Effects of simulated occupational task parameters on balance

The effects of single-handed load holding, length of the base of support, and standing surface condition (narrow and wide construction beams) on balance were investigated in twenty-three healthy men between the ages of 18 and 55 years old. Balance during quiet standing was evaluated from postural sway measurements derived from center of pressure (COP) displacement. These measurements included the range or maximal displacement of the COP in the anteroposterior (AP) and mediolateral (ML) directions, the elliptical area, and mean sway velocity. Holding a load in the hand did not significantly affect postural sway measures (p > 0.05), although the effect of surface condition was significant on all COP measures (p < 0.001). Lengthening the base of support did not affect the ranges or elliptical area, but increased the mean velocity of sway (p = 0.001). Changes in the dimensional characteristics of the surface condition and length of base of support affected postural sway, possibly by requiring adjustments to balance and motor control strategies. Further research is required to determine if these changes are detrimental to maintaining balance and increase the risk of falls for workers in similar environments.     

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 effects of a simulated head-up display speedometer on perceptual task performance

This study compared the effects of simulated head-up display (HUD) and dashboard-mounted digital speedometers on key perceptual driving tasks in a simulated driving environment. Subjects were 20 male and female volunteers ranging in age from 19 to 51 years. A videotape, taken from the driver's perspective, of a car traveling along a memorized route served as the test scene. While viewing the test scene subjects performed tasks related to navigation, speed monitoring, and salient cue detection. The simulated HUD speedometer produced generally superior performance on the experimental tasks; most important, it enabled subjects to respond significantly more quickly to the salient cues. Implications for the effects of HUDs on automobile safety are discussed.     

Exploring the effects of agent trust and benevolence in a simulated organizational task

Executives argue intuitively that trust is critical to effective organizational performance. Although articulated as a cognitive/ affective property ofindividuals, the collective effect of events influencing(and being influenced by) trust judgments must certainly impact organizational behavior. To begin to explore this, we conducted a simulation study of trust and organizational performance. Specifically, we defined a set ofcomputational agents, each with a trust function capable of evaluating the quality ofadvice from the other agents, and rendering judgments on the trustworthiness of the communicating agent. As agent judgments impact subsequent choices to accept or to generate communications, organizational performance is influenced. We manipulated two agent properties(trustworthiness, benevolence), two organizational variables (group size, group homogeneity/liar-to-honest ratio), and one environmental variable (stable, unstable). Results indicate that in homogeneous groups, honest groups did better than groups of liars, but under environmental instability, benevolent groups did worse. Under all conditions for heterogeneous groups, it only took one to three liars to degrade organizational performance.     

Subjective discomfort in a simulated repetitive task

Abstract

Subjective discomfort was recorded in a semi-paced laboratory experiment, where ten female subjects assembled (strenuous task) and disassembled (less strenuous task) pieces of water tubes. It was recorded five times during each session which lasted between 69 and 151 min and during five consecutive sessions. The subjects rated both the general discomfort and localization of the discomfort. The time course of the general discomfort showed an ascending trend and there were only minor differences between the strenuous and less strenuous task. The localization of the discomfort centralized to neck and shoulders and there was some inconsistency between the localization and the kinesiological analysis of the muscle activity. The results imply that the general discomfort rating is easily biased. The local discomfort rating seems to be more reliable for ergonomic purposes.     

Self-initiated and respondent actions in a simulated control task

Operators often need to combine self-initiated and respondent actions. Two experiments dealt with the relative importance of these two types of actions as a function of the predictability of the system and the available information. Participants monitored three stations with different frequencies at which interventions were required. They were aided by warning cues, indicating the need for interventions. The frequencies of inspections of the stations, the response to the warning system and the overall performance were assessed for warning systems with different diagnostic properties. Participants adapted their responses to the relative frequency of required interventions and the reliance on and compliance to the warning system depended on the warning characteristics. The results support the notion that events, such as warning signals, have a complex role in the ongoing activity of the operator and are integrated into the set of information from external and internal sources that guide the operators' actions.     

