I did some heavy apnea sprints and apnea running that i'm not really used to yesterday (felt really good and i want to do it again but i noticed this morning as I was walking to class doing breatholds as usual a pain about 2 and a half inches below where my sternum ends and to the left right at where the edge of the ribcage is. I would feel it whenever i would have a contraction and also when i would breath very deeply. what do u think this is? should i lay off for a while or just continue training and see if it comes back?