CUSTOM BOOT FITTING

by Dr. Robert Scott Steinberg
Getting to the Root of the Problem

You return to the ski shop complaining about THOSE boots you purchased two weeks ago. They're "killing" your feet, they don't fit right! Your inside ankle bones have been rubbed raw. You had to over tighten the buckles to get some measure of control. As a result, your circulation was cut off, and your feet got very cold. You do not have any idea what's wrong. Sound familiar?

Or, frustrated with the lack of edge hold, you want to demo a new pair of skis, exchange the boots for a different brand, or, at the very least, have some custom work done to the boots you are stuck with. You don't know which to try first. You just want to do something, but what?

As unlikely as it might seem, there is an easy CURE for these litany of ills, and the first place to begin is with the foot. Standing in the store does not put much of strain on the foot and ankle, so the boots you purchased felt great. But all that changes when you hit the slopes. When you make a turn, centripetal force loads the bottom of the foot with tremendous force.This in turn collapses the arch, the ankle bones drop, and the lower leg internally rotates. This places the center of the knee too far to the inside. Often, this is mistakenly viewed as a need for canting. It usually is not.
Prevention

What can be done to correct and prevent this biomechanical mess; prescription ski boot orthotics and custom boot fitting. The first thing is a custom insole, or an orthotic. What are the differences between the two? Custom insoles are made by ski shop technicians to accommodate and support the foot, and improve comfort. Prescription orthotics are medical devices, made by a physician, or made on his prescription, and CORRECT abnormal alignment of the foot, ankle, lower leg, and knee. A ski boot orthotic is far different then a running orthotic, so don't put running orthotics in you ski boots (For this article I will refer to both orthotics and custom insoles as "custom insoles.")

Custom insoles can alleviate the pain that saps the fun and excitement from a winter vacation, and replace it with comfort, warmth, and improved performance. Without adequate foot support, all skier's feet excessively pronate (collapse) to some extent. A properly molded and fitted custom insole improves bone alignment, relieving the ankle's tendency to chafe against the inside of the boot during edging and carving. They also greatly reduce the amount of knee angulation and canting required to achieve good edge-hold on hard packed snow.

Besides proper support, the correct custom insole helps the foot's natural shock absorber -- its arch structure of bones, ligaments, joints and muscles -- absorb the jackhammer impact of a session through the most ornery mogul field. For those few individuals with high arched feet (supinated), the extra layer of elasticity afforded by a custom insole, combined with improved distribution of foot pressure, greatly enhances comfort and performance. And, because even normal arches flatten during turns, every skier on the slopes will benefit from properly fitted custom insoles.
The Bones Inside the Foot

While foot structures differ, custom insoles are adept at improving skier comfort and performance by "managing" the foot and ankle's motion inside the boot. The human foot and ankle are formed by a complex system of 28 bones, more then 55 articulations (joints), at least 77 ligaments, and 13 plus muscle groups. Together, they move in more then one direction at a time, adapting to uneven surfaces, and changes in balance. They work as a system to absorb shock, put "spring" in your step, and "lock-up" to form a rigid lever for efficient propulsion.

As a Podiatrist specializing in sports medicine, I know that many feet and ankles are not biomechanically sound. As a ski boot fitter, I am also familiar with the problems experienced by skiers with poor foot structure. My research indicates that poor biomechanical alignment is a significant contributing factor in a skier's inability to "get-it-all-together"! A custom insole that offers the right combination of control, support, and flex, can go a long way in correcting most fit problems.

Walking and Skiing Stresses

The "normal" foot is designed to function through a regular gait cycle, such as walking or running, with a "strike-and-flex" pattern that begins as the heel hits the ground. Weight then progresses along the OUTSIDE edge of the foot, rolling from the outer portion of the ball of the foot toward the big toe. Weight is not supposed to pass though the longitudinal arch. Because the foot's bone structure is (in structurally normal feet) arched, both longitudinally and in cross-section, it can absorb considerable shock. This protects the foot, ankle and knee.

But unlike a gait cycle, alpine skiing places all the weight on the INSIDE edge of the foot, directly down through the arch. Visualize your body's position while making a carved turn. Your knee is angled inward and your weight is directed to the inside edge of the ski. This movement collapses the arch, and stretches the Plantar Fascia (a band of tight tissue on the bottom of the foot that connects from the heel to the toes). Over stretching this band causes the pain and burning (plantar fasciitis) sensation often experienced by skiers who otherwise have no other boot fit problems. If you do experience this pain, you will not be able to "push" your ski into a turn and keep consistent pressure to the edge. (This Plantar Fasciitis is also experienced by runners, rollerbladers, and areobic and step participants.)

