I'm very happy to see this thead! I'm on week 4 of the nhs version of c25k (UK healthcare). I'm running sometime on road, sometime off road. Absolutely loving it, though trying to take it easy as I have thyroid issues. I'm not having breathing or aching issues, but I do keep an eye on my heart rate as asthma inhaler plus thyroid tend to raise my heart rate fairly fast. I would love to get to the point of running 3-5k a couple of times a week. I have noticed that it's giving me nice strong leg muscles for cycling, which is a bonus.