Monday, November 20, 2017

When is the ski boot is a liability for a ski racer?

Getting a boot set up on world cup skiers, is not as easy at it may first appear. The best skiers are in very stiff boots, and they dictate how you will stand on your skis. If the angles are not correct relative to the leg and ankle, adaptive movements are required to overcome the mis-alignment.

How is the correct set up achieved? The process starts with a complete analysis of the foot and ankle. Also, a fitting evaluation is incredibly important, especially for how the ankle and foot sit in the boot.  Next is analysis of how the boot cuff acts on the leg. This is measured statically standing and can also be done dynamically indoors on an angled slant board. The last but not least part of the set up is the boot sole canting angle. 

All of these steps leads to a functional alignment of the leg, boot and ski. This helps the skier move the body optimally to align with the forces working on the body.  When one part of this process isn't right, adaptive movements become part of the skier's technique. 

The top racers on the World Cup are great athletes and they can adapt to a compromised boot set up. Although to the regular viewers the skier maybe skiing fine, the ski actually isn't doing the job it could with the right set up, therefore, it affects speed down the course.

The lines or arrows demonstrate the mis-alignment, those lines should be more parallel and in line with each other. The ankle/boot is leaning or positioned outboard relative to the angles the skier would want to produce. Although the ski is bend at this instant in the sequence, this cannot and it will not, be held, or sustained. The ski will let go because the forces are not in line with the boot. The forces are too strong for the boot to be holding the ski/ski on edge. Notice how far the skier is leaning, this is adaptive, when the boot can't get to the angles needed the skier adapts by creating less ideal angles with other parts of the body or movements, that they feel can help. With this set up the ankle is locked out of the most necessary movement a skier at this level should be able to create.
Above the gate the angles are not developed yet with the lower body, the legs are stiff, not moving to create angles. All the weight is on the inside ski.

The blue arrow points to a de-cambered ski, which has no pressure on it. The red bent arrow shows what the ski should be doing, bending into an arc. All of the body is balancing on the inside ski, not ideal for this phase of the turn. The upper body is leaning away from the forces under the foot, rather than toward them. When the ankle is blocked and the cuff too strong this is a common look, at all levels of racing.

The untrained eye will except this as the best one can do in a tough turn on very hard snow. However if you compare this to the same skier in the same type of turn in previous boot set ups, there is a huge difference. You can visit other posts here on this Blog, to see the differences for this skier's technique.


horizonstar said...

Great long video and analysis of Shiffrin's Killington GS form by Reilly. You guys read from the same play book!

Unknown said...

So I don't understand it at all. Looks like in this day and age athletes do everything possible to get the competitive advantage. Often illegal stuff . Just look at Lance Armstrong or Russian Olympic team . Then it becomes mind-boggling to me that the athlete of Shiffrin caliber would not do something that's legal to improve her chances. If boot set up an alignment is available, why would not she use it ??? Don't get it. Please explain.

Harald Harb said...

Alex, you are right, you would wonder why? The reason is they either don't see it or they don't know how to fix it. Sometimes the arrogance of the boot companies is so big they tell the racer there is nothing wrong, because they set up everyone like this. I know of many occasions when an athlete has been told, it works for our best racers so it's good enough for you.