Hey…
Im abit curious.
Do you have trouble getting your HR up, at endurance intervals - like sweetspot or treshold work? - Because i think im in a similar situation - where if I sprint, or is in competetion i can get my HR up high - but in the trainer - my intervals at sweetspot/threshold, is way lower than trainingpeaks sugest my zones are.
But outside going up a hill full gas the HR can be quite high.
I have a low resting HR too… When out of shape its around 48-50 - and in shape, ive gotton as low as 30 - i havent had a BR test tho.