Originally Posted by
Trakhak
Tomato coupe saved me a bunch of typing. In short, there are three possible states of pedal effort on a fixed-gear bike: a level of pedal effort sufficient to drive the rear wheel; a level of pedal effort sufficient to keep from slowing the rear wheel; a level of pedal effort insufficient to keep from slowing the rear wheel.
You and Tomato Coupe are both assuming a level of "pedal effort" is always required to move the legs. This just isn't true. A cyclist just has to relax. Any object, even your legs, once set in motion, will continue in motion unless acted upon by an opposing force. You can even experience this on a free hub bike if you set your mind to just letting it happen. It's just that you don't get the same degree of positive feedback as you do with a fixed hub.
As for whether the clicking pawls represent more or less energy loss than that lost in the silent frictions inside our legs is really beside the point: a clicking pawl will never move your bike forward, but the your warmed-up legs will.