of the ground’s surface plane related to the fall line, it is more relevant to the physics of ground reaction force. Because the steering angle is only in reference to the BoS and CoM, it is more about the anatomy and its separation mobility. Similar to the lift coefficient resulting from the attack angle in golfing or aeronautics, the attack angle in skiing produces a lift coefficient from the ground reaction force created. The steeper the angle of attack, the more GRF resulting in more lift. While there may be only one steering angle per turn (if located at the intersection where the paths of the CoM and BoS cross), the attack angle can change throughout the turn (with tipping) as the fall line is always present underneath us regardless of its direction.
Bigger steering angles are more associated with shorter radius turns. The larger the turn, the smaller the steering angle. Big attack angles are equally achievable in both small and large radius turns but will be more abrupt in small turns. Bigger steering angles require more mobility for more separation between the CoM and BoS. While rotary separation may be most relevant regarding the development of these angles, all separation including flexion, extension, angulation and inclination in addition to rotation, the five fundamental movement patterns executed between the CoM and BoS, will be required for big steering angles. Skidding through the attack angle is going to muffle the GRF output compared to railing through it. (GRF in moguls an entirely different convo)
A good way to remember the attack angle is “attacking the fall line”. Because high performance skiing is entirely offensive in nature, the phrase, “attacking the hill” comes to mind. The more we steer against the fall line, vs with it, the bigger the attack angle and the more dynamic and aggressive the ground force produced. The more we turn away from the fall line, the more we are turning “into” the hill as we put our CoM in a gradual collision course vector with the rising surface plane of the ground. The more we steer away from the “fall” line, the more we steer into a “rise” line (not exactly the rise line in a race course which is based on the location of the gate). In freeskiing, the rise line is simply the opposite of the fall line and thus present at every location. In addition to the natural undulations of any typical slope, the calculation of ground force from attack angle vs ground force from random undulation would be difficult. The bigger the attack angle, the steeper the rise line generally encountered as a result. But a rise line in a fall away undulation can be canceled out or magnified with a rising undulation. Typically, we are always experiencing either a fall line or a rise line to some degree as our CoM is rarely traveling in the same exact direction as the plane of the ground underneath us. A bigger attack angle in the sagittal plane, the bigger CoM to slope collision angle will be in the vertical axis and will produce similar results of bouncing a ball off a sloped surface, hence ground reaction force. As the direction (vector) of our CoM loses altitude over the rising slope underneath us, we use that externally applied collision force, more specifically its vector of deflection, to create a passive output of gross motor flexion between the CoM and BoS. The higher the angle of attack, the more “ground force flexion” we will have to use. Ground force flexion is much quicker/snappier, more powerful and more inherently timed with the fundamental attributes of the turn than trying to initiate and manage the flexion ourselves. (referring to “dynamic” flexion or flexion “movement” that is traded off with an equal amount of extension within the same turn cycle and not “static” or “stance” flexion that is maintained throughout the entire turn cycle).
It is literally the direction of the ski (BoS), both in reference to the fall line and the CoM, their outcome of ground reaction force created and biomechanical separation required that will prescribe the duration, intensity, rate and timing of the rotary, flexion, extension, angulation and inclination that occurs between the CoM and BoS. For pure carved turns in particular, the DIRT that is actively/directly applied at tipping then becomes the DIRT that is passively output within the five fundamental movements of separation between the CoM and BoS. If we treat these ideally passive outcomes as active inputs, we are held back from experiencing the true benefits and power of a dynamically carved turn.
