I m a 31 male, in great shape. I was working out this morning and noticed a subtle pain underneath my left chest area, seemingly originating under the left breastplate. Almost directly underneath my left nipple, and on the left side of the left pectoral muscle. Though it feels like the pain is coming from underneath the rib cage a bit. Now I did take a pre-workout stimulant before the workout, but I have done this in the past and have never experienced this kind of issue. Not sure if that rules it out, but wanted to put it out there. The pain is dull and has come and gone throughout the day. It wasn t debilitating, nor did it prevent me from doing anything today. To be honest I really only noticed it when I was sitting down watching TV. I don t have a shortness of breath or any of the other symptoms of heart related issues (so I believe). But I was a bit frightened by it and figured I would check on here. FYI, yesterday I did work out my chest, and the pain did not increase during the cardio portion of my workout this morning. Any help is appreciated.