hi i was pulling two seized metal parts with my hands close to my chest and used all my force i arched my back , suddenly i heard a loud cracking sound in my sternum and a sharp pain . it took the breath out of me for a while .this was a couple of weeks ago now and i only get a dull pain when i push the palms of my hands together. if i sit up in bed and twist my upper body i feel a cracking sensation deep in my sternum 3 inches down from collar bone.