Simulated Work Tasks Research Articles

An Evaluation of Impact Wrench Vibration Emissions and Test Methods

In the interest of providing more effective evaluations of impact wrench vibration exposures and the development of improved methods for measuring vibration emissions produced by these tools, this study focused on three variables: acceleration measured at the tool surface, vibration exposure duration per test trial, and the amount of torque required to unseat the nuts following a test trial. For this evaluation, six experienced male impact wrench operators used three samples each of five impact wrench models (four pneumatic models and one battery-powered model) in a simulated work task. The test setup and procedures were based on those provided by an International Organization for Standardization (ISO) Technical Committee overseeing the revision of ISO 8662-7. The work task involved the seating of 10 nuts onto 10 bolts mounted on steel plates. The results indicate that acceleration magnitudes vary not only by tool type but also by individual tools within a type. Thus, evaluators are cautioned against drawing conclusions based on small numbers of tools and/or tool operators. Appropriate sample sizes are suggested. It was further noted that evaluators could draw different conclusions if tool assessments are based on ISO-weighted acceleration as opposed to unweighted acceleration. As expected, vibration exposure durations varied by tool type and by test subject; duration means varied more for study participants than they did for tool types. For the 12 pneumatic tools evaluated in this study, torque varied directly with tool handle acceleration. Therefore, in order to reduce vibration exposure, tools should be selected and adjusted so that they produce no more than the needed torque for the task at hand.

Applying authentic learning to Social Science: A learning design for an inter-disciplinary Sociology subject

As universities move towards more vocationally oriented courses, students expect pedagogic practices that make closer ties to potential workplaces. The pedagogical approach of authentic learning is well suited to this purpose as it proposes an apprenticeship-type model and a model that brings simulated work tasks into the classroom. In the social sciences, authentic learning is under-utilised and under theorised as these subject areas do not fit easily into these models. An alternative model of authentic learning aims to offer students opportunities to ?enmind? the requirements of a discipline, be critically reflective about that discipline, and to develop the skills to bring the discipline into their subjective experience. Using this model for authentic learning as a starting point, the authors have examined the applicability of authentic learning to the social sciences, derived relevant design principles and applied these to produce a learning design for a sociology subject that can be tested and critiqued. The purpose of this paper is to present this learning design as a starting point for discussion about a new form of authentic learning.

User evaluation of ontology as query construction tool

This study examines the use of an ontology as a search tool. Sixteen subjects created queries using Concept-based Information Retrieval Interface (CIRI) and a regular baseline IR interface. The simulated work task method was used to make the searching situations realistic. Subjects' search experiences, queries and search results were examined. The numbers of search concepts and keys, as well as their overlap in the queries were investigated. The effectiveness of the CIRI and baseline queries was compared. An Ontology Index (OI) was calculated for all search tasks and the correlation between the OI and the overlap of search concepts and keys in queries was investigated. The number of search keys and concepts was higher in CIRI queries than in baseline interface queries. Also the overlap of search keys was higher among CIRI users than among baseline users. These both findings are due to CIRI's expansion feature. There was no clear correlation between OI and overlap of search concepts and keys. The search results were evaluated with generalised precision and recall, and relevance scores based on individual relevance assessments. The baseline interface queries performed better in all comparisons, but the difference was statistically significant only in relevance scores based on individual relevance assessments.

Shoulder Muscle Activity Increases With Wrist Splint Use During a Simulated Upper-Extremity Work Task

The purpose of this study was to test the hypothesis that wearing a wrist splint while performing a common light manufacturing task (moving an object from a bin) increases shoulder muscle activity. Electromyography (EMG) signals were evaluated from the anterior, middle, and posterior deltoid, trapezius, supraspinatus, and infraspinatus of 14 volunteers while they moved an object from a bin. Two test conditions were measured: with and without a wrist splint. The height of the bin was also varied. Wearing a wrist splint increased maximum EMG for all six muscles and average levels for the deltoid (anterior, middle, posterior) and trapezius. As bin height increased, maximum muscle activity increased in the deltoid (anterior, middle, and posterior) and trapezius, and the average increased in the deltoid (middle and posterior) and trapezius. Workplace factors can modify the activation of a patient's shoulder muscles when he or she is wearing a wrist splint. An ergonomic job analysis should be conducted for patients who are returning to work wearing wrist splints.

