The video illustrates a tremor compensation system using electrical stimulation. Based on information from wearable sensors, the controller applies higher currents to induce stronger co-contraction whenever tremor increases. Tremor is produced using an auxiliary stimulator.
You can find detailed info on the corresponding paper1.
References
1.
Bo, A. P. L. & Poignet, P. Tremor attenuation using FES-based joint stiffness control. in 2010 IEEE international conference on robotics and automation vol. 1 2928–2933 (IEEE, 2010).