There have been always speculations regarding the future of work or the work in the future. In Western countries some megatrends like globalization, dynamic of markets, demographic change, change of values und technological progress are increasingly influencing the conditions for work. Considering different target groups such as employer associations, unions or scientists and international organizations, like ILO or WHO, leads to different but also common valuations of the future of work. In this paper all the sources that help to understand which developments we have to expect, will be considered. The changes are described and valuated by German HR Managers of larger organizations, a representative of the German unions, the German Human Factors and Ergonomics Society (Gesellschaft für Arbeitswissenschaft), studies related to work policy, the German Technology Assessment Office, the International Labor Organization, the World Health Organization, the International Commission on Occupational Health as well as the International Ergonomics Association. In addition, a selected publication regarding the future of management has been included. Referring to this data base, the following demands can be formulated for instance:

• Development of strategies of internationalizing resp. to deal with the consequences of globalization on different levels

• Development of competencies to deal with (permanent) changes

• Development of instruments to deal with personal consequences of restructuring processes

• Investment in workability and employability as a consequence of demographic changes

• Researching the working conditions determined by new technologies (like nano- or biotechnology or ambient intelligence)

Redefining work and dealing e.g. with precarious work Based on these demands, in a next step the meaning of "ability for the future" regarding work has to be clarified. Which understanding of work will be adequate, when we discuss the future? Which function will or shall have work in the future? Are we only talking about "paid work"? By opening this discussion, different levels or target groups have to be considered:

• Governments/society/regions

• Enterprises/organizations/institutions

• Employees (with a specific target group approach)

But these different levels are interrelated: Work that meets the demands of the future needs an organization that concentrates on respective challenges and necessary (governmental, societal and economic) frame conditions. Talking about the ability to cope with the future in 2010 cannot be done without including the aspects of sustainability. This needs respective management concepts, which include a stakeholder-orientation representing the three-pillar-model of sustainability. By taking this broader approach to sustainability, work would then be able to cope with the demands of the future, if the "social capital" would be preserved or even enlarged by respective forms of work organization. Thus, there is a need for sustainable work systems as part of a comprehensive corporate sustainability concept. The concept of sustainable work systems is not widespread. Though not new, it reflects developments related to globalization and the use of information and communication technology. In general this leads to a more intensified work, connected with short term goals which demand a high flexibility and adaptability of people in unsecure conditions of employment. Therefore, there is a danger to consume human resources instead of regenerating and developing them. The demands of sustainability sometimes (when having a short time perspective) lead to the necessity of acceptable compromises. This demands a design concept of work, which contributes to its social role of satisfying needs and to an economic and societal development in a long term perspective. Irreversible damages concerning social, ecological and economical capital have to be avoided on an individual, corporate and societal level, but furthermore this capital has to be conserved and enlarged. Based on this definition strategic and operational activities can be deployed. Last but not least: We need a new perspective considering human factors or ergonomics interventions: These interventions are not only causing costs, but by using e. g. sociotechnological approaches they can also contribute to the survival of organizations. This implies new valuation concepts. If we also look at people who are unemployed or handicapped, then it becomes obvious, that we have to invest more in alternative possibilities of employment. All these challenges demand a cooperation of politics, society, employers and unions, but also scientists to develop sustainable solutions.

Practical Relevance

The changes of frame conditions for work, but also the way work has changed require a closer look to see if we accept this development as "given", or whether politics, employers, unions and science have to deal with these challenges in a joint approach. This paper delivers a basis for an offensive discussion of this topic.

Vol. 2 - 2010

Motion analysis and motion modeling to increase efficiency of robot-human cooperation

Author: Dino Bortot, Hao Ding, Fabian Günzkofer, Dominik Stengel, Klaus Bengler, Frank Schiller, Olaf Stursberg

Keywords: Motion capturing, motion modeling, robot-human cooperation, efficiency, safety

Summary

Robot-human cooperation scenarios are a growing field of research. Since the use of robotics has been characterized by a distinct separation between humans and robots thus far, the safe and simultaneously efficient collaboration between the two has yet to be analyzed. This topic contains several different research areas:

• Investigation of user-friendly, intuitive communication modalities (natural language, gestures, facial expressions)

• Research on cooperations in which humans and robots have to accomplish a common task

• Analysis of the physical interaction of humans and robots: whether the robot touches the person or the person touches the robot

• Investigation of the coordination of human movements/actions and those of the robot (Collision Avoidance).