Classification of metabolic and respiratory demands in fire fighting activity with extreme workloads

Fire fighting work comprises work tasks requiring an energy yield at maximal or close to maximal levels of the individual. Due to the very nature of fire fighting more complex physiological variables are difficult to measure. We measured metabolic and respiratory responses in 15 male, professional fire fighters during simulated work tasks on a test ground. Work time was on the average 22 min with individual components of work tasks lasting 2–4 min. The mean oxygen consumption for the whole exercise (22 min) was 2.75±0.29 l/min. The most demanding work task demanded an oxygen uptake of 3.55±0.27 l/min. Corresponding values for respiratory minute volumes were 82±14 and 102±14 l/min, respectively. Heart rates averaged 168±12 for the whole test and 179±13 beats/min for the heaviest work task. Two new classes for classification of intensive and exhausting, short term physical work are proposed for inclusion in ISO8996 and values for relevant parameters are proposed.

The Relative Effects of Different Frequencies of Feedback on Work Performance

This laboratory simulation examined the relative effects of two frequencies of feedback on work performance under hourly pay and incentive pay. The study had four experimental conditions: feedback delivered after every session under hourly pay and under incentive pay, and feedback delivered after every fourth session under hourly pay and under incentive pay. Thirty-five college students were randomly assigned to one of the four conditions. Each participant attended 24 thirty-minute sessions. Participants performed a simulated work task on the computer that consisted of computer-related activities such as dragging, clicking, and typing. The dependent variable was the number of correctly completed units of work. An analysis of covariance was conducted to analyze the data using pretest scores as a covariate. Participants who received feedback every session completed significantly more work units than participants who received feedback every fourth session. In addition, an interaction between feedback frequency and pay systems was found: Feedback delivered every session was more effective than feedback delivered every fourth session under the incentive pay system, but not under the hourly pay system. The results suggest that the relative effects of feedback frequency may depend upon the extent to which feedback is correlated with differential consequences for performance.

Prediction of development of fatigue during a simulated ambulance work task from physical performance tests

The aims of this study were (1) to identify which physical performance tests could best explain the development of fatigue during a simulated ambulance work task, (2) to investigate the effect of height and weight and (3) to investigate in what respects these findings differ between female and male ambulance personnel. Forty-eight male and 17 female ambulance personnel completed a test battery assessing cardio-respiratory capacity, muscular strength and endurance, and co-ordination. The subjects also completed a simulated ambulance work task — carrying a loaded stretcher. The work task was evaluated by development of fatigue. Univariate and multiple regression analyses were used to investigate to what extent the tests in the test battery were able to explain the variance of developed fatigue. The explained variance was higher for female than for male ambulance personnel (time > 70% of HRpeak: R2 = 0.75 vs 0.10, accumulated lactate: R2 = 0.62 vs 0.42, perceived exertion: R2 = 0.75 vs 0.10). Significant predictors in the models were VO2max, isometric back endurance, one-leg rising, isokinetic knee flexion and shoulder extension strength. Height, but not weight, could further explain the variance. The high physical strain during carrying the loaded stretcher implies the importance of investigating whether improved performance, matching the occupational demands, could decrease the development of fatigue during strenuous tasks.

