Arm pain can be a very mild experience or an extremely painful one. Arm pain can even be life-threatening as it can be associated with symptoms of a heart attack (myocardial infarction). In instances of a heart attack, other symptoms other than arm pain may be difficulty breathing, pressure on or around the chest area, and nausea. More often, arm pain is caused by an injury to the skin, muscles, joints, or bones in the arm. Arm injuries can happen from playing sports, performing manual labor duties, repetitive overuse, trauma, and improper exercise technique.