I had two people tell me this today at work. And they added "for a run" as they know I am a runner. I felt a pang at this each time but it's too complicated to explain the knee injury as right now I am walking pretty normally. I limp on occasion but it is subtle. And I realize how profoundly i have changed. I am used to 6 days of sweating a week. Right now I just break a sweat working on strength workouts or easy spinning.
An interesting article about all the benefits of one workout: Link