Boot intended for use in a physical activity using a sliding or rolling sports device, in which the heel of the boot is free during the movement of the foot, this boot comprising: - a base (12, 120, 200), - adapting means (25, 140), comprising ∘ an element for binding to the sports device, that is to be attached in a front region of the base of the boot, with respect to a direction of extent of the foot, and ∘ a heel that is to be attached in a rear region of the base of the boot, with respect to said direction of extent of the foot, it being possible to attach each one removably with respect to the base, characterized - in that said binding element and said heel are connected by a planar flexible leaf (12, 120, 200), the flexible leaf being an integral part of the base (12, 200) or a part used in conjunction with the base (12, 200), wherein the base can comprise walls (201, 203) and possibly a part forming a reinforcement, in order to hold the rear portion of the upper of a boot, - in that the boot further comprises removable means (222, 223, 225, 227) for varying the flexibility of the flexible leaf, these removable means comprising one or more inserts or pins (222, 223) and/or one or more plates or leaves (225, 227) that are to be inserted into said flexible leaf or against the latter, and - in that the boot comprises means (481-484, 4801-4804, 92, 94, 96, 97, 920, 940, 960, 970) for attaching, by means of screws or using slides or by clipping, the adapting means (25, 140) with respect to the flexible leaf, in one position or in multiple positions that may be discrete or continuous. - a base (12, 120, 200), - adapting means (25, 140), comprising ∘ an element for binding to the sports device, that is to be attached in a front region of the base of the boot, with respect to a direction of extent of the foot, and ∘ a heel that is to be attached in a rear region of the base of the boot, with respect to said direction of extent of the foot, it being possible to attach each one removably with respect to the base, characterized ∘ an element for binding to the sports device, that is to be attached in a front region of the base of the boot, with respect to a direction of extent of the foot, and ∘ a heel that is to be attached in a rear region of the base of the boot, with respect to said direction of extent of the foot, - in that said binding element and said heel are connected by a planar flexible leaf (12, 120, 200), the flexible leaf being an integral part of the base (12, 200) or a part used in conjunction with the base (12, 200), wherein the base can comprise walls (201, 203) and possibly a part forming a reinforcement, in order to hold the rear portion of the upper of a boot, - in that the boot further comprises removable means (222, 223, 225, 227) for varying the flexibility of the flexible leaf, these removable means comprising one or more inserts or pins (222, 223) and/or one or more plates or leaves (225, 227) that are to be inserted into said flexible leaf or against the latter, and - in that the boot comprises means (481-484, 4801-4804, 92, 94, 96, 97, 920, 940, 960, 970) for attaching, by means of screws or using slides or by clipping, the adapting means (25, 140) with respect to the flexible leaf, in one position or in multiple positions that may be discrete or continuous.