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ECCENTRIC CONTRACTION. Increase of tension within a muscle while lengthening. For example, the brachialis exerts a force resisting the pull of gravity when extending a flexed forearm slowly.
ECHOGRAPHY. The use of ultrasonic energy for imaging internal organs and tissues. Same as sonography. (See ULTRASONICS.)
ECOLOGICAL STRESS VECTOR. Any vector in the environment producing a physiological response in man. Such response may or may not be pathological. Major stress vectors are: climatotaxis, biotaxis, mechanotaxis, chemotaxis, particulotaxis (q.v.).
EFFECTIVE TEMPERATURE. A measure of "warmth as related to comfort." Combines environmental factors, humidity, true temperature, and air velocity to provide a scale of subjective comfort. Two experimental scales of the American Society of Heating and Ventilating Engineers pertain to normally-dressed and partially-dressed people. A comfortable effective temperature is significant in maintaining high productivity and good quality control. (Corrected effective temperature (CET) is often used in place of effective temperature.)
EFFERENT. Conveying away from a biological processing station, specifically by conveying nervous impulses from a neural center to a muscle. (See AFFERENT.)
ELASTIC LIMIT OF TISSUES. The level of physical deformation caused by the application of a force beyond which tissue damage occurs and beyond which the tissue will not return to its original function when the force is removed.
ELECTRICAL-SILENCE. Absence of a measurable action potential in a biological structure. A zero recorder pen deflection should ideally occur during electromyography of a non-contracting muscle. In practice, true electrical-silence cannot be observed unless random noise signals are filtered out.
ELECTROCARDIOGRAPH. A recording galvanometer which produces an analog representation of the electrical activity of the conductive tissues of the heart, i.e., an electrocardiogram (ECG or EKG). Useful in the diagnosis of heart disease and assessment of work stress in health and disease.
ELECTRODE. A device used to sense the electric potential of body tissues or to transmit such a potential. It can be surface-mounted as a skin electrode, internally mounted as a needle electrode, or as a very fine wire inserted into the muscle. An effective electrode minimizes contact resistance and junction potentials. (Used in myography, cardiography, and encephalography.)
ELECTROMYOGRAPHIC KINESIOLOGY. The analysis and evaluation of human motion patterns by means of electromyography. Useful in establishing optimal motion patterns through workplace and tool design.
ELECTROMYOGRAPHY. The technique of recording the electrical potential generated by muscle activity. Surface electromyography will provide a measure of muscular sequence and physiological effort associated with a particular task.
ELECTROPHYSIOLOGICAL APPARATUS. Research and evaluation devices which sense bioelectrical signals from heart, muscles, brain, etc. The sensed signal is amplified and displayed in the form of an analogue or digital readout. Examples: electromyography, electrocardiography, polygraph, (q.v.).
EMPIRICAL WORKPLACE DESIGN. Design based on operating characteristics and mechanical needs of equipment or on previous experience with similar work situations. Must normally proceed through a number of "improvements'' to adapt to the needs of the worker.
ENDOCHTHON. Innate, originating from within. In hand-operation of a lever, the power is endochthonous to the operator. (See EXOCHTHON.)
ENVIRONMENTAL ENGINEERING. Application of engineering principles to create and maintain surroundings which are favorable for the sustenance of lift.
ENVIRONMENTAL INPUTS. Often used as synonym for ecological stress vector (q.v.). More accurately, the following factors to which the worker responds either physiologically or behaviorally; economic, social, managerial, mechanical, climatic, psychological. The resulting outputs are economical (in the form of production), emotional (in the form of employee behavior), and physiological (in the form of employee health and fatigue).
ENVIRONMENTAL STRESS VECTOR. Synonym for ecological stress vector (q.v.).
EPICONDYLE. A raised area (bump) on the condyle of a bone, from which muscles originate. E.g., the flexor muscles of the fingers originate from the medial epicondyle of the humerus.
EPICONDYLITIS. Inflammation or infection in the general area of an epicondyle, e.g., tennis elbow.
EPIPHYSIS. The ends of a long bone. Joint surfaces are always part of the epiphysis.
EQUILIBRIUM. State of a system or a body in which internal change does not occur. In mechanics, the sums of all forces and moments are zero.
ERECTOR SPINAE MUSCLES. Large back muscle which originate on the sacrum and lumbar vertebral bodies and insert on the rib cage and thorasic vertebrae. The muscle is comprised of three components: 1) spinalis, 2) longissimus, and 3) ilio-costalis. The erector spinae are the primary muscles recruited during lifting activities.
ERGONOMICS. The application of a body of knowledge (life sciences, physical sciences, engineering, etc.) dealing with the interactions between man and his total working environment, such as atmosphere, heat, light and sound, as well as all tools and equipment of the workplace.
ERGONOMIC ANALYSIS. Application of the principles of ergonomics to study in detail all of the specific elements which are pertinent to a man-equipment or man-task interface.
ETIOLOGY. The study of causes of disease. In biomechanics, etiology of trauma or work strain is complicated because the site of such trauma is often remote from the focus of work stress. Industrial hygiene experience is a valuable aid to determining causes of workplace-generated trauma.
EXOCHTHON. Outside of and not inherent to a body. Operation of pneumatic or electrical tools requires management by the operator of power which is exochthonous to his system, i.e., not generated by him. (See ENDOCHTHON.)
EXTENSION. Straightening of a curve or angle; the position of the joints of the extremities and back when one stands at rest, or the direction of motion that tends to restore this position; the opposite of flexion.
EXTENSOR MUSCLE. A muscle which when active increases the angle between limb segments, e.g. the muscles which straighten the knee or elbow, open the hand or straighten the back.
EXTENSOR RETINACULUM. Also known as transverse dorsal ligament. A membranous band of fibers at the back of the hand which forms a tunnel through which the extensor tendons of the fingers pass. The retinaculum acts as a guide and prevents the tendons from bow-stringing when the wrist is hyper-extended.
EXTENSOR TENDON. Connecting structure between an extensor muscle and the bone into which it inserts. Examples are the hard, longitudinal tendons found on the back of the hand when the fingers are fully extended. (See TENDON, EXTENSOR MUSCLE, INSERTION.)
EXTERNAL MECHANICAL ENVIRONMENT. The man-made physical environment, e.g., equipment, tools, machine controls, clothing. Ant: internal (bio)mechanical environment (q.v.). external working environment, The environment external to the body at the workplace. Of particular importance in ergonomics because of the effect of surroundings on work performance. It includes immediate environment such as tool handles, clothing, temperature, humidity, pressure, and composition of atmosphere. (See GILBRETHIAN VARIABLES, INTERNAL (BIO)MECHANICAL ENVIRONMENT.)
EXTRINSIC. Anatomical term referring to a component, usually a muscle that originates outside of the structure on which it acts, e.g. relating to vision, the extrinsic muscles of the eye are located in the orbit and move the eyeballs. The intrinsic muscles (q.v.) are located within the eyeball and operate the iris and lens. Ant: intrinsic.
EYE SCANNING. Binocular scanning of the visual field by movement of the eyeballs alone and without head rotation through use of the extrinsic muscles of the eye. Eye scanning is a rapid and easy process, but can be effectively performed only with a central visual cone of 60 degrees or loss of depth perception will result.
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