A direct application of the variable-gain super-twisting algorithm (VGSTA) is implemented for torque feedback on a handlebar of a riding simulator. This control strategy aims to compensate perturbations changing with the system states. Thanks to the good tracking performance and robustness/insensitiveness of such a control method, a precise estimation of the rider's torque applied on the riding simulator handlebar is possible. A first-order sliding-mode observer with stabilization is designed for the estimation of the unknown input rider action. Experimental implementation and analysis are provided to point-out the effectiveness of the proposed approach.