Abstract: A arm extension exercise machine which utilizes a frame-journaled rotating effort arm which is mechanically linked to a frame-journaled rotating weight arm which, together with the frame of the machine and the connecting link joining them, form a simple planar double-rocking-lever four-bar linkage which acts in conjunction with the rotating weight arm to vary the resistive force applied to an operator's arm extending muscles through body-machine contact with the rotating effort arm throughout the range of the exercise movement.

Abstract: A frontal calf exercising machine which utilizes a frame-journaled rotating foot-engaging assembly to apply resistive force couples to the tops of an operator's feet and bottoms of his heels through circular paths about the axes of rotation of his ankle joints. This frame-journaled rotating foot-engaging assembly is mechanically linked to a frame-journaled rotating weight arm, which, together with the frame of the machine and the connecting link joining them, form a simple planar double-rocking-lever four-bar linkage which acts in conjunction with the rotating weight arm to vary the resistive force applied to the dorsi-flexing muscles of the operator's feet through body-machine contact between the operator's feet and the rotating foot-engaging assembly throughout the range of the exercise movement.

Abstract: A shoulder-joint horizontal-flexion exercise machine (pec-deck or pectoral fly machine) which applies a predetermined variably resistive force to an operator's shoulder-joint horizontal-flexion muscles through the use of a kinematically derived double-rocking-lever four-bar linkage, whose rocking follower lever constitutes a rotating weight arm to which weights are loaded, and whose rocking driver lever is mechanically linked, through rigid connecting rods, to a pair of offset rigid counter-rotating assemblies which rotate on axes which are approximately common with the vertical axes through the operator's shoulder joints. These counter-rotating assemblies contain body-machine force-transmitting contact surfaces which engage the operator's upper arms and apply resistive force to the same through circular paths about the vertical axes of rotation of the operator's shoulder joints.

Abstract: A leg extension exercise machine which utilizes a frame-journaled rotating effort arm, which is mechanically linked to a frame-journaled rotating weight arm, which, together with the frame of the machine and the connecting link joining them, form a simple planar double-rocking-lever four-bar linkage, which acts in conjunction with the rotating weight arm to vary the resistive force applied to the operator's leg extending muscles through body-machine contact with the rotating effort arm throughout the range of the exercise movement.