Today, I was not in mood to do strenght training in the gym, and it was late to play drums. So, I went for power walking into the night, to think about some things, some ideas etc. One idea that I've had before and came back to my mind is 'activity density'. It's not a revolutionary idea but it's a nice one. The idea is increasing our 'productivity', not by multitasking, but by picking activities that contribute to more than one area in our lives. For example, for me, playing drums has a high density: this is a very good exercise; a wonderful musical pleasure; a great cognitive training; a great way to make friends; and so much fun! (though it's not so good to my ears, but I use ear plugs - sometimes). The very same power walking has a good density: it's an exercise; a moment to think without distractions; an experiment (yes, I copied the Seth Roberts' idea - again - of monitoring glucose and evaluating what things affect it); a moment to feel alertness (when I see suspicious people on the dark streets, booooooo! :-D).
So, a great way to be productive is increasing the activity density of our time.
Productivity = Σ(Activity Density x Mental Focus x Time Spent)