Because it is not cost-effective. Before discussing the cost-effectiveness, let's introduce a video to give you a more intuitive impression of the motivation and work done by human movement. The german man whose height 174 cm and weight is 95kg is called Robert F. Rstemann, a track cyclist who has won many world-class racing championships. f？ The work done by Rstemann * * * is 0.02 1 kWh (kWh), which is 75,600 joules. If the utilization rate reaches 100%, a girl with a weight of 100 kg can rise vertically by about 150 meters. That sounds great, right? If converted into electricity, the electricity consumption price of residents in Zhao is about 0.6 yuan/kWh (1 kWh is 1 kWh), f? The electricity produced by rstemann is worth 0.0 1.26 yuan-almost 1 3 cents. According to the results, we need 18 F? Rstemann can drive, 43,000 F? Rstemann can fly a plane and won't last for a few minutes. Three students from Berkeley University have done research on "Collecting electricity through fitness equipment" and written a paper (Harvesting manpower as an alternative energy source in fitness facilities: a case study). In the experiment, they used 28 elliptical machines in Berkeley Sports Center, and the results are as follows: It is estimated that the electric power collection elliptical machine can collect-10000 kWh of electricity every year. The average annual power consumption of the RSF of Berkeley University is-1600,000 kWh. 1 ratio of item to item 2 -0.6%. It is estimated that the value of electricity collected every year is 1000 USD. The cost of refitting the electric power collection elliptical machine is $20,000. Profit cycle-20 years. Profit cycle considering discount rate-more than 30 years. The expected service life of elliptical machine is -6 ~ 7 years. In a word, this is a loss-making business.