First time post and even asking the question. Not sure if it's heart/muscle? i'm 39. When i exercise and i'm breathing in it almost feels like my heart pops. if i look down it is about 1 inch to the left of my middle of the ribs and probably about 1/4 inch to 1/2 inch up the under my ribs. it only seems to happen when i'm on the treadmill or running. only seems to happen when i'm breathing in about the end of the breathing in process. i do usually eat/drink water before i work out so not sure if that is the issue. it doesn't really hurt but it is a weird feeling with it going on. Thanks for any comments back.
Not so sure that your heart could "pop." Just my layman's opinion (but I've been dealing with heart issues for over 20 years so I've done a lot of research too) but the heart doesn't normally "pop." Muscles would though I would suspect or bones. Seems like a bone/muscle issue to me. The heart is more likely to skip or jump beats, give you pain that's deeper or cause an odd heart rhythm. I doubt it's your heart.