Balance, The Keystone of Skiing
If the foundation of expert level skiing were to be condensed into to a single word, that word would have to be balance. While true expert skiing requires the possession of a variety of skills, the bulk of those skills are either intended to ensure balance is maintained, or are dependant on a stable state of balance for efficient execution.
So what is meant by the word balance? While the term is tossed around pervasively in the ski world, few possess an in-depth understanding of what balance is beyond the simple concept of remaining upright. There's so much more to it than that, and acquiring a more extensive level of knowledge about balance in skiing allows participants in the sport to gain a clearer concept of how it's attained, how it's managed, and how the refinement of the skills involved can take overall performance to a new level. This article is intended to provide that knowledge.
A simple explanation of balance would be that it's the management of forces. However, for that statement to provide any value, it needs much expansion. There are two sets of forces involved in skiing. I'll call them internal forces and external forces. Internal forces are those we personally create that are born of muscular effort. External forces are those natural forces acting on us as we ski that are not of our bodies direct creation. Efficiency in skiing comes from reducing internal force employment as much as possible, while exploiting the existing external forces to accomplish our goals. More on that later.
There are two primary external forces involved in skiing; gravity and centrifugal force. Gravity is a constant while we ski. It's a vertically orientated force that always acts on us at the same magnitude. Centrifugal force is simply the momentum that acts on a turning object. In this case the object is a turning skier. Its effect is felt as a horizontal force attempting to toss the skier to the outside of the turn. It's the same force that causes us to tip sideways and slide across the seat of a car when making a sharp, high speed turn.
These two forces, gravity and centrifugal force, combine to produce a single force that acts on our Center of Mass (CM) in a singular direction. Just to clarify here, Center of Mass (CM) represents the single point at which a rigid body could theoretically be balanced on the head of a pin. Likewise, our Center of Mass (CM) represents the central point of all forces acting on our body, and thus serves as a valuable tool for analyzing balance.
So, in review, I said gravity and centrifugal force combine to produce a single force, of singular direction, that acts on our CM. That force is called the resultant force. Imagine a still picture of a skier making a turn. Now imagine a dot representing that skier's CM placed somewhere in the area of his lower torso. Emerging from that dot (his CM) will be two arrows. The first will represent gravity, and it will be a vertical arrow that extends from the skiers CM to the ground. The second will be a horizontal arrow that emerges from the skiers CM and points toward the outside of the turn. This second arrow represents the centrifugal force acting on the skier. Somewhere between those gravity and centrifugal force arrows will be a third arrow that represents their cumulative effect. That arrow with be the resultant force arrow. It will emerge from the CM and extend to the ground on an angle somewhere between 0 degrees (vertical) and 90 degrees (horizontal). If all skier resistance to the combined turn forces were removed, the skier's body would be propelled in the direction of this third arrow. The technical name of that third arrow is the resultant force vector, and coming to understand the nature of it is key to coming to understand balance.
More to come on that subject, but first, how did you do? Were you able to follow the visuals and formulate a clear mental image of the force picture? To be sure, take a look at this link. It provides an excellent representations of the image described above.
The yellow arrow represents gravity, the blue centrifugal force, and the green the resultant force vector.
Now that we have a general idea of the way external forces impact a skier, let's continue. At this point I need to explain how the angle of the resultant force vector (the green arrow in the link) is determined. As I explained, it's a result of the cumulative effect of the gravitational and centrifugal forces acting on the skier. If the actual magnitudes of gravity and centrifugal force happened to be exactly the same, then the resultant force vector would be tilted at 45 degrees, precisely half way between the gravity and centrifugal force vectors. If, on the other hand, centrifugal force happened to be larger in magnitude than gravity, the resultant force vector would tip closer toward the 90 degree centrifugal force vector. And if gravity happened to be higher in magnitude than centrifugal force? That's right, the resultant force vector would be less than 45 degrees, closer to the 0 degree gravity vector.
OK, so now that we understand what determines the tip angle of the resultant force vector, lets discuss the significance. Pay close attention now, because this next statement is of great importance. The point at which the resultant force vector contacts the ground represents the balance point. I'll say it one more time. THE POINT AT WHICH THE RESULTANT FORCE VECTOR CONTACTS THE GROUND REPRESENTS THE BALANCE POINT. What is the balance point you ask? It's the point on the ground where if the end of a steel rod were placed, with the opposite end of the rod placed on a rigid bodied skier's Center of Mass (CM), and the skier had no body part touching the ground, he/she would rest in perfect balance upon that rod. Simply put, it's the point on the ground upon which the skier could stand on one foot in perfect balance.
