Online Exclusive: Who Needs Custom Footbeds?

Published February 28, 2006 09:10AM

During the mid stance phase of walking (when the foot is in total contact with the ground) the foot is in a mobile adaptive or flexible condition. It is supposed to “pronate” to reduce shock to the leg, knee and back. This is the position the foot is in when it is “fixed” inside a ski boot. It is because the foot is flexible inside a ski boot that issues of foot pain and loss of turning efficiency come into play.

In a ski turn the foot must bear a load up of to 3 times your body weight. Boot fit problems occur as the foot is forced to pronate (flatten) causing pressure of the foot against the boot shell. Typically this pressure occurs at the base of the little toe (sixth toe syndrome), the navicular and medial malleolus (inside ankle bones), and heel. Also, because the foot is flexible, the muscles and tendons of the foot are “fighting back” to resist the pronatory movement (flattening of the arch) causing aching in the arch and mid-foot. The obvious cure for this foot pain is to provide more architectural support for the foot in the boot.

Everyone’s feet are different and boot manufacturers design the boots to fit the greatest variety of feet possible. If they were to make the footbeds in the boots too supportive it would “offend” some peoples’ feet and therefore they would not buy them. This is also why boot manufacturers tend to make their liners very cushioned, to initially feel comfortable to the greatest variety of foot shapes. The problem with this approach is that if the liner is too soft there is a corresponding loss of performance as the foot moves inside the shell.

On the performance side, because custom footbeds/ski orthotics reduce pronation there is a more direct and efficient transfer of pressure from the lower leg to the ski edge. As the knee passes over the mid line of the foot, leverage to the edge is maintained by supporting the foot so that energy is not lost to the foot flattening. You can demonstrate this to yourself by standing with your shoes off and knees flexed over the toes. As you move your knee to the inside, you will notice the foot flattening as you start to exert pressure on the inside. This flattening of the foot translate to a loss of the effective lever arm of the lower leg to the ski edge.

Most of the ski orthotics/footbed systems use a semi-weight bearing method of capturing the shape of the bottom of the foot. Material is heated in an oven and the foot impression is taken by standing on or pressing the foot into a “pillow”. This provides a very natural model of the bottom of the foot without creating too much arch. It is not desirable to have the arch too high as this will tend to throw the knee to the outside making it difficult to get leverage on the ski edge. After the ski orthotics / footbeds have been molded to the foot, there needs to be materials added to insure stability of the ski orthotics / footbeds in the boot.

The need for canting the bindings on the ski is greatly reduced by providing proper foot support in the boot while aligning the knee between the first and second toe. This is the optimal position of the knee just before the ski edge is pressured. However, for some people it will not be possible to get the knee into this position if they are excessively bow-legged, knock-kneed or have ankle inflexibility. In these cases it will be desirable to have cants or wedges placed under the bindings to help put the skier into the most efficient position possible.

If your feet have stopped growing, your ski orthotics/footbeds should transfer to your next pair of boots. Some minor trimming or adjustments may need to be made. However, the ski orthotics/footbeds for your ski boots may also work in your in-line skates. Footbeds designed for skiing will not work well in other footwear because they will most likely be too narrow and the materials too stiff. Using your ski orthotics/footbeds in shoes that flex at the forefoot will likely cause them to crack.

Your ski orthotics/footbeds can dramatically change the way a boot fits. With the foot supported, you may find that you will fit into a boot at least a half size smaller. This is because with proper support, the foot will not lengthen as it does when it pronates (flattens). The foot will also not be as wide if the mid-foot is supported. If there is an adjustment that can be made to the cuff of the boot, it should be done with the footbeds in place.

For more information on custom footbeds and orthotics, please visit www.footdynamics.com.