The research project EsIMiP (efficient and safe interaction between human beings and intelligent production facility) deals especially with the latter three points. A level of robot-human cooperation in a production environment is necessary which not only meets all the requirements of safety issues, but is also aimed at achieving maximum efficiency.
In recent years the development of environmental sensors has advanced a great deal. Robots now have information about static and dynamic aspects of the environment. As a consequence they are able to adapt their behavior during production processes, if it becomes necessary. This means that they can switch their operating mode from a normal state to a state of reduced performance (e.g. lowering velocity or emergency stop). However a better alternative is re-planning the robot’s trajectory, to create a sufficient distance from the human. As a consequence collisions can be avoided and the system’s efficiency is maximized.To realize the re-planning of trajectories, a fundamental understanding of human motions is necessary. Only if you can predict human motion behavior, can information about the upcoming position of the human body/body parts be determined. Knowing the human`s location defines certain spatial parts of the production environment that can be used by the robot without endangering the human’s safety. Many motion capturing systems are available, each of them with its own advantages and disadvantages. Motion capturing systems have to be used; firstly to develop motion models by verified analysis, secondly to track the human in the later application. One of the many existing methods is the marker based photoelectrical tool ‘Vicon’ which is applied by the research team. Pulsed infrared light (780 nm) is emitted and reflected off the markers. It then reaches back to the lenses of the cameras. By the use of multiple cameras the absolute coordinates of the markers can be determined and thereby motions precisely followed.A variety of complex factors determine human motion behavior, such as their motion intentions (e.g. goal-oriented), their emotional state, the motion context etc.One type of approaches in the literature assumes that humans tend to follow typical motion patterns. If those patterns are known, it is possible to use them to predict the future human motion, instead of explicitly modeling all the factors.A probabilistic framework, namely ‘Hidden Markov Model’ (HMM) is often used because it can represent the uncertainties associated with sensor noise and take into account the model’s incompleteness.Alternatively, a topological map can be considered to model the occupancy grids of the human motion at each time step with corresponding probabilities. The human workspace is divided into several motion probability grids. Each grid cell stores a probability measure denoting the likelihood that the given grid cell is occupied.A main goal of the investigations is the creation of models to describe motions. To compare them, the gathered results of the experiments must first be normalized. After this process information about the velocity and acceleration of motions can provide indication of motion patterns. The idea is to predict the further development of a motion once you have tracked and reconstructed the initial part of the movement.Frank Arlt discovered the existence of leading parts of the body for every goal-oriented motion. This body-part moves in a determined plane, which can improve the predictability of the motion (at least the direction).
Digital human models (DHM) are needed to represent the detected shape and position of the human body. Joint angles, postures and the distance between the robot and the human can be calculated with the help of a DHM. They exist in many different versions; depending on the application several levels of detail are implemented. For the application ‘robot-human cooperation’ real-time capable motion capturing has to be ensured; therefore the model to represent the human must not be too complex. A DHM consisting of six cylinders could be conceivable: one for each leg, one for each arm, one for the torso and one for the head. The attempt to represent more of the complexity of the human body (including more joints with their associated degrees of freedom) leads to extensive computation effort for real-time applications.Within the research project three different scenarios are going to be investigated. The first one is a robot-human cooperation in a large production environment, where the human is able to walk around; the DHM consists of one cylinder only. The level of detail is low.In the second scenario a human sits at a workbench and collaborates with the robot. The DHM is reduced to the arm only, but represented more accurately.The third scenario combines the elements of the first two: a human collaborating with a robot in a large production environment, where the human’s movements are observed and modeled from the bird’s eye view as well as from a closer look at individual parts of the body.
At the beginning of the project experiments are done for the first two scenarios.
The next step in research could be the development of DHMs to improve the realistic representation of the human and therefore increase the efficiency of robot-human cooperations even more.

Practical Relevance

Human-robot interactions are characterized by the fact that the two partners complement each other and weaknesses of one partner can be compensated by corresponding strengths of the second partner. For example, you could improve the ergonomics of a workplace by making the robot handle the load weight and therefore ease the working conditions for the operator, who could undertake mentally demanding tasks. Simultaneously the efficiency of the entire system can be increased by cooperative interaction.

