"FARTLEKS" is a funny word. My kids like to laugh and say, "Dad, enjoy licking your farts!"
What it really means is, "Any form of intervals in which the emphasis is on enjoyable speed rather than the discipline usually associated with intervals. This tends to produce a more effortless version of good running form."
And so this is what I've been doing around Ithaca several days per week, as I move from one appointment to the next, or as I find different places to break out my computer for work. I'm running in bursts--for a total of about 3 1/2 miles per day--and with my laptop-carrying backpack strapped on, which weighs around 15-20 lbs.