So I recently put MapMyRide on my phone. Saturday I had a little time and got an hour's ride in even though it was 40 degrees and windy (wind chill into the 30's). My ride was along the Heritage Trails of Pittsburgh - essentially a flat trail with some small, very short climbs. I checked the stats when I was finished and it showed over 570 calories burned. Into the wind, I maintained perhaps 11.5 mph into the wind (13 mph wind, with gusts to 20) and around 13 mph on the return on a MTB with 26 x 2.00 tires.
This just seems wildly optimistic on the calories burned, or am I completely misunderstanding MapMyRide?