Co-Production at the hospital:Development of an instrument to analyze conditions for active participation of patients

Ergonomic work design in the operating room - a methodological challenge to accomplish complexity

What is Work? A consideration of the relation of Entropy,Energy and Ergonomics

Assessment of the vibration induced forces transmitted in the joints of the human body by means of a biomechanical models

Quantitative Prediction of Manual Material Handling Hazards

Dynamic information in integrated surface electromyograms

Analysis of muscular load and its effects

The „Dortmund Approach “ for the biomechanical analysis of spinal load during manual materials handling

Physiological costs during working at the discounter checkout – Left-to-right scanner checkout versus traditional keyboard checkout

Prognosis model for working load in private homes

Evaluation of the Application of Virtual Reality Presentation Techniques in an eLearning Module on the Ergonomic Design of Work Systems

On the importance of the eyes-off-the-road time in road vehicles

A Comparison of Variables Measuring Fatigue

Experimental investigation of shifts of the decision criterion during quality inspection

The Contribution Made by Electrophysiological Methods of Investigation Towards Strain-reducing Design of Hand-operated Tools (as illustrated by the example of grapevine pruning shears)

Information Presentation and visual Performance in Head Mounted Displays with augmented Reality

Intercultural (online-)Learning

Vol. 1 - 2005

Musculoskeletal stress and strain of big samples with different workload -comparison of methods  (Vol. 1 – 2005)

Authors: Felix Klimmer, Hannagret Kylian, Klaus-Helmut Schmidt, Claus Jordan, Alwin Luttmann and Matthias Jäger

Keywords: · Musculoskeletal stress and strain · Musculoskeletal complaints · big samples · Methods

Summary

Physical complaints related to work are often associated with high physical load during daily occupational work.Disorders and complaints regarding the musculoskeletal system are the most frequent reasons for sick leave (Riihimäki,1991;Winkel&Westgaard,1992;Kuhn,1996).Working under uncomfortable conditions (inclined trunk,torsion of the spinal column,heavy loads)increase the disorders and complaints.Moreover, psychological and psychosocial factors must be taken into account (Theorell et al.,1991;Nachemson,1992,1993;Bongers et al.,1993). Two questionnaires were developed,both of them estimating musculoskeletal stress,for assessing the physical load during daily professional work,and for the analysis of such factors mentioned above.Furthermore,the questionnaires should be suitable for the use with big samples,that ’s why,they had to be short and simple.Both versions were tested on reliability and validity. Both questionnaires take into account both,the body postures, which are essential for fulfilling the daily work,and,the weights, which subjects had to lift or to move.The subjects were asked for a judgement of an average frequency of occurrence of particular body postures,and the handling of loads with different weights during ordinary daily work.The first questionnaire consist of 19 items:five items concerning the posture of the trunk (trunk upright,trunk slightly inclined,trunk strongly inclined,trunk twisted,trunk laterally bent),three items concerning the posture of the arm (both arms below shoulder height,one arm above shoulder height,both arms above shoulder height),five items concerning activities of the legs (sitting,standing,squatting,kneeling,walking/moving),and six items concerning the lifting or carrying of different heavy weights (light:<10 kg,medium:10-20 kg,heavy:>20 kg) either with upright trunk or with inclined trunk (Klimmer et al.,1998).The second questionnaire consist of 27 items,and asked for the conceivable combinations of three body postures (trunk upright,trunk slightly inclined,trunk strongly inclined)with three arm postures (arms hanging,arms bent or slightly stretched forward,arms strongly stretched forward),each separately for three categories of weights lifted during the work:light weight (<10 kg),medium weight (10-20 kg)or heavy weight (>20 kg). The physical work load of each person,expressed as the total compressive force acting at the lower lumbar spine (lumbosacral disc L5-S1)was estimated.Therefore,weighting factors for all body positions and loads contained in the items were determined with the use of the biomechanical model ”Der Dortmunder ” ((Jäger et al.,1992,2000).These weighting factors were multiplied by the item scores of the corresponding body postures reported in the questionnaires,and were added up afterwards to indices of physical work load. For assessing the strain caused by daily occupational work, the subjects were asked about musculoskeletal complaints they feeled in different body regions during the last 12 month: complaints in the back,the neck,the shoulder,and the hip. These reports were collected by means of a German version of the Nordic Questionnaire (Kuorinka et al.,1987). Data for the analysis of stress and strain were derived from 411 employees of a nursing home for elderly people,who took part in a longitudinal study with a regular questioning after three intervals,each of half a year.The participants filled out the questionnaires in groups of 5 to 25 people.Data of subjects were subdivided in 3 subgroups referring to different duties with different physical work load:physical care /nursing, housekeeping,psychosocial care.Each subgroup was analysed separately. The indices which were derived from the self-reports with both questionnaires are discriminating significantly between the groups of workers in different job categories,and this referring to both,the subjective perception of the physical load during daily work,and the reported musculoskeletal complaints caused by the daily work.Test-retest correlations of all indices were satisfactory at all times of questioning (all >.60)and all indices showed a high stability in the course of the longitudinal study. The calculated power of the questionnaires to predict the musculoskeletal complaints from the self assessed physical stress was a little different for both questionnaires,but for both questionnaires adequate fields for application could be found. Furthermore,the questionnaires data seems to be not only a consequence of different physical work load,but also depend -at least to a reasonable extent -on subjective perception of differences or changes of the work conditions,e.g.,in the health care of elderly people.

Practical Relevance

Development of reliable and valid questionnaires estimating musculoskeletal load during daily occupational work, especially when the focus is laid on
lifting or moving of loads with different weights. The questionnaires are suitable for the use with big samples.

Evaluation of a head-mounted display and a hand-held display with a target detection task  (Vol. 1 – 2005)

Authors: Claudius Pfendler, Heino Widdel and Christopher Schlick

Keywords: · Head--mounted display · Hand--held display · Performance · Workload · Simulator sickness

Summary

New information technologies such as Helmet-Mounted Displays (HMD)are used to support task accomplishment in many areas of human activities.Favored areas are diagnosis,assembling and orientation tasks.A main advantage of HMDs is that additional information essential for the task execution can be projected directly into the field of view of the operator and additional eye move-ments,which might detract from the external view,are not necessary. But there are also disadvantages.If the density of presented information is too high the visibility of the external world might be degraded.Information on the HMD can also distract the attention of an operator from the external view.A reduced transparency of the HMD ´s mirror can affect vision and impair color perception.It is considered that a high frequency of accom-modations cause eye strain,headache and similar discomforts.Finally,the low wearing comfort resulting from the weight of the helmet or visor,unbalanced point of gravity of the system etc.leads to performance degra-dation and feelings of discomfort.Unfortunately,there is only few infor-mation on such factors and only a small number of empirical examinations have been attempted. That is why the problem was investigated in the present experiment using a target recognition task.To take into account also long term effects,attention had to be sustained for about two hours under monotonous conditions.The targets (helicopters and land vehicles)were presented in a monocular HMD.Simultaneously,there was a simulated traffic scenario on a screen in front of the subjects where the target appeared some seconds later and had to be detected while a number of distractors were presented at the same time.The subjects had to move the pointer at the centre of the targets and to click at them.The land vehicles differed in shape:The turret had three different heights and a sensor on the turret was present or absent.The helicopters differed in colour:There were two different colours of the body of the helicopter and three different colours of the skids.The distractors had slightly different combinations of these characteristics than the targets.143 targets were presented in each trial,about one in a minute.As a comparison,a Hand-Held Display (HHD)was also used in a separate trial.Both trials, which lasted 130 minutes each,were identical and could not been influenced by the subjects ´ responses..Independent variables were display mode (HMD/HHD),vehicle type (helicopter/ ground vehicle),and trial section (four sections). Objective and subjective data were measured as dependent variables.Objective data were detection times and number of correct responses (hits).Subjective data were results of the Workload Trend Test (Belastungsverlaufstest BLV)and of the Simulator Sickness Questionnaire (SSQ).The BLV measures workload related experiences of subjects in the four subscales Psychological Stress,Psychological Fitness,Performance Aversion,and Fatigue .The SSQ is composed of the three subscales Nausea, Oculomotor,and Disorientation as well as of the Total Scale. The experiment was conducted with 12 subjects in a within subject design.All subjects performed the target recognition task with HMD and HHD separately on two successive days. Half of the subjects began with HMD followed by HHD,the other half vice versa,to counterbalance series effects.Before the first trial all subjects had to perform a 10 minute training for the target recognition task.The BLV and the SSQ were administered before (pretest)and after (posttest)the target recognition task. The results show no significant differences in detection times and percentage of hits between HMD and HHD.The pretest subscale scores of the BLV do not show significant differences between the HMD and the HHD.This means that the subjects have the same baseline before using both displays.The posttest BLV subscale results document significantly higher scores in psychological stress and fatigue with the HMD reflecting the deteriorating effect of the HMD on vision.The hypothesis is tentatively formulated that a higher effort is invested resulting in a higher stress load with the HMD to compensate for the performance deficiencies compared to the HHD.So,the performance of the HMD reaches approximately the same level as that of the HHD but at the expense of a higher effort.In the long run fatigue effects can be observed.But still other detrimental factors are involved with the HMD as can be seen with the SSQ results. All pretest scores of the SSQ show approximately the same results for the HHD and the HMD,documenting that the posttest result comparisons are valid.The latter comparisons reveal that the subscales Nausea,Oculomotor,Disorientation,and the Total Value have significantly higher scores with the HMD than with the HHD.These symptoms of simulator sickness caused by the inconsistent feedback of the visual and vestibular motion cues are assumed to be produced when fixating the pictures in the HMD while moving the head at the same time.Therefore,when an application of HMDs is planned,these deteriorating psychological factors should be reflected in advance in addition to the low wearing comfort of the technical equipment.When there are no other serious arguments against their use,in most cases an HHD will probably be a better choice.

