DYNAMICS OF PATHOLOGICAL GAIT

This paper is aimed at applying tools of dynamical systems theory to the evaluation and treatment of movement disorders. A key notion in this approach is that qualitative changes in movement coordination emerge spontaneously as a result of unspecific and continuous changes in control parameters. Our research on the dynamics of gait indicates that gradually varying walking velocity as a control parameter results in systematic changes in the frequency and phase relations of arm and leg movements as well as in the phase relation of pelvic and thoracic rotation within the bipedal walking mode. Identification of these intrinsic dynamics of gait enables the classification of pathological coordination patterns. Stability and the ability to make transitions between patterns (adaptability) are important issues in the evaluation of movement disorders. For exercise therapy this implies that the patient must learn to tap the appropriate control parameter in order to facilitate spontaneous emergence of the desired coordination pattern. The use of perceptual information in the form of external auditory and visual rhythms can have positive influences on hemiplegic and Parkinsonian gait by synchronizing the movements of the body segments. The effects of rhythmic exercises are, however, very sensitive to the nature and magnitude of the rhythms manipulated. It is concluded that a systematic investigation of the role of perceptual control variables is a necessary prerequisite to understand and treat movement disorders.