Objective
The objective was to determine the effect of two head-mounted display (HMD) augmented reality (AR) devices on muscle activity and eye strain of electric utility workers. The AR devices were ...the Microsoft HoloLens and RealWear HMT-1.
Background
The HoloLens is an optical see-through device. The HMT-1 has a small display that is mounted to the side of one eye of the user.
Method
Twelve power plant operators and 13 manhole workers conducted their normal procedural tasks on-site in three conditions: HoloLens, HMT-1, and “No AR” (regular method). Duration of test trials ranged up to 30 s for operators and up to 10 min for manhole workers. Mean and peak values of surface electromyographic (sEMG) signals from eight neck muscles were measured. A small eye camera measured blink rate of the right eye.
Results
In general, there were no differences in sEMG activity between the AR and “No AR” conditions for both groups of workers. For the manhole workers, the HoloLens blink rate was 8 to 11 blinks per min lower than the HMT-1 in two tasks and 6.5 fewer than “No AR” in one task. Subjective assessment of the two AR devices did not vary in general.
Conclusion
The decrease in blink rate with the HoloLens may expose utility manhole workers to risk of eye strain or dry-eye syndrome.
Application
HMD AR devices should be tested thoroughly with respect to risk of eye strain before deployment by manhole workers for long-duration procedural work.
The number of seats per airplane has increased over the years, leading to a decrease in seat width and legroom. Using the HFES Multivariate Accommodation Testing Tool, the percentage of the general ...population accommodated in a static seated posture was calculated with respect to two important design dimensions of airline seats, seat width and legroom. Results from this article can inform seat manufacturers and airlines on how to design seats that physically accommodate the largest number of passengers. This paper does not address passenger safety and comfort, which are complex, multi-factor issues that extend beyond physical accommodation.
Positioning a computer keyboard with a downward slope reduces wrist extension needed to use the keyboard and has been shown to decrease pressure in the carpal tunnel. However, whether a downward ...slope of the keyboard reduces electromyographic (EMG) activity of the forearm muscles, in particular the wrist extensors, is not known.
Sixteen experienced typists participated in this study and typed on a conventional keyboard that was placed on slopes at angles of 7.5, 0, -7.5, and -15 degrees. Electromyographic activity of the extensor carpi ulnaris (ECU), flexor carpi ulnaris (FCU), and flexor carpi radialis (FCR) muscles was measured with surface electrodes, while the extension and ulnar deviation angles of the right and left wrists were measured with electrogoniometers.
Wrist extension angle decreased from approximately 12 degrees of extension while typing on a keyboard with a 7.5-degree slope to 3 degrees of flexion with the keyboard at a slope of -15 degrees. Although the differences were in the range of 1% to 3% of maximum voluntary contraction (MVC), amplitude probability distribution function (APDF) of root-mean-square EMG data points from the ECU, FCU, and FCR muscles varied across keyboard slopes.
Wrist extension decreased as the keyboard slope decreased. Furthermore, a slight decrease in percentage of MVC of the ECU muscle was noted as the keyboard slope decreased. Based on biomechanical modeling and published work on carpal tunnel pressure, both of these findings appear to be positive with respect to comfort and fatigue, but the exact consequences of these findings on the reduction or prevention of injuries have yet to be determined. The results may aid physical therapists and ergonomists in their evaluations of computer keyboard workstations and in making recommendations for interventions with regard to keyboard slope angle.
Celotno besedilo
Dostopno za:
DOBA, FSPLJ, IZUM, KILJ, NUK, OILJ, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK, VSZLJ
Two head-mounted augmented reality (AR) systems, Microsoft HoloLens and RealWear HMT-1, were tested to determine their effect on blink rate and muscle activity of the neck and shoulder muscles of ...electric utility manhole workers. The task of splicing a cable was performed under three conditions: HoloLens, HMT-1, and No AR (normal). Surface electromyography (sEMG) of the right and left sternocleidomastoid, splenius, semispinalis capitis, and upper trapezius muscles were measured on 13 manhole workers, and a small camera recorded blink rate of the right eye. Results revealed, in general, no significant differences in 50th and 90th percentile sEMG between the three conditions. There was no difference in blink rate between the HMT-1 and No AR, but the HoloLens blink rate was 7.8 to 11 blinks/min lower than the HMT-1 for two of the three tasks. A decrease in blink rate of these magnitudes may indicate risk of eye strain to manhole workers who use an OST AR device without appropriate rest breaks. Head-mounted AR devices deployed for underground utility workers warrant further study.
