In the age of fossil fuels, human power was neglected but the hazardous environment pollution caused by fossil fuel again brought the human power resources in the stream of renewable power resources. So in recent past, vast research has been taking place to harness human power for energizing various process units. This review paper is based on one of that renewable power resources which is human power. Human has applied energy through the use of arms, hands and back, with the invention of bicycle and pedaling, legs also began to be considered as a means to develop power from human muscles. A person can generate four times more power by pedaling than by hand-cranking. The power levels that a human being can produce through pedaling depend on how strong the pedaling person is and on how long he or she needs to pedal. If the task to be powered will continue for hours of time, 75 watt mechanical power is generally considered the limit for a larger healthy non-athlete. A healthy athletic person of the same build might produce up the twice the amount. Therefore human power may be used for a process if the power enables a person to drive device at same rate as that achieved by hand-cranking but with far less effort and fatigue.