I recently resumed doing cardio, aiming for 30m per day at a minimum with occasional two-a-days if I get bored. I track my HR with a Polar H10, and have aimed for 50-70% of my max HR. I’m 43, so 50-70% would mean 89-124bpm.
My average bpm has steadily gone down from the high 120s, to the high 110s, and my most recent average bpm was 98. I assume this is the result of my body adapting. But should I have been pushing harder to maintain a high bpm all this time?
I do think that conditioning work should be progressively loaded so that exertion levels remain similar as your fitness improves. This is akin to adding weight to the bar as you get stronger. As far as when this becomes absolutely necessary and the exercise isn’t working anymore due to you being too fit, I can’t say for sure. As conditioning efforts gradually fall further and further into z1 and below, they seem to contribute less to cardiorespiratory fitness improvement compared to being in z2.
Thanks. Are there any telltale signs I should look for that might tell me when it’s not worth further “loading” my cardio?
I don’t think that’s a thing or concern, similar to asking when it’s not “worth” adding weight to the bar or doing more reps when you’re stronger or fitter. The training should always match your current fitness levels.