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GAIT ANALYSIS. Study of human locomotion. Analyses can be kinematic, kinetic, electromyographic, or some combination of these techniques. Used in the design of ramps and lower limb prostheses, evaluation of load-carrying situations, and in defining neurological or structural abnormalities of gait. Factors examined include muscular activity and coordination, ground reaction forces, joint and limb segment positions, forces and accelerations, and postural changes.
GANGRENE. A condition in which a localized area of body tissue dies and decays. Gangrene occurs in many forms, but primarily refers to death or necrosis of tissue, as caused by loss of blood flow to a specific area (e.g. arterial injury or occlusion, frostbite, etc.), infection by bacteria (e.g., gas gangrene associated with traumatic wounds), or both. Diabetic workers are more susceptible to gangrene than others due to circulatory insufficiency associated with the disease. Also, paraplegic workers are subject to decubitus ulcers over the buttocks which are associated with a lack of sensation which predisposes the workers to unrelieved sitting pressures which in turn occludes capillary circulation long enough to cause tissue death.
GILBRETHIAN "SYSTEMS CONCEPT". The original notion calling for matching of the internal physiological and biomechanical environment of the worker with his external physiological and mechanical environment. First postulated by Frank B. and Lillian M. Giibreth in 1911 by their setting forth comprehensive list of interacting variables affecting the worker, his environment, and his motions requirements. (See GILBRETHIAM VARIABLES.)
GILBRETHIAM VARIABLES. System of three sets of variables intrinsic to every task. They are variables of the worker relating to anatomic and psychological factors: variables of the environment including physical and economic factors: and variables of motion including effort and movement patterns. The variables are used as a basic tool in work system analysis and design.
GLENOID CAVITY. Glenoid cavity is used commonly with reference to the socket of the shoulder joint formed by the scapula (q.v.) to receive the humerus (q.v.). Syn: joint socket.
GLUTEUS MAXIMUS. Large muscle of the rump which acts across the hip joint and extends the thigh, i.e., brings the thigh from the position occupied in sitting to the position in standing. It is an important muscle for walking, lifting and standing. Electromyogram of the gluteus maximus is a good index of the relative muscle activity during lifting.
GONIOMETER. An instrument by which angles of joint rotation are measured, either statically or during movement of the joint. Important in the evaluation of industrial workplace layouts and in the analysis of the body in motion (See REFLEX GONIOMETRY.)
GRASP REFLEX. A reflex which is both basic and conditioned. It is initiated by stimulation of the median nerve (q.v.) sensory feedback area in the hand. Surgeons need a well conditioned grasp reflex so that when surgical tools are being transferred, the surgeon can concentrate on the patient. However, in the machine shop people have lost fingers by reflexively grasping moving saw blades, etc. (See PREHENSILE.)
GROOVING. Designing a tool with grooves on the handle to accommodate the fingers of the user. Considered, a bad practice, because of the great variation in the size of workers hands. Grooving interferes with sensory feedback. Intense pain may be caused by grooving to the arthritic hand.
GROUND REACTION FORCE. A gravitational force produced by the weight of an object against the surface on which it lies.
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