04 Performance

The myth of flex

Somewhere in the history of skiing, the concept of knee flexion became integral to the collective notion of performance skiing.   Granted, some range of movement is required, but nowhere near what one might think.  Particularly not on contemporary skis.  And probably not in the direction one might assume.

The amount of flex required of a boot is dictated by the intended end use, and how ‘misaligned’ the user is while in that particular boot.

A downhill racer will want a ‘softer’ boot than a slalom specialist, to favor glide and ‘float’ over impulse (force x time).  A mogul skier will want more range than a skier who never leaves the groom, as the demands on the suspension system is greater. In this context, too much flex will allow the distal end of the tibia to ‘crash’ into the Astragalus/Talus. (I have seen the x-rays…)

In general, the average skier should require little more flex than is allowed by compression of the padding in the tongue.  The desire for more is a pretty good indicator that one or more geometric parameters is out of whack.  Granted, more flex will act as a bit of a ‘movement filter’ allowing mistakes to go unpunished, and this can be a good thing for the novice.  However, the feedback loop is compromised when the plastic does not provide ‘pushback’.

‘Bending’ a boot has little or nothing to do with strength. Skiing well in a stiffer boot, however, has a lot to do with finesse.

Knee tracking?

Knee tracking has about as much to do with quality skiing as does boot flex. Assuming we are not always equally weighted on both skis, and assuming the mobility of our hips and ankles has not been compromised, accommodating some deviance should not be a problem….

On the other hand, many skiers have difficulty progressing beyond the ‘open parallel’ stage, precisely because equipment affects their mobility.


“I’m picking up Good Vibrations…”

Performance boots deliver greater performance not only due to their stiffer flex (which translates subtle and accurate movements), but because the firmer plastics generally enhance the sense of touch.

As an organism, we are largely dependent on our sense of touch for spatial awareness. The ‘transmissibility’ of our boots thus affects our movements.  The more we can feel of the surface beneath our feet, the more intuitive our movements will be.  If we dull our sense of touch with a ‘dead’ plastic, the ride may feel smoother, but we will become more reliant on our sense of sight, and our movements will become more hesitant and ‘mechanical’ as a result.  This is especially noticeable in foggy, stormy weather, and/or the surface softens.


Liner composition will also affect spatial awareness and feedback.  This is perhaps the primary reason why ‘race room’ or plug boots come with minimalist liners that are both very thin, and unfortunately, cold.  In recent years, these liners have improved drastically, using more durable and warmer materials.

Many stock liners use an outer covering that does not stretch.  If your foot feels restricted in the liner outside of the shell, you can provide some ‘give’ by carefully slicing through the outermost layer of fabric in the affected area(s).

The liner is the intermediary between the shell and your foot.  As such, the materials matter, but there is little sense in spending a wad on a custom liner until the rest of the boot geometry has been customized.

One can easily spend a lot on aftermarket liners, without an appreciable improvement in skiing performance.

Regardless, comfort, warmth and performance need not be mutually exclusive.   The only requirements: A bit of interface engineering.  And time.  And money.

I. Newton and foot structure.

Newton’s third law states something to the effect that ‘for every action, there is an equal and opposite reaction”.  E.G., you would not notice the contact between your Navicular bone and the boot shell on a weighted foot, if the snow surface was not pushing back at you.  Which means that the collapse of your foot in the boot is activating your ski, even when you may not intend to do so.  The shell is there to support your foot, and transmit intentional inputs to the ski.  Most of those inputs should be directed downward, through the sole of your foot, rather than sideways.  Uneven medial/lateral shell contact may also knock your ankle joint ‘out of line’ once the ski begins to talk.  This will affect your mobility, and limit some of your movement options.  Imagine skiing well wearing a sneaker.  Then imagine invisible support around that system.


Sunlight and heat are the sworn enemies of the ski boot.  For health and long life, store them in a cool, dark location.  Boot plastic will eventually ‘die’, and either tear, snap apart, or become so lifeless that you will feel like your feet are in a fog.