I do the machines in the fitness center then swim a few laps in the pool. I tried using the elliptical machine and that killed both of my knees. I can do the recumbent bike, but I have one at home that I seldom use. So, to get my cardio workout in I swim laps. I always stretch out in the pool when I'm done. It feels really good! For some reason, today has been the worst day for both knees than I've had in a long time. My new knee shouldn't be giving me pain like this. My goal is to work it and if it's loose it should get worse and show up sooner rather than later. I'm not getting any younger and if a revision is in my future I want it done sooner! I still have my old knee hanging over me, too. I won't even consider getting it done until this tkr is right.