Sorry I missed this when you first posted. I'm just coming back from 6 months off the bike due to a medical issue. While I tried to do power walking for a bit, I ended up having some scary symptoms so it ended up truly being about 4 months with no exercise whatsoever. I was also pretty fit before I was taken out of commission and had great endurance like it sounds like you do. I have been back on the bike for about 2 1/2 months now, and I feel great. The first couple of weeks were the hardest.

My doctor instructed me to keep my HR below 160 for the first 6 - 8 weeks, which is pretty low as my max is 190 and my LT is about 180. But that was a really good bit of advice as it allowed my body to build a base and get in sync. I found the first few rides it was very tough to keep my HR down. Now I am back to normal. You'll get there quickly.

Good luck. And congrats on the 15 lb weight loss! At least it all turned out well.