Abstract: A single-piece strong, flexible back support for use in seats such as automobile seats or office chairs, includes a central body portion with outwardly extending support fingers such that an arch having a variable apex is formed when the back support is subtended longitudinally. The longitudinal location of an apex and the shape of the arch formed on the back support changes responsively to a load imposed by a person's back. The inventive back support is capable of taking a variety of shapes thereby providing maximum comfort and support regardless of the user's spinal curvature or posture and position relative to the back support.