Principle of Spectral Reciprocity in Biomechanics of Locomotion and Rehabilitation.

Providing the technical means to prevent collapse or falls in patients with different types of pathology in motion and balance control is one of the traditional problems in rehabilitation engineering. A means of addressing the problem using assistive devices, including prostheses, is to restrict the mobility in certain anatomical or artificial joints by applying corsets, braces, brakes and locks. The restriction of mobility in the joints increases local stiffnesses, and in a sense, tunes the spectrum of oscillations in these joints out of resonantly dangerous zones. So far, these efforts for limiting unwanted mobility are mostly empirical within rehabilitation technologies, and we suggest that they can be optimized with algorithms for controlling the spectrum of oscillations used in multi-linked technical systems. Further, we suggest that tuning out of resonance is inseparable from the phenomenon of tuning into resonance that is widely recognized in biomechanics of locomotion. These considerations result in our postulating the principle of spectral reciprocity in locomotion.