Augmented reality (AR) is a technology that combines real and virtual information presented to the user in an interactive way in real time. The Microsoft HoloLens and RealWear HMT-1 are two common ...types of head-mounted AR available to industrial field workers. These two AR systems were tested on how they affected blink rate, an indicator of eye strain, and electromyographic (sEMG) activity of the neck and shoulder muscles of electric utility power plant operators while they performed five routine inspection tasks of coal equipment. The inspection tasks were conducted under three conditions: HoloLens, HMT-1, and No AR (regular method). Workers communicated with the HoloLens with a right-hand gesture and by voice input to the HMT-1. The duration of the inspection tasks ranged from an average of 10 to 28 sec. Twelve experienced power plant operators participated in the study. sEMG) of the right and left sternocleidomastoid, splenius, semispinalis capitis, and upper trapezius muscles were measured, and a small camera recorded blink rate of the right eye. Results reveal generally no significant differences in 50th and 90th percentile sEMG between the three conditions for all eight muscles. Although the means of blink rate appeared consistently lower with the HoloLens than the No AR and HMT-1 (approximately 4.4 blinks/min), these differences were not significant at the 0.05 level (p=0.06 to 0.17). Future studies should investigate a larger sample size of workers wearing AR devices for longer time periods (> 30 min) to determine long-term effects of AR devices on muscle activity and eye strain. A system of hardware, software, and experimental protocol was developed that follow-up studies may employ to test physiological effects of AR devices.
Objective: The primary purpose of this study was to determine whether conventional anthropometric databases of the U.S. general population are applicable to the population of U.S. electric utility ...field-workers.
Background: On the basis of anecdotal observations, field-workers for electric power utilities were thought to be generally taller and larger than the general population. However, there were no anthropometric data available on this population, and it was not known whether the conventional anthropometric databases could be used to design for this population.
Method: For this study, 3 standing and 11 sitting anthropometric measurements were taken from 187 male field-workers from three electric power utilities located in the upper Midwest of the United States and Southern California. The mean and percentile anthropometric data from field-workers were compared with seven well-known conventional anthropometric databases for North American males (United States, Canada, and Mexico).
Results: In general, the male field-workers were taller and heavier than the people in the reference databases for U.S. males.The field-workers were up to 2.3 cm taller and 10 kg to 18 kg heavier than the averages of the reference databases.
Conclusion: This study was justified, as it showed that the conventional anthropometric databases of the general population underestimated the size of electric utility field-workers, particularly with respect to weight.
Application: When designing vehicles and tools for electric utility field-workers, designers and ergonomists should consider the population being designed for and the data from this study to maximize safety, minimize risk of injuries, and optimize performance.
Objective: The objective of this research is to determine the best location to place a conventional mobile computer supported by a commercially available mount in a light truck cab.
Background: U.S. ...and Canadian electric utility companies are in the process of integrating mobile computers into their fleet vehicle cabs. There are no publications on the effect of mobile computer location in a vehicle cab on biomechanical loading, performance, and subjective assessment.
Method: The authors tested four locations of mobile computers in a light truck cab in a laboratory study to determine how location affected muscle activity of the lower back and shoulders; joint angles of the shoulders, elbows, and wrist; user performance; and subjective assessment. A total of 22 participants were tested in this study.
Results: Placing the mobile computer closer to the steering wheel reduced low back and shoulder muscle activity. Joint angles of the shoulders, elbows, and wrists were also closer to neutral angle. Biomechanical modeling revealed substantially less spinal compression and trunk muscle force. In general, there were no practical differences in performance between the locations. Subjective assessment indicated that users preferred the mobile computer to be as close as possible to the steering wheel.
Conclusion: Locating the mobile computer close to the steering wheel reduces risk of injuries, such as low back pain and shoulder tendonitis.
Application: Results from the study can guide electric utility companies in the installation of mobile computers into vehicle cabs. Results may also be generalized to other industries that use trucklike vehicles, such as construction.
