In the recent years, energy harvesting has become increasingly popular for powering low-energy devices. Therefore, human power has become a promising energy source in providing electrical energy. Thus, the general principles, structures, requirements and potentials of human kinetic energy harvesting technologies are presented. Commonly, human kinetic energy harvesting systems have to be adjusted to the human locomotion. For the purpose of maximizing the power output, results of biomechanical analyzing methods are presented to identify resonant frequencies and bandwidths. With focus on inertial electromagnetic generators, further challenges and potentials are discussed to optimize the power conversion. In doing so, mechanical and electrical characteristics of the generator structure are examined and optimization problems are derived. One major issue within power maximizing is to match the resonant frequency and achieve a suitable electromechanical coupling. Parameter dependencies are identified by using analytic and numerical representations of generic electromagnetic generators.