Abstract: A machine applies a cyclic localized thrusting force against the back of a patient recumbent upon his or her back on a support bed in order to manipulate the user's back or spine. Several (typically three) spaced-apart thruster members reciprocate between a first position retracted into the support bed below its top surface and a second position thrusting into pressured contact with the patient's back. The reciprocal thrusting is variable and controllable in real time with respect to the locations, area, patterns of contact, amplitude, frequency, numbers of cycles, pressure, and number of separate sites. Spinal therapy normally performed by a human therapist may correspondingly be comprehensively mechanically replicated.