This study investigated changes in median sensory nerve conduction velocity (SNCV) over several weeks of exposure to a voluntary, moderately forceful, repetitive pinching task performed for food rewards by a small sample of young adult female monkeys (Macaca fascicularis). SNCV, derived from peak latency, decreased significantly in the working hands of three of the four subjects. The overall decline in NCV was 25%-31% from baseline. There was no decrease in SNCV in the contralateral, nonworking hands. Several weeks after being removed from the task, SNCV returned to within 87%-100% of baseline. MRI showed enlargement of the affected nerves near the proximal end of the carpal tunnel, at the time of maximal SNCV slowing. This new animal model demonstrates a temporally unambiguous relationship between exposure to a moderately forceful, repetitive manual task and development of median mononeuropathy at the wrist, and recovery of SNCV following termination of task exposure. This study contributes to the pattern of evidence of a causal relationship between manual work, median mononeuropathy, and carpal tunnel syndrome in humans. In the future, this new animal model could be used to characterize dose-response relationships between risk factors and carpal tunnel syndrome. ß

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Kneeling in a restricted posture during manual materials handling has been associated with increased risk of low back pain. Little is known about the effect of kneeling posture on spinal loads. The purpose of this study was to compare differences in spinal loading between kneeling and standing postures for lifting tasks. Twelve subjects asymmetrically lifted luggage of three weights to three heights from floor while kneeling. Three subjects also performed the same tasks from waist height while standing. An adapted free-dynamic EMG-assisted biomechanical model was used to calculate spinal loads. Statistical analysis showed that there was no difference in compression between kneeling and standing (p=0.9605), but kneeling resulted in increased anterior-posterior and lateral shear forces on the lumbar spine (p =0.0002 and p<0.0001, respectively). Spinal loading changes while kneeling in a restricted posture may increase the risk of low back injury and must be considered in ergonomic job design.

In general, K-12 students have little opportunity to control feedback from the various factors in their educational environments. However, leading theories of human-system interaction suggest participants in a system will perform better if they have some degree of control over their interaction with the design of the system's features. In an effort to provide an added degree of control to students in one high school while also attempting to address concerns about computer use-related musculoskeletal discomfort in students, an experiment was conducted with the goal of identifying effective means through which students could learn about healthy computing. One group of students (n = 8) participated in a knowledge discovery process facilitated by an ergonomist, a second group of students (n = 6) participated in a training session conducted by the first group of students, and a third group served as controls (n = 7). Results of a comparison of scores for pre-and post-intervention surveys that tested students' abilities to recognize problematic computer use conditions and make appropriate recommendations for change showed an increase for the first and second groups, and no increase in the control group. Another positive sign from the first group was their sustained participation, on their own time, in the learning process over the course of several weeks. Pros and cons of the learning methods are discussed.