A doctor bed is provided for holding a circularly cylindrical metering rod, including a housing of a homogenous material, which is designed with a cross section at right angles to the cylinder longitudinal axis of the metering rod and has a circularly cylindrical recess which surrounds the metering rod with a form fit over at least 180\xb0. The converter circuit comprises a switch arrangement with two or more controllable electric switches connected in a switching configuration and controlled so as to provide a current drive of electric energy from an associated electric source connected to a set of input terminals. The user preferably controls the actuation of a first actuator to incrementally pivot the exercise table about a support structure thereby inverting the user’s body.