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Abduction Junction

The shape of things to come


by Brent Amsbury, Certified Podiatrist

The last few seasons, if you have been really keeping your ear close to the ground regarding ski boots, the biggest rumbles have been made on a idea of lasting (foot shape of footwear) ski boots with an abducted stance.

For those of you who are wondering what abduction means, it is this. To stand with your feet pointing out like a duck.

A majority of the human population will naturally stand in this position when asked to stand erect and comfortably.

A small portion of the human population will not, they will stand either with their feet straight ahead of them, or their feet will point inward, not unlike another fowl, the pigeon. Thus the moniker, pigeon toed.

Ski boot manufacturers have all had some experience with building other footwear other than ski boots. Many manufacturers either began their operations ages ago either building ice skates or hiking boots, and all them understood that to make either types of footwear comfortable for the masses, you had to design a shape that fit the greater majority of foot shapes and stances out there. Therefore the slightly abducted stance became the default pattern for all footwear, including ski boots.

Abduction has always been an essential part of ski boot building, not only for comfort, but to help drive the center of knee mass over medial (inside) portion of the foot. To help you understand this better, stand up right now and stand with your feet pointing straight ahead. Now, flex at the knees and watch where your knee wants to track relative to the position of your foot. In the majority of cases, it will track laterally (outside) towards toes 3 to 5.

Now put your feet in an abducted position, lets say about 5 degrees out, just slightly duck footed. Flex again at the knees and watch the knee tracking. Again, in the majority of cases, the knee will now track right over the big toe. This is exactly where a ski boot needs to drive the majority of forces from your lower extremity through the knee and into the ski. Get this knee tracking just right, and balancing on a ski edge or ice skate blade becomes almost effortless.

With the advent of shape skis, a couple of bugaboos began to appear in regards to ski boots. First, most boots only had slight amounts of abduction in their lasts, so with some skiers their knees would still continue to track slightly laterally.

On a shape ski, this could have very disappointing results. Because the outside edges of the skis have just as much sidecut as the inside edges, even the slightest bias of force to the outside side would cause ski tracking and turning problems. Second, a straighter lasted boot will distribute it width fairly equally on both sides, so on the inside (medial) there will be a significant amount of ski boot extending over the ski. With the increased edge angles that shaped skis were capable of, the phenomenon of 'boot-out' began to appear. While skiers were happily testing the new frontier of carving with deep trenches and extreme edge angles, their boot would hit the snow and release their ski from the carve.

Of course, this could lead dangerous crashes and many racers were known to grind or shave material from the outside shell of their boots to give them precious extra millimeters of clearance.

In response, two immediate changes came into effect. The narrowing of boots, ie. the 'plug' boot, and an increased amount of abduction into the last of ski boots. The first manufacturer to label this lasting change was ATOMIC, with the 'differential' concept. These boots had more abduction in them, thus the inside of the boot was moved away from extending over the ski. The result was less boot-out and a stronger bias to drive the knee over the medial part of the foot towards the big toe.

Some manufacturers, instead of increasing their abduction, most notably LANGE and NORDICA, instead went to narrower boots with thicker inner shell walls, so if more abduction was needed, it could be shaped into the last post production via a technician with a grinding tool.

One notable application was Dachstein (now defunct), the heel had a mechanical pivot operated by a worm drive and hex wrench, so the heel ledge could rotate from abduction to adduction to customize the knee tracking according to the needs of the skier.

Alas, the evolution of abduction was not satified.

FISCHER skis, in an effort to debut an all new line of ski boots, introduced the SOMA concept. This was a radically abducted ski boot, where the heel was now centered inboard of the ski boot sole, and the forefoot much further outside of the boot sole. Their conclusion was that with shape skis being the default standard of skiers in the world, that skiers should be standing as naturally on their skis as they would be in their street shoes.

NORDICA just recently followed suit with their Aggressor ski boots that are also radically abducted. Nordica instead of rotating the foot in the center (which inboards the heel, and outboards the forefoot) like Fischer, only rotates at the heel which displaces only the forefoot.

Both of the these methods achieve similar results. The knee tracking forces not only are biased to the inside edge to a greater extent, but the tracking force continues to follow the radius of the ski through the apex of the turn.

There are advantages and disadvantages to this current trend of abduction of ski boots. The advantage being that younger ski racers and skiers growing up with these more naturally stanced ski boots, will be able to achieve a higher level of performance on shape skis than those who transitioned through the evolution of straighter lasted boots and straight side-cut skis. Current World Cup racers are still using the straighter lasted ski boot shape, but developing juniors on being supplied the abducted models. The disadvantage is that for the minority of the human population that does not naturally move or stand in an abducted stance, this boot trend could potentially alienate them from the sport of skiing.

Currently, most recreational ski boots still use the less abducted stance that has been the standard for the past 20 or more years, and boot manufacturers have been only applying the greater abduction to race and performance models.

I hope that ski boot manufacturers with their recogniton of abduction and its benefits, they will also recognize that there are skiers that cannot and will not be able to use this current trend.

Happy skiing!

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