A ski includes an elongated ski body having a bottom layer defining a bottom surface of the ski, a top layer defining a top surface of the ski, and a middle layer disposed between the bottom layer and the top layer, in which the middle layer includes a negative Poisson's ratio (NPR) foam material having a Poisson's ratio of between 0 and 1.

A ski includes an elongated ski body having a bottom layer defining a bottom surface of the ski, a top layer defining a top surface of the ski, and a middle layer disposed between the bottom layer and the top layer, in which the middle layer includes a negative Poisson's ratio (NPR) foam material having a Poisson's ratio of between 0 and 1.

A binding system for attaching a snowboard boot onto a snowboard, wherein the binding system has a first portion suitable for being attached or secured to a boot and a second portion suitable for being attached to a snowboard. The first portion has at least one pin. The second portion includes a base structure suitable for being attached to the snowboard and having at least one engagement seat, a spoiler pivoted to the base structure having at least one attachment seat suitable for engaging the at least one pin of the first portion, a lever pivoted to the spoiler suitable for locking or unlocking the spoiler, and a spring that pushes the lever toward the locking position.