FR 82.17503 discloses such a boot designed more particularly for competitive use.
In this known boot, the internal tightening device is constituted by two sections enclosing the instep area, which are attached at one end to the mounting insole and are equipped at their free end with supplementary tightening means, constituted, for example, by a lacing system.
Such a construction makes it possible to obtain excellent position maintenance of the foot in the boot and to center the foot on the sole. It is thus particularly well suited to the practice of alternating steps.
Given the development of the new skater's step technique, this tightening device is found to embody certain deficiencies, illustrated in FIG. 1, which illustrates the assembly of a known boot 1 with a ski 2 in the thrusting phase during the performance of the skater's step.
As this figure shows, in this phase the skier exerts on the ski 2 a thrust directed laterally to his path.
Under the effect of this thrust, the foot tends to flatten against the outer edge 1a of the boot, such that the thrust force P of the skier is exerted on the outer part of the ski.
The vertical resultant Pv of this thrust force then constitutes, along with the reactive force exerted in the vertical direction R by the snow 4, a moment of force which is especially pronounced because the lever arm d between these two forces is high. This moment of force tends to force the ski flat against the snow, thus impairing the biting action of the edge required for this phase of the movement.
Furthermore, when not in the thrust phase, the foot tends to become recentered in the boot, thus bringing about lateral movements of the foot within the boot which generate friction and the risk of injury.