Why is this so important? Because it's the core principle behind all balance and force management strategies. If we can learn to manipulate the ground impact point of the resultant force vector, what we now know to be the balance point, we gain complete control over how we choose to distribute our weight upon our skis. We can move the balance point directly under our outside ski, so that all of our weight is on that ski. We can move it under the inside ski so that all of our weight moves to that ski. We can place it half way between our feet so that equal weight resides on both feet. Or, we can choose to place our balance point at any location between our feet we wish to produce the exact weight distribution we desire. We can also move our point of balance along the fore/aft plane to produce whatever tip, tail or neutral pressure on the skis we seek.
Sounds great, doesn't it? So how do we do it? Well, I'm glad you asked. It all has to do with managing that resultant force vector we just learned about. For any particular moment, in any particular turn, only one resultant force vector angle can exist. Why? Because, as we've learned, that angle is dependant on the magnitude of gravity and centrifugal force. We know that gravity is a constant, so the variable in the equation is centrifugal force. The magnitude of centrifugal force is dependant on two primary factors; the shape of the turn and the speed of the turn. The faster a skier is traveling, and the sharper a skier turns, the higher centrifugal force will be. The higher centrifugal force, the larger the angle of the resultant force vector, and visa versa.
As you can see, the only means we have of changing the angle of the resultant force vector is to change the shape or speed of our turn. So, if carving and turn shape are our primary objectives, then varying those factors in the interest of changing the angle of the resultant force vector to alter it's ground impact point is not an option. Whatever the centrifugal forces happen to be at a particular moment in our chosen turn is what they are, making the resultant force vector angle un-modifiable. We must therefore find another way to manage our balance point.
If changing the angle of the resultant force vector is not an option, how do we alter the point at which it impacts the snow? In other words, how do we change our balance point? Very easy. We simply move the point from which the resultant force vector emerges; our Center of Mass (CM). By moving our CM laterally we move our point of balance laterally the exact same amount.
To make this easier let's refer back again to this link.
And before I continue, who can identify the flaw in this diagram? I'll help you. The green arrow indicates that the Hermann's balance point is directly under his outside foot. If this were the case, all of his weight would be concentrated on that foot. However, observing the snow flying off his inside ski clearly indicates that some weight does reside on that ski. Obviously his balance point is not under his outside ski, but rather lies somewhere between his feet. And we can be even more precise than that. From the obvious greater bend in his outside ski we know that the majority of his weight resides on his outside ski. This would mean that his balance point is between his feet, but much closer to his outside foot. That is where the green arrow should really be pointing, not directly at his outside foot as it is in the picture.
With that correction established we can continue. Can you see how if Hermann were to move his CM to his right, the ground impact point of the green arrow would move to his right accordingly? What effect do you think that would have? That's correct, his balance point would move closer to his outside ski, thereby removing another portion of what little weight resides on his inside foot and deploying it to his outside foot. And if he moved his CM to his left? Right again, the ground impact point of the green arrow (his balance point) would move toward his left (inside) foot, directing more of his weight to his inside ski. If he moved his CM far enough left he could move his balance point directly under his inside ski, which would move all his weight onto his inside foot.
That's all there is to it. When turn shape is our priority, altering our balance point by changing the angle of the resultant force vector is not an option, so we must move the entire vector by moving our CM. And that raises another a question; how do we move our CM while not affecting the shape of our turn? While it would be a simple matter to incline our body more or less to move our CM laterally, the problem would be that in doing so the amount our skis were tipped on edge would change also. When the edge angle changes, the shape of our turn changes as well, defeating our objective, changing the centrifugal forces, changing the angle of resultant force vector, and throwing the whole balance equation out the window. Not at all what we want. What we need to do is maintain our edge angle while we move our CM laterally. We do that through the use of angulation.
More articles are soon to be published here in reference to angulation, but for the time being suffice to say that angulation is the articulation at the joints that results in an angular diversion of connected body segments. Through angulation our shin can be tilted at one angle to the snow, while the thigh is tilted at another. Likewise, through angulation the angle of the thigh can differ from that of the torso. Each degree of body segment divergence moves our CM laterally, which moves the resultant force vector laterally, and thereby moves our point of balance. This is how we move our CM (and thereby our balance point) while leaving our edge angle and turn shape intact.