Practical Relevance

In civil as well as military areas use of Head-mounted displays is planned or already realized.The results of the present experiment show however that the use might be accompanied by workload and fatigue problems as well as by symptoms of simulator sickness.Therefore,it is recommended to prefer Hand-held displays if there is no serious disadvantage.

Laboratory application of mechanical vibration dummies in place of human test subjects for vehicle seat testing (Vol. 1 – 2005)

Authors: Matthias Schwarz and Stephan Riedel

Keywords: · whole-body vibrations · vehicle seat testing · vibration test rig · vibration dummy · seat transmissibility factor

Summary

Tests for the evaluation of vibration-reduced seats may still require an exposition of heavy vibrations on the subject.The inclusion of humans in experimental procedures on vibration test rigs demands the compliance to high safety and medical-ethical rules.Furthermore,it is expected that the measurement results will be influenced by numerous individual factors of available test persons.This raises the question if a vibration dummy can be used which simulates the dynamic behaviour of the sitting man.It should be verified by a Round-Robin-Test. The experimental setup was based on a servo-hydraulic shaker for vertical whole-body vibrations,which was controlled by a personal computer including an application program.This program generated the test signals for the vibration process as well as carried out the acquisition,analysis and recording of real time series data.The process visualisation tool made it possible to tune the appropriate parameters via mouse-click as well as to show the current signals during the runs. The vibration test rig consisted of a single-axis actuator with a service platform to mount the seat test samples.For testing,the mounted vehicle seat had to be loaded with the corresponding body mass.The random vibration excitation at the seats was parameter defined in frequency f,weighted acceleration a w and the maximum power spectral density G P (f)max .For the determination of the reduction of vibration,the acquired vibration accleration data of the seat surface and of the service platform were put into relation.The calculated Seat Effective Amplitude Transmissibility factor (SEAT)represents here an indicator for the obtained reduction of the vibration intensity. The dummy was a two-mass model with a pin-jointed rocker at a spring damper system.The main parts of the dummy (back and back side)were covered with body contoured plywood plates. The effective vibration mass of the dummy was configurable by insertion of corresponding mass pieces. For the investigation,four vehicle seat types from articulated trucks,earth-moving machinery,industrial trucks,and agricultural wheeled tractors in conjunction with the appropriate test signals were selected.Each laboratory conducted four seat test series which comprised three persons per subject group (55 kg and 98 kg)and the adequately configured dummy.These values were based on the 5th and 95th percentile masses of typical workmen. The testing was expanded with subjects weighing 75 kg to obtain a larger range concerning the international population.All trials were repeated three times to ensure 5%tolerance conformity of the arithmetic mean of weighted seat acceleration.In seven testing laboratories,the total of 40 male and 14 female subjects have participated in the trials.With one exception,all valid values lay within a deviation of 5%from the average,whereas between the participating laboratories the SEAT factors had a large variance.It was evident that the determined SEAT values of the dummy lay systematically under the values of subjects with the same mass.The variance became manifest in dependence on the vehicle seat type;the variances had higher values for excitations at the lower frequency range than at the upper one.According to these findings it was planned to revise the dummy.A number of new test series should clarify to which extent an optimal parameter approximation of the dummy is attainable. The results of the check-up indicated,that the modification (reduction of vibration masses,change in damping)leads in average a better simulation of the dynamic behaviour of humans. However,the intended approximation could be attained only at the upper frequency range,while the transfer behaviour remained almost unchanged at the lower frequencies.Therefore,the modified dummy does not allow to specify a continuous transfer measure across the entire signal spectrum.Based on these results, it was decided to retain the primary model,but to apply a constant coefficient to adjust its transfer values. For the determination of a uniform adjustment factor,the averaged SEAT values of subjects were divided respectively by the averaged SEAT values of the dummy.The total arithmetic mean (1.15)of these proportions was subsequently selected as the coefficient for the dummy.It was verified that all charged transfer values were consistent within a 5%tolerance band across the entire frequency range of the test signals.It is expected that by using this coefficient the dummy will also simulate other subject groups accurately. The investigation has also shown the limits of the available model concept regarding the mechanical feasibility.However,it has to be stated that this model is generally applicable to simulate the dynamic behaviour of human test subjects.The systematic deviations of the transmissibility factors between model and subjects could be sufficiently reduced by a constant factor, whereby the dummy satisfies the tolerance conformity for standardised seat testings (cf.ISO 10326-1:1992). In summary,it can be said that the mechanical vibration dummy as a substitute in seat test procedures is scientifically justifiable and in practice absolutely advantageous.Compared to hu- man test subjects,the vibration dummy is always available, tolerant to overload and reproducible in ist vibration properties.

Practical Relevance

The results of the investigation show that the mechanical vibration dummy is appropriate to simulate the dynamic behaviour of human subjects and fulfils the tolerance criteria, which are defined in standards for vehicle seat tests.

Correlates of absence differences between organizations  (Vol. 1 – 2005)

Authors: Klaus-Helmut Schmidt, Barbara Neubach and Herbert Heuer

Keywords: · absence culture · between--organization differences · job satisfaction · organizational commitment · well—being

Summary

The study of absenteeism has enjoyed a long and extensive history.Literally hundreds of studies have been conducted on the causes,correlates,and consequences of absence from work and several reviews of the literature have been published. The vast majority of these studies has been done on the level of individuals as units of analysis and considered absence as a form of withdrawal from work.This notion has most often been examined by correlating measures of work-related attitudes like,for example,job satisfaction and organizational commitment with absenteeism.Existing meta analyses show that overall job satisfaction and satisfaction with the content of work itself are the best predictors of absenteeism with population estimates for these correlations ranging from low to the mid 20s.In general,the relationship between organizational commitment and absence is somewhat lower. However,when frequency of absence is used as criterion,the strength of the relationship approaches those found for overall job satisfaction. During the last decade,research has begun on how other levels of analysis might further knowledge of absenteeism. This research was stimulated by the notion of absence cultures (Chadwick Jones,Nicholson &Brown,1982)which are expected to develop in different organizations,departments and work groups and shape individual absence behavior.For studying those social influences,Johns (1997)has proposed a hierarchy of research strategies starting from the demonstration of between-unit differences in absenteeism, going on to analyses of social correlates of absence,up to examinations of cross-level effects in which absence patterns at a higher level are mirrored in individual behavior. The present study is based on data from 111 offices of a large administrative authority that allowed the application of the first two strategies.Two sets of variables were assessed:a) employee attitudes (job satisfaction,organizational commitment)and well-being measures,and b)absenteeism indicated by measures of absence frequency and time lost (sum of days absent).Both sets of variables were measured at the individual level and aggregated at the office level.In all, 22 292 employees participated in the study,with complete data from 18 171 employees. Analyses of variance with offices as independent variable revealed highly significant between-office differences in both absence indexes as well as in all attitudes/well-being measures. Furthermore,all attitudes/well-being measures showed significant office-level relations with both absence indexes, with sizes being highest for absence frequency.After control for the influence of office size,regression analyses indicated that the attitudes/well-being measures explained additional significant portions of absence variance ranging from 14 % for the time lost index to 16 %for the frequency index.Finally, additional utility analyses confirmed the practical significance of the found relationships.For example,offices in the top quartile on job satisfaction had,on average,2.35 absence events and 9.65 days absent per employee and year,whereas in offices from the bottom quartile of the satisfaction distribution,on average,3.03 absence events and 13.41 days absent did occur.

