What's so special about a 10k? Why can't I just run a 5k and be done with it? Running a 10k is twice the distance, twice the effort, and twice the suck.  But, here's a few reasons why people still endure the pain.

5 kilometers.  This is roughly equivalent to about 3.11 miles.  If you were to ask the average non-runner whether they thought that running 3.1 miles was a lot, the answer will most likely be "heck yeah",  "that's too far",  "why would I want to run that much?"