Effect of personal protective eyewear on postural stability

Vision is a significant factor in postural stability; this study is the first to report on the effect of OSHA regulated personal protective eyewear on physiological factors associated with postural stability. Twenty college students between the ages of 19 and 25 were randomly tested in each of three eyewear conditions (control, new, and artificially aged) using a NeuroCom Balance Master System and the mCTSIB protocol. Subjects were pre-tested with no eyewear (control) on each day followed by a 5-min assembly task with random eyewear assignment. Subjects were then post-tested following the same protocol while wearing the eyewear. Data were evaluated using a two (pre/post) x three (eyewear) repeated measures analysis of variance (ANOVA). There was a significant main effect for both the eyes open/firm flat surface, and eyes open/foam flat surface conditions (p 相似文献   

Effect of personal protective eyewear on postural stability

Vision is a significant factor in postural stability; this study is the first to report on the effect of OSHA regulated personal protective eyewear on physiological factors associated with postural stability. Twenty college students between the ages of 19 and 25 were randomly tested in each of three eyewear conditions (control, new, and artificially aged) using a NeuroCom^® Balance Master System and the mCTSIB protocol. Subjects were pre-tested with no eyewear (control) on each day followed by a 5-min assembly task with random eyewear assignment. Subjects were then post-tested following the same protocol while wearing the eyewear. Data were evaluated using a two (pre/post)?×?three (eyewear) repeated measures analysis of variance (ANOVA). There was a significant main effect for both the eyes open/firm flat surface, and eyes open/foam flat surface conditions (p???.05). These findings suggest that while personal protective eyewear may serve to protect an individual from eye injury, an individual's use of such personal protective eyewear may have deleterious effects on sensory input from the visual system and compensatory strategies to maintaining or regaining postural stability. Individuals who employ protective eyewear on a daily basis need to be aware of the effect of altered visual input resulting from eyewear on their postural stability, especially during sensory-challenging tasks, such as navigating ladders, scaffolding and elevated surfaces, typically found in construction environments.     

Impact of information display on worker performance for wood frame wall assembly using AR HMD under different task conditions

Augmented Reality (AR) head-mounted displays (HMDs) provide users with an immersive virtual experience in the real world. The portability of this technology affords various information display options for construction workers that are not possible otherwise. However, the impact of these different information presentation options on human performance should be carefully evaluated before such technology is deployed in the jobsite. In this paper, we describe a research effort examining how different information displays presented via AR HMD influence task performance when assembling three sized wooden wall frame assembly tasks. We asked 18 construction engineering students with framing experience to finish three wood frame assembly tasks (large, medium, and small) using one of the three information displays (AR 3D conformal, AR 2D tag-along, and paper blueprints). The task performance was measured by time of completion and framing errors, which were analyzed and compared among each factor.     

Effects of backpack and double pack loads on postural stability

Measurement of postural stability is crucial for identifying predictors of performance, determining the efficacy of physical training and rehabilitation techniques and evaluating and preventing injuries, particularly for heavy load carriage in hikers, mountain search and rescue personnel and soldiers. This study investigated the effect of load distribution on postural stability in an upright stance using backpack and double pack loads under conflicting or impaired somatosensory, visual and vestibular conditions. The sensory organisation tests were conducted on 20 young adults before and after a 10-min level walking exercise. Young adults’ ability to use inputs from somatosensory and visual systems to maintain postural stability was significantly reduced following a 10-min walking exercise with a heavy backpack (30% of body weight), whereas no significant changes were observed for double pack carriage. Thus, the distribution of heavy loads to the front and back provides superior balance control compared with back-only loading.

Practitioner summary: This study investigated the effects of heavy (30% of body weight) load distribution on postural stability after a 10-min walking exercise. Backpack carriage significantly reduced postural stability, whereas there was no significant effect under double pack loads. Distribution of heavy loads on the front-and-back is desirable for superior balance control.     

Effects of music tempo and task difficulty on multi-attribute decision-making: An eye-tracking approach

This study examined the effects of music tempo and task difficulty on the performance of multi-attribute decision-making according two alternative perspectives: background music as the arousal inducer vs. the distractor. An eye-tracking based experiment was conducted. Our results supported the arousal inducer perspective that, with the same level of decision time, participants made decisions more accurately with the presentation of faster than slower tempo music. Further, faster tempo music was found to improve the accuracy of harder decision-making only, not that of easier decision-making. More interestingly, our exploratory analysis on eye fixations found the occurrence of adaptive behavior, namely, that the search pattern of participants became more intra-dimensional under the faster tempo music as compared with the slower tempo music.     

