mechanism 12 includes a pair of rocking links 36 and 38 that are rotatably attached at their upper ends to an upper shaft 40 by a set of bearing mounts indicated at 42 and 44 in this embodiment the upper shaft 40 is mounted on the vertical support structure or member 17 such that the lower ends of the rocking links 36 and 38 can have at least a limited arcuate motion in the preferred embodiment the shaft 40 is mounted for example by a set of bearings on the member 17 such that it can also rotate also included in the mechanism 12 are a pair of rocking link shafts 46 and 48 that are secured in the lower ends of the rocking links 36 and 38 by another set of bearing mounts indicated at 50 and 52 the bearing mounts 50 and 52 permit the rocking link shafts to rotate on the lower ends of the rocking links each of the rocking link shafts 46 and 48 has attached to it for rotation an outer crank arm 54 and 56 respectively the ends of the outer cranks 54 and 56 are then pivotally connected at a hub 58 and 60 to the pedal links 22 and 24 thereby serving as a connection assembly of the pedal levers 22 and 24 to the rotating rocking link shafts 46 and 48 also attached for rotation to the rocking link shafts 46 and 48 are a.