I live outside of Reading PA (about 30 min from Lancaster). It's not uncommon to see some Amish young adults (men and women) in the local road or trail races in Berks County (I'm sure there are more Amish runners in Lancaster or York Counties but I don't travel to those races just because of schedule). I don't recall their times from these races though but I have seen some of them place in their respective age groups or overall race races. I have also seen them run in some kind of running shoe while still wearing their normal life attire - nothing "top of the line" like what most runners wear, but something simple, low cost, and athletic structured.
On a side note: I think I saw that guy run the Garden Spot Marathon a few years ago. But then again, Stolzfus is a common Pennsylvania Dutch name around here, like Moyer and Yoder.