How can we get them to notice us?

Me and My best friend really like these two guys, we see them on the track near our apartment running training every Tuesday and Thursday evening. They both work at a take away most weekends so we often go there but they never notice us. One of our friends knows them because of this we know they are best friends since they were 16 (there 21 now) and that they want to travel, they like running, swimming and kayaking and have never had a relationship, they are doing business in college. Me and my friend have tried flirting with them but they just don't seem to notice us. We haven't really talked to them, only said hi and they say hi back or when they take our order at the take away but that's it.
Why don't they notice us? What can we do? How can we get them to notice us?

Sounds like they are either shy or simply not interested. If the former, invite them to something, and then up the flirting once the drinks are flowing. If the latter, move on.