Self-initiated and respondent actions in a simulated control task

Operators often need to combine self-initiated and respondent actions. Two experiments dealt with the relative importance of these two types of actions as a function of the predictability of the system and the available information. Participants monitored three stations with different frequencies at which interventions were required. They were aided by warning cues, indicating the need for interventions. The frequencies of inspections of the stations, the response to the warning system and the overall performance were assessed for warning systems with different diagnostic properties. Participants adapted their responses to the relative frequency of required interventions and the reliance on and compliance to the warning system depended on the warning characteristics. The results support the notion that events, such as warning signals, have a complex role in the ongoing activity of the operator and are integrated into the set of information from external and internal sources that guide the operators' actions.     

Situation awareness and driving performance in a simulated navigation task

The objective of this study was to identify task and vehicle factors that may affect driver situation awareness (SA) and its relationship to performance, particularly in strategic (navigation) tasks. An experiment was conducted to assess the effects of in-vehicle navigation aids and reliability on driver SA and performance in a simulated navigation task. A total of 20 participants drove a virtual car and navigated a large virtual suburb. They were required to follow traffic signs and navigation directions from either a human aid via a mobile phone or an automated aid presented on a laptop. The navigation aids operated under three different levels of information reliability (100%, 80% and 60%). A control condition was used in which each aid presented a telemarketing survey and participants navigated using a map. Results revealed perfect navigation information generally improved driver SA and performance compared to unreliable navigation information and the control condition (task-irrelevant information). In-vehicle automation appears to mediate the relationship of driver SA to performance in terms of operational and strategic (navigation) behaviours. The findings of this work support consideration of driver SA in the design of future vehicle automation for navigation tasks.     

Vertical vibration frequency and sitting posture effects on muscular loads and body balance

This study examined the effects of whole body vibration and sitting posture on muscular load, body balance and discomfort. An electric vibrator, a surface electromyography measurement system and a balance evaluation system were used in the experiment. Nine test conditions were studied consisting of three vertical frequencies (no vibration, 20 and 40 Hz) and three sitting postures (erect, bent-forward and twisted). Study results showed that whole body vibration had significant effects on the muscular loads in the torso muscles, body balance and perceived discomfort. Adverse effects generally increased with high-frequency vibration. No significant muscular load difference and balance difference were observed among sitting postures at any frequency. Significant discomfort differences between the erect and twisted postures were found with no vibration or at low frequency.Relevance to industryAttention should be paid to the negative effects of vibration transmission on the human body at worksites. The results from this study should be useful for whole body vibration risk assessment and control measures.     

The effects of a 1-year physical exercise programme on development of fatigue during a simulated ambulance work task

The aim of the study was to evaluate the effects of individually prescribed physical exercise programmes on development of fatigue during the carrying of a loaded stretcher up and down the stairs. Nineteen ambulance personnel performed the training for 1 year. Testing occurred before and after 1 year of the training. Both the training group (n = 19) and the control group (n = 15) were assessed for physical capacity and lactate concentration in blood and ratings of perceived exertion during carrying a stretcher on the stairs. When comparisons were made between those who had been training three times/week for 1 year and the control group, lactate concentration was significantly decreased. In conclusion, markers of fatigue during stretcher carrying can be reduced by the use of individually prescribed physical exercise programmes.     

The effects of a 1-year physical exercise programme on development of fatigue during a simulated ambulance work task

The aim of the study was to evaluate the effects of individually prescribed physical exercise programmes on development of fatigue during the carrying of a loaded stretcher up and down the stairs. Nineteen ambulance personnel performed the training for 1 year. Testing occurred before and after 1 year of the training. Both the training group (n = 19) and the control group (n = 15) were assessed for physical capacity and lactate concentration in blood and ratings of perceived exertion during carrying a stretcher on the stairs. When comparisons were made between those who had been training three times/week for 1 year and the control group, lactate concentration was significantly decreased. In conclusion, markers of fatigue during stretcher carrying can be reduced by the use of individually prescribed physical exercise programmes.     

Effects of imperfect automation on decision making in a simulated command and control task

OBJECTIVE: Effects of four types of automation support and two levels of automation reliability were examined. The objective was to examine the differential impact of information and decision automation and to investigate the costs of automation unreliability. BACKGROUND: Research has shown that imperfect automation can lead to differential effects of stages and levels of automation on human performance. Method: Eighteen participants performed a "sensor to shooter" targeting simulation of command and control. Dependent variables included accuracy and response time of target engagement decisions, secondary task performance, and subjective ratings of mental work-load, trust, and self-confidence. RESULTS: Compared with manual performance, reliable automation significantly reduced decision times. Unreliable automation led to greater cost in decision-making accuracy under the higher automation reliability condition for three different forms of decision automation relative to information automation. At low automation reliability, however, there was a cost in performance for both information and decision automation. CONCLUSION: The results are consistent with a model of human-automation interaction that requires evaluation of the different stages of information processing to which automation support can be applied. APPLICATION: If fully reliable decision automation cannot be guaranteed, designers should provide users with information automation support or other tools that allow for inspection and analysis of raw data.     

