Jacqueline Reynolds Mozrall

The effects of complex wrist and forearm posture on wrist range of motion

Previous research on wrist functionality has focused almost entirely on range of motion (ROM) in 2 or 3 isolated planes (flexion/extension, radial/ulnar deviation, and forearm pronation/supination), without investigating the potential effects of complex wrist/forearm posture on ROM. A quantitative analysis of these effects on wrist ROM was performed. ROM was measured in one plane using both a manual method and an electrogoniometer while the participant maintained a fixed, secondary wrist and forearm posture. The study revealed that combinations of wrist/forearm postures have significant effects on wrist ROM; the largest effects are those of wrist flexion/extension on radial deviation ROM. The study also found that, consistent with previous research, wrist deviation measurements obtained with an electrogoniometer were significantly different from those obtained manually. Biomechanical theories for the results obtained are discussed. This research could be used to enhance ergonomic evaluation techniques by providing a more accurate risk assessment of certain complex wrist postures, particularly those in which wrist flexion/extension is combined with radial deviation.

Effects of physical exertion on task performance in modern manufacturing: a taxonomy, a review, and a model

Modern manufacturing systems have the characteristic of demanding human cognitive task performance in an environment where sudden physical demands are also possible. There is little research addressing the effects of physical work on cognitive task performance and it is not well organized for application to manufacturing systems design. This paper uses an initial three-dimensional taxonomy to review the literature. Some clear findings emerge, but many studies produced contradictory results. While part of the contradiction was due to experimental technique, some was also due to the lack of a detailed structure to guide future research. Such a model is thus proposed, using the concept of limited resources for both the cognitive and physical aspects of tasks. In addition, specific predictions of research needs for modern manufacturing systems arise.

Effects of pace and stress on upper extremity kinematic responses in sign language interpreters

Sign language interpreters suffer from high levels of upper extremity disorders and burnout due to the physical and cognitive demands of interpreting. The objective of this research was to quantify the wrist kinematics of interpreting and to assess how speaker pace and psychosocial stress influence wrist kinematics. Professional interpreters interpreted a pre-recorded lecture, while the speaking pace of the lecture varied. One group of subjects was exposed to environmental conditions intended to induce stress. Several wrist kinematic variables of interpreting exceeded previously established high risk benchmarks for development of upper extremity disorders in industrial tasks. Wrist velocity and acceleration increased significantly with pace, with increases ranging from 10.7–18.6%. Increased psychosocial stress resulted in significant increase of left hand (non-dominant) wrist velocity and acceleration, with increases ranging from 14.8–19.5%. These results provide an objective assessment of the biomechanical demands of interpreting and support earlier research into different types of work, which found deleterious effects of psychosocial stress on the biomechanical responses of the lower back.

A corporate-wide ergonomics programme : implementation and evaluation

The challenge of introducing an ergonomics programme into a diverse and relatively loosely-structured corporation is considered. A programme based on a de® ned multi-step problem-solving process was developed and implemented. An audit of this programme was undertaken in nine divisions, covering each division headquarters and 157 workplaces in 11 plants. From the audit a set of future needs was derived, with changes in the organization, the ergonomic analysis methods, and the speci® cation of solutions.

The effects of whole-body restriction on task performance.

Many occupations, particularly involving maintenance operations, require individuals to perform both physical tasks and mental tasks in restricted spaces. Researchers have examined physical task performance under various restrictions; however, little research has investigated the effects of restricted space on cognitive tasks. Cognitive task performance in restricted spaces presents cognitive demands (i.e. the task itself) as well as additional physical demands (e.g. awkward postures), which may adversely affect task performance or operator workload. This research focused on the effects of whole-body restrictions on cognitive task performance. An experiment was conducted that examined 9 levels of restriction created in a laboratory: an unrestricted control, 6 single whole-body restrictions at two severity levels (2 lateral, 2 sagittal and 2 vertical) and 2 multiple restrictions (sagittal/vertical, lateral/sagittal/vertical). An inspection task served as the cognitive task. Behavioural, physiological and psychophysical measures were collected and analysed to measure the operator and performance effects. Operator response differences were found among the various forms of restriction as well as the severity level of similar forms of restriction. Increasing restriction significantly affected the behavioural and physiological operator response as opposed to the cognitive response.

Biomechanical Comparison of American Sign Language Interpretation and Conversation

Sign language interpreting is an occupation that requires a combination of high physical and cognitive demands. Professional sign language interpreters frequently suffer from work-related musculoskeletal disorders, but the problem does not seem to be as widespread for Deaf people who, similar to interpreters, frequently use a signed language. This study compares the biomechanics of American Sign Language (ASL) interpreting with the biomechanics of ASL used in casual conversation between professional interpreters and Deaf students. Results indicate that interpreters use, on average, 22% larger wrist deviations and 7% higher levels of wrist velocity when they interpret, compared to when they use ASL in conversation. During conversation, no significant differences in wrist kinematics were observed between the Deaf students and interpreters who participated in the conversation. However, the Deaf students tended to sign with larger wrist deviation than the interpreters.

The Effects of Complex Wrist and Forearm Posture on Wrist Range of Motion

In order to minimize the risk of repetitive trauma injuries, postures or motions that place joints near the limits of their range of motion (RoM) should be avoided. Before it can be determined that a posture or motion approaches the limit of a joints motion, these limits need to be established. Previous research on wrist functionality has focused almost entirely on RoM in two or three isolated planes (flexion/extension, radial/ulnar deviation, and forearm pronation/supination), without investigating potential effects of complex wrist/forearm posture on RoM. Since most practical applications of this wrist motion data involve more than these isolated planar deviations, the effects of complex wrist/forearm posture on wrist functionality need to be understood.

An Undergraduate Human Factors Workbook

The Industrial and Manufacturing Engineering (IME) Department at Rochester Institute of Technology (RIT) requires undergraduate students to take two courses in human factors, with both courses possessing a laboratory requirement. In an effort to consolidate support materials for the undergraduate human factors courses, a supplemental workbook was developed. The workbook provides both the students and instructors with a varied selection of laboratory exercises and homework problems which are directly relevant to the material being covered in the lectures and laboratories. The workbook includes specific guidelines for the required laboratory format, a selection of laboratory exercises and homework problems, and appendices which include supplemental material related to the laboratory exercises and a large set of human factors references. The workbook has been very beneficial for instructors, for it provides an organized set of information which directly supports both the lecture and laboratory material. Questionnaire data obtained from students identified good features of the workbook, as well as areas which needed improvement.

Effects of Pace and Work Stress on Upper-Extremity Kinematic Responses in Sign Language Interpreters

Sign language interpreting is an occupation that suffers from high levels of repetitive motion injuries (RMIs) and burnout due to the high physical and cognitive demands of the interpreting task. The objective of this research was to determine the effects of work pace and psychosocial stress on the wrist kinematics of sign language interpreting. It was found that neither pace nor stress affected mean wrist position, but increased pace resulted in a significant increase of both mean velocity and acceleration, with increases ranging from 10.7–18.6%. Increased psychosocial stress resulted in a significant increase of left-hand (non-dominant) mean velocity and acceleration, with increases ranging from 14.8–19.5%. No effect of stress was observed for the right hand. In addition, several wrist kinematic variables of interpreting exceeded previously established high risk industrial benchmarks. The results of this work support earlier research which found deleterious effects of work stress on the biomechanical responses of the lower back.