Read a good overview of the state of human-powered exercise machines in gyms in IEEE’s latest Spectrum. The article refers to some of the inventors and businesses featured on this site, including Mike Taggett, the Green Revolution, ReRev, and the Green Microgym. Like The Human-Powered Home, it points out the relatively low capacity of human power compared to other energy sources — and explains that human power is not economical. But most of us aren’t doing it to save money on electric bills. At least, not yet.