A design for snowsports devices such as skis and snowboards uses non-Newtonian materials. Non-Newtonian materials exhibit rate-sensitive characteristics, with stress vs. strain properties dependent on the rate of loading. The snowsports device with non-Newtonian materials has variable stiffness and damping, with both increasing according to an increased applied load-rate such that a single snowsports device exhibits soft flex characteristics under low applied load-rates, but stiffer flex characteristics under high applied load-rates. The flex of the snowsports device is self-adjusting, with no manual adjustment input required by a user. The non-Newtonian material may be incorporated into the structure of the snowsports device in a number of different ways, including in the core, in composite sheet layers, and other locations.