Practical Relevance

The results suggest to extend the traditional individual-focused measures of absence prevention by organization –or unit -related interventions.Initiating programs of health promotion and work design under strong participation of the employees,presenting aggregated absence feedback,and introducing flexible working schedules are possible examples for such interventions.

Competency development of environmental agents in companies:options and methods  (Vol. 1 – 2005)

Authors: Andreas Homburg and Anja Baumann

Keywords: · Conservation · ecological behavior · social influence · environmental agents · competency development · staff development

Summary

One of the important factors in the development of proenvironmental behavior within companies is the competency of the individuals responsible for environmental protection measures (e.g.environmental managers).Obstacles for such individuals include a low amount of motivation by other agents,an indifferent corporate culture and missing support by the management. In this paper,we first present a psychological view of the environmental issues involved.We propose that environmental protection policies necessarily involve a process of intentional social influence.From a social psychological perspective, behaviour is changed,stabilised and controlled in this process via communication and interaction between a ”source “ and a ”receiver “.It therefore includes the following aspects:In an action context (e.g.,organisation,work group)environmental agents purposely influence (i.e.change,stabilise,control)the relevant behaviour of target persons (e.g.,colleagues, superiors)with certain means of influence (e.g.,conversation, target values)so that the behaviour is performed in an environmentally friendly way.Environmentally friendly (or non polluting)actions refer to behaviour that minimizes anthropogenic pollution.This social influence can be more or less effectively exerted by proponents of environmental protection measures (i.e.,environmental agents). When we view environmental protection as a process of social influence,and this influence is thwarted by certain obstacles, then several competencies are needed to change and stabilise environmentally relevant actions effectively and efficiently: (a)environmental protection should here be understood as the exertion of social influence (”basic knowledge “);(b) environmental agents should thus know which elements in this process restrict environmental protection and how these elements can be recognised (competencies for analysis);and (c)environmental agents should be able to use a wide variety of instruments of social influence in order to use these elements optimally to influence change). The present study explored promising components for competency development of environmental agents which put the following questions:(1)Which activities do environmental agents perform and which supporting elements do environmental agents perceive in their organisational context? (2)Which means for the exertion of influence do they use?(3) Which personal convenient strategies of influence are recommended by environmental agents?(4)Which sort of training do environmental agents want? Interviews with 22 environmental protection agents working in manufacturing were conducted,and the following conclusions were reached about how such competencies could be developed.First,environmental agents should be able to involve the senior management.In particular,it is important to include environmental targets in the establishment of company goals.Second,employees should be encouraged to be active supporters of the policy,in particular,using a participative process to engage their support.Finally,it is concluded that training sessions are an appropriate way of strengthening competencies of social influence.

Practical Relevance

The conversion of environmental protection measures is a central task for enterprises.The present study suggests strategies for better social influence methods for environmental protection.

Eliciting Experience in Task Design – Task Oriented Information Exchange in CIM—Technologies  (Vol. 1 – 2005)

Authors: Winfried Hacker, Rüdiger von der Weth, Ariunaa Ishig and Gerhard Luhn

Keywords: · Tacit knowledge · Quality circle · Task design

Summary

In the micro-chip production of a highly automated enterprise a mismatch became evident between the task instructions and the offered task-related information on the one hand and the actually applied expert strategies of the operators on the other. This mismatch was the reason to start a specific series of problem solving sessions in small groups,called Task Oriented Information Exchange (TIE),in order to identify the actual knowledge of the operators about work processes.This was used (1)to identify possible improvements in the technological processes and (2)to support the development of a task related information system with actual instructions relating to the improved procedures. (1)The research process started with a combination of observations and interviews for 16 work places,each with two different operators.This enabled a description of the work process and the usage of information.In the TIE-groups this description was controlled and amended by the observed workers.Based on these results deficits were identified and improvements have been developed and implemented. The description of the results of these processes comprises several dimensions.The first dimension was the type of improvement in the proposals (organisation of work processes, information design,social aspects).A further distinction has been made between the expected effects of the formulated goals (long term effects,medium term effects,short term effects) and also,whether cooperation with other departments was necessary or not.Using these three types of categorization the results can be summarized as follows:Most of the goals were related to improvements of the work processes and the information design,social aspects didn ´t play a role.A lot of short term measures (i.e.in less than three months)were implemented during the TIE process.According to a follow up questionnaire most of these short term goals could be reached.Activities with respect to medium term and long term goals have been started but had still not come to an end when the follow up study was made.The biggest problems arised in the case where cooperation with other departments was necessary.The overall satisfaction with the results and the motivation of the participants was high.Learning processes have been reported. (2)In two groups the specifications of the design process for the information system were also developed.These specifications have been used for the design of three information systems for different work places .This systems should support the operators in finding information about the work place quicker than before:

Ø      in the case of open questions and problems

Ø      during the training of new processes

Ø      giving instructions to new colleagues.

Therefore the design of the user interface should strictly follow the users ´ work process. So the result of observational study and the first TIE sessions were also used by the designer of the information system who developed it in close contact with the TIE teams. Three months after the installation the users assessed the improvements of the information system.The results in many cases were significantly positive.Operators found the new information system far more comfortable and actual.It was judged to be useful for familiarizing themselves and new colleagues with new work processes.Additionally an analysis of the design process was carried out by two expert engineers working in the microprocessor plant.These expert ratings were reliable (k=.85).The quality of the design process described above was compared with the common way to generate work information in the plant .The comparison was made with a checklist based on ISO 13407.According to the results the cooperative design process was found more participative than the old approach of generating work information. The study shows,that participative problem solution procedures based on the expert knowledge of the employees can be useful for many purposes also in industries with highly automated CIM technologies.

Practical Relevance

This paper describes the strategy and the efficiency of methods removing deficiencies in the design of working processes, instructions and task-related information systems.Specific hybrid group discussion methods aiming at the cooperative identification of possible improvements,at the design of relevant measures and at their implementation can be applied successfully in highly automated CIM-technologies.

Vol. 2 - 2005

Co-Production at the hospital:Development of an instrument to analyze conditions for active participation of patients (Vol. 2 – 2005)

Service quality at the hospital is increasingly becoming subject of analysis and design.The article tries to demonstrate potentialities to assess conditions for active participation of patients and in so doing enhance quality management.

Ergonomic work design in the operating room - a methodological challenge to accomplish complexity (Vol. 2 – 2005)

Authors: Matthias Göbel, Swantje Zschernack and Wolfgang Friesdorf

This paper shows the challenges to design complex work system via the example of the surgical operation room. Characteristic system attributes are outlined in order to explain the emergence of  complex system behaviour and its accomplishment for work system design.

Reorganisation of clinical processes and in-patient orientation (Vol. 2 – 2005)

Authors: Klaus J.Zink, Christoph Esser, Johannes Palm and Annette Blaudszun

-         selection of various strategies which are promoting a patient and employee orientation,

-         development of organisational structures specifying quality and process standards to create business opportunities,

-         external and internal network of included parties,

-         training of employees involved with the reorganisation process,

-         introduction of a documentation system for timely and extensive data and information exchange,

-         set-up of a system of key indicators based on questionnaires for patients,employees,admitting doctors, institutions (e.g.rehabilitation centers,homes for elderly people)and other cooperation partners as main target groups.

Many hospitals in Germany are not prepared for the current and oncoming demands caused by the health care reform. In particularly the compensation system „Diagnosis Related Groups “,effective since 1/1/2004,leads to the necessity of a reorientation for many hospitals in order to manage restricted financial budgets.The basic considerations discussed in this paper intend to sensitise necessary reorganisations on one side,but also point out,that such a change can only be successfully realised as an organisational development process.Furthermore,some important elements for such a transformation concept are being discussed that can give a first orientation to any hospital.

Psychological work load of nurses and physicians in hospitals (Vol. 2 – 2005)

There are only a few empirical studies investigating the psychological work load of physicians in hospitals.Our study is able to expand current knowledge on this topic.Moreover, results of the comparison of work load between nurses and physicians can serve as a starting point for the joint improvement of working conditions for both professions within the complex system ”hospital “. The results of an earlier organisational development project, conducted in an other hospital,can be taken as an example for the possibility of jointly optimizing the two work subsystems and thus enhancing autonomy,improving cooperation and substantially reducing work-stressors.