Effects of display position of a visual in-vehicle task on simulated driving

To determine the relative safety of onboard display positions while driving, participants performed a lane-keeping task in a driving simulator. Concurrently, they reacted to a light by pushing the brake pedal. A secondary task was projected onto a display at one of the seven different locations in the cockpit. Behavioral data, eye movements, and subjective rating scales showed that the manipulation of display information during driving disturbed drivers' performance exponentially as a function of distance between the line of sight to the outside primary task and the onboard display position. Vertical eccentricity had a greater detrimental effect than horizontal distance. Under a certain condition with a high secondary task load, reaction time of pushing the brake to the outside stimulus nearly doubled with a diagonal eccentricity of 35 degrees as compared to lower eccentricities. Subjective workload measures complement the behavioral data of clear detrimental effects with eccentricities of at least 35 degrees .     

The operators' estimation of a track's statistical parameters in a simulated object-location task

Abstract

Kalman filtering, and similar statistical analyses, have been widely adopted to provide the operator with statistical information as an aid in object location tasks. However, there is little available research to indicate how the operator will use the information to make judgements about the standard deviations associated with the current and future predicted estimates of the coordinates of an object's location. Hence an experiment was carried out to observe and analyse subjects' judgements associated with the estimated coordinates of an object moving in a two dimensional space. The results lead to the conclusion that naive subjects make judgements of standard deviations which can be related to the spread of the point estimates of an object's coordinates. The judgements of standard deviation were not related to the measures of variability associated with the generation of the track. These conclusions are discussed in terms of matching the man to the mathematics of the software generating the display.     

The effects of speed,frequency, and load on measured hand forces for a floor to knuckle lifting task

The purpose of this study was to describe and quantify measured hand forces during floor to knuckle lifting of various loads. Hand forces of five subjects were measured with a strain gauge apparatus for normal and fast speeds of lifting at 1,4, and 8 l/min. The pattern of hand force over time exhibited peaks in force in the shape of a spike for all fast lifts, indicating that subjects did not lift smoothly. For normal speed of lift, only one of the five subjects executed some lifts smoothly, indicating that it may be possible to lift smoothly, but most lifters probably do not. Peaks of horizontal and vertical components of hand force were tabulated by speed of lift, frequency, and load.     

The effects of speed, frequency, and load on measured hand forces for a floor to knuckle lifting task.

The purpose of this study was to describe and quantify measured hand forces during floor to knuckle lifting of various loads. Hand forces of five subjects were measured with a strain gauge apparatus for normal and fast speeds of lifting at 1, 4, and 8 l/min. The pattern of hand force over time exhibited peaks in force in the shape of a spike for all fast lifts, indicating that subjects did not lift smoothly. For normal speed of lift, only one of the five subjects executed some lifts smoothly, indicating that it may be possible to lift smoothly, but most lifters probably do not. Peaks of horizontal and vertical components of hand force were tabulated by speed of lift, frequency, and load.     

Investigating haptic distance-to-break using linear and nonlinear materials in a simulated minimally invasive surgery task

Accurate detection of mediated haptic information in minimally invasive surgery (MIS) is critical for applying appropriate force magnitudes onto soft tissue with the aim of minimising tissue trauma. Force perception in MIS is a dynamic process, with surgeons’ administration of force into tissue revealing information about the remote surgical site which further informs the surgeons’ haptic interactions. The relationship between applied force and material deformation rate provides biomechanical information specifying the deformation distance remaining until a tissue will fail: which is termed distance-to-break (DTB). The current study demonstrates that observers can detect DTB while deforming simulated tissues and stop before reaching the tissues’ failure points. The design of training simulators, control devices and automated robotic systems for applications outside of MIS is discussed.

Practitioner Summary: In MIS, haptic information is critical for applying appropriate forces onto soft tissue to minimise tissue trauma. Observers used force information to detect how far they could deform a virtual tissue before it would break. The design of training simulators, control devices and automated robotic systems is discussed.