My wife and I have been runners for 25+ years, although she is the more religious one. She has run several marathons (I ran Boston once). A year or two ago she was doing a lot of running in a "fitness challenge" and got stress fractures, so started into cross training. Once she got into cross training, she decided to try triathalons, hence biking. Since she didn't want to do it alone, that's how I got back into biking this past year. After a season, we're both wishing that we had gotten serious about cycling 20 years ago -- it is so much easier on the joints, yet is really excellent exercise, and damn -- it is a whole lot more fun than running!