sorry to hear. rowing, for me, is cathartic.  

 I like it too, but bad lower back in try to fix with strength 😞 

 Have you ever heard of, or used, a reverse hyper? Supposed to do wonders for the lower back. Here's a collapsable one:

https://www.roguefitness.com/westside-scout-hyper 

 Thanks, I had not but will look into this! 

 was going to say rower also, if that doesnt work, assault bike - aka the devils bicycle ? 

 Great add