Sports boot equipped with an immobilization device during the pivoting of the upper

A rigid shell sports boot comprising:

• a shell base overhung with an upper adapted to pivot in both a front-to-rear and rear-to-front directions, the upper being provided, in a dorsal zone with an immobilization device with respect to the shell base, said device being active in at least one of the pivoting directions by means of an abutment zone obtained on said shell base, the immobilization device being equipped with a maneuvering member equipped with a rotational cam that acts on a mobile element adapted to cooperate, in a given angular position of the cam, with the abutment zone of the shell base, wherein the immobilization device comprises a second mobile element that can be actuated by means of the rotational cam and that is adapted to cooperate with a second abutment zone obtained on the shell base in at least one given angular position of the cam, the cooperation of such second mobile element with such second abutment zone being adapted to bring about the immobilization of the upper in at least one of its two pivoting directions, the cooperation of the first mobile element with the first abutment zone bringing about the immobilization of the upper in the other of its two pivoting directions.