Work load and days lost due to illness – exploratory time series analyses of a longitudinal study on the nursing staff of a general hospital (Vol. 2 – 2005)

The economic pressures exerted on hospitals are leading to attempts to reduce costs by reducing staff,irrespective of the increasing demands on the nursing staff.The results of the present study show that such a one-sided economic strategy will not be effective,since it will lead to an increase in days lost and in overtime work,which will increase costs at other points within the overall (hospital)system. The methodological approach used here seems to be suitable for improvements in personnel planning in hospitals from an economic as well as from an ergonomic perspective.

Measurement of postures and action forces to determine the lumbar load of care-activities (Vol. 2 – 2005)

The research project,partly described in this paper,was initialized to receive indicators for the lumbar load of health-care workers during patient transfers.These data are used by the Statutory Accident and Health Insurance Institution for Health Services and Welfare Care for the assessment of lumbar diseases and in addition for the development of preventive measures to avoid diseases of the lumbar spine.

Prospective Simulation – A concept for the methodological complementation of medical simulator settings (Vol. 2 – 2005)

The current paper describes a concept for a methodological supplementation of patient simulations which is relevant for other simulation domains as well.By using the proposed concept safety related anticipants of health care workers might be improved.The concept further allows for better connecting data from problems in clinical practice (e.g.from incident reporting systems)and simulations.

Vol. 3-4- 2005

What is Work?A consideration of the relation of Entropy,Energy and Ergonomics (Vol. 3-4 – 2005)

Author: Heiner Bubb

Keywords: · work · science of work · ((micro-)ergonomics · Turing--machine · entropy · occupational shift

Summary

As long as anyone can remember work defines human life.But a fundamental definition of work never was attempted seriously for the long history of entire philosophy.Of course,we find different views of work during the period of Greek philosophy that emphasized the preference of contemplation against the work of the craftsman.The Jewish and Christian traditions as well considered work as a natural part of life that should not get the upper hand over our relation to god. In the historical development these aspects have influenced our relation to work essentially.Especially Martin Luther has defined work radically as service for god and by this at last he influenced the understanding of work by the secular Puritanism and Calvinism.No longer the couple ”work and poor “ is relevant but now the couple ”work and richness “ predominates as god rewards the industrious man by richness. However,first the science of works (”ergonomics “ from the Greek words ”ergon “ for work and ”nomos “ for science)) coming into existence during the 19^th century has concerned itself with the work and tried first definitions of the idea of work.One of its aims is to make the load of work tolerable by ergonomic design principles.By the so-called ”prospective ergonomics “ measures of reduction of work load should be done already in the design phase. An important influence of our understanding of work has the closed loop paradigm (see figure 1).It allows the definition of work quality as the relation of task and result and defines work performance as the work quality in relation to the afforded time.The closed loop paradigm shows a further important aspect.By work the information of the task is transformed into the information of the result.Turing described the principal parts of this process.The information processing system (in our case the human worker)detects a symbol.In the next step it deletes the symbol and finally in a third step it moves the next symbol on the vacant position.By this process a new order is realized (see figure 2). When we consider the manual montage process we find the same elements.The moving elements ”reach “,”grasp “,and „bring “ are corresponding to the Turing elements ”detect “, ”delete “,and ”move “ ((see figure 3).Also a montage process realizes a new order that of course is not given by nature. When we have a closer look on the Turing process,we have to distinguish between the routine part of work that is described by the Turing process itself and a second part the creative work .The creative work corresponds to the question what symbol should be detected and demands a decision. Thus creative work is an essential part of human behaviour.In contrast routine work can be automated. Understanding work in terms of creating new orders by means of the Turing process the definition of information is to be specified according to Wiener (1948)and Shannon &Weaver (1949)as ”negentropy “.Thus human work is a process of creating order which corresponds to an increase of information. Human work creates or preserves a desired state of order against the natural tendency of increasing entropy (which is the decrease of information).Therefore human work always requires conversion of energy according to the universally valid second fundamental theorem of thermodynamics. Conversion of energy means the applying of physical force. All the industrial revolutions dealt with the invention of tools which facilitate the ”preservation of order “ to a higher degree (see figure 4).In the first industrial revolution fossil fuels were made usable systematically.With the second industrial revolution the introduction of systems for power supply, especially of electricity,made energy available ubiquitously. Presently the third industrial revolution substitutes the process of creating order with technical system (by computer based information technologies)and provides by means of networks an ubiquitous availability of the produced information.This development causes in its consequence an occupational shift (see figure 5).Especially the disappearance of heavy physical work,at least in the technological developed countries,and the automation of well pre-programmable procedures is the result.The change from producing work to service work is the inevitable result (see figure 6). Regarding the lifecycle of products with its phases generation of the product idea,conception phase,definition phase, development phase and use human work is increasingly replaced by machines.Nowadays computers substitute human cognition in the definition and development phase.This development has effects for human work.To mention are the decentralisation of jobs,flexible working hours,more intensive and more precise control of the work performance and the individualisation of products. In summary a trembling question comes to mind:”Do we run out of work?“ Will we reach a degree of technical perfection and automation that kicks humans out of the system,so we reach a paradisiacal state of ”dolce fa niente “?This assumption would require an absolute state of order which only can be reached theoretically.Especially in the service sector tasks only to be fulfilled by humans will persist.On account of the increasing entropy,natural as well as technical systems will lose their state of order in a not predictable way.With losing their state of order they lose their operability and effectiveness. Thus,to restore the ordered state human creativity and intelligence is needed. So we don ’t run out of work.But there will be a shift in the focus of human work.According to Rifkin (1997),the first sector work,i.e.gainful occupation will lose its predominating importance.In contrast second sector family-work and third sector citizen-work will gain importance.The public administration has to consider this development in terms of monetization family-and citizen-work.Last but not least the science of work has to deal with the tasks occurring with and within work of the second and third sector.

Practical Relevance

Reflecting human work and the occupational shift form an information-theoretical view regarding entropy a heuristic value for science of work future research can be deduced.The automation of routine work should lead to stronger focus on creative and innovative work as well on the service sector. Further on the occupational shift refers to new research fields in family work and citizen-work.

Assessment of the vibration induced forces transmitted in the joints of the human body by means of a biomechanical models (Vol. 3-4 – 2005)

Author: Martin Fritz

Keywords: · whole--body vibrations · hand--arm vibrations · simulation · transfer functions

Summary

Epidemiological research in many countries reveals that an elevated risk of health impairment is given by long-lasting exposure to hand-arm or whole-body vibration of high intensity.Meanwhile it is commonly accepted that the mechanism of the degeneration of the arm joints or the lumbar spine is triggered by the forces transmitted in the joints or the spine.The forces cannot be measured under vibration. However,they can be simulated by means of biomechanical models. The model of the hand-arm system consists of four masses with inertia of rotation representing the hand with its palmar tissues,the forearm and the upper arm.The masses are connected with linear springs,dampers,and torsion springs. For the translational and rotational movements of the masses the equations of motion were derived and summed up into a inhomogeneous differential matrix equation.The harmonic solution of this equation leads to an algorithm enabling the adaptation of the model to the properties of the hand-arm system by iterative variation of the model parameter.During this process attention was paid not only to a good fit of the parallel to the longitudinal axis of the forearm the greatest values were obtained for the forces between the two masses near the driving point,whereas the torque at the system support attained the highest value compared with the other torques. The forces transmitted in the arm joints can be derived from the simulated forces only with some modifications.Since the rotation effect of the muscles was imitated in the model by torsion springs the muscle tension compressing the articular bone ends together were not included in the simulated forces. This must be regarded in order to obtain a realistic assessment of the joint forces. In the model of the standing or sitting operator the trunk with the viscera,neck,head,legs,and the arms are represented by 27 rigid bodies.The rigid bodies of the trunk and neck are connected by visco-elastic elements which have the same deformation properties as the motion segments of the spine. The trunk,neck,and legs muscles are imitated by 106 so-called force elements which exert constant forces to maintain the given body posture and additionally vibration induced cyclic forces. Under a random test vibration the courses of the displacements of the model bodies and of the forces in the leg joints and the motion segments of the spine were simulated.The cyclic forces reached their greatest magnitudes at frequencies between 4 and 6 Hz.In the standing posture the cyclic ankle forces were higher than those in the knees and the hips and they nearly come up to the forces in the lumbar spine.Furthermore, under equal vibration stress in the standing and the sitting posture the simulation indicated that the differences between the compressive forces in the lumbar spine were small.Thus it cannot be stated that concerning the lumbar spine a lower health risk is given for the standing operator as it is assumed in the literature. From the transfer function between the vertical seat acceleration and the compressive force in the motion segment L3-L4 new weighting factors were derived.Using these force-related factors for the frequency weighting of the seat acceleration instead of the factors given in the norms and standard the cause of the degenerative diseases of the lumbar spine will be regarded by the vibration evaluation.

