A human power conversion system incorporates two or more electric machines to aid in the powering of a vehicle through energy conversion. A first electric machine is coupled with the human powered input and acts as a generator when a human power input is not sufficient to produce electrical power that is provided to a second electric machine that propels the vehicle. The vehicle may be a bicycle and the first electric machine may be coupled to the crank. A bi-coupled electric machine including the first and second electric machines with a common rotor or stator may be employed and coupled to the crank and/or the driven wheel. Power produced by the first electric machine may be provided directly to the second machine or may be stored in a battery and used to propel the vehicle or power other electronic components.