What causes this?

Hm, I’m not really sure what you mean by ‘bubble’ about to burst in your heart? But, I suggest if it’s REALLY that bad, you should go to the doctor and check it out.

Otherwise, you should definitely keep yourself hydrated throughout the day. Drink a lot of water all day, but not too much right before you exercise.

ALWAYS stretch before AND AFTER you jog.

depending on what part of your side it is on it could be a heart murmer ( a strange rythm and can cause pain) I have one and have had it since I was 6 months old.

do you stretch out before you run and also do you run they walk?? cause if you dont stretch and walk and run that can be it I mean you said you just started yesterday and well you have to get your body to get use to jogging you cant just go a jogg before getting your body use to it!

hope I helped!! :)

I have the same problem when I exercise. It’s actually a great thing although it hurts very bad.

It means you’re blasting any fat on you’re abs, so the muscles are tightening.

when you run your side always hurts you shudnt job you shud walk its better to walk to be honest,, I don’t know why those things hurt but they do for me to its normal thats why I walk and not jog its peicful and works better