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In “normal” human locomotion (ambulation, gait), the reader is given the opportunity to discover how individual joints and muscles function in an integrated manner to maintain upright posture and produce motion of the body as a whole. Knowledge of the kinematics and kinetics of normal ambulation provides the reader with the necessary foundation for analyzing, identifying, and correcting abnormalities in gait.
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Walking is probably the most comprehensively studied of all human movements, but the variety of technologies, coupled with the diversity of disciplinary perspectives, has produced a complex and sometimes daunting literature. The fundamental biomechanical requirements of the movements that compose gait are logical and easily understood. The purpose of this chapter is to provide comprehension of normal ambulation mechanics that will serve as the foundation for analysis of normal and abnormal locomotion, including walking, running, and stair climbing.
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Early gait analysis involved cinematographic film and time-consuming frame-by-frame hand-digitizing of markers that had been placed on body landmarks to evaluate movement kinematics. Ground reaction force data from force platforms were then included to provide an estimate of joint kinetics. The accuracy, and quantity, of data were limited by the digitizing approach, though our current understanding of normal human locomotion was directly informed by this early research. The past two decades have witnessed an explosion of technical advancements in motion analysis that offer the ability to quickly and reliably collect and process large amounts of data from a variety of movements. The next major advancement in gait analysis has already begun and involves assessment of motion outside of a clinical or laboratory setting, including in the community and even in people’s homes.
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A modern gait laboratory (Fig. 14–1) includes some kind of motion analysis system that tracks segment motion or precise marker locations to generate three-dimensional anatomical coordinate data 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 including the position (center of pressure), magnitude, and orientation of ground reaction forces. EMG systems provide simultaneous information of muscle activity using surface electrodes, or sometimes, indwelling electrodes. At a minimum, kinetic data (force platform) and EMG data are typically sampled at 600 or 1200 Hz (samples per second), while kinematic (segment movement) data are sampled at 60 or 120 Hz. An excellent and engaging report of the evolution of clinical gait analysis, including motion analysis and EMG, can be found in Sutherland’s articles.1, 2
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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.3 The alternating movements of the lower extremities essentially support and carry ...