The significance of a cool-down after intense aerobic exercise lies primarily in its ability to facilitate recovery and prevent injury. A cool-down typically includes low-intensity exercise that gradually lowers the heart rate and promotes blood circulation to restore normal physiological processes. It helps in the removal of lactic acid and reduces muscle stiffness, thereby decreasing soreness and aiding recovery. Additionally, cool-downs can contribute to a sense of completion and mental relaxation after a rigorous workout.