Human power

Human power is work or energy that is produced from the human body. It can also refer to the power (rate of work per time) of a human. Power comes primarily from muscles, but body heat is also used to do work like warming shelters, food, or other humans. World records of power performance by humans are of interest to work planners and work-process engineers. The average level of human power that can be maintained over a certain duration of time⁠ is interesting to engineers designing work operations in industry. Human-powered transport includes bicycles, rowing, skiing and many other forms of mobility. Human-powered equipment is occasionally used to generate, and sometimes to store, electrical energy for use where no other source of power is available. These include the Gibson girl survival radio, wind-up or (clockwork) radio and pedal radio. Normal human metabolism produces heat at a basal metabolic rate of around 80 watts. During a bicycle race, an elite cyclist can produce close to 400 watts of mechanical power over an hour and in short bursts over double that—1000 to 1100 watts; modern racing bicycles have greater than 95% mechanical efficiency. An adult of good fitness is more likely to average between 50 and 150 watts for an hour of vigorous exercise. Over an 8-hour work shift, an average, healthy, well-fed and motivated manual laborer may sustain an output of around 75 watts of power. However, the potential yield of human electric power is decreased by the inefficiency of any generator device, since all real generators incur losses during the energy conversion process. It is possible to use exercise equipment for power generation, by attaching the moving parts to components of electric generators; some home gym equipment uses DC generators to power readouts, displays, and control the amount of resistance offered by the machine. The amount of energy generated is so small compared to industrial power sources that the cost of conversion equipment makes it financially impractical.