Dramatic relocations of our balance point can be achieved through this means. Some people envision our CM as a fixed point on our body somewhere at the center of our lower torso, but in actuality the CM moves around a body as stance is manipulated via angulation. In fact, with extreme applications of angulation techniques, the CM can even be moved entirely outside the body. This capability provides us with great balance point manipulation potential.
Look once more at the Hermann link. While at first glance he may seem quite inclined, closer inspection shows that he is employing angulation at the knee and hip. If you were to draw a line along his shin, and then project that line above his knee, you would see that it does not follow his thigh. His thigh actually angles slightly up above the line. That divergence of thigh from shin is called knee anglulation. Now project the existing green arrow up and see that his head is located above that line. That divergence of lower body from upper body is called hip angulation. Both the knee and hip angulation he's using serve to move his CM to his right and move his balance point toward his outside ski. If he were to eliminate these angulation techniques his balance point would be much further left than it is in the picture, and his inside ski would be greatly over weighted.
At this point I want to share with you a crucial secret of upper level skiing. Great skiers are able to adjust their balance point at will through the means I've explained, and then perform on that chosen balance point with ease. They can execute any turn shape they desire while distributing their weight in any manner they choose. For them, making a turn with all their weight on their inside ski is no more difficult than making that same turn with all their weight on their outside ski. They can alter their weight distribution in any manner they choose, at any point during the turn they choose, and continue to execute at a level that appears to observers to be effortless.
Watch Bode Miller ski. Some believe him to always be skiing on the edge of disaster and out of control. A closer look reveals that a more accurate explanation is that he has refined his ability to perform at a very high level across an extreme range of balance points. He exploits that ability to extract the most possible speed from the race course and his skis. While he often appears to be out of balance to the casual observer, the reality is that he is performing consistently within his individual, self-developed balance parameters. That he can lose a ski while traveling 60 mph down a race course and then casually continue to negotiate the course on his single remaining ski shows the level to which he has refined his balance versatility and adaptability.
It is such versatility that needs to be pursued by all skiers who desire to significantly ratchet up their performance level. As skiers expand their ability to perform outside of a limited balance point comfort zone, they'll suddenly find their confidence soar. New technical challenges can be met with less reservation because the skier knows that if that new challenge causes him to be jolted out of his old balance comfort zone, he has the skills to continue to perform on the unintended balance point while leisurely returning to the desired balance point. Possessing such skills also provides the capability to quickly learn and adopt into one's technical repertoire advanced techniques that require fine control and modification of the balance point during different phases of a turn. It's for these reasons that I call balance the keystone of skiing. Only through a devoted effort to refine and expand one's balance skills can skiers realize full personal potential. Our soon to be available balance DVD's in our FOUNDATIONS instructional series will focus on the development of those skills, and will help even students who are extremely balance skill limited develop the ability to perform proficiently across a very wide balance point spectrum.
So far we've learned that we manage our balance point by moving our CM, that we move our CM without changing our edge angle and turn shape through the use of angulation, and we've become aware of the importance of developing the ability to perform across a wide range of balance points. With that knowledge in hand we can move onto the next topic of discussion; balance efficiency.
While we've learned that we have the option and means to locate our balance point anywhere within our base of support ( the area at and between our feet) we choose, we also need to understand that from an efficiency standpoint some choices are better than others. To fully understand this topic we must separate the discussion into the two distinct planes of balance that exist; lateral and fore/aft. Lateral balance refers to how we distribute our weight between our feet, and fore/aft refers to how we concentrate our weight, front to back, along the base of our foot.
Efficiency in lateral balance is highly based in the concept of structural alignment. As we tip our skis on edge by inclining our body, our inside leg must shorten to allow our outside foot to remain in contact with the snow. We shorten the inside leg by bending, or flexing, the inside knee. See link:
That flexing of the inside knee causes the shin and thigh to loose their structural alignment. When a leg is extended, as the outside leg is when executing a turn, the bones of the upper and lower leg are aligned, and the turn forces can be supported through the compression resistance of the bones. This is a very efficient means of resisting turn forces that requires minimal muscular involvement.
When a leg is severely flexed, as is the case for the inside leg during a high edge angle turn, the upper and lower leg bones become very misaligned and can no longer provide force resistance through compression. Now the muscles must be recruited to assume the role of force resistance. This is a less efficient means of force resistance that carries a much smaller threshold of maximum force load that can be supported. It's for this reason the outside leg provides the strongest mechanism for resisting external turn forces, and why the majority of our turn force intensified weight should be directed to the outside leg. Or, in the language of us knowledgeable people, the balance point should be moved close to the outside ski. It need not be 100 percent on the outside foot, and there can be good reasons for distributing extra pressure to the inside foot for certain situations and at certain points during a turn. However, as a general rule, the greatest efficiency is achieved when weight distribution is outside ski dominant, as Hermann is in the above link.