Within-Document Retrieval: A User-Centred Evaluation of Relevance Profiling

We present a user-centred, task-oriented, comparative evaluation of two within-document retrieval tools. ProfileSkim computes a relevance profile for a document with respect to a query, and presents the profile as an interactive bar graph. FindSkim provides similar functionality to the web browser “Find” command. A novel simulated work task was devised, where participants are asked to identify (index) relevant pages of an electronic book, given topics from the existing book index. The original book index provides the ground truth, against which the indexing results of the participants can be compared. We confirmed a major hypothesis, namely ProfileSkim proved significantly more efficient than Find-Skim, as measured by time for task. The study indicates that ProfileSkim was as least as effective as FindSkim in identifying relevant pages, as measured by traditional information retrieval measures, and there is some evidence that ProfileSkim is a precision-enhancing tool. Based on qualitative data from questionnaires, we also provide strong evidence to support our conjecture that the participants would be more satisfied when using ProfileSkim than FindSkim. The experimental study confirmed the potential of relevance profiling for improving within-document retrieval. Relevance profiling should prove highly beneficial for users trying to identify relevant information within long documents.

The Effects of Personality Type and Stress on Muscle Activity during Simulated Work Tasks

The research presented here explores the relationships between individual (e.g., personality type) and environment (e.g., time stress) psychosocial factors and muscle activity. Twenty-five subjects participated in this laboratory study. Personality type was assessed using the Jenkins Activity Survey. Participants (12 Type A and 13 Type B) performed a pipetting task under verbally imposed “no time stress” and “time stress” conditions. Independent variables included personality type, gender, condition order, and stress condition. Dependent measures included normalized integrated electromyography (NIEMG) from ten muscles. The effect of personality type on muscle activity was completely moderated by gender. Type A female dominant flexor activity was 57% of the Type B activity. Type A male dominant flexor activity was 188% of the Type B activity. Time stress increased muscle activity by 9 to 23% in six of the muscles sampled. However, the dominant flexor and extensor activities only increased (by 25 to 29%) for females. This study demonstrates the feasibility and importance of including individual and environment psychosocial factors in biomechanical evaluations.

The effect on heart rate and facial skin temperature of wearing respiratory protection at work.

Twelve New Zealand workers from a range of occupations were studied to investigate the effect of wearing air-filtering respiratory protection on heart rate (HR) and facial skin temperature (Tlip and Tcheek) whilst working. All variables were measured continuously during simulated and actual work. The former allowed physiological measurements to be undertaken during the physical activities carried out during the work task without respirators and without exposure to hazardous airborne substances. Mean heart rates in subjects moving without respirators ranged from 75 to 94 beats/min and from 77 to 98 beats/min during respirator use at work. Mean skin temperature under the mask (Tlip) increased in 11 of the 12 subjects while using respirators (range 1.2-4.8 degrees C) but Tcheek only increased in four (range 0.6-1.5 degrees C). The use of simulated work tasks in the experiment was a compromise. The heart rate data from the real and simulated work indicated that effort and workload, though not identical, were similar. The increase in skin temperature under the mask may account for the reluctance of individuals to wear respiratory protection at work. This region of the face is very thermosensitive.

Determining what should be taught during lift-training instruction

Every year many workers who perform manual materials handling tasks receive training on lifting techniques. The goal of these training programs is to reduce the biomechanical loads experienced by the spine, thereby reducing the potential for low back injury. The purpose of this article was to determine the effectiveness of specific lifting techniques used in the training of 955 material handling workers at 14 grocery, retail, and beverage distribution centers in controlling the three-dimensional spine moments experienced during simulated work tasks. Each subject underwent up to five one-on-one training sessions with a coach over a 12 month period (time = 0, 1 month, 3 months, 6 months, and 9 months) while instrumented with the LiftTrainer TM biofeedback system. This PC-based system quantified the tri-axial moments at L5/S1 as trainees lifted and provided the coach with real-time audio feedback and post-lift charting to quantify progress. The coach used the objective data in guiding the trainee towards behaviors that reduced one or more of the directional moments. Within each training session, several different techniques were usually suggested by the coach. At the completion of the session each trainee was rated on a 4-point scale as to how well each of the techniques was adopted. These scales became the independent variables in three multiple regression analyses used to determine which techniques account for the within session change in the moment values and which could best be used to predict performance at the end of a session. Results indicated that trainees should be taught to slide boxes close prior to lifting, move the box and body together, initiate the lift by shifting the gaze upward, and think strategically about the lifting task in order to reduce the forward bending moments. Twisting moments were reduced by keeping the box close, moving the feet, and moving the box and body together. The lowest side-bending moments occurred with smoother lifts and the use of body english during load placement.

