Hi all, I've just started a walk to run schedule this week, having never done any running before. I really like the idea of the freedom of running, just chucking on my trainers and going out when it suits me, rather than sticking to what the local leisure centre has to offer. I've got a question though, towards the end of my second outing, I had what feels like a slight popping sensation at the back of my knee. Can anyone shed any light on what this might be? Also, is it usual to feel absolutely knackered towards the end!! Thanks!!