I just completed week 6 run 1 and found it tougher going than running the 20 minutes straight on the last run! Why is that?! I must say my legs were still aching from the 20 minutes and felt tired. But my breathing was not so great either. Saying that I did have my 6 year old daughter on her bike with me so was trying to keep an eye on her as well as trying to keep my mind on the running!