Physical Medicine and Rehabilitation (86)

Simulated work performance tasks in persons with neuropathic and myopathic weakness. (University of California, Sacramento, CA) Arch Phys Med Rehabil 2000;81:938–943.This study aimed to determine the test‐retest reliability of selected simulated work performance tasks in persons with neuropathic and myopathic weakness and control subjects, and the association between muscular performance during these work tasks and conventional isolated muscle group testing. Measurement of 3 tasks was performed on a work simulation device on 2 different days separated by 1 week. Associations between work task performance and previously reported strength measures in 6 muscle groups by hand‐held dynamometry (HHD) were examined. This study was conducted in the human performance laboratory of a university and consisted of a convenience sample of ambulatory outpatients with hereditary motor and sensory neuropathy, type I (n = 9), myotonic muscular dystrophy (n = 10), and able‐bodied controls (n = 11). Mean between‐session differences for work simulation tasks ranged from −11% to +4% for peak torque and from −12% to +12% for total work; test sessions did not differ significantly for either patient or control groups. All groups had between‐session intraclass correlation coefficients usually> 0.80, which indicated good consistency. In general, correlations between peak torque during work simulation and HHD were strongest in the control group. Conclude that persons with neuromuscular weakness reliably performed the simulated work tasks examined in this investigation. Work simulation tasks may be a useful tool to assess muscular performance in persons with neuromuscular weakness. Comment by Miles Day, MD.This article addresses something that is very important when evaluating patient progress during rehabilitation. It is common in rehab to evaluate muscle groups and to determine a muscular performance by using isolated muscle group testing. The problem with this is that it doesn't necessarily correlate with tasks that patients perform on a day‐to‐day basis. The purpose of the study was to determine the test‐retest reliability of selected simulated work performance tasks in patients with neuropathic and myopathic weakness and control subjects and the association between muscular performance during these work tasks and conventional isolated muscle group testing. The work simulation tasks included knob‐turning (alternating pronation and supination), linear motion (alternating push/pull motion), and lever arm (push‐down motion). This study did accomplish its goals. The peak torque and total work measured in work simulation tasks did not differ significantly between test and retest sessions for either the patients with neuropathic and myopathic weakness or the control groups.This study addresses an issue that other studies have not. Just because a patient shows improvement in strength measure by hand held dynamometry does not necessarily mean that he or she will be able to accomplish tasks that are performed at home. The main goal of rehabilitation is for patients to be able to perform activities of daily living around the house and at work. If this is not accomplished then their rehabilitation is for naught.

Simulated work performance tasks in persons with neuropathic and myopathic weakness

Kilmer DD, Aitkens SG, Wright NC, McCrory MA. Simulated work performance tasks in persons with neuropathic and myopathic weakness. Arch Phys Med Rehabil 2000;81:938-43. Objectives: To determine the test-retest reliability of selected simulated work performance tasks in persons with neuropathic and myopathic weakness and control subjects, and the association between muscular performance during these work tasks and conventional isolated muscle group testing. Design: Measurement of three tasks performed on a work simulation device on two different days separated by 1 week. Associations between work task performance and previously reported strength measures in six muscle groups by hand-held dynamometry (HHD) were examined. Setting: Human performance laboratory of a university. Participants: Convenience sample of ambulatory outpatients with hereditary motor and sensory neuropathy, type I (n = 9), myotonic muscular dystrophy (n = 10), and able-bodied controls (n = 11). Main Outcome Measures: For work simulation, isokinetic peak torque and total work; and for HHD, maximal isometric torque. Results: Mean between-session differences for work simulation tasks ranged from −11% to +4% for peak torque and from −12% to +12% for total work; test sessions did not differ significantly for either patient or control groups. All groups had between-session intraclass correlation coefficients usually >.80, indicating good consistency. In general, correlations between peak torque during work simulation and HHD were strongest in the control group. Conclusion: Persons with neuromuscular weakness reliably performed the simulated work tasks examined in this investigation. Work simulation tasks may be a useful tool to assess muscular performance in persons with neuromuscular weakness. © 2000 by the American Congress of Rehabilitation Medicine and the American Academy of Physical Medicine and Rehabilitation

