I just started running 2 weeks ago, but i have been biking for awile. I usually ride at the minimum 100 miles a week. Two days after my very first run I couldn't beleive the burn in my legs. It felt like I had done heavy squats in the gym! I rode a century over the summer and did not have any pain after. I guess my point is running and biking somehow affect the leg muscles differently! I ride my bike on the days i dont run and have had no fatiging problems.....but everyone is different.

Hey  --- come on over to the dark side -- triathlons...

After you get done with your 5K program -- and with all that biking done -- heck you're a shoe-in for a

duathlon; and as the  guy said -- might as well add swimming too.

Most du/tri training programs essentially do what you are doing, in terms of splitting the  run, bike, and swim

days ( On the higher end of tri training, usually swimming gets added to either the bike or run day).

If you were to refrain -- it would be desirable, typically, to put a rest day either in front of or after your longest run/bike day --

but for a 5K program that's probably not even necessary.

Hey there!  I run 4 days a week and teach spin class 2 days a week and I think they work well together.  and because your cycling 6 miles that should be a nice easy ride (if its not too hilly).  They both work different muscles in your legs so you should be fine!  Good luck!