Abstract: An improved lumbosacral backrest having a back engaging contour which is adjustable under power or manual operation to accommodate users' backs which vary widely in configuration and dimension. It has a contour defined by a segmented regulator spindle inserted between a foundation frame and resilient back support, the regulator spindle being adjustable along the back support and adapted to define a transverse plane of rigidity at the proper level and shape to provide comfortable support for the individual user's back.The backrest includes appropriate power means for actuating the regulator spindle to effect massaging action on the lumbosacral region of the back.It further includes manual means for adjusting the regulator spindle and which is operable when the power means for effecting massaging action has been deenergized.