Since health questions seem to get a pretty good response on this forum, I thought I'd throw this out there. When I stretch, if I push my shoulders back and stick out my chest, my sternum pops - similar to cracking your knuckles. It seems to happen after I've been sitting for a while (I sit a lot at my job). This just started happening recently (maybe over the past month or so), but I'm only 22 years old. It's not painful, just a dull pop. Is this normal? Has anyone else experienced this? My ex-girlfriend used to have this happen and I couldn't understand it. Now it happens to me too. I don't have the best posture, so maybe I just need to stop slouching.