An adjustable mattress foundation for beds, having head, and foot sections of adjustable inclination, and a stationary center section for supporting the user's buttocks, with locking gas springs being employed as force providers and counterbalances in selectively adjusting the angle of inclination for the head and foot sections, with the actuation of the head and foot sections being effected by the pivoting a single control rod. Changes can be made in the torque application of the device on the foundation head and foot sections for different weights and stiffnesses of mattress by a simple adjustment. The width of the stationary section has a minimum width requirement in order to minimize the force required to make changes in inclination in the head and foot sections with respect thereto, and have minimum stress exerted on the mattress.