With flash photography you are exposing for 2 light sources, ambient and flash. So if the ambient gives you for example 1/10 at f4 and you choose 1/60 at f8 nothing or very little of the ambient light will be caught by the sensor, so only that which is illuminated by the flash will register. Flash duration is very brief and will "freeze" all but the fastest action, consequently the runners will be illuminated by the flash and will be frozen in time, however the background may be totally black therefore you need to expose for that also, it's a juggling act between the two. You won't need high speed synchronization that I think is used more in bright daylight.
PhilV is your man to ask for extra guidance and confirmation my post is accurate.