Guessing wildly I'd say a road bike is almost 2X more efficient, i.e., 60 on a fully sprung mountain bike burns as many calories as 100 on a road bike.
Any real studies on this?
A quick google produced:
(one person's calculations involving a road bike and some suppositions
about mountain bikes)
Neither of these seem to be "real" studies, but the consensus seems to
be that mountain bikes require about 15% more power from the rider than
It would be higher than 15% even if you weren't dragging a brake w/ under inflated tires on fluffy sand.
I know this from the additional meal I need to eat the day after riding the MTB. I'll try another MTB. If no improvement then I'll start photographing the machines with IR in the dark after a ride.
The waste heat is going somewhere.