I'm 52 years old.
My heart rate when I wake up is usually around 50 bpm. After getting out of bed my resting heart rate is around 60-65 bpm.
If I calculate my max heart rate (220-52) I get 168.
I recently used an Apple watch to get my maximum heart rate while doing jump burpees under a Tabata timing (20 sec. work/10 sec. rest) and the highest heart rate registered was 176.
168 and 176 are close, but I can feel a difference in intensity when the rate difference is around 10 bpm, but to be truthful, I'm thinking of something more like the difference between 155 and 165, where 155 feels much more sustainable.
Anyway, my question is whether I should use 168 or 176 for setting target heart rate for exercise. I'm specifically thinking of Tabata where I understand I should be getting up to the 90% of max heart rate range.
My taskmaster self says use the higher range. My over the hill self says the lower range stays out of the miserable range and probably will give me the training effect I want: stay fit as I age and have a descent 1 mile running pace when winter ends and I can get out to run.