Abstract: Double crank alternating cycle traction system in which two independent free-turning cranks with a dynamic articulation at the place where the force is applied are strategically added to a conventional pedal cycle. The operation of the resulting mechanical composition increases the mechanical advantage of the original system. The invention is applicable to pedal cycles, mainly all kinds of bicycles, i.e. bicycles, tricycles, four-wheeled bicycles, moved by the extremities of the human body, i.e. the hands or feet.