Practical Relevance

An improved assessment of the vibration induced health risk should be attained by means of the simulated forces.Furthermore,the forces can be used to derive new factors for a force related weighting of the accelerations taking into consideration the cause of the degenerative diseases.

Quantitative Prediction of Manual Material Handling Hazards (Vol. 3-4 – 2005)

Authors: Issachar Gilad and Moran Elnekave

Keywords: · work--sampling · postural analysis · work-measurement

Summary

The discipline of ergonomics is based on data measured in the work-area,and therefore,works well with work-measurement methodologies.The purpose of ergonomic analyses many times is to make recommendations for improvements.In most cases,it is not enough to attend the work-area and view a couple of work-cycles.Consequently,many analysts and academicians use videotaped scenarios of the work-area.This paper describes a methodology for coupling ergonomic and work-measurement analyses.Moreover,using a case study, we show how the approach may be implemented.The methodology combines a detailed ergonomic analysis of joint postures of the upper body and a rapid work-sampling technique,carried out on a PC playing back a digital video scenario.Using the proposed methodology it is possible to identify the factors that may produce injury.Such a procedure is easy to use and can serve as a valuable tool for assessing hazards in work-situations.

Practical Relevance

Simple work-sampling technique combined with PC-based video scenario analysis of postures to assess risks.

Dynamic information in integrated surface electromyograms (Vol. 3-4 – 2005)

Author: Matthias Göbel

Keywords: · electromyography · integrated EMG · signal--to-noise-ratio · motor coordination · sensory feedback

Summary

Electromyography (EMG)studies muscle function through analysis of the electrical signals emanated during muscular contractions.Asynchronous firing of the different motor units and variation of firing rate and motor unit recruitment builds an interference pattern at a surface electrode.The EMG signal is,hence,described as a train of quasi randomly shaped spikes varying in amplitude and duration without an identifiable sequence.In spite of its noisy character,significant information can be processed from the EMG signal.There is a correlation between the number and intensity of generated spikes and the muscular contraction force.Thus,the average EMG signal intensity increases with muscle contraction.This makes it possible to evaluate exerted muscular force by means of electromyography and enables a wide application of electromyography to study muscle load and muscle fatigue. However,the noisy character of the raw EMG interferes the activity function in a way that it may be smoothened only by a long integration time,which again disables the tracking of fast changes in muscular activity.This limits the application of electromyography to analyse dynamic movements pattern and motor coordination functions. Signal analysis describes the surface electromyogram as an amplitude-modulated signal using noise as a carrier and being modulated by the muscular activation function.It can be shown that interference components occur in the integrated EMG,resulting in a significant amount of noise introduced into the intensity function when rectifying electromyographic spike pattern.Based on a detailed signal analysis the formation of noise and distortion can be outlined,showing in which way signal characteristics and filtering affect the signal to noise ratio.Even with best electrode configuration and filter setting, a significant amount of noise occurs in the averaged EMG if fast changes in the activity function shall be tracked. The individual spectra of noise can be computed to a large extend from inherent raw electromyogram characteristics. Based on the computation of appearing noise and distortions in given electromyograms an adaptive filtering procedure is proposed which suppresses about of the 90%interference signals without limitation of output bandwidth. The application of such a fast averaged EMG is shown by studying sensory feedback in movement control.Any controlled motor action requires sensory control.Incorporating visual,haptic,and kinaesthetic sensory modalities builds a nested closed loop feedback system.For the design of work systems and user interfaces this requires to know the extent of the different sensory modalities being actually involved into motor control in order to provide adequate feedback and training conditions. Because neuronal information flow cannot be analysed directly,electromyographic information represents the most direct access to motor control processes.EMG thus represents the output of the motor system fed into the muscles which then provide the transformation to mechanical force.The output information of human closed loop feedback system contents specific attributes related to the incorporation of feedback caused by the neuronal delay of information processing in biological systems.Any delay within a feedback loop derogates the quality of control because any corrections can take effect only decelerated.In order to obtain significant feedback control this requires to intensify feedback which again causes oscillatory components due to the delayed effect of feedback.For movement control such oscillations are externally suppressed by mass inertia of extremities,but are still detectable in EMG ’s.Decomposition of the higher frequent components of the EMG according to their frequency (which again corresponds to information processing delay) allows to discover the degree of sensory feedback applied actually for movement control. Using the example of the learning process of a manual assembly task it can be shown that the different sensory modalities contribute in very different ways to motor performance.With few experience,increasing kinaesthetic feedback leads to a decreased task performance.The other modalities do not already affect motor processes significantly.With progressing experience subjects learn to incorporate visual control for increased task performance.This is also true for haptic feedback with longer experience.The learning process to incorporate sensory feedback takes place during exercise and degenerates during rest brakes for kinaesthetic and visual feedback.Anyhow,haptic feedback is trained exclusively by mental processes during work breaks.Generally,the degree of sensory feedback involved in motor control decreases slightly with age.

Practical Relevance

The expression of energetic and information processing performance is mostly based on human motor output.In order to design motor tasks with focus on human motor co-ordination and control a method to obtain a precise muscular activation function with high temporal resolution is proposed. With a subsequent signal processing approach the effect of sensory feedback can be analysed during complex movements.

Analysis of muscular load and its effects (Vol. 3-4 – 2005)

Authors: Klaus Hecktor and Matthias Jäger

Keywords: · stress · strain · task analysis · evaluation · work design

Summary

Even with the level of automation currently to be found within the working environment,there is still a frequent occurrence of activities involving physical load,the performance of which can lead to an excess strain for the respective persons.The majority of work-related diseases resulting to work absence are caused by complaints and impairments regarding the muscular and skeletal systems (Bödeker et al.2002).Causes can be excess strain resulting from the handling of medium to heavy objects in which an unfavourable relationship between muscular strain and individual ’s capacity cannot be ruled out.With respect to fatigue and overload,an disadvantageous work-to-break ratio is also a relevant factor in identifying the causes of impairments.The unfavourable postures and movements during working activities can also be regarded as causal for muscle-related impairments and complaints during sustained constrained postures such as those occurring during overhead activities at assembly workstations (Landau et al.2004),for example,or in case of office work resulting from repetitive movements of the computer mouse (Luttmann et al.2002). The performance of any activities which are predominantly affected by muscular exertion,consequently calls for an analysis of stress and strain for the executing persons in order to avoid excess strain and potential impairments.This requirement implies the determination of the energetic loading placed on the cardiac-circulatory and musculoskeletal systems which are particularly active  during the performance of sustained physical activities and operations.On account of the diversity of work demands and,in the following,of data and calculations to be taken into account,it often proves recommendable to perform the analysis and evaluation applying a computer-assisted system.The specifications of the respective stress-and-strain indicators of the corresponding organs and systems are continuously simulated throughout the entire activity and,subsequently,evaluated by means of individually defined maximal permissible specifications for the individual indicator.Such an evaluation of the results of simulations or measurements,which includes potentially necessary suggestions for (re-)arrangements of occupational activities,enables the consideration of relevant measures for stress reduction and the avoidance of potential adverse effects in the work design procedure.

Practical Relevance

In the working environment,activities involving high physical load are still to be found that can lead to adverse effects,in particular,with respect to the cardiac-respiratory and musculoskeletal systems.For the avoidance of these negative consequences,it is therefore recommendable to perform task analyses in order to predict the stress and strain occurring during the performance of an activity by employing appropriate prognostic methods and to derive and provide for suitable measures of work design.

The „Dortmund Approach “ for the biomechanical analysis of spinal load during manual materials handling (Vol. 3-4 – 2005)

Authors: Matthias Jäger and Alwin Luttmann

Keywords: · manual materials handling · biomechanical modelling · load on the lumbar spine · lumbar load-bearing capacity · recommended values · cumulated dose

Summary

The Dortmund Approach aims at a biomechanically oriented assessment of the load on the spine for occupational manual materials handling.The procedure for biomechanical modellings used for a quantitative determination of lumbar load is explained,and the application in various occupational fields is presented exemplarily.The variety of vocational exposures commonly requires a three-dimensional dynamic methodology including the determination of various load characteristics,in particular for the description of the actual and the cumulative load.For the assessment with respect to biomechanical overloading risks,different recommendations for lumbar load-bearing capacity should be applied at short and long-time exposures.

