Why does my back hurt when i cough?

Back pain from cough: Your lungs fill your chest cavity .When you cough, you take a deep breath in, then the vocal cords close. This causes a rapid increase in pressure within the chest cavity by contracting the muscles between the ribs and the diaphragm muscles. Then the vocal cords open to let the air out rapidly. The high pressure in the chest as well as the contraction of the muscles cause the back pain.