Abstract: A treadmill exercising apparatus of the inclineable slider bed type in which the apparatus frame at its head end is equipped with a cross member that is coupled to a pair of spaced apart threaded screw members for changing the inclination of the treadmill frame, in which the coupling of the frame cross member to the respective threaded screw members is by way of special nut assemblies that each include a tubular member or shell fixed to the respective ends of the frame cross member, a lower nut member that is keyed to the tubular member involved at that end of the cross member, and is in load transmitting relation to the screw member it engages, and on which, the respective tubular members rest, and an upper nut member that is keyed to the respective tubular members for lost motion movement relative thereto, but which is not in load transmitting relation to the respective screw members, whereby the upper nuts are free to float longitudinally of the respective screw members to accommodate tolerance variations