My heart rate reserve (HRR) is low. My resting HR is 40+/- 2 bpm and my max HR is 147 bpm giving me an HRR of 107bpm. Two factors have dramatically reduced my HRR over recent years: I’m now 67 years old and probably most importantly I’ve been (successfully) treated for Atrial Fibrillation (Afib) by 2x cardio ablations. Before treatment (in 2018) my max HR was around 180bpm with a resting HRR of 39bpm. I train consistently and follow pyramidal training approach, with a mix of “Zone 2”, “Sweetspot” and “VO2max” sessions over ca. 8 hours a week. Given my somewhat unusual physiology, should I be using standard HR zones, HRR zones or watts to define my zones and would it make any difference to my cycling performance in masters road and crit races?
Train by power, because this is a direct measure of the work being done. HR is only useful as a secondary metric.
At the lower levels say Zone 1/2/3 I would train by heart rate because that is an indication of how hard your body is working. If you use power or try to maintain a certain power on a day when you are tired, unwell or just having an off day your heart rate could be well above or sometimes even below what you are aiming for during the session. Power is just power it doesnt care how you feel. Heart rate is the real indication of the amount of stress you are putting on your system. If you try to hit a specific power target for a workout, just because “I must do that power” regardless of how you actually feel and ignoring heart rate then you are missing the point of the workout in the first place.
My HRR is even lower than yours. My max is 148 and resting anywhere between 45 and 50 bpm, I am 72 years old . My training is similar to yours but dont use "standard " HR zones but work out what percentages of your heart rate apply to each zone and stick with that. Blindly using power targets regardless of what is actually happening to your body during a workout as I mention in my below reply for me anyway is not the correct way to train. I would only ingore heart rate targets during short sprints where power rises too quickly for the heart rate to catch up. Even during slightly longer Vo2 max sessions i would keep an eye on heart rate. Power is a good indication of any progress you may be making for a given effort as hopefully your heart rate will drop slightly for the same power or your power will increase for a given heart rate as you get fitter but in my opinion training generally by heart rate is the better option