English: Video of a complete use session with a gyroscopic exercise tool, from 'winding up' with a shoe string until stopping the fast turning movement with the second, unused hand. In between, the man stops the hand movement and lets the rotor run for a short while without force, before making a slight movement with the holding hand to continue exercising.
The physics of the device is more complex than seems at first sight even to an engineer or physicist. In the video, it can frequently be seen that the yellow fast rotating mass makes also a second, slow movement of max. some rotations per second, which results from the two ends of its main turning axis wandering around in the groove in the ball-shaped hull. This is not erroneous as it may first seem, but a "natural" behaviour of the device even necessary. The ends of the main turning axis transmit the forces from the rotor onto the ball via this groove, and the different individual forces at the two ends of the axis produce the slow turning movement, as they lead to different frictional forces of the fast turning axis ends in the groove.

Warning: The shown speeds are in part very high and lead to high forces acting on the arm muscles and bones. For normal and regular exercise, lower speeds are recommended.