I just noticed today when I done a 120km spin my average HR was higher than usual but with a low enough effort. My max HR is 182 and my average today was 149bpm BUT WOULD usually be lower for the same effort. Just wondering if there is an obvious answer.
Dehydrated? Over caffeinated? Drank alcohol last night? I know all of these things affect my HR.
Impending illness could be another reason so keep an eye on that for the next couple of days.