Arm weakness can limit the range of motion of your arm and affect your daily activities. Causes for weakness in arms include trauma from an injury, repetitive strain injury, nerve damage or compression in the neck or upper back, or blockage in the bloodstreams. Left arm weakness with chest pain may need immediate medical attention. Common characteristics of arm weaknessIf you're experiencing arm weakness, it can likely be described by the following:Objective weakness: This is muscle weakness tha