The first time I tried that Nike thing... like 3 years ago... was my first run in many years. As I was running, every time I saw another K tick over I was motivated to keep going, even though I was dying. I kept going right up to the 10km mark.
Needless to say, for the next week movement was near impossible
How I managed 10ks on a cardiovascular level (shit,
any level) coming from 0% fitness is beyond me; it was all done at a decent pace.
I so wasn't overtraining. Obviously I'm not crazy enough to try something like that out of the blocks now.