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Certain disorders of motor function manifest themselves most clearly as impairments of upright stance and locomotion; their evaluation depends on knowledge of the neural mechanisms underlying these peculiarly human functions. The analysis of stance, carriage, and gait is a particularly rewarding medical exercise; with some experience, the examiner can sometimes reach a neurologic diagnosis merely by noting the manner in which the patient enters the office. Considering the frequency of falls that result from gait disorders and their consequences, such as hip fracture, and the resultant need for hospital and nursing home care, this is an important subject for all physicians. The substantial dimensions of this social and economic problem are well described by Tinetti and Williams.

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The normal gait seldom attracts attention but it should be observed with care if slight deviations from normal are to be appreciated. The body is erect, the head is straight, and the arms hang loosely and gracefully at the sides, each moving rhythmically forward with the opposite leg. The feet are slightly everted, the steps are approximately equal, and the internal malleoli almost touch as each foot passes the other. The medial edges of the heels, as they strike the ground with each step, lie almost along a straight line. As each leg moves forward, there is coordinated flexion of the hip and knee, dorsiflexion of the foot, and a barely perceptible elevation of the hip, so that the foot clears the ground. Also, with each step, the thorax advances slightly on the side opposite the swinging lower limb. The heel strikes the ground first, and inspection of the shoes will show that this part is most subject to wear.

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The normal gait cycle, defined as the period between successive points at which the heel of the same foot strikes the ground, is illustrated in Fig. 7-1, based on the studies of Murray and coworkers and of Olsson. In this figure, the cycle is initiated by the heel strike of the right foot. The stance phase, during which the foot is in contact with the ground, occupies 60 to 65 percent of the cycle. The swing phase begins when the right toes leave the ground. For 20 to 25 percent of the walking cycle, both feet are in contact with the ground (double-limb support). In later life, when the steps shorten and the cadence (the rhythm and number of steps per minute) decreases, the proportion of double-limb support increases (see further on). Surface electromyograms show an alternating pattern of activity in the legs, predominating in the flexors during the swing phase and in the extensors during the stance phase.

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Figure 7-1.
Graphic Jump Location

The normal gait cycle, based on the studies of Olsson and of Murray et al. See text for details.

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When analyzed in greater detail, the requirements for locomotion in an ...

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