I have been doing 20-25-30 mile jaunts on my roadbike at a decent clip, usually burning 1000-1500 or more calories on my roadbike. At the end I feel awesome, but my legs are exhausted.
I broke my wheel (silly spokes), and haven't been in a fix-it mood lately, so I just took a climb on my mountain bike. I did a ~7 mi loop, half up hill (pretty gnarly, 6mph climb for 15 minutes). My heart rate was ~165 the entire time. Mapmyride/my garmin both say ~530 calories. I am dead exhausted (more so than a long road bike trip on fairly flat).
My question is ... Why can I burn so many more calories on long rides, but right now I dont think I could go another 10 feet after the climb? Is it simply a matter of output power (ie, pretty near to max output climb for 15 minutes, vs a 80% max effort road bike?)
Is there a benefit to the high intensity climb over a longer higher-calorie ride?