Z94.2 - Anthropometry & Biomechanics: Biomechanics Section
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FATIGUE. That physiological state characterized by a lessened capacity for work and/or the inability to maintain consistent work quality levels. May be due to intensive mental or physical activity or depletion of physiological reserves.
FEEDBACK SYSTEM. A control system in which information from the controlled element is returned to the controlling element. The controlling element then modulates its requirements of the controlled element according to performance requirements. In biomechanics, muscle coordination by visual or tactile signals are examples of feedback systems. Improper performance by a worker may be caused by interference in his feedback system (disease) or improper operation of his sensors (optical illusion). Homeostatic systems are examples of physiological feedback systems. (See HOMEOSTASIS.)
FEMUR. The long bone of the upper leg (thigh). The upper end (head) of the femur articulates with the pelvis to form the hip joint, the lower end (condyles) articulates with the tibia to form the knee joint. The hip and knee joints often are the site of arthritis (q.v.), which may make walking painful and limited (elderly workers).
FIBULA. The smaller bone of the lower leg (shank). Extending from just below the knee to the ankle joint, it is lateral and posterior to the tibia (q.v.), which is the main load-bearing bone. The fibula is attached to the tibia by the interosseus membrane and provides a site for muscle attachment. The lower end (lateral malleolus) forms the lateral side of the ankle joint itself, is essential to ankle stability, and often is injured by twisting forces.
FIFTH LUMBAR VERTEBRA. The lowest vertebral element in the lumbar region, in the small of the back immediately above the sacrum. Because the flexible lumber section is adjacent to the rigid sacral and pelvic structure, the fifth lumbar vertebra and adjacent discs are subjected to high stress, especially in lifting tasks. Trauma due to excessive stress at this site can cause lower back pain and pain in the legs. (See LUMBOSACRAL ANGLE, HERNIATED DISC.)
FIXED LINKAGE MECHANISM. Linkage formed between skeletal elements of man and machine in a man-machine system. Movement of any link produces movement in other links, e.g., machine operator and drill press. Configuration of fixed linkage systems determines biomechanical efficiency of work, e.g., seat height at drill press.
FLEXION. Movement at a joint whereby the angle between two bones connected at a joint is changed in a manner tending to approximate the body segments it connects. Motion of this type is produced by contraction of flexor muscles.
FLEXOR MUSCLE. A muscle which, when contracting, changes the angle between two limb or body segments in a manner tending to approximate the segments it connects. The principal flexor of the elbow is the brachialis muscle. Flexors of the fingers and the wrist are the large muscles of the forearm originating at the elbow. (See EXTENSOR MUSCLE.)
FLEXOR RETINACULUM. Touch fibrous ligament forming the ceiling of the carpal tunnel (q.v.). Also called transverse carpal ligament, this structure prevents bow-stringing of the flexor tendons at the wrist.
FORCE PLATFORM (PLATE). (See REACTANCE PLATFORM.)
FORCE-TIME. Applied force multiplied by time of application. Used to quantify isometric work (q.v.) and has the dimensions of linear impulse, for short time duration phenomenon.
FUNCTIONAL ANATOMY. Study of the body and its component parts, taking into account those structural features related directly to physiological function. E.g. functional anatomy of elbow defines relative flexor force developed by biceps and brachialis at various degrees of flexion.
FREQUENCY. The number of repeated occurrences in a given time interval. The frequency of electrical or mechanical activity is usually specified as cycles per second (c.p.s.) or hertz (Hz).
FREQUENCY. 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.
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