Originally Posted by
mcjimbosandwich
At constant effort, see how much HR drift. I think it could be interpreted (barring things such as huge elevation changes, humidity, heat, etc) as a sign that the aerobic base is not strong enough.
not necessarily that the aerobic base isn't strong enough, but an indicator of the strength of that base. also, aside from external factors that you mentioned, it may indicate from day to day an overall fatigue level or even so much as a diet/hydration deficiency.