Abstract: An energy absorbing unit for physical exercising devices is arranged as an asynchronous motor the stator of which has windings to be connected to an AC supply and cooperates with the rotor of ferromagnetic material having a circular circumference, and an input shaft and an epicyclic gearing arranged inside the rotor circumference operatively connecting the input shaft to the rotor with the input shaft adapted to be driven by the training person, in order to generate an electromagnetic motive force on the rotor to tend to drive it in the direction opposing movement of the shaft by the training person and thereby act as a braking force on the shaft independently of the movement thereof.