A boot that includes a shell base and a collar, an articulation provided between the collar and the shell base, such that the collar can pivot with respect to the shell base about an articulation axis, which is substantially perpendicular to the longitudinal axis, and further including a device for blocking the rearward rotation of the collar with respect to the shell base, the devices for blocking the rearward rotation including the following: a rocker mounted so as to rotate with respect to either the collar or the shell base, around a first pivot, the pivot being oriented along a first axis and the rocker having an elongated shape between an upper end and a lower end, and the first pivot being positioned in the vicinity of one of the two ends; a support base, positioned in the vicinity of the other of the ends, including a first support surface, which is capable of coming in contact with either the shell base or the collar; and a lever mounted so as to rotate with respect to the rocker around a second pivot, the second pivot being oriented along a second axis, parallel to the first axis, and the second pivot being positioned between the first pivot and the support base, the lever including an actuating palette and a cam surface.