I know that’s a bit beyond the scope of the topic but what’s the goal here? Aka is there a why to this resolution or is it just something you have set your mind to because?
If the focus is on weight loss, forget about heartrate and just walk if you have the time to spare.
If the focus is on improved cardiovascular health choose based on what you like to do and find convenient. Some examples can be stairs, cycling, running, skipping rope, swimming(although I wouldn’t advise it because despite being great under many metrics the amount of time and commitment is way beyond any other form of cardio unless you happen to own a pool, aka you are likely setting yourself up for failure if you pick swimming). If this is all the training you do your muscles will not be a limiting factor, it may take you a while to get things in motion but muscle soreness improves a lot when put under similar stressors. If you go to the Gym you might want to try the elliptical but literally any cardio machine will do. If you pick something with high impact your joints are likely going to become a limiting factor much more significant than your muscle recovery in the long term.
At the end of the day my advice would be to pick more than one option, for example while swimming is generally unadvisable for the commitment if you were to go for something like running or cycling it can leverage a more rested upper body and give you more time to recover. You don’t have to pick one and do that one and that one only, especially if you want to train everyday. If your legs are sore and you can’t run you can probably drop your ass into a pool and use those arms. Remember also that your body adapts to training, if your recovery can’t handle higher volumes of training right now, work your way up, however you decide to do it.
