My wife doesn't ride anymore due to balance issues. However she likes to walk including walking about a dozen marathons. She now has me doing about 3 half marathons with her a year. We have one coming up in early May (Flying Pig in Cincinnati) so I'm walking about 10 miles a week for training.

"Training for walking?" you may scoff. Even with training, I'll be more sore the next day after a half marathon than if I'd done a century ride.

One thing that's important to remember is good shoes. I spend over $130 on shoes and retire them to things like yard work after 400-500 miles.