Effects of BMI and task parameters on postural sway during simulated small parts assembly

Postural stability is critical for ensuring a safe workplace. Employees with poor stability are more prone to falls and injuries while at work. In this study, postural sway of participants in different obesity categories was evaluated while performing an assembly workstation task. The study included three workstations: those designed for the 5th, 50th and 95th percentile workers based on anthropometric data tables. Force plates were used to study the differences in postural sway in both the medial–lateral and anterior–posterior directions. The results revealed that the obese class 1 and obese class 2 groups’ anterior–posterior sway was significantly larger than that of the normal weight groups while performing assembly work tasks. Also, pace type (self-paced or time-paced) and workstation (5th, 50th and 95th percentile) significantly affected the postural sway. The postural sway was not affected by gender differences. Workstations should be designed to accommodate the increased postural sway of obese workers.     

The roles of task difficulty and prior videogame experience on performance and motivation in instructional videogames

Videogames are an increasingly popular instructional tool. This research investigated how various strategies for modifying task difficulty in instructional videogames impact learner performance and motivation. Further, the influence of prior videogame experience on these learning outcomes was examined, as well as the role prior experience played in determining the optimal approach for adjusting task difficulty. Participants completed a game-based training task under one of four task difficulty conditions: static, increasing, adaptive-low and adaptive-high. All participants completed an identical pre-training trial, 10 practice trials varying in difficulty level according to condition, and a final performance trial. Results demonstrate that learner performance and motivation significantly improved in all difficulty conditions. Further, prior videogame experience was found to significantly influence these learning outcomes and a three-way interaction was detected between performance, task difficulty condition, and experience. The results of this research provide information useful to instructional videogame developers and instructors utilizing videogames as instructional tools.     

Modeling the effect of task and graphical representation on response latency in a graph reading task

We report an investigation into the processes involved in a common graph-reading task using two types of Cartesian graph. We describe an experiment and eye movement study, the results of which show that optimal scan paths assumed in the task analysis approximate the detailed sequences of saccades made by individuals. The research demonstrates the computational inequivalence of two sets of informationally equivalent graphs and illustrates how the computational advantages of a representation outweigh factors such as user unfamiliarity. We describe two models, using the ACT rational perceptual motor (ACT-R/PM) cognitive architecture, that replicate the pattern of observed response latencies and the complex scan paths revealed by the eye movement study. Finally, we outline three guidelines for designers of visual displays: Designers should (a) consider how different quantities are encoded within any chosen representational format, (b) consider the full range of alternative varieties of a given task, and (c) balance the cost of familiarization with the computational advantages of less familiar representations. Actual or potential applications of this research include informing the design and selection of appropriate visual displays and illustrating the practice and utility of task analysis, eye tracking, and cognitive modeling for understanding interactive tasks with external representations.     

Effects of conflict alerting system reliability and task difficulty on pilots' conflict detection with cockpit display of traffic information

A total of 24 pilots viewed dynamic encounters between their own aircraft and an intruder aircraft on a 2-D cockpit display of traffic information (CDTI) and estimated the point and time of closest approach. A three-level alerting system provided a correct categorical estimate of the projected miss distance on 83% of the trials. The remaining 17% of alerts were equally divided between misses and false alarms, of large and small magnitude. Roughly half the pilots depended on automation to improve estimation of miss distance relative to the baseline pilots, who viewed identical trials without the aid of automated alerts. Moreover, they did so more on the more difficult traffic trials resulting in improved performance on the 83% correct automation trials without causing harm on the 17% automation-error trials, compared to the baseline group. The automated alerts appeared to lead pilots to inspect the raw data more closely. While assisting the accurate prediction of miss distance, the automation led to an underestimate of the time remaining until the point of closest approach. The results point to the benefits of even imperfect automation in the strategic alerts characteristic of the CDTI, at least as long as this reliability remains high (above 80%).     

Effects of conflict alerting system reliability and task difficulty on pilots' conflict detection with cockpit display of traffic information

A total of 24 pilots viewed dynamic encounters between their own aircraft and an intruder aircraft on a 2-D cockpit display of traffic information (CDTI) and estimated the point and time of closest approach. A three-level alerting system provided a correct categorical estimate of the projected miss distance on 83% of the trials. The remaining 17% of alerts were equally divided between misses and false alarms, of large and small magnitude. Roughly half the pilots depended on automation to improve estimation of miss distance relative to the baseline pilots, who viewed identical trials without the aid of automated alerts. Moreover, they did so more on the more difficult traffic trials resulting in improved performance on the 83% correct automation trials without causing harm on the 17% automation-error trials, compared to the baseline group. The automated alerts appeared to lead pilots to inspect the raw data more closely. While assisting the accurate prediction of miss distance, the automation led to an underestimate of the time remaining until the point of closest approach. The results point to the benefits of even imperfect automation in the strategic alerts characteristic of the CDTI, at least as long as this reliability remains high (above 80%).     

