I am a avid bodybuilder and was doing shoulder dumbbell presses above my head. Heavy set on the last rep my arm formed an exact right angle and as I was trying to push the weight up my muscles gave out and the weight fell pulling my right angled arm backwards. I dropped the weight immediately but heard a pop and crackle. My arm had a little numbness and then felt fine. Today it is sore with some achy pain coming from the top/in front. I sometimes still feel some crackling/popping.