The theoretical basis serves as the foundation for the development and understanding of the analysis of a direction change in skiing. It is essential because it provides a solid context and justification for the study, allowing to conceptualize it in a well-founded manner.
The following considerations will focus on the technique used by recreational skiers, even if they are applicable in competition. Although there are similar technical elements, we must highlight the marked difference in intentions between a recreational skier and a racer.
Recreational skiers essentially seek to maintain balance, control their speed and trajectories with minimal muscular effort within their comfort zone, as they aim to enjoy several hours on the slopes through efficient skiing. They have time to choose when to change directions and where to do it, as well as choosing their own line of descent while controlling their speed, but not at any cost, rather with the minimum effort necessary because they also intend to control their balance and trajectories.
During ski lessons, recreational skiers learn how to ski in control and their main preoccupations are about safety, stability and stopping. Recreational skiing is developed in an open environment, seeking not only a functional technique but also an aesthetic skiing style, given the individual factor of feeling good while skiing.
In contrast, racers aim primarily to be the fastest in order to win the competition in which they have approximately up to two minutes of descend. As they pass through fixed gates, they have little time to decide when to start their turns and not much options about where to do it. Since their intention is to reach maximum speed, they will do whatever is biomechanically necessary to attain it. To achieve this goal, they will not hesitate to ski riskily, pushing their limits of balance, speed, and muscular effort, thus applying an effective but not efficient technique.
During training sessions, athletes learn how to ski faster, and their main preoccupations are about risk, recoveries and acceleration. Ski racing is developed in a closed environment, and racers do not seek an aesthetic skiing style but rather one that is functionally valid for their purpose: winning the race.
Let us remember that efficacy refers to goal achievement regardless of the mode or process used to succeed, and efficiency denotes the manner of achieving it through the best use of the possessed resources.
We refer here to the fact that, when skiing, the laws of biomechanics consider that minimum energy is achieved when our body moves in such a way as to save muscular effort, so we say that we are skiing efficiently.
Now, does the technique makes the skier or does the skier makes the technique? Technique makes the recreational skier, while the racer makes the competition technique, that is, his personal technique.
Although racers are initially technically trained, when they reach a certain level they determine their own technique in order to attain their goal, that is, winning regardless of the amount of technical resources or muscular effort to be used. Therefore, once this level is reached, they will ‘build’ their own technique, the one that gives them the best results individually.
Recreational skiers pursue efficiency because, as they ski most of the day, they must be efficient in the use of their technical resources, as well as in the dosage of their muscular efforts. Unlike the racer, the recreational skier is ‘made’ by the technique, since it has been analyzed and conceived according to physical and biomechanical bases by technicians who study it, taking advantage of the construction and performance characteristics of the available skis.
Currently, technical perfection has been achieved to such an extent that carving is the ultimate technical expression, the essence of postmodern skiing, and recreational skiers and racers use it to their advantage.
Therefore, we repeat, we will analyze the technique of the recreational skier here, based on physics and biomechanics. A universal ski technique with the particularity of being able to be used by everyone.
We consider skiing as a means of moving across the snow with an alternating activity of our lower limbs and the compensation of the trunk, when necessary, to maintain a dynamic balance. Skiing motion is carried out in straight and curved lines. The latter is achieved by direction changes which can be successive (linked) or alternating. A complete cycle of a direction change is understood to be when the direction of motion is reversed to the opposite side of the previous one.
In this direction change, the skis, sliding on the inner edges and describing a continuous curved line, at a given moment and at the skier’s discretion, change the curved trajectory in the opposite direction. This is possible thanks to the change of side of both edges. When skiing with parallel skis, a complete direction change is only possible by changing both edges.
We begin our analysis of skiing turning modes from de relationship of the Center of Mass (CoM), situated at our pelvis, and the Center of Pressure (CoP), situated at our feet. This two point of references are in constant connection when changing direction.
Taking the distance between the CoM and the CoP as parameters for edge changes, we consider that there are three commonly ways to change direction with parallel skis: Direction Change by Extension, by Flexion, and Neutral Direction Change.
We also postulate that, when changing direction while skiing, we perform the same movements in one activity that we do during our daily life: walking.
When walking, according to our bipodal morphology designed to move a large, tall mass from a small, agile base, our balance shifts from one foot to the other, with moments when we are supported on both feet, then moments standing on one foot when we shift our weight to that foot to lift and bring the other forward and take the next step by oscillating our whole body, after which we return to moments of being supported on both feet again.
Direction changes when skiing, the same as walking, consist of a stable, longer phase with bipodal support (on both feet) and an unstable oscillating phase of short duration with monopodal support (momentary support on one foot).
To execute a direction change in skiing it is necessary to break the balance formed by the centripetal posture, in which we are standing on both feet, and move to a single-foot stance at the Inflection Point (I.P.), i.e., a point of a curve at which a complete change in the direction of the curvature occurs.
The single-foot stance is the starting point for our body’s oscillation, which plays a fundamental role in allowing the edges to change sides and initiate the direction change. This body oscillation movement can be well used or can be wasted.
In other words, during most of the turn on skis we stand on both feet, with a prevalence on the outer/downhill foot, but at the precise moment of the direction change -the inflexion point- our support tends to be monopodal as we shift our weight from the outer/downhill foot to the inner/uphill foot.
Given the three different modes of changing direction according to the relationship between the CoM and the CoP, we will describe this usual motion mode of single-leg and double-leg support when walking to present a biomechanical analysis of the different phases involved when changing direction in linked parallel turns, which are the Generation Phase, the Monopodal Phase, the Oscillation Phase, and the Bipodal Phase.
