Fair enough, good point.

Humans are efficient, and there are also huge losses in converting the energy from work to electricity, and then further converting this to whatever voltage you actually need, while also likely first charging a battery somewhere so you can use it at a different time than you are cranking/pedaling…

However humans are also strong and can think of mechanisms that help with leverage and whatnot; for example an elliptical machine would probably be better than a bike.

With that being said the power you can generate is still pretty small; around 100Wh is floating around. If you worked out more you’d make more, obviously, but that might not be feasible.

It’d still be more than enough for essentials like charging your phone though.