Cardio for permanent walk profile

I am 50 years old and used to run, albeit not fast. I got the job done. Over a year ago my chronic injury caught up with me and after several attempts to move off temp profile and get back to ankle pain free running, my PA placed me on permanent walk profile. My challenge is to keep doing alternative forms of cardio. I have discovered racewalking. Race walked two half-marathons that I previously ran. What have you found that wotks for you in keeping up the cardio when you have a permanent walk profile?