The goal of this study was to determine the systematic effect that varying the slope angle of a computer keyboard along with varying keyboard height (relative to elbow height) have on wrist extension ...angle while typing. Thirty participants typed on a keyboard whose slope was adjusted to +15°, +7.5°, 0°, -7.5°, and -15°. The height of the keyboard was set up such that participants' wrists were at the same height as their elbows, above their elbows, and four cm below their elbows. Results showed that as keyboard slope angle moved downward from +15° to -15°, mean wrist extension decreased approximately 13° (22° at +15° slope to 9° at -15° slope). Keyboard height had a similar effect with mean wrist extension decreasing from 21.8° when the keyboard was lower than elbow height, to 7.3° when the keyboard was higher than elbow height. Potential application of this research includes the downward sloping of computer keyboards, which could possibly be beneficial in the prevention of musculoskeletal disorders affecting the wrist
Smart Trigger Nagurka, Mark L.; Marklin, Richard W.; Larson, Nathaniel R.
Professional safety,
08/2017, Letnik:
62, Številka:
8
Journal Article
Recenzirano
In Brief
Accidental discharge of a fastener from a pneumatic nail gun can result in acute injury to construction workers or consumers. Such injuries most commonly impale the hands, arms and legs.
A ...smart trigger system can reduce the risk of acute injuries by detecting whether the surface is an intended substrate for fastening.
This article details the development of a smart trigger system, including testing methodology and results.
Pneumatic nail drivers, commonly called nail guns, are used in construction and manufacturing, especially with high-volume fabrication and production (Figure 1, p. 32). They are powered by compressed air, operated by a finger trigger and are particularly useful for repetitive, intensive operations, such as nailing wooden studs, floor joists and plywood sheathing, and fastening roofing materials such as shingles to sheathing. In the past 20 years, pneumatic nail drivers, some of which can insert up to eight fasteners per second, have effectively replaced the hammer for driving fasteners on construction sites.
Pneumatic tools have two main types of trigger modes. With a contact-actuated trigger (CAT) tool, a worker can repetitively discharge fasteners by continuously pressing the trigger and bumping the tool's nosepiece against the work surface. With a sequential-actuated trigger (SAT) tool, the worker presses the tool's nosepiece against the work surface and then presses the trigger to discharge a fastener. A SAT tool requires the worker to remove contact with the nosepiece and release the trigger before another fastener can be discharged. Wood frame building workers and residential roofers typically use CAT tools because they have higher production rates than SAT tools (i.e., more fasteners are installed per unit time).
Celotno besedilo
Dostopno za:
BFBNIB, CEKLJ, DOBA, IZUM, KILJ, NMLJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Design of computer keyboards no longer is limited to the flat keyboards that are typically shipped with personal computers. Keyboards now exist that are split into halves and these halves can be ...slanted away from each other (creating a triangle between the halves), sloped downward toward the visual display terminal, tilted upward like a tent, or simply separated. These design features are intended to alleviate discomfort and possible musculoskeletal disorders that have been suggested to be associated with the extensive use of conventional computer keyboards. The geometry of conventional keyboards requires the wrists to be in 10 degrees to 15 degrees of ulnar deviation and 20 degrees of extension and the forearms to be nearly fully pronated while typing. A review of the available experimental data collected on 10-digit touch typists indicates that (1) keyboards with a slant angle (half of the opening angle) of 10 degrees to 12.5 degrees or keyboards with halves separated to approximately shoulder width are both effective in placing the wrist in near neutral (0 degree) ulnar/radial deviation when typing, (2) wrist extension can be reduced to near neutral (0 degrees) when a keyboard with a negative slope of 7.5 degrees is used, contingent on the wrist rest also sloping with the keyboard, and (3) tilting the keyboard halves 20 degrees to 30 degrees is effective in reducing forearm pronation to approximately 45 degrees. These studies also indicate that experienced 10-digit touch typists readily adapt (within 10 minutes) to these individual alternative keyboard features, and can type with approximately the same speed and accuracy as with the conventional keyboard. While placing the wrist and forearm in a more neutral position could, in theory, reduce the incidence of musculoskeletal disorders, randomized controlled trials are necessary before strong recommendations can be made on the effectiveness of alternative keyboards for the prevention and/or treatment of musculoskeletal disorders. In the absence of these randomized controlled trials, the information in this article provides preliminary guidance to clinicians in their evaluation of computer keyboards and workstations and their recommendations to patients.
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