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Boot Fitters Alignment Is Key Says Dr D
Article reproduced with permission from Dr. Matt DiStefano (jdistefa)
Original publication: Winter '09 edition of Starting Gate magazine, Alpine Ontario (c) all rights reserved.
ALIGNMENT IS KEY, SAYS DR D
Alignment of the lower extremity in skiing has been subject to a considerable amount of voodoo. Fortunately, the subject has been written about with a great deal of clarity since the early 1970s.
Attention to alignment is best seen in motorsports. Constant changes in suspension set up are made in response to tires, temperature, moisture, track, and driver preference. Cars are aligned in three dimensions camber, caster, toe - much like we can do with ski boots. Historically, ski race equipment testing has been focused on skis (tires) and little attention has been paid to the systematic assessment and testing of boot alignment (suspension).
What are the benefits of improving alignment? Carving is a result of technique, equipment and alignment. Poor alignment can impact efficiency, training volume, and perhaps even safety. Loose and dynamic balance is enhanced by improving alignment to create a big sweet spot on the skis. Fighting the equipment demands compensation in technique and a Loss of relaxation and feel which impacts speed.
The boot should not interfere with mobility, yet has to be stiff enough to transfer energy to the skis. The shell should be contoured around bony prominences to minimize pain. A narrow toe box will impair balance by pushing the big toe laterally which de-functions the medial column of the foot. Consider shaping the shell to allow for movement of the inside ankle bone and navicular. Measure canting both before and after shell shaping – often the apparent requirement for canting will be minimized after appropriate shell work.
As a general rule of thumb, stiff orthotics go in soft shoes, soft orthotics go in stiff shoes. Since a ski boot is the stiffest shoe out there, a flexible foot bed maintain some degree of mobility. Pronation is a required movement in skiing - overly stiff or contoured footbeds will block technique. The last of a race ski boot already does much to support the foot. Significant foot deformities should be corrected by accurate posting angles, including the forefoot if necessary. Any posting should respect the inherent varus angles present in some bootboards. Do not expect un posted footbeds to make a big difference in static canting measurements.
Cuff adjustment aligns the cuff to the same angle as the lower leg so that the skier can stand on a flat ski. Cuff alignment is adaptive not corrective. It has minimal impact on knee alignment unless set at extremes of range. Canting corrects the position of the knee relative to the working edge of the ski. Use shims under the boot or between the binding and ski. Make small incremental adjustments. Grind bootsole to desired amount, add plates, and use cat tracks to protect the correction. Canting probably functions more as a proprioceptive 'nudge' rather than as an absolute correction. Always assess the result on hill- that is the gold standard, not an indoor measurement.
Never cant a knee more than 2 degrees inside. This preloads both the MCl and ACl and puts the knee at higher risk for injury. Canting to reach a technical goal rather than biomechanical correction is misguided, and again risks injury.
Fore/aft balance can be adjusted by changing the delta (binding platform) angle, ramp angle, heel lift, forward lean shim, and boot flex. Gender, calf muscle volume & height, ankle flexibility, degree of pronation, and foot:tibia:femur length ratios all need to be considered when making fore/aft adjustments.
Watch the athlete ski in different turn shapes at speed on hard snow to assess alignment. Don’t be afraid to measure, test, video, and use timing to confirm your impressions. Encourage feedback from the athlete. Don't just read - do: Modify your own equipment and test it so that you develop a kinesthetic understanding of these principles.
Visit www.alpineontario.ca for more on this story
The Athletic Skier, Warren Witherell & David Evrard
The Skier's Edge, Ron LeMaster
www.gmolfoot.com Greg Hoffman
Anyone with questions on this article is welcome to send a Private Message to jdistefa, and he will post a reply in the thread.
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