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INTRODUCTION

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Gait Analysis

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In human locomotion (ambulation, gait), the reader is given the opportunity to discover how individual joints and muscles function in an integrated manner both to maintain upright posture and to produce motion of the body as a whole. Knowledge of the kinematics and kinetics of normal ambulation provides the reader with a foundation for analyzing, identifying, and correcting abnormalities in gait.

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Walking is probably the most comprehensively studied of all human movements, and the variety of technologies, coupled with the diversity of disciplinary perspectives, has produced a complex and sometimes daunting literature. The biomechanical requirements of the movements that explain gait are logical and easily understood if the detail is not permitted to cloud comprehension. The purpose of this chapter is to provide this comprehension of gait that will serve as the foundation for analysis of normal walking and of gait deviations.

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In early gait analysis, investigators used cinematographic film and until about 20 years ago, sophisticated analysis required frame-by-frame hand-digitizing of markers that had been placed on body landmarks. These data were coupled with knowledge of the center of pressure (CoP) of the foot-floor forces derived from a force platform to give complete, if simplified, kinetic information. This is referred to as the inverse dynamic approach with link segment mechanics. Electrogoniometers fastened to joints were also commonly used to describe joint motion and still have applications.1 Similarly, electromyography (EMG) has been used for many decades, although the expectation that it would be possible to convert those signals to force values in simple, useful ways has not been fulfilled. However, the past two decades have witnessed an explosion of technical advancements in motion analysis that offer the ability to collect and process large amounts of data. As with the development of any science, the knowledge available far exceeds its current applications.

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A modern gait laboratory (Fig. 14–1) includes some kind of motion analysis system that employs precise marker locations that are subsequently used to model a several-segment body with joint centers and centers of mass. Also included are one or more force platforms that provide simultaneous foot-floor forces. EMG systems provide simultaneous information from surface electrodes, or, sometimes, indwelling electrodes. An excellent and engaging report of the evolution of clinical gait analysis, including motion analysis and EMG, can be found in Sutherland's articles.2,3

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Human locomotion, or gait, may be described as a translatory progression of the body as a whole, produced by coordinated, rotatory movements of body segments.1 The alternating movements of the lower extremities essentially support and carry along the head, arms, and trunk. The head, arms, and trunk constitute about 75% of total body weight, with the head and arms contributing about 25% of ...

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