Well it's nice to see it proven.
At least in one experiment, anyway. My take on this is that an upright cycling posture is better than a supine one, if only when looking at a lab test of endurance.
I once 'raced' a recumbent with full aero fairings along a freeway from Bargo to Picton in NSW, Australia. I (on my 'real' bike) had more power up the hills but he certainly had the top speed advantage! So there is certainly an aero advantage to 'lying down on the job' but from a physical endurance perspective there's a decided disadvantage of some 10%. Anyway...
From the European Journal of Applied Physiology; Jan2006, Vol. 96 Issue 1, p1-9. Authors: Egaña, Green, Garrigan and Warmington, from the Department of Physiology, Trinity College Dublin, Ireland and the School of Biological, Biomedical and Molecular Sciences, University of New England, NSW, Australia.
To quote from the abstract, "The time sustained during a graded cycle exercise is ~10% longer in an upright compared with a supine posture. However, during constant-load cycling this effect is unknown. Therefore, we tested the postural effect on the performance of
high-intensity constant-load cycling." So they tested constant-load and found that "there is a very large postural effect on performance during constant-load cycling exercise and this effect is significantly larger in men than women". So upright beats supine, particularly for men. Not sure what this means to the crazy racing folk who sit on an 'upright' bike but bend down so far that they are almost parallel to the ground but I suspect they are successfully adapting the efficient upright style to gain an aero advantage. The racing tuck is a compromise,
and of course we can always sit up and stretch.
Other compromises made for racing include the need to 'pull up' on the bars when climbing or sprinting, so the bars have to be close enough to do so comfortably whilst being low enough to gain an aero advantage. Anyway, I suspect it still beats lying down!
Aside from all that, recumbents are almost invisible and need a flag on
a pole to be seen. They are pretty cool devices though.