So at Xmas I smashed myself up on a downhill drop off , broke my collarbone and tore my thumb … opposite sides…
I’m now 8 weeks post surgery for both , and have been sitting on turbo bike for the last 4 weeks , although I’ve only been managing small short easy spins … this week I feel a significant improvement in the collarbone , although todays x ray showed another 4 weeks is needed , but I can now reach to the hoods and apply light pressure. The thumb is more problematic for handlebars and have been told another 6 weeks but I can at least apply full pressure on the hand to hold me up but I have to keep alternating between sitting up and then learning forward…All very depressing as this year I had many xc races planned and was the fittest and strongest I’d ever been …
SO . the point of my question , sitting up on the bike obviously makes my hr spike and due to body healing it’s been high af . It is now coming down as my position gets more flexible and I’m healing … in relation to the power it’s the equivalent of tempo hr for recovery /warm up power … should I be riding mostly to hr and just not worry about power or ride to power ( zone 2) and not worry about hr? It does spike up horribly if I go over 120 watts tho . Very depressing . So I’ve probably answered my own question in that I should keep riding to hr for now …ai has tanked my ftp so not worried about that going down as it’s gone 
but just feel like these super easy spins aren’t really achieving much and it’s 10 weeks of fitness lost …the thought of another 4 just in recovery mode is depressing …anyone else been through the comeback stage like this ? How did you manage with hr / power etc
When I had my bowel cancer op back in 2019, when I got back on the trainer I dropped my FTP by an arbitrary 50w. Whilst I was cognisant of % max HR I prefer for the higher end stuff (Z3-7) stuff to follow power as its more reactive and immersing. For Z1/2 or two stuff I generally follow HR to ensure it is an actual recovery. I had intended to tweak the power FTP but it felt right and kept my HR where I wanted it to be so I left it.
Your hr is elevated because you lost fitness from time off. A lot of that can quickly come back with low aerobic riding. My advice is don’t push intervals/power until you are ready. If you know your heart rate zones then keep it easy until then.
My best fitness ramps after injury were done using heart rate zones. Lots of easy, building up to 2 hour rides, then once feeling better (about a month of that) I added tempo intervals by HR. My tempo intervals usually are 144-148bpm range and that has been reliable for me for 8 years. Then after a month of endurance + tempo I returned to training by power. Have done that several times. Last time I went from 265W FTP down to 200W (rough estimate using power-to-hr). Then a month of mostly endurance by HR, then a month of endurance + tempo by HR, and after 2 months my ftp was back in the mid 250s. Thats when I returned to doing intervals by power. All based on having reliable HR zones for easy endurance and tempo rides. If someone says “you don’t have to train to train” - my advice is ignore it - you are training!
Hope that helps.
Thank you ! that is helpful and good to know, I do know my hr zones however they are based on lactate threshold ,which I fear may have changed due to loss of fitness , so as I know my max hr il base it off that instead