Ergonomics, loss management and surveillance: Biomechanical, psychophysical and physiological loads and industrial handwheel actuation.

摘要

The impact of occupational injury upon industry is profound, particularly with respect to afflictions involving the musculoskeletal system. This thesis describes how ergonomics, surveillance and loss management fit together in a seamless system targeted at controlling and preventing these afflictions. It contains several new discoveries concerning the ability of a worker to operate an industrial handwheel. We revealed that currently existing standards for the design of this task are insufficient.;The analysis of workers in the field revealed that the flexor carpis radialis, and erector spinae muscles were very active. A series of laboratory experiments were undertaken to determine the effect of trunk posture, upper extremity position, handwheel height above grade, distance and contour of foot support, and pitch angle orientation upon maximal strength, electromyographic activity (EMG), perceived exertion, oxygen consumption and heart rate. Upper extremity adduction strength and EMG was not affected by axial trunk rotation; however, upper extremity position did affect these variables. Maximal voluntary two-handed counter-clockwise net tangential static force was found to be below those forces required to actuate handwheels in the field. Hence, it is not surprising that overexertion injuries are commonly observed. To control for these types of injuries, the static force demands of the task should reside well below 700 N.;Handwheel pitch angle and height above the grade significantly affected the compression as well as shear forces acting upon the low back, exceeding their tolerance. As high as 99% of the referent population is incapable of generating sufficient upper extremity strength to safely complete the task. Both static and dynamic handwheel operation was studied using psychophysical methods. It was revealed that a handwheel height of 93 cm induced the least amount of perceived exertion during both actuation and operation. The physiological experiments revealed the task to be very heavy work, based upon observed levels of oxygen consumption and heart rate. The results indicate that the task imparts a great psychophysical and physiological load on the worker and that these factors must be considered in the design of such control devices in an effort to optimize the fit between this task and the worker.