For the HNers not used to running, every long-distance running is more a matter of strategy than speed. Even in the Olympics. Go watch a 5,000 meters of any Olympic Finals and try to analyze why the losers sometimes could have easily ran faster than the time of the winner (according to their historic results) and still they didn't.

I started running in March of this year, after having lived 35 years of my life believing that there was something wrong with me that physically prohibited me from running. Every time I tried running, I would end up gassed very quickly, with my heart rate shooting up to 180 bpm. I tried all sorts of things, but it turned out, I just ran too fast. Surprisingly, this isn't something anyone thinks to tell beginning runners: slow down. I found that I had to focus on running slower than was comfortable in order to get my endurance up. It required real, conscious effort to slow down.

I don't know how many people experience this problem, but I know it was a giant hurdle for me. Your app seems like a really fantastic idea.