Originally Posted by HTupolev

But these situations aren't analogous to what we're talking about. You're comparing something which isn't good at storing incident mechanical energy (a human body) with something that is (a flywheel, essentially).

In a world with perfect mechanisms and no air resistance, if you were on a perfect electric motorbike that could convert energy on the downhill into battery juice, you actually COULD go up and then down a hill with no net loss in battery power.

By the way, the "compensation" concept I brought up is used in the real world all the time in heavy lifting applications. Consider an elevator, with a pully at the top of the shaft, connecting a cable between the elevator itself and a counterweight that weighs about the same as the elevator. Besides acceleration, all the elevator motor has to do is combat air and cable friction; trading gravitational potential between a counterweight and the elevator is basically free for constant-speed motion.
This is what's happening with weight on your cranks.
You're instead envisioning a counterweightless elevator, with a person at the bottom of the shaft hanging onto the elevator cable, attempting to use their arm strength to lift and lower the elevator.