The Unsupported Foot and Ankle

Listed below is a detailed list of the effect edging has on the unsupported foot:

1. The arch collapses and the instep moves up and down causing the ankle bones to 
    also move up and down.
2. The front of the foot spreads out and the foot lengthens.
3. The foot rolls from the outside to the inside as edging pressure is applied.
4. The above movements causes the ankle to shift to the inside of the boot increasing
    pressure and rubbing.
5. Finally, the leg follows, twisting and moving up and down inside the boot.

None of these movements contribute to efficient skiing. They are wasted motion and wasted energy.

Specifically, these dynamic motions create the following foot, ankle and knee problems.

1. As the foot spreads, there is an increased pressure along the big toe and 5th toe.
2. As the foot lengthens, the toes hit the front of the boot.
3. The medial ankle bone comes to rest on the lower ridge of the boot's ankle pocket;
    not a soft place.
4. Because the arch is unstable, it can not act as a shock absorber. Shock is then
    transferred to the knee.
5. When the foot rolls to the inside, the ankle slams against the inside edge of the boot.
6. Internal rotation of the leg stretches the Medial Collateral knee ligament. Knee
    angulation must be exaggerated to achieve edging.
7. The multidirectional moments of the leg irritates the shin and pinches the calf.

Addressing the Root Problem

Instead of stabilizing and cushioning the foot, many boot fitters "accommodate" sore spots with padding, wedges, and lifts. Even worse, they punch and stretch the shell. But, an expanded shell only gives the pronated foot MORE room to spread. The ROOT problems listed above still remain! This vicious cycle takes another "turn" when skiers have to over-buckle their boots in an effort to "hold" their foot still. This restricts circulation and results in cold feet.

A point to remember: The goal of a custom insole is to support the foot in its "neutral" position, blocking EXCESS motion. Make sure the custom insole material is not so rigid that it blocks all motion. This would interfere with the arch's natural ability to absorb shock. Some older custom insole systems produce very hard and rigid insoles. (Running orthotics also get very rigid at cold temperatures.)

Foot Types and Complications

Custom insoles help the "normal" foot maintain its neutral position, preventing excess pronation and the over-stretching of the Plantar Fascia. For those with already pronated (flat) feet, custom insoles prevent, (and an orthotic can correct) deformation of the foot's structure. The opposite problem, SUPINATED feet, created a different set of problems:

1. The foot has a high arch and thus a high instep.
2. The foot is less flexible, and often rigid.
3. The toes are often pulled back (hammertoes).
4. The supinated foot only contacts the ground at three points: heel, and 1st & 5th
    metatarsal heads.

The benefits of a custom insole can not be over emphasized for the supinated foot. It provides FULL contact to the bottom of the foot, and increases shock absorption.

Fit and Performance

I have discussed the many fits benefits provided by custom insoles. Increased performance will be the real payoff. Of course, we ski better when our feet do not hurt! In addition, the full contact support that preserves neutral position, stops wasted motion, and markedly improves edging efficiency. A skier will set and release their edge quicker, without over-twisting the knee. Keeping the knee in a stronger biomechanical position, affords additional protection.

Nineteen years of skiing, research, and custom boot fitting has shown that all skiers will benefit from custom insoles. This is the easiest, and should be the first step in customizing the boot's fit.

Dr. Robert Scott Steinberg is board certified in medicine and surgery of the foot and ankle. He is a surgical instructor and Director of Podiatric Medical Education at Norwegian-American Hospital in Chicago. He maintains a practice in Hoffman Estates, Illinois. In addition to his 24 years experience as a podiatrist, Dr. Steinberg has been custom fitting ski boots for over 19 years and is recognized by "Ski Magazine" as one of the country’s best ski boot fitters. He is a member of PSIA (Rocky Mountain and Central Divisions), was a member of the Vail/Beaver Creek Ski School for a season, and was also a consultant to the Vail/Beaver Creek Ski School for three seasons, doing research on the biomechanics of skiing as it relates to ski boot fitting. He is currently the director of boot fitting services at Aspen Ski and Patio, Barrinngton, Illinois, and a consultant to Kenny's Double Diamond Ski Shop and The Double Diamond/Jeannie Thoren Ski Clinic, in Vail, Colorado. If you have any questions: e-mail: doc@footsportsdoc.com; (847) 934-3777, or FAX (847) 991-1009. © 1985-1999