When doing intervals indoors (on spin bike) I am running from base of 155 to a series of peaks 165/70. This can go on for an hour. On the road bike I seem unable to hold 160 for any time at all, and this is driving me nuts. I know the indoor trainer environment is hotter (I drip sweat) but why can I hold so much higher an HR (average and peak) indoors? I even feel more power, but no meter on the spin bike. This is not in a class (eg group ride effect, etc.) Anyone else an indoor Lance, out door slug?