Is it impractical (or impracticable?) or inefficient to harness the power generated by a bunch of people on cardio machines and convert it to reusable energy?
The technology seems to exist already, so is there a reason that no one's implemented this?
At the very least, I'd think, gyms could use the power generated to power the cardio equipment itself ... but I have no idea of the scale or, really, the faintest clue about how power generation and consumption works. Which is probably why this idea is so brilliant.