We have this habit of power walking as often as possible, preferably each afternoon, for around 9-10 km. Giving the quality of the experience, it is always great to do it. In 2 out of 3 cases I carry a camera. I actually bought the Fujifilm X20 especially for these walks (and for going to work), because often-times it is annoying to carry a DSLR. Power walking/running with a D7100 plus a mounted 70-200mm is a bit clumsy. But it adds quite a bit of weight and it is a good enhancer of the exercise, so I do it sometimes when the light is really good.
Results may vary though. Sometimes I am really inspired, sometimes I can barely get a good shot. In some really rare cases, I hit the jackpot. And those afternoons are the best. Exercise and passion in the middle of the Swedish summer… Best!