Practical Relevance

Manual materials handling and force exertion are characteristics of a high number of occupational activities.In consequence of the accompanying high load on the musculoskeletal system and,in particular,of the lumbar spine diseases and complaints as well as absenteeism caused thereby are to be found with high frequency.Applying the Dortmund Approach the determination of the mechanical load on the lumbar spine and its assessment related to short time as well as long-lasting occupational activities with load manipulations can be achieved.This approach enables a substantiated derivation of preventive measures of work design.

Physiological costs during working at the discounter checkout – Left-to-right scanner checkout versus traditional keyboard checkout (Vol. 3-4 – 2005)

Authors: Karsten Kluth and Helmut Strasser

Keywords: · product ergonomics · checkout · physical strain · electromyography

Summary

In order to enhance eye contact with the customer,a frontal orientation of the cashier to the conveyor belt is generally recommended.Furthermore,from a work-physiological point of view,movements of the left hand-arm system from left to right across the slot scanner seem to be superior to conventional manual movements of the left arm from right to left.Prior to introduction into thousands of shops of a food discounter,a correspondingly designed checkstand with interior and exterior dimensions according to ergonomic requirements,and a placement of the scanner compatible to the left elbow and shoulder joint,via electromyographic methods was evaluated in comparison with a traditional keyboard checkout with backward movements. Laboratory tests were carried out during which the physiological costs of altogether 8 muscles of the left and right hand-arm-shoulder system (m.extensor digitorum;m. flexor carpi ulnaris;m.biceps brachii;m.deltoideus pars clavicularis,pars acromialis,and pars spinalis;m.trapezius pars descendens sinister and dexter)were measured twice during alternating working at the scanner checkout and the manual keying in of prices.It may be mentioned that the conventional checkout had been used successfully over more than 20 years.Ten professional and experienced cashiers (all female subjects (Ss)with an age of 28.2 ± 6.2 years and an employment of 8.3 ± 4.8 years))participated in the 4 working phases,each with a duration of 15 min whereby they had to check items which had been put on the conveyor belt out of 5 identically filled carts.The items represented a retail assortment for a shop ’s product range varying in size,shape, and weight.Utilizing a portable data recording system, electromyographic activity (EA)of the 8 muscle groups was simultaneously recorded during the 4 working phases,which were separated by 5-min breaks.Measurements of the maximum activity,EA max ,via maximum voluntary contractions of all 8 muscles – which were necessary for calculating standardized electromyographic activity (sEA)used to reveal muscle strain as a percentage – were always taken at the end of the experiment to avoid errors and fatigue-induced transfer effects for the actual EA values during alternating work at the two checkouts. The results of the averaged and standardized electromyographic activities of the 8 monitored muscles showed that a large variation of strain between the muscles exists,but test and retest clarified that the level of the sEA values for the different muscles and conditions was reproducible and stable.The activation of most muscles acting on the shoulder (m.trapezius pars descendens,dexter and sinister),the upper arm (frontal,middle and spinal part of the left deltoid),and the hand (m.extensor digitorum and m.flexor carpi ulnaris of the right hand)showed clear differences which could be associated with the type of the price input.Both during the test and the retest,the 15-min mean values of all muscles revealed similar levels,whereby the scanner checkout – with the exception of the biceps and the descendent part of the right trapezius muscle – proved to be associated with substantially lower physiological cost. Additionally,extra physiological costs of the examined muscles and muscle parts due to work with the conventional cash register system was calculated.When the actual 1-min sEA(t) values of each working phase had been related to the overall mean from the two scanning phases (S1 and S2)according to the formula (sEA(t)-sEA ·(S1+S2)/sEA ·(S1+S2),increases or decreases of physiological costs for the 8 muscles could be quantified.Via this procedure it could be shown that,for the left hand-arm system,about 20%of physiological cost to the descendent part of the trapezius,the acromial and the spinal part of the deltoid,and even more than 30%to the frontal part of the deltoid,can be spared by working at the scanner checkout.For the right hand-arm system,the increase in physiological cost due to keying in of prices manually is much higher.Increases amounted to about 100%for the m.extensor digitorum and to about 40-50%for the flexor carpi ulnaris.In contrast to these,mostly high significant effects,there are less favorable effects on the descendent part of the trapezius of the right body half.An increase of about 10%was measured which,however,could not be proven to be statistically significant.Only marginal and inconsistent effects (neither increases nor decreases of muscle strain)were found for the biceps of the left arm.All in all,the ergonomically designed left-to-right throughput scanner checkout led to objectively verifiable and plausible reductions of muscle strain.

Practical Relevance

The results of this study reveal the necessity for manufacturers to develop user-friendly checkouts for the market.But these products normally need a systematic ergonomic evaluation. The data of the study can be used by job analysts to grade the level of muscle activity required by different checkout systems during the registration of the prices and the handling of the goods.Furthermore,product designers can be endorsed in justifying changes in the design of checkouts aiming at reducing muscular strain of the upper extremities and the back.

Prognosis model for working load in private homes (Vol. 3-4 – 2005)

Authors: Günter Eissing and Pia Neumann

Keywords: · household · load · strain · activities · prognosis

Summary

Housework is often small estimated in the public.This estimation is to be examined by the results in the presented study of the stress and strain by the work situation in private homes.The stress and strain of domestic activities aren ’t proofed for about 20 years.Based on this investigation there exist only publications of Grandjean (1973)and Diebschlag (1984),which judged activities in private homes regarding the muscular work as moderately severe. The execution of such ergonomic studies is connected with a large expenditure.Therefore a prognosis model of the load and demand of the activities is determined in order to be able to transmit the data for example also to similar households. Therefore an ergonomic investigation was carried out to get the data of altogether 30 private homes.The selection of these households took place on the basis of to a large extent constant and some variable characteristics.An analysis of the working process (collection of the exercised activities,the activity element as well as the body position)with simultaneous measurement of the heart rate was accomplished as well as a data determination by means of questionnaires. A prognosis model was determined to forecast the work pulse.The model was based on a multiple linear model.Only values of activities which have a duration of more than fives minutes are used.The most influence on the work pulse have the activities and the combination of the body position and activity element.The coefficient of determination amounts to 24,8 %(r ²=0,24).  The validation of the model gives information about deviations from the linearity,normality,variance homogeneity and about possible outliners.Therefore only significant variables were considered in the model.Some are even highly significantly. Further the examination of the residues shows that a large homogeneity of the data is present (Neumann 2005).Also a comparison of the model values as well as the level of significance with the actually measured values shows a high agreement.Between the model values and the measured values no significant differences exist. Field investigations are connected with an enormous expenditure.In order to be able to accomplish further investigations the data of the prognosis model can be used as reference values.Thus a beginning is taken up,which Laurig already introduced 1984 as ‘Prospective ergonomics ’.

Practical Relevance

The stress and strain of domestic activities aren ’t proofed for about 20 in ergonomic studies.The current results show clear differences in the comparison with the past studies.A prognosis for the activities in the private homes supplies reference values for further investigations to analyse the work pulse with activities as well as to consider the strain of activities.

Evaluation of the Application of Virtual Reality Presentation Techniques in an eLearning Module on the Ergonomic Design of Work Systems (Vol. 3-4 – 2005)

Author: Dietmar Gude

Keywords: · eLearning · virtual reality · evaluation · acceptance · usage · sustainability

