a cycle that uses both arm and foot motions to drive it . unlike other designs that connect the hand and foot movements to a single crank mechanism , the instant design uses two sets of gears that are stacked . four straight toothed racks are positioned between the drive gears . the toothed racks are connected to the hand and foot levers so that as the levers are manipulated , the racks are moved back and forth . this reciprocating motion turns the gears , transferring energy to the main drive gear , which turns the wheels . the drive gears are paired so that one set is always providing power from each operating lever . the operating levers are designed to alternate -- i . e ., left hand forward left foot back at the same time as the right hand is back and the right foot is forward . thus , with each stroke , power is transmitted to the wheels .