Objective: To measure forces applied to the body and associated changes in physiologic responses during axial spinal unloading (gravity-dependent traction) using the LTX 3000(TM) Lumbar Rehabilitation System. Design: Lumbar unloading was induced in 17 healthy subjects. The following parameters were measured: (1) percentage of total body weight unloaded; (2) forces applied onto and below the rib cage and local changes in cutaneous blood flow; (3) alteration of the applied forces to the seat strap associated with lumbar lengthening; and (4) changes in respiratory rates, respiratory minute volumes, heart rate, and blood pressure. Results: The average pressure applied to the rib cage for thoracic immobilization without unloading was 73 ± 26mmHg. Lumbar unloading caused these pressures to increase by approximately 30%, causing complete but temporary occlusion of cutaneous blood flow in this region. Significant, but normal, reactive hyperemia occurred upon release of the rib support pads (p -< .05). Axial spinal unloading using an LTX 3000(TM) induced changes in heart rate, blood pressure, and respiratory rates of magnitudes similar to those reported with the use of other traction devices. Conclusion: The forces applied to the rib cage by the LTX 3000(TM)) for proper lumbar unloading caused changes in physiologic responses, but these changes were reversible and can be considered clinically unimportant and thus should not be contraindications to the use of this device by the general population.