an energy absorbing extruded bumper for a vehicle is disclosed . the extruded bumper is formed from a lightweight metal , preferably aluminum base alloy material . the extruded bumper includes an outer wall , an inner wall , a top wall connecting the outer and inner walls , and a bottom wall connecting the outer and inner walls . extending between the outer and inner walls are two or more s - curved trigger stiffeners . the trigger stiffeners include an upper s - curved trigger stiffener connecting the outer and inner walls and a lower s - curved trigger stiffener connecting the outer and inner walls . the lower s - curved trigger stiffener is spaced apart from the upper s - curved trigger stiffener .