Abstract: A modular harness assembly worn by a person during physical exercise or rehabilitation. The modular harness assembly includes a non-stretchable waist belt that is secured around the waist of the patient or user, and can be associated with one or more auxiliary, non-stretchable harness component that can easily be added or removed from the waist belt. The auxiliary harness components can include a shoulder harness, a thigh harness having a movable connection to the waist belt proximate the hip joint, and a pelvic harness. The modular harness assembly can be used in combination with a hoisting system such as a block and tackle pulley system that is mounted onto a rolling carriage and an overhead rail.