Summary

The interest in providing learning services via the World Wide Web,in the form of eLearning applications,has increased greatly during recent years.Shortcomings of traditional text- oriented applications,especially with regard to low completion rates,have let to the proposal to apply techniques from the field of virtual reality (VR),to present learning content in a more vivid and interactive way.To test the validity of this proposal,the acceptance and usage of such a VR-enhanced eLearning application on the ergonomic design of work systems was investigated. The purpose of this application was to familiarize the users with the systematic evaluation of work systems.In this context, the rationale of introducing VR techniques was to provide a training setting that mimics the conditions under which real- world work systems are commonly evaluated.That is,the user is presented a three-dimensional model,in which he or she can navigate and interact with its components,to find out the ergonomic deficiencies.In doing so,the user is guided by a number of questions covering the requirements relevant to the work system under consideration.Answering these questions,the user is provided with feedback whether his or her assessment was correct and how to verify this feedback in the model.Currently,the application contains five learning units,two utility vehicle scenarios and three computer workstation scenarios. To determine the acceptance and usage of the application,the course of interaction and its time structure were recorded. These data allowed to ascertain,e.g.,the time the application was used,the frequency with which the different scenarios were accessed,and to what degree the corresponding learning units were completed.The users were identified by a login mechanisms,the required username and password were defined during an initial registration procedure,in which general personal data were recorded (age,gender,occupation,nationality;  and previous knowledge in the fields of ergonomics and virtual reality),in addition.These data were utilized to differentiate a number of user groups and to compare their ways of interacting with the application.The results reported here are based on data recorded during 600 days,300 days before and after the end of the funding period of the underlying project,to determine the sustainability of demand for this eLearning service. During this period of time,587 people registered to use the eLearning application.Despite the initial expectation,the majority of the users were not students,but rather the largest group comprised professionals from the service sector. Moreover,while most of the users were from Germany,more than one-third came from other countries,underlining that the service was of interest for a wide and international audience. On the average,the users interacted with the application for about 20 minutes.This value can serve as a benchmark for the adequate size of learning units in eLearning applications.The standard deviation of usage time indicates a high level of interindividual variability,suggesting to provide units of different sizes and allowing the users to select those matching their individual requirements. Each user accessed about two of the scenarios,with those on computer workstations being much more popular than those concerned with utility vehicles.On the average,about 0.3 scenarios were completed,by answering all accompanying questions.This finding is in line with the international literature,in which the completion rates of eLearning applications are reported as being ‘notoriously low ’.In this respect,there were no systematic differences between the two scenario types. The method applied here allowed to determine at which stage the drop outs occurred.It became apparent that the crucial stages were located at the beginning of working with a scenario.One-fourth of the drop outs occurred while the users were waiting for the VR-models to be downloaded on their computer,pinpointing a bandwidth problem which overstrained the patience of several users.If the download was completed successfully,in almost all cases the users started to interact with the model.However,with a much lower frequency the users answered the first question,accounting for another quarter of the drop outs,and this trend continued to the stage that the first 25%of the questions were answered. In the following stages drop outs were rather infrequent,i.e., after answering the first 25%of the questions in most cases the learning unit was completed.The contrast between the frequencies with which the users interacted with the VR-model and answered the accompanying questions – originally provided to guide them through the systematic evaluation of the work system under consideration – indicates that often they preferred an explorative rather than a systematic learning strategy,which is in line with the constructivist theory of learning. Finally,there were no substantial systematic differences between the user groups on how they handled the eLearning application.This implies,i.a.,that it can be used in an adequate way even without previous knowledge in the fields of ergonomics and virtual reality.This finding indicates that the range of application of VR presentation techniques is not restricted to academic education,but rather includes the field of lifelong learning.In addition,most usage aspects remained stable after the end of the funding period,with the exception that there was a moderate decline of the number of new users that registered to access the service.In sum,this provides evidence for the sustainability of demand,but also indicates some need to reinforce marketing-related activities.

Practical Relevance

In the context of the initiative of the European Union of becoming the world ’s most dynamic knowledge-based economy,the concept of eLearning is an important instrument to modernize the educational systems.The utilization of virtual reality (VR)techniques allows to present learning content in a vivid and interactive way,thereby contributing to the frequency and intensity with which eLearning services are used.The evaluation of prototypical applications allows to derive suggestions on how to tap the potential associated with VR technologies in a suitable way for this field of application.

On the importance of the eyes-off-the-road time in road vehicles (Vol. 3-4 – 2005)

Author: Wilhelm Bernhard Kloke

Keywords: · head--up display · automobile · velocity display · eyes--off-the-road time · eye movement · ergonomics

Summary

Head-up displays are well established in aircraft cockpits.The situation in road vehicles is different.Some manufacturers propagate the use of HUDs to display velocity measurements along with other traffic information.The basic problems such as providing enough contrast and luminance,seem to be solvable technically.Expected advantages of this technology could be decreased eyes-off-the-road time and decreased accommodation time.In this article it is shown that published results from optical physiology can be used to estimate these times,and to compare them between the HUD and conventional instrument design.Physiological arguments for the notion, that no accommodation and vergence times need to be added, have been found.Therefore,the predicted improvement for the task of reading the velocity instrument of 100 ms is considered marginal,at best.The driver task is determined by issues more important for security such as using the interior and offside mirrors,which take more time and effort to accomplish.The ecology of the human vision system seems to be well equipped for the task of reading the velocity display in the conventional setup.

Practical Relevance

Advertising statements about the ergonomic benefits of using HUDs in road vehicles are put into the context of physiological knowledge about the vision processes involved in reading the velocity instrument.It is shown how the eyes-off-the-road time can be computed using published data.

A Comparison of Variables Measuring Fatigue (Vol. 3-4 – 2005)

Authors: Shrawan Kumar,Mircea Fagarasanu,Yogesh Narayan and Narasimha Prasad

Keywords: · muscle fatigue · vastus lateralis · vastus medialis · fatigue with maximal contraction · fatigue with submaximal contraction · comparison of variables measuring fatigue · isometric fatigue

Summary

The current study compared the relationship between force decline in fatiguing Maximum Voluntary (MVC)contractions and 40%MVC and various criteria used to determine localized muscle fatigue.Twenty subjects with no history of quadriceps injury in the last year performed an attempted knee extension from 90° knee flexion isometrically in MVC and 40%MVC. EMG from vastus lateralis and vastus medialis 2 and 4 cm proximal to myotendinious junction were recorded using bi-polar active electrodes.The force was measured using a load cell.The blood volume and blood deoxygenation were measured by NIRS spectroscopy and the heart rate was recorded by a Polar telemetry heart rate monitor.After obtaining basal physiological values the subjects performed a MVC. After five minute rest,they performed a 40%MVC fatiguing contraction.After a 20 minute rest,they gave their MVC contraction while all variables were being continuously recorded at 1 kHz except the subjective ones.The subjective variables were recorded before and after the MVC;but for 40%MVC,they were recorded at the start,and every minute thereafter till the end of the contraction.The EMG was full wave rectified and linear envelope detected.The force was significantly correlated with all variables (p<0.001)but EMG amplitude had the highest correlation(r =.4 to r =.790;p<0.001). ANOVA,based on a linear mixed effect model revealed,the variables were significantly different between the genders (p<0.01).No one variable emerged as the best to mirror the force fatigue.However,the fitted mixed effects model explained 60.2%to 64.4%of variance for MVC for females and males respectively (p<0.001).For 40%MVC similar values are 68.6% (p<0.001)and 71.9%for females and males (p<0.001).

Practical Relevance

Not available.

Experimental investigation of shifts of the decision criterion during quality inspection (Vol. 3-4 – 2005)

Author: Martin Schütte

Keywords: · decision criterion · visual quality inspection · feedback

Summary

Due to the globalization of markets and as a consequence thereof the severe competition of companies the quality of products has become an important business objective.This has the companies prompt to establish so-called quality assurance systems in order to achieve higher quality of their products.In conjunction with this the implementation of the principle of self inspection took place transferring more responsibility for the quality of products to the employees. The transfer of quality inspection tasks to the employees involved as a problem the partly low reliability of human decisions concerning the quality of products.Deficits in workplace design are one reason for this.Furthermore the performance of quality inspectors depends on the probability of faulty objects.Results of research into vigilance demonstrate that quality inspectors adopt a conservative decision criterion if the probability of faulty objects is low.For the company such a decision criterion has the disadvantage that faulty objects are delivered to the customer.On the other hand if the probability of faulty objects is high quality inspectors adopt a liberal decision criterion which also brings along a drawback for the company because faultless products are classified as waste.Generally the proportion of faulty objects remains not stable but fluctuates due to abrasion of machines or maintenance respectively repair of tools. Nevertheless there are only few studies investigating the influence of continuously degrading or improving product quality on the decision behavior of quality inspectors.Furthermore the performance of quality inspectors depends on the particular feedback system in use.Even if it is well known that rapid feedback has a positive effect on the performance  of quality inspectors there are only few studies giving information about the type and regularity of feedback to prefer. Therefore the aim of the present investigation was to prove,in which way the decisions of quality inspectors are influenced by (1)a systematic change in the probability of faulty products, (2)the kind and (3)regularity of feedback.The experimental task resembles a visual inspection task demanding the evaluation of the accuracy to size and the geometry of die cast components.Such a task is widespread in the electrical and plastics industry.Accordingly the form and colour of the ex- perimental object was akin to a real manufactured product. The simulated production batch included 688 error free and 112 faulty objects.The proportion of faulty objects was manipulated in three ways.In the first condition the relative proportion of a faulty object constantly amounts to 14 per cent.In the second condition the proportion increased from 11 to 17 per cent (on average 14 per cent).In the third condition the proportion decreased from 17 to 11 per cent (on average 14 per cent).During task execution the test persons received either no feedback or information about the number of missed faulty objects or about the number of missed faulty objects as well as the number of false alarms.Feedback was given either constantly after inspection of 20 objects or after inspection of a varying number of objects which however amounts to 20 on average.The whole experiment run computer-controlled whereas the test objects were presented on a 17"black and white monitor.72 participants (aged between 18 and 37 years) took part in the experiment.They were instructed to prove as quick and accurate as possible,whether the height of each object fulfills the specification. Based on the rates for hits and false alarms the so-called c-index was calculated for each person and experimental condition.The c-Index is a measure describing the response bias.Data evaluation was done using a 3-factorial analysis of variance (factor 1:regularity of feedback;factor 2:type of feedback,factor 3:profile).The results verify that type of feedback has a significant influence on the response bias. Furthermore the triple-interaction has also a significant effect indicating that the different combinations of the levels of the three independent variables are connected with specific effects  If test persons received no feedback the c-index reached a positive value referring to a conservative decision criterion. Since assumptions concerning the probability of faulty objects determine the decision behavior this result is comprehensible because usually it could be expected that the proportion of error-free objects is higher than the proportion of faulty objects. In this case a conservative decision criterion has the advantage that a large proportion of error-free objects is correctly identified.If information is given in terms of the proportion of missed faulty objects as well as false alarms again a conservative decision criterion appeared.This result is in accordance with signal detection theory predicting a conservative decision criterion if the proportion of error-free objects is high and the relative costs of false alarms and missed faulty objects are equal.But in practice quality inspectors usually get only information concerning the number of customer complaints that is the number of missed faulty objects.Under such feedback condition there are no differences in c index regarding constant or variable feedback intervals as well as a constant or a decreasing proportion of faulty objects.The c-index reached a value indicating a neutral decision criterion.In contrast if the proportion of faulty objects increases a liberal or conservative decision criterion appeared in dependence of the regularity of feedback.All in all the experimental results demonstrate that the decision criterion varies in dependence of the particular level of the factor profile if feedback is given about the relative number of missed faulty objects in irregular intervals.Therewith quality inspection does not happen according to a stable and consistent norm.

