A model of induced coupled movements in the human body: a case study.

We present a case study of involuntary motion in one part of the body induced by a voluntary motion in another part. The case investigated was that of a steady-state motion of the fingers at various frequencies, which induced a similar kind of motion in the legs. These phenomena were observed in a subject practicing sphincter gymnastics, a physical therapy method in which repetitive motion of different muscles is exercised, and is known to induce motions in other muscles of the body. We show that a linear model, for which we give an experimental transfer function and demonstrate its validity, can describe the generation of the induced periodic motions by the voluntary motions. We compare the results of the transfer function with those of Von Holst's statistical analysis.