Originally Posted by howardjd .
Yeah I realize all of that. The point is that because gravity is a conservative field if you finish where you start you've done no work in the Gravitational field, you've only expended energy to overcome frictional resistance. Speaking along the lines of the Work-Energy theorem Work is only done in conservative fields(path independent in calculus terms). The frictional losses in cycling in work-energy physics jargin are not technically considered work, they are considered simply frictional losses.
That'd be great if you were not moving around in a fluid. To eke out the most efficiency on a decent, you have to coast - or else you are loosing that potential energy gained on the climb to overcome increased aero drag of moving faster than your average speed over the course.