A sport boot, particularly for performing a gliding sport, produced from an outer sole capable of being fastened at least to one forward part on a gliding member, and including a lower shank connected to a rear heel cap on which a rigid collar is hinged which is designed to surround the lower leg and which extends towards the top of the shank starting from the hinge beyond the upper end thereof, the boot also including an energized arrangement for the angular longitudinal control of the gliding element in the air in respect to the sole of the boot during the phase of advancement of the gliding element, which are disposed between a fixed point of the shank and a movable point of the hinged collar, and which include at least one resilient member constituting an energy source capable of being tensed in the course of a pushing phase on the ski and to relax in the course of the advancement phase, wherein the resilient member which constitutes the energy source is connected with a disengaging arrangement such that it is activated only between a position of the boot of equilibrium which is essentially median, and a position at the end of pushing.