I started doing "powerwalks" on most of my mornings. I aim for the upper end of zone 2 (ca. 135 bpm in my case), which is basically walking as quickly as I can without running, for about 30 minutes. It's really great, as it's both a form of sport/cardio and a mentally refreshing walk. No headphones or input, but I do take a pocket notebook with me so I can write stuff down that pop in my head. On the days I manage to do it, I feel better, calmer, more focused, and my sleep the following night is more restful.