Because of the more delicate nature of the spinal column, back protectors require that lower levels of force be transmitted. The introduction to EN 1621-2 states that approximately 13% of motorcyclists injured in road accidents have an injury to this back region. However, only 0,8% of the injured riders suffer a fracture of the spine and less than 0,2% of injured riders have a serious back injury resulting in neurological damage. This is supported by evidence from the MAIDS Report (2004), the most comprehensive in-depth data currently available for Powered Two-Wheelers (PTWs) accidents in Europe. Serious spinal injures are usually caused by axial forces due to blows on the head, or bending and twisting forces on the back caused by blows to the shoulders, hips and other parts of the body. In the Cambridge Standard for Motorcyclists Clothing, Roderick Woods asserts that the majority of spinal injuries are caused by blows to the hip and shoulders. In the rare circumstance that a motorcyclist received a direct blow to the back the damage would be unmitigable by armor. The concept of a "back protector" is therefore not endorsed by Woods. Although back protectors, as defined in the standard, cannot protect against axial forces they are required to protect the scapula and there is now considerable anecdotal evidence that wearing a certified back protector can significantly reduce trauma in a major accident as they reduce the effect of impacts on the ribs and lessen the blows to internal organs too