xiii, 79 p. : ill. A print copy of this thesis is available through the UO Libraries. Search the library catalog for the location and call number. / Subacromial impingement syndrome is the most common disorder of the shoulder. Abnormal superior translation of the humeral head is believed to be one of the major causes of this pathology. The overall purpose of this study was to better understand glenohumeral kinematics in normal healthy individuals using fluoroscopy to help comprehend the mechanism of shoulder impingement. This research was divided into three sections: a validation study to measure humeral head translation, a comparison between dynamic and static arm elevation and lastly, humeral head translation after a suprascapular nerve block. In the first study, fluoroscopy was used to take images of human cadaver shoulders. Scapular orientation was manipulated in different positions while the humerus was at 90 degrees of elevation. Humeral head translation was measured using two methods and was compared to the known translation. Additionally, the accuracy of the contour registration method to measure 2-D scapular rotations was assessed. For the second study, subjects elevated their dominant arm while fluoroscopic images were taken. An edge detection software was utilized to digitize points on both the humeral head and glenoid. Humeral head translation and scapular upward rotation were measured using a contour registration method with respect to the glenoid during arm elevation. Five different arm elevation angles were investigated to measure differences in humeral head translation between trials. There was no difference found between humeral head translation and scapular upward rotation between static and dynamic shoulder elevation. For the third study, humeral head translation was measured before and after a suprascapular never block. The humeral head was superiorly located and the scapula was more upwardly rotated after the block. The differences were observed during mid range of motion. This result showed that there was a compensatory increase in both humeral head translation and scapular upward rotation due to the nerve block. These results suggest that increasing muscular strength and endurance of the supraspinatus and infraspinatus muscle could prevent any increased superior humeral head translation. This may be beneficial in preventing shoulder impingement or rotator cuff tear over time. This dissertation includes unpublished co-authored materials. / Committee in charge: Andrew Karduna, Chairperson, Human Physiology; Li-Shan Chou, Member, Human Physiology; Louis Osternig, Member, Human Physiology; Stephen Frost, Outside Member, Anthropology

Epidemiological evidence suggests an association between exposure to non-neutral working postures and work-related musculoskeletal disorders (MSDs) of the low back and shoulder. Accurate and precise quantitative estimation of exposure to non-neutral working postures is, therefore, essential for evaluating worker risk, developing and testing ergonomic interventions, and improving worker health and well-being. Current methods used to directly estimate occupational exposure to non-neutral postures may be obtrusive, often lack sufficient portability for field use, and have limited accuracy and precision when used to measure dynamic or complex motions. Inertial measurement units (IMUs) are emerging instrumentation devices that measure and report an object's orientation and motion characteristics using multiple electromechanical sensors (i.e., accelerometers, gyroscopes, and/or magnetometers). They have been observed to accurately monitor body kinematics over periods of relatively short duration in comparison to laboratory-based optical motion capture systems. Limited research, however, has been performed comparing exposure information obtained with IMUs to exposure information obtained with other field-capable direct measurement exposure assessment methods. Furthermore, insufficient information on the repeatability of IMU-based estimates over a substantial time period (e.g., a full work shift) and inadequate knowledge regarding the effects of different IMU sensor configurations and processing methods on the accuracy and repeatability of estimates of exposure obtained with IMU systems contributes to a lack of their use in epidemiological field studies. This thesis was designed to address these issues and expand upon the current scientific literature regarding the use of IMU sensors as direct measurement devices for assessing exposure to non-neutral working postures in the field. Chapter I provides a background and justification for the work. Chapter II presents the findings of a laboratory-based, manual material handling study that was performed to compare estimates of thoracolumbar trunk motion obtained with a commercially available IMU system with estimates of thoracolumbar trunk motion obtained with a field-capable reference system, the Lumbar Motion Monitor (LMM). The effects of alternative sensor configurations and processing methods on the agreement between LMM and IMU-based estimates of trunk motion were also explored. Chapter III presents the results of a study performed to evaluate the accuracy and repeatability of estimates of trunk angular displacement and upper arm elevation obtained with the IMU system examined in Chapter II over the course of an eight-hour work shift in both a laboratory and field-based setting. The effects of alternative sensor configurations and processing methods on the accuracy and repeatability of estimates of trunk angular displacement and upper arm elevation obtained with the IMU system were also studied. Chapter IV presents the results of a randomized, repeated measures intervention that demonstrates the utility of the IMU system examined in Chapters II and III as a direct measurement instrument for comparing "ergonomic" and conventional examination equipment commonly used by ophthalmologists. Finally, Chapter V summarizes the major findings, discusses their practical implications, and provides suggestions for future research.

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