The transition from text-oriented software to graphically-based software has brought about a rapid increase in the number of mouse users. Recently, increased usage of the mouse has been linked with the development of cumulative trauma disorders. This investigation concerns the effects that mouse surface height and wrist support have on wrist posture. Distance between targets and target width were varied to determine performance time and performance accuracy throughout the conditions. Results showed that the presence of a wrist support decreased wrist extension and radial deviation, and increased wrist flexion. However, wrist support had no significant effect on ulnar deviation. There was a significant interaction of support and surface height for wrist extension. Surface height had a significant effect on all dimensions of wrist posture. Higher surface height resulted in increased flexion and ulnar deviation, and decreased extension and radial deviation. Distance between targets was a significant effect for ulnar deviation. The long distance resulted in a greater amount of ulnar deviation. Accuracy was significantly affected by distance between targets and target width. There was a significant interaction of distance and width for flexion. When distance between targets and target width were converted to Indices of Difficulty (ID), it was found that as ID became larger, movement time between targets became longer (as predicted by Fitts' Law). / Master of Science

No description available.

No description available.

No description available.

No description available.

The primary purpose of this study was to determine the responsiveness of the active wrist joint position sense (JPS) test to detect wrist sensori-motor status change at 8 and 12 weeks following distal radius fracture (DRF) treatment intervention. Responsiveness, defined as the instrument's ability to accurately detect change, was analyzed via distribution- and anchor-based statistical methods. Distribution-based analysis encompassed both group- (i.e., effect size [ES], standardized response mean [SRM]) and individual-based (i.e., minimum detectable change [MDC]) statistical indices. Anchor-based analysis was used to determine the minimal clinically important deficit (MCID) value by linking active wrist JPS test scores to Patient Global Impression of Change (PGIC) scale values. The secondary purposes of the study were to: 1) compare the active wrist JPS test responsiveness as reflected by its MCID value between non-surgical and surgical DRF treatment interventions, 2) compare the active wrist JPS test responsiveness as reflected by its MCID value between participants with high- and low-pain levels, 3) compare the active wrist JPS test scores between participants with high- and low-pain levels, 4) assess the relationship between active wrist JPS test MCID value and function, and 5) determine the intra-tester reliability of the PGIC scale for assessing global health status change following DRF treatment intervention. A prospective cohort study design was utilized. Thirty-three participants between 25 and 90 (mean 59.72) years of age following any non-surgical and surgical DRF treatment intervention were recruited. The active wrist JPS test was determined to be highly responsive based on group-based statistical indices (ES [8 weeks = 1.53, and 12 weeks = 2.36] and SRM [8 weeks = 1.57, and 12 weeks = 2.14]). Statistically significant MDC values were 4.28 and 4.94 deg at 8 and 12 weeks following treatment initiation, respectively. Clinically meaningful MCID values at 8 and 12 weeks were 5.00 and 7.09 deg, respectively. Responsiveness levels were not significantly different between the two treatment and pain-level groups at 8 and 12 weeks post DRF treatment intervention. High-pain participants demonstrated significantly greater JPS deficits at both 8 and 12 weeks, and a significant association existed between active wrist JPS test MCID value and function. The PGIC scale intra-tester reliability was found to be high (ICC = 0.97). Based on this study's findings, clinicians can use this highly responsive test with confidence to measure statistically and clinically meaningful conscious wrist sensori-motor function change following DRF treatment. / Kinesiology

Work-related musculoskeletal disorders (WMSDs) are a major source of lost productivity and revenue in the workplace and disability in workers. There is strong evidence for a relationship between physical risk factors, such as repetitive motions and excessive force, and the development of WMSDs; yet there are unexplained discrepancies in determining which workers are more at risk. Researchers hypothesize that non-physical factors in the workplace, or psychosocial factors, may contribute to the development of WMSDs. The following study examined the effects of two psychosocial factors, mental workload and time pressure, on perceived workload and physiological reactions of the lower arm and wrist during typing activity by measuring muscle activation patterns, wrist posture and movement, key strike forces, and subjective assessments of overall workload. The results indicate that increases in time pressure lead to increases in lower arm muscle activation, key strike forces, and wrist deviations. Key strike forces may increase with higher mental workload levels, but other effects of mental workload were not clear. Perceived overall workload (time load, mental effort load, and stress load) increased with mental workload and time pressure, and typing performance decreased. The evidence from this study suggests that these psychosocial factors (mental workload and time pressure) mediate physical risk factors to increase risk for WMSD development in the upper extremities. The results illustrate the need for those designing jobs and work tasks to consider both physical and psychosocial aspects of the working environment to prevent injuries in employees. / Master of Science

