A combination unit for hydrotherapy and exercise having a rubber dampening pad containing pre-drilled holes for the interchanging of exercise devices such as treadmills, bicycles, and elliptical machines. , then print image data is prepared. Alternatively, the wireless communication device is coupled to the tab at a feedpoint selected at a location differing on each of the tabs where the conducting area per unit length of the longitudinal centerline axis of each tab varies with distance along the longitudinal centerline axis of each of said tabs from its feedpoint. The magnetic element includes at least three magnet actuators which each have a distance sensor associated therewith and which are arranged around the substrate support such that distances between the magnet actuators and the frame, and between the substrate support and the test probe, are adjustable. Design validation ensures that the design satisfies a set of performance requirements at each design phase, while validation of prototype implementation ensures the prototype behaves in conformance to the predictive model. According to a variant, the bolts are permanently secured to the first part so as to prevent rotation of the bolts.