Auditory and visual distractor decrement in older worker manual assembly task learning: Impact of spatial reasoning,field independence,and level of education

This study examined the impact of age on manual assembly task learning in the presence of visual and auditory distracters. Manual assembly task learning (e.g., number of learning trials needed to obtain consistently accurate assembly and near asymptote performance times) was studied in men and women between 18 and 65 years of age. Higher spatial reasoning capabilities were associated with fewer trials to reach the learning criterion, faster manual assembly times, and material prophylaxis for the type of distractors addressed in this study that are likely to be encountered in the workplace. Years of formal education and field independence showed no impact on distractor‐based decrements in task learning. For the oldest group of subjects (>50 years), concomitant presentation of visual and auditory distractors that are commonly encountered in industry were associated with a greater number of learning trials that were needed to achieve asymptotic manual assembly task learning. Spatial reasoning and field independence measures were lower in the older than in the younger age groups (p < 0.05). When spatial reasoning was treated as a covariate, however, nearly all age differences found in learning performance in the face of distractors were removed. The findings suggest that selection of workers based on spatial reasoning ability, rather than age, would yield better manual task learning in the face of visual and auditory distraction. © 2009 Wiley Periodicals, Inc.     

The effects of a lower body exoskeleton load carriage assistive device on limits of stability and postural sway

The study investigated the effects of using a lower body prototype exoskeleton (EXO) on static limits of stability and postural sway. Measurements were taken with participants, 10 US Army enlisted men, standing on a force platform. The men were tested with and without the EXO (15 kg) while carrying military loads of 20, 40 and 55 kg. Body lean to the left and right was significantly less and postural sway excursions and maximal range of movement were significantly reduced when the EXO was used. Hurst values indicated that body sway was less random over short-term time intervals and more random over long-term intervals with the EXO than without it. Feedback to the user's balance control mechanisms most likely was changed with the EXO. The reduced sway and relatively small changes in sway with increasing load weights suggest that the EXO structure may have functioned to provide a bracing effect on the body.     

The effects of a lower body exoskeleton load carriage assistive device on limits of stability and postural sway

The study investigated the effects of using a lower body prototype exoskeleton (EXO) on static limits of stability and postural sway. Measurements were taken with participants, 10 US Army enlisted men, standing on a force platform. The men were tested with and without the EXO (15 kg) while carrying military loads of 20, 40 and 55 kg. Body lean to the left and right was significantly less and postural sway excursions and maximal range of movement were significantly reduced when the EXO was used. Hurst values indicated that body sway was less random over short-term time intervals and more random over long-term intervals with the EXO than without it. Feedback to the user's balance control mechanisms most likely was changed with the EXO. The reduced sway and relatively small changes in sway with increasing load weights suggest that the EXO structure may have functioned to provide a bracing effect on the body.     

The impact of collaborative and individualized student response system strategies on learner motivation,metacognition, and knowledge transfer

This study investigated the impact of collaborative and individualized student response system‐based instruction on learner motivation, metacognition, and concept transfer in a large‐enrolment undergraduate science course. Participants in the collaborative group responded to conceptual questions, discussed their responses in small groups, and provided a revised response to the question (peer instruction [PI]). A comparison group provided individualized responses (IRs) to the same questions. Results of the motivation measure revealed a drop in confidence for students in both groups. This may be explained by a significant increase in the knowledge of cognition in both IR and PI groups, which likely mediated a recalibration of confidence to a lower, yet more realistic level. A significant interaction was found between gender and student response system strategy relative to the regulation of cognition, revealing that females improved in the PI group, while males reported improvement in the regulation of cognition in the IR group. A custom instrument was developed to measure near and far concept transfer abilities. The PI group scored significantly higher on the test of near transfer than the IR group.     