A study was conducted to investigate the effects of certain cinematic choices on people’s ability to judge the posture of the wrist from video images. Deviated wrist postures, which are associated with the performance of many tasks, have been reported to play a role in hand and arm discomfort and in a variety of disorders. The goal of this study was to gain a better understanding of people’s performance in judging wrist posture as well as people’s ability to judge their performance. One objective was to determine the relative performance effects of one still image, two still images, and full-motion images. Other objectives were to determine the effect on performance relative to three different views and ten different wrist positions. It was also of interest to begin to understand how these three independent factors may interact with one another and also how the three dependent variables-accuracy, certainty, and decision time-related to one another. A second experiment also investigated the display effects of a single still image vs. full-motion video. A second factor that was investigated was the performance effects of more complex hand positions (i.e., while holding objects and performing real tasks). In the first Experiment it was found that a view which was normal to the thumb-side of the hand resulted in significantly better performance than a view oblique to the hand. This effect held for each of the Display Methods and for seven of the ten wrist positions. It was hypothesized that this effect may be due to the inherent superiority of one view over another. An alternative possibility is that the thumb-side view offered participants the opportunity to compare what they saw on the screen to their own hands. It was suggested that these alternative possibilities be tested as the results may either support efforts to find “the best view” or to develop ways to provide “comparison postures.” In the first experiment there were significant main and interaction effects for the dependent variable, accuracy. There were also significant main effects found for certainty and decision time, but no interaction effects were found. An interesting finding from the first experiment was that people were generally overly confident of their performance. In most instances, participants’ performances were not related to their perceived performances. For the full-motion images, half of the participants’ perception of their performance was negatively correlated with actual performance. As would be expected, two views were generally found to be better than one view. However, it was also found that a particular single view (thumb-side) resulted in a level of performance that was not significantly different from two-still combinations which did not include the thumb-side view. No significant effects were found for the second experiment and the levels of performance were found to be similar to the first experiment under the oblique view condition. As a background to the experimental investigations, literature pertaining to these four areas was reviewed: The relationship of wrist posture to hand and arm disorders, methods of observing posture, advancements in video technology, and considerations regarding the nature of video as a two-dimensional display format. Also explored were differences in public perception about the task-related “causes” of hand and arm disorders vs. the clinical and observational findings that were reviewed. It was suggested that the ergonomic community bears some responsibility for these differences. Better methods are needed not only to observe human factors, but also to communicate our observations amongst ourselves, to other professionals, and to anyone who could benefit by such knowledge. / Master of Science

Since the introduction of graphical user interfaces (GUI), input control devices have become an integral part of desktop computing. When interfacing with GUIs, these input control devices have become the human's primary means of communicating with the computer. Although there have been a number of experiments conducted on pointing devices for desktop machine, there is little research on pointing devices for wearable computer technology. This is surprising because pointing devices are a major component of a wearable computer system, allowing the wearer to select and manipulate objects on the screen. The design of these pointing devices will have a major impact on the ease with which the operator can interact with information being displayed (Card, English, and Burr, 1978). As a result, this research is the first in a series to investigate design considerations for pointing devices and visual displays that will support wearable computer users. Twenty soldiers participated in an experiment using target acquisition software with five pointing devices and two visual displays. The findings of the research strongly support the use of a relative mode-pointing device with rotational characteristics (i.e. trackball or thumbwheel) over other designs. Furthermore, the results also suggest that there is little difference between pointing devices operated with the thumb and index finger for target acquisition tasks. This study has also showed that there were little differences in pointing and homing time for pointing devices across the two visual displays. Finally, the study demonstrated that the Fitts' law model could be applied to hand-operated pointing devices for wearable computers. This is important because it allows the future development of pointing devices to be compared with the devices tested in this research using the Fitts' Law Index of Performance calculations. / Master of Science

In recent years, increased emphasis has been placed on the development of parallel-architecture mechanisms for use as robotic manipulators. Parallel robots offer the benefits of higher load-carrying capacity, greater positioning accuracy and lower weight when compared to serial devices. However, robotic wrist development has traditionally focused on serial mechanisms having a large, spherical workspace and simpler kinematic solutions. The Carpal wrist is a unique parallel mechanism consisting of a fixed base and a movable output plane connected via three serial kinematic chains. The forward and inverse kinematic problems of the Carpal wrist are solved closed-form, making the device suitable for use as a new type of robotic wrist. The closed-form solutions are dependent upon the assumptions that the fixed and moving planes are symmetric about a mid-plane and that the three kinematic chains connecting the planes are identical. This thesis investigates the errors that result from those assumptions being violated due to manufacturing and assembly errors. In the non-ideal model, pose error is found by iteratively solving a system of equations describing the output plane position and orientation and comparing them with the ideal solution. The error model is a tool for predicting the effects of kinematic parameter errors on the positioning accuracy and reachable workspace of the Carpal wrist. In this work, a general error model is developed and validated for a range of parameter error values. Special-case results are presented for errors in the individual parameters. / Master of Science