Practical Relevance

The study gives information about the design of feedback conditions for visual quality inspection tasks.

The Contribution Made by Electrophysiological Methods of Investigation Towards Strain-reducing Design of Hand-operated Tools (as illustrated by the example of grapevine pruning shears) (Vol. 3-4 – 2005)

Authors: Jurij Wakula and Kurt Landau

Keywords: · vine--pruning shears · evaluation · strain analysis · field and laboratory studies · product design

Summary

Objective electrophysiological measurements (pulse rate and EMG)were used in field and laboratory studies to evaluate hand-operated grapevine shears produced by four manufacturers.Five of the shears investigated were readily available on the market.A sixth model was a prototype about to go into serial production.The salient features and parameters (e.g.cutting principle,type and form of grip,weight,center of gravity,distance between hand and blade,span of grip)of all the shears were documented and analyzed.Strain levels (working pulse rate (WPR)and relative electrical activity (rEA) in three muscles:m.flexor digitorum superficialis,m.biceps brachii and m.deltoideus pars spinalis)in seven workers were determined and analyzed in field studies .The studies were conducted in the Rheingau wine growing region.No significant differences in overall physical strain arising during vine pruning were observed with any of the hand-operated shears tested.Although the working pulse rate levels measured in three workers reached or slightly exceeded the set limits for continuous strain,analysis of the working pulse rate curves over the full work period revealed no increases.The vintners themselves decide when and for how long breaks can be taken and these appear to be appropriate for the hardness of the work performed. Investigation of local strains revealed that shears using the knife-edge principle caused higher muscular strains than those using the shearing cut principle. The laboratory study comprised three different investigation cycles,in which four types of shears were analyzed in eight volunteers.The first two cycles analyzed the action of the shears in various hand positions (normal hand position,wrist not inclined and hand in supination position)without actual cutting.The forearm was pointing forward at right angles to the upper arm,which hung relatively freely,and the shears were actuated at one-second intervals for one minute to the beat of a metronome.There was a two-minute rest break before repeat of the test with the next type of shears.The third test cycle involved cutting an actual vine at five-second intervals, with a total of ten cuts for each type of shears.In order to ensure that the results would be reproducible,the vines used in this test were all more or less of similar thickness.There was again a rest break after ten cuts before the volunteer continued the test with the next pair of shears.The maximum gripping forces exerted in the working hand of each of the eight volunteers were also measured isometrically.EMG measurements in two muscles were used (m.flexor digitorum superficialis and m.extensor digitorum)to determine the local strains.Each volunteer was asked to give a subjective assessment of each type of shears at the end of each test cycle. Analyses of strain on the m.flexor digitorum superficialis during actuation of the shears without actual cutting and with the hand in the normal position yielded the following results: the lowest level of strain was caused by the shears using the „shearing “cut principle.The tests with hand in supination position yielded the same ratings.As expected,the strains arising in the normal position were,with one exception,less pronounced in all volunteers in the normal hand position than in the supination position. Compared to simple actuation of the shears,actual vine-cutting led to an increase in local muscle strain which ranged from two-to fourfold,depending on the volunteer and the type of shears being tested.The degree of muscle strain involved in actual vine-cutting ranged in most of the volunteers between 20%and 40%of maximal contraction.The lowest strain during vine-cutting was measured with the shears using the „knife-edge “principle caused.

Practical Relevance

The results of the work and strain analyses were used to draft design recommendations for the products (e.g.design of grip, force transmission,stability of the cutting edges).Although these point to possible ways of achieving improvements in shears design,further studies are needed to investigate their exact effect.

Information Presentation and visual Performance in Head Mounted Displays with augmented Reality (Vol. 3-4 – 2005)

Authors: Martina Ziefle, Olaf Oehme and Holger Luczak

Keywords: · augmented reality · head mounted display · LCD · visual search performance · font size · display size · visual fatigue

Summary

As augmented reality in head mounted displays (HMD)is a promising current displaying technology for a broad field of applications,it is of crucial interest that the displaying meets demands of visual ergonomics and provides an optimised information processing.Two displays,a LCD display and a HMD were compared regarding speed and accuracy of visual performance.In addition,the display size and the font size were varied.Scrutinizing the impact of the display types,both displays were used once as a „cuing “ display,,in which the to be searched for target was faded in,and once as a „reading “ display..The results revealed a distinct superiority of the LCD over the HMD in speed and accuracy. Furthermore, performance was significantly lower when information density was high and a small font was present,what was especially disadvantageous when the HMD was used as a reading display.Also,the HMD task difficulty was judged as higher compared to the LCD.It is concluded that with respect to visual ergonomics the current HMD technology is not yet fully developed to guarantee a fast and frictionless visual processing.

Practical Relevance

The findings of the present study might be insightful for all application fields which make use of display technologies as main human-computer interfaces.The results detail under which circumstances the visual quality of the HMD is yet satisfactorily, but also,under which conditions performance decrements have to be faced.Finally,some proposals for further optimising the technology are developed.

Vol. 5 - 2005

 Physiological Cost of Energy-Equivalent Exposures to White Noise,Industrial Noise, Heavy Metal-Music, and Classical Music (Vol. 5 – 2005)

The results of the study show again, in accordance with prior investigations, that the energy equivalent approach to rating acoustic exposures leads to gravely misconceiving assessments of their actual specific aural effects. Regarding, e.g., 4 times higher physiological costs, the hearing has to pay for heavy metal-music compared to classical music, apparently the conclusion is true that the type of music is decisive for its impact on the hearing. Furthermore, the special risk which has to be taken by modern music productions such as heavy metal, hardrock or techno is founded in the fact that exposure levels in discotheques, during open-air concerts or via walkman exposure are substantially higher than the audience is exposed by music compositions during symphony concerts or opera performances.

Self-reported upper body discomfort due to driving: effect of driving experience, gender and automobile age (Vol. 5 – 2005)

Authors: Joseph Giacomin and Antonio Screti

Keywords: · discomfort · driving · automobile · experience · gender · Borg

 Intercultural (online-)Learning (Vol. 5 – 2005)

Authors: Rosina M.Gasteiger, Christina Rautenstrauch and Verena Stengel

Keywords: · Intercultural learning · online-learning · intercultural learning model · international human resources development

Possibilities for incorporating e-learning in intercultural trainings are described by a model of intercultural learning. With in this scope, relevant conditions for the design of Blended Learning and instructions in intercultural trainings are specified. Considering one practical example, new cooperative learning methods in combination with e-learning are shown to be effective in intercultural trainings.