[kazinator]

Running means you are jumping through the air, so that at most one foot is in contact with the ground at any time. This can be done without moving forward, so there is no lower bound which separates running from walking. Walking means that at least one foot is in contact with the ground at all times, and there are at least brief periods of double support (two feet down).

I can walk up to an 8:30 mile pace. Elite race walkers can outwalk recreational runners; the paces are around 6:00 at that level, which is astonishing (though not in comparison with elite running of course).

If someone covered some distance at 11:00 to the mile, we have no idea whether they ran or walked without eye witness or video evidence of what it is their legs were doing.

I definitely ran my first marathon in 2003, in some 5:05:12. That's like 11:44 to the mile or thereabouts. I definitely made a point of not taking any walking steps in this thing. It happened by accident several times, but I immediately went back and re-ran those small stretches of the course where I had strayed from the pure running discipline. On subsequent ones, I didn't make a point of that at all, just the first one. I've never taken planned walking breaks or walked extensively, but I never re-ran any walked steps. The clock is ticking; no time for foolery! :)