Tom, I was in similar situation to you, only I was older (58) when I had my AVR. But I wanted something that would not impair my physical capabilities, or at least would degrade my workouts to a minimal degree. I'm more a bicyclist than a runner, but I do a lot of cardio in the gym, including treadmill, rower, elliptical, and stationary bicycle. On the weekends and after work when the weather is nice I hit the local bike trails for a good cardio workout. I wear a heart rate monitor when cycling, to track one workout to the next, and to make sure I'm not goofing off or pushing too hard. My primary symptoms prior to AVR were chest pain (and a lot of it). Immediately prior to AVR the Cardiologist put me on a "couch potato" regimen (i.e., no workouts at all - he was afraid working out would kill me). That was like death to me. My primary reason for choosing mechanical vs biological was to avoid the re-operation that would be inevitable with a biological, but I can understand how someone who has to have the surgery would consider it a hard choice. I went through the same quandary.
The surgery just about killed me. Not sure what it was, as I was in good shape going in to it. The 20 lbs or so of IV fluid they loaded into me sure didn't help, but I think beyond that just the stress of the operation and the inflammation to the heart and surrounding area has a lot to do with it. I ran into some complications following surgery. The anesthetic shut down my intestines so food wasn't being processed. After that problem was resolved I had "heart pauses" or "heart block", and they had to move me to intensive care. The next day they implanted a pacemaker to prevent the heart block. I was in the hospital for nine days. I was back at work, and back in the gym for very easy workouts three weeks after surgery. The first few workouts were more psychological than physical. The first workout just about brought tears to my eyes, as I viewed that as the turning point on the road to recovery. I was back on my bicycle within 6 - 8 weeks of surgery, and back to about 75% functionality within 3 - 4 months. Getting that last 25% of physical conditioning; i.e., back to at or near 100% of pre-op physical condition, took about a year.
But I kept at it with regular workouts in the gym that (typically) consist of about half an hour on the weight machines, followed by 15 minutes on the stationary rowing machine, 15 minutes jogging on the treadmill, and 30 minutes on the elliptical machine. When I'm on my bicycle, a typical ride is around 18 miles in about an hour and 10 minutes. I generally keep the heart rate in the 140 to 160 range, and have had it in the 170's many times on the hills. The On-X mechanical valve functions superbly at all heart rates, and I have had no problems with it at all. A nice side benefit is that I no longer have any chest pain at all.
That's a quick and dirty of my experience. Your experience may be different. But if I had to do it over again, I would do it the same, because I'm very satisfied with the On-X valve, and I sure would not want to go back on the cutting board again.
Best of luck, Dan
Sorry, just had to throw a joke in. Been a bad day.