Experimental components for the evaluation of interactive information retrieval systems

This paper presents a set of basic components which constitutes the experimental setting intended for the evaluation of interactive information retrieval (IIR) systems, the aim of which is to facilitate evaluation of IIR systems in a way which is as close as possible to realistic IR processes. The experimental setting consists of three components: (1) the involvement of potential users as test persons; (2) the application of dynamic and individual information needs; and (3) the use of multidimensional and dynamic relevance judgements. Hidden under the information need component is the essential central sub‐component, the simulated work task situation, the tool that triggers the (simulated) dynamic information needs. This paper also reports on the empirical findings of the metaevaluation of the application of this sub‐component, the purpose of which is to discover whether the application of simulated work task situations to future evaluation of IIR systems can be recommended. Investigations are carried out to determine whether any search behavioural differences exist between test persons‘ treatment of their own real information needs versus simulated information needs. The hypothesis is that if no difference exists one can correctly substitute real information needs with simulated information needs through the application of simulated work task situations. The empirical results of the meta‐evaluation provide positive evidence for the application of simulated work task situations to the evaluation of IIR systems. The results also indicate that tailoring work task situations to the group of test persons is important in motivating them. Furthermore, the results of the evaluation show that different versions of semantic openness of the simulated situations make no difference to the test persons’ search treatment.

Breathing patterns and heart rate during simulated occupational upper limb tasks in normal subjects.

Despite the arms being used extensively in the performance of many occupational tasks, little is known about the pattern of breathing and physiological cost of such work. The purpose of this study was to establish whether a simple change in arm support could alter the workload, pattern of breathing and respiratory muscle recruitment during a low intensity arm task. Ten normal subjects performed a simulated work task when sitting, once with the arms supported and once unsupported. Subjects were required, over a five-minute period, to repeatedly pick up a 2 kg object, inspect and hold it for 15 seconds and then pack it in a box. Breathing pattern responses, measured by pneumotachograph and respiratory inductive plethysmography, were minute ventilation (VE), respiratory frequency (Rf), tidal volume (VT) and change in functional residual capacity (FRC). The main findings were that unsupported arm work was more physiologically demanding than supported arm work. During work VE increased as a result of a change in respiratory frequency but not VT which was much more limited when the arms were unsupported. At the completion of activity, when the arms were unloaded, VT initially increased as VE decreased. FRC and VT were reduced during arm work and increased during recovery, mainly as a result of a change in ribcage excursion. These findings support the theory that during arms activity, intercostal and accessory respiratory muscles act to stabilize the arms and torso, impeding chest wall movement and shifting the respiratory load from these muscles to the diaphragm. This may adversely effect performance of workers who have ventilatory limits to arm work tasks.

The development of a method for the evaluation of interactive information retrieval systems

The paper describes the ideas and assumptions underlying the development of a new method for the evaluation and testing of interactive information retrieval (IR) systems, and reports on the initial tests of the proposed method. The method is designed to collect different types of empirical data, i.e. cognitive data as well as traditional systems performance data. The method is based on the novel concept of a ‘simulated work task situation’ or scenario and the involvement of real end users. The method is also based on a mixture of simulated and real information needs, and involves a group of test persons as well as assessments made by individual panel members. The relevance assessments are made with reference to the concepts of topical as well as situational relevance. The method takes into account the dynamic nature of information needs which are assumed to develop over time for the same user, a variability which is presumed to be strongly connected to the processes of relevance assessment.

Normalization of electromyogram in the neck-shoulder region.

