Without delving into the detail of the workouts in relation to altitude gained, your life stresses will have an effect on your resting HR. The increase in resting HR is approximately 10% you shouldnt be overly concerned about this rise as you have increased your training hours. Your body is still adapting to the load. If you take a recovery week, then I’d bet your resting HR would come back to the 58 figure , ignoring life stress issues.
Resting HR is very individual - it’s generally lower in fit people but is not always an indicator of fitness. Mine is usually 36bpm with a max of 178bpm but I think I have quite low blood pressure as I sometimes get dizzy spells when I stand up Anyhow - yours is still lower than the average 70-80bpm for an adult and as mentioned it doesn’t always correlate with fitness. What it does correlate with is stress (as you mentioned), workout fatigue and over training which can lead to an increase and onset of illness (important currently) - all can lead to an increase which you should take action over…but the actual value isn’t so important
My resting heartrate will be higher the night after a really big effort and will be higher the more stress I put on my body. It fluctuates between 48 and 63. Lots of other things have an impact as well. Alcohol, eating late, external stress, poor sleep.
I’m not sure I understand your concern on the workouts. If I’m reading correctly, the workouts you are comparing are different. Even though your average watts may be equivalent, a lot goes into that average heart rate. I don’t think you can draw comparisons.
Not sure I can exactly. Rides A and B and C and D are different routes. D is done indoors. They have different elevation profiles, durations, average grades. You could have been coasting more in one than the other and you could have dug deeper on a climb in another. If all of these were indoors doing the same workout, you might could draw comparisons, but then you have other physiological reasons heart rate can vary, such as fatigue, whether you rode the day before, hydration level, air temperature, recent sleep, and a number of other factors.
Did you get a resting HR from a Garmin watch?
My RH according to it was 54bpm but the min was 48bpm. I not sure what average Garmin reports but I wouldn’t put too much faith on it. Other days it’ll say my resting HR is 47bpm and it bouncy around a bit. Also whenever I do a workout the watch nomal reads 10bpm or more less than my HR strap.