freely a return system not shown makes it possible to reposition the mechanism on restarting in one particular embodiment of the invention said at least one wheel is set in rotation progressively the demultiplication between the displacement of the operating member and of the rolling object is not constant but decreases so as to make best use of the effort applied to said member it is convenient to start the rolling object with a high level of demultiplication which may then decrease as the rolling object accelerates this may be achieved with existing mechanical systems such as rod or cable systems spiral gear systems as described in french patents 0309582 and 0406393 spiral pulley systems as described in the as yet unpublished french patent application 0508771 or by any other per se known variator system in one particular embodiment of the invention the speed of displacement of the rolling object reaches the speed of translation of the operating member which permits continuous movement at the end of the transitional speeding up phase of the rolling object this equality of speeds is obtained by carefully calculating the demultiplication of the mechanism and may ideally take the form of the operating member coming into contact with a stationary part of the rolling object causing the operating member to function identically to an operating member of a conventional rolling object it will be noted that continuity between the end of the transitional phase and the continuous operating mode is in the spirit of the above stated patents in one particular embodiment of the invention the.