My last couple of runs (W7R2 &3) I have found real difficulties with my breathing. Not the usual lung burning towards the end issues. My lung capacity seems to have improved quite a lot with doing lots of gm cardio between runs etc. This comes on much earlier, only a couple of minutes into the run in fact, and seems to be my stomach. It feels like a a tight rubber band has been pulled around my middle - not a pain, just really tight. I have never worn a corset, but it is how I imagine it to be. It really just seems to be my stomach muscles being very tense, but it seems to stop me breathing in all the way. I can't breathe from the diaphragm, which seems to really reduce my breathing efficiency and make the run a struggle from the getgo.
Anyone know what this is and what one can do to counter it?