an article of sport footwear with a shell formed with two , respectively forward and rearward , longitudinally opposite openings which extend from a shell entrance and identify two lateral sides , with a bootleg pivoted on the shell and at least one fastening device bridging the corresponding opening and being adjustable in length , whose opposite ends are anchored on respective lateral sides of the shell proximate to the entrance to limit the rearward swing range of the bootleg and / or the forward flex of the boot .