Effects of response and stability on scheduling in distributedcomputing systems

An examination is made of the effects of response and stability on scheduling algorithms for general-purpose distributed computing systems. Response characterizes the time required, following a perturbation in the system state, to reach a new equilibrium state. Stability is a measure of the ability of a mechanism to detect when the effects of further actions will not improve the system state as defined by a user-defined objective. These results have implications for distributed computations in general. Analysis is based on formal communicating finite automata models of two distinct approaches to the scheduling problem, each using the objective of global optimal load balancing. The results indicate that absolute stability is not always necessary in dynamic systems for the same reasons that relatively small amounts of instability are tolerated in the design of analog control systems. It is shown that response is a very important first-order metric of dynamic scheduling behavior, and that response and stability are related     

The development of a model to predict the effects of worker and task factors on foot placements in manual material handling tasks

Accurate prediction of foot placements in relation to hand locations during manual materials handling tasks is critical for prospective biomechanical analysis. To address this need, the effects of lifting task conditions and anthropometric variables on foot placements were studied in a laboratory experiment. In total, 20 men and women performed two-handed object transfers that required them to walk to a shelf, lift an object from the shelf at waist height and carry the object to a variety of locations. Five different changes in the direction of progression following the object pickup were used, ranging from 45° to 180° relative to the approach direction. Object weights of 1.0 kg, 4.5 kg, 13.6 kg were used. Whole-body motions were recorded using a 3-D optical retro-reflective marker-based camera system. A new parametric system for describing foot placements, the Quantitative Transition Classification System, was developed to facilitate the parameterisation of foot placement data. Foot placements chosen by the subjects during the transfer tasks appeared to facilitate a change in the whole-body direction of progression, in addition to aiding in performing the lift. Further analysis revealed that five different stepping behaviours accounted for 71% of the stepping patterns observed. More specifically, the most frequently observed behaviour revealed that the orientation of the lead foot during the actual lifting task was primarily affected by the amount of turn angle required after the lift (R(2) = 0.53). One surprising result was that the object mass (scaled by participant body mass) was not found to significantly affect any of the individual step placement parameters. Regression models were developed to predict the most prevalent step placements and are included in this paper to facilitate more accurate human motion simulations and ergonomics analyses of manual material lifting tasks. STATEMENT OF RELEVANCE: This study proposes a method for parameterising the steps (foot placements) associated with manual material handling tasks. The influence of task conditions and subject anthropometry on the foot placements of the most frequently observed stepping pattern during a laboratory study is discussed. For prospective postural analyses conducted using digital human models, accurate prediction of the foot placements is critical to realistic postural analyses and improved biomechanical job evaluations.     

Effect of visual displays and locations on laparoscopic surgical training task

The number of minimally invasive surgical (MIS) procedures has substantially increased since its introduction due to health and recovery benefits for patients. However, there are potential performance issues in MIS for surgeons due to perceptual processing demands associated with supporting technologies. Monitor location has been identified as a major factor influencing performance in these types of procedures. This study examined the effect of multiple monitors on performance during a laparoscopic surgical training task (peg transfer among instruments). Twenty-four novice subjects were exposed to different monitor conditions including a default position, a biomechanically compatible position, and a position collocated with the operating surface as well as the combination of the latter two. Subjective rankings and cognitive workload were also assessed. Results revealed a significant effect of monitor position on task time when compared to subjects' baseline training task time using the default monitor setup. Collocating the monitor with the operating surface was shown to be superior in terms of task time. There were no significant differences among monitor positions in terms of perceived workload. The results of this study provide an applicable guide for the design of MIS setups in the operating room to promote surgeon performance.     

Effect of elliptic handle shape on grasping strategies, grip force distribution, and twisting ability

A generic torque model for various handle shapes has been developed and evaluated using experimental data. Twelve subjects performed maximum isometric torques using circular and elliptic cylinders in medium and large sizes (circular: r = 25.4, 38.1 mm; elliptic: semi-major/minor axes = 30.9/19.3, 47.1/27.8 mm) finished with aluminium and rubber, in two opposite directions. Torque, grip force distribution, and finger position were recorded. Maximum torques were 25%, 7%, and 31% greater for the elliptic, large-size, and rubber-finished cylinders than for the circular, medium-size, and aluminium-finished cylinders, respectively. Greater torque for the elliptic cylinders was associated with 58% greater normal force that the subjects could generate for the elliptic than circular cylinders. The model suggests that greater torques for the large-size and rubber cylinders are related to long moment arms and greater frictional coupling at the hand-cylinder interface, respectively. Subjects positioned their hands differently depending on torque direction to maximise their normal force and torque generation. STATEMENT OF RELEVANCE: Desirable handle features for torque generation may be different from those for grip only. Design of handles per advantageous handle features (e.g., shape, size, and surface) may help increase people's torque strength and contribute to increased physical capacity of people.