Linear and curvilinear electromyogram (EMG) normalization methods were compared among ten healthy men during a simulated work cycle demanding attention and static holding of the arm ('Solitaire test'). Maximal voluntary contractions (MVC) and gradually increasing contractions up to 70% of MVC were used for normalization in different arm postures. The test contractions studied included inward and outward rotations, abduction, shoulder elevation, and flexion in different arm positions. The shoulder load moment was calculated for the flexion tests using a simple two-dimensional model. The effect of arm posture on the EMG versus shoulder load moment relationship was studied on the following muscles: supraspinatus, infraspinatus, trapezius (three parts), deltoid (two parts) and pectoralis major. All muscles participated in the MVC tests performed, and its was not possible to suggest a single recommended test for each muscle. Differences in normalized EMG median values ranging up to 30% of MVC were found between linear and curvilinear normalization methods. Short-term repeatability of normalization based on a contraction with gradually increasing force was good. Arm posture affected the relationships between shoulder load moment and EMG activity of all muscles studied. Arm posture did not, however, have a significant effect on the estimated amplitude probability distribution functions during the simulated work task. Therefore, at least for the tasks studied, the principle of normalizing in the middle position of the range of movement was deemed acceptable.

A Comparison of Arm and Leg Exercise Testing to Predict Cardiovascular Responses to Simulated Work Tasks in Stable Cardiac Patients

Nine older men with previously documented myocardial infarction (MI) (age = 63, Max METs = 8.3), were evaluated to determine cardiovascular responses to simulated work tasks. Heart rate (HR), oxygen uptake (VO2), systolic (SP) and diastolic (DP) pressures were first measured during symptom limited arm (AXT) and treadmill (TXT) exercise tests. Subjects subsequently performed three graded work task simulations—weight carrying (WC), repetitive lifting (RL), and overhead work (OW)—which required combined static-dynamic exercise commonly encountered in work activities. VO2, HR, SP, and DP were measured during each work task. Regression lines and confidence intervals for HR, SP, and DP vs percent VO2 max were constructed for AXT and TXT. For each work task, at equivalent percent VO2 max, the frequency of HR, SP, and DP values that fell within ± 1 SD of the TXT and AXT regression lines were compared by chi-square analysis. AXT was a significantly better (P < 0.02) predictor of SP during WC and OW and for DP during each simulated work task. In addition, the HR and VO2 attained during WC and RL were close to maximum VO2 and HR achieved during AXT. AXT provides a more accurate prediction of BP responses and percent VO2 max and percent HR max required for simulated work tasks involving upper body muscle groups.

An exploratory study of moderate physical activity and selected design attribute effects on earmuff attenuation.

Hearing protective devices are tested for their attenuation characteristics under controlled laboratory conditions. Unfortunately, these tests overestimate the typical attenuation performance of the devices in the field, posing the possibility of inadequate protection for the user. Many factors may affect achieved in-field attenuation. This research investigated the influence of the user's work-related movement and variations in headband compression force and earcup cushion material (liquid- or foam-filled) on the frequency-specific noise attenuation achieved with earmuffs. Real-ear attenuation at threshold (REAT) testing procedures were used to collect attenuation data on 24 subjects both prior to and following completion of a simulated work task. Statistical analyses indicated that moderate work-related movement significantly decreased low-frequency attenuation but by only a small amount (1.5 dB at 125 Hz). A high headband compression force was found to increase attenuation by approximately 1.5 to 4 dB at 125, 250, 500, and 8000 Hz. There was no significant difference at any frequency between cushion types. The results indicate a small effect of moderate physical work activity on hearing protector effectiveness and illustrate the importance of certain earmuff design parameters to achieved attenuation.

How Physical Work Activity and Certain Earmuff Design Attributes Influence Achieved Hearing Protection

Laboratory tests of personal hearing protectors typically overestimate the attenuation performance of the devices in the workplace, where a number of factors reduce protection levels. This research investigated several practical factors including the influence of the user's work-related movement, and variations in headband compression force and earcup cushion material (liquid- or foam-filled) on the noise attenuation achieved with earmuff hearing protectors. Attenuation data were collected on 24 subjects both prior-to and following completion of a simulated work task. Work-related movement was found to significantly decrease attenuation. A high compression headband provided increased attenuation, while there was no significant difference between cushion types as to protection achieved.