The other plane of balance is fore/aft. The human foot is a magnificent balance mechanism. Within the foot are multiple bone trusses that are designed to spread and tension when compressed through the application of our body weight, thereby providing a stable platform upon which to establish and manage balance. This is called a through the foot balance platform. For these trusses to perform as designed, weight must be distributed across the entire fore/aft base of the foot. Weight distribution exclusivity on either the heel or the ball disables the proper balance functioning of the foot and requires the substitution of a less efficient balance platform. That substituted platform often involves leveraging the leg against the boot cuff, which requires a more intense recruitment of muscular activity.
From a pure efficiency perspective, weight should be distributed across the base of the foot so that approximately 60 percent of a skiers weight is assigned to the balls of the foot and 40 percent is assigned to the heel. This allows the foot to function as designed and provide the efficient through the foot balance platform we desire. Of course, as we know there are few absolutes in skiing, there will be times when altering that distribution pattern will provide situational benefits that will make worthy the sacrifices made in balance platform efficiency. These special situations include the intensifying of turn shape and engagement that can be accomplished by loading the front of a ski at the beginning of a turn, or the speed generation that can be created by loading the tail at the end of a turn. However, for general purposes, the design of shape skis allow them to be skied very effectively with neutral fore/aft pressure via the efficient, through the foot balance platform explained above.
Finally, I want to introduce the concept of how we can use the external forces of a turn to facilitate turn transitions through balance management skills. A transition is the period during which one turn is concluded and a new turn begins. As you know, during a turn we locate our CM in such a manner that our point of balance is placed in the relative vicinity of our outside ski. Doing so requires we locate our CM somewhere toward the inside of our turn, inside the vertical plane of our feet. To initiate a new turn we'll need to move our CM back across the vertical plane of our feet, and to the opposite side of our skis. How are we going to do that? Well, we could use our muscles to drive our CM across our skis and into the new turn, but there's a more efficient way that requires less muscular involvement.
The more efficient means to move our CM across our skis during a turn transition is to use the forces of the old turn to set our CM in motion and move it into the new turn. We do that by manipulating our state of balance. I'll explain.
Imagine a skier in the final phase of a turn. Her balance point is located between her feet, close to her outside ski, and she's in balance because she's allowing the external forces to naturally distribute her weight upon her feet according to the balance point she's chosen, creating outside ski dominance. She's also fore/aft neutral, standing with her weight evenly distributed on a through the foot balance platform. In summary, she's in a very efficient state of balance.
Now imagine that she's come to the point at which she wants to end the turn she's currently making and transition into a new one. How can she use the forces of the old turn to accomplish this? She can do it by creating a temporary state of imbalance. In a stable state of balance each foot assumes a force support role dictated by the location of her balance point. If she artificially alters those load bearing roles by relaxing the downhill (outside) leg and/or pressing down on the uphill (inside) foot, balance equilibrium is disrupted because the point of pressure (central pressure point) no longer coincides with the balance point. This causes balanced force resistance to be removed, and the existing external turn forces are allowed to drive the CM across the skis and into the new turn.
The same thing can be simulated right at home in your living room. Would you like to try it? Stand with your weight evenly distributed on both feet. Now push down on one foot without moving your CM laterally. What happens? You tip away from the foot your pushing down on, right? Do you know why? It's because you've disrupted your state of balance by separating your point of pressure from your balance point. That removes your balanced resistance to the external forces, in this case gravity, and allows them to have their way with your CM. The same result can be achieved by relaxing one leg, as that too moves the point of pressure away from the balance point. Give it a try. These living room simulations replicate what occurs when the same balance disruption techniques are employed to execute a turn transition on snow. This external force driven transition technique represents yet another strategy that employs the principles of balance to elevate skiing to a new paragon of efficiency.
In conclusion I want to reemphasize the crucial role the expansion of balance skills plays in the elevation of one's technical expertise. Refining one's ability to perform across a broad spectrum of balance point parameters opens doors to a level of on snow performance unknown to most recreational skiers. High level skiing is all about versatility, and balance is the foundation of that versatility. I highly encourage all who have demonstrated a serious interest in improving their skiing by persevering through the reading of this entire article to pursue the development of the balance skills we teach in our Balance DVD's. They're the very skills the best skiers in the world have developed through hard work and insightful coaching, and have used to achieve their success.