Functional Analysis and Modeling of Goal-Directed Arm Movements

Author: Thomas Alexander

Keywords: Digital human modeling, functional data analysis, motion simulation, motion variance, Fitts’ law

Summary

Digital human models are frequently used for workplace design. They model human dimensions and postures validly, but do not consider variances and changes during movements appropriately. An alternative approach is described which is based on empirical movement data from motion capture experiments. It utilizes methods of functional data analysis (FDA) in order to describe and model central trend and dispersion of movements. The approach is used for modeling goal-directed arm movements at an experimental console workplace at a control room.
Characteristics and capabilities of the human operator are the core components of an ergonomic workplace design. This requires the appropriate consideration of anthropometric body dimensions and human motion for spatial workplace design. If this is not the case, limited comfort, reduced performance and unhealthy work postures are likely to occur. Dimensions and functional measures (e.g. reach range) have to be included into the design as early as possible in order to prevent these shortcomings. For this reason various software-tools are available which support the designer and ergonomist during their work. These digital Human Models (DHMs) model and simulate dimensions, postures and movements of the future operators to a special extend. They have sufficient functionality for various applications in product design (primarily vehicle design), occupational health, and workplace design.
However, each type of work or posture is characterized by a dynamic part. Purely static postures can be observed only very rarely for short periods of time only. Instead, today’s workplace design supports dynamic changes of posture (e.g. in case of dynamic seating). Consequently, dynamics and changes of posture have to be taken into account and integrated into design tools. A consistent workplace design includes each: static as well as dynamic, spatial as well as temporal aspects.
Digital Human Models (DHMs) already include functions to simulate human movements. Their models come from biomechanics and are by and large based on industrial and sport sciences. These models reach from temporal measures, e.g. MTM- or WF-methods, and highly-complex methods, e.g. inverse kinematics or dynamics. But with modeling variability of movements each method comes to its limits. However, this is essential because designing for “the” mean person or “the” mean movement is not sufficient for ergonomic workplace design.
Human movements differ from each other, similar to anthropometric dimensions. This is because of the complexity of the human movement system and a diversity of influencing intra- and interindividual factors. Reducing the complexity to single movement trajectories simplifies important characteristics too much and might lead to design shortcomings and errors. One simple solution is to include extra safety spaces, but this is not sufficient for workplaces with limited space. Instead, the variability and variance of human movement have to be modeled, analyzed and considered appropriately.
This paper describes an alternative approach. It is based on empirical movement data from motion capture experiments rather than a theoretical internal skeleton of a human model. This way it follows the same method as early exoskeletal drawing templates, which model contours of the human body rather than joint structures. The model is based on a hierarchy of variable body parts, which are connected to each other by joints. Trajectories of external anthropometric landmarks from motion capture experiments are used to parameterize movement functions for each landmark. The functions themselves were polynomial functions of different orders for the trajectory of the effecting finger and for the affected joints of the kinematic chain. The trajectory was modeled by a polynomial function of 5^th order, while polynomial functions of 3^rd order were applied for modeling the joint movements.
Subsequently, methods of Functional Data Analysis (FDA) were applied to determine central trend and dispersion of the set of trajectories. FDA describes statistical methods to extend statistics to functional analysis. It has been successfully used to describe temporal changes in various domains. For the described approach, a time-dependent mean function and a time-dependent variance function were calculated on base of the single movement trajectories and functions. This way, a more comprehensive model of human movements was implemented.
An experiment was carried out to analyze this approach. 60 male participants aged between 19 and 27 years volunteered for the experiment. 44 anthropometric dimensions were measured. The results showed no significant difference to the male population of that age so that body dimensions are considered as representative. The setup consisted of a console workplace at a control center. The control panel included 14 targets positioned as a 3 x 4 matrix (distance 20 cm) and 2 additional targets on the right side. The targets were switches which were lighted in a pseudo-random order. Participants took a comfortable seating posture and reached to the targets during the trial. 15 anthropometric landmarks were captured by a Qualisys Motion Capture system with a measurement rate of 60 Hz. In total, 3.360 different movements were captured and processed for the subsequent analysis.
At first, regression analyses were carried out to determine the accuracy of the functional description of each trajectory and joint movement. They revealed a sum of squared error (SSE) between 22 and 326mm², a mean squared error (MSE) between 1 and 8mm², and a root mean squared error (RMSE) between 1 and 3mm. The median of RMSE of the joint movements were between 1,8 (index finger), 1,5 (wrist), 0,8 (elbow), and 0,5 (shoulder). This was comparable to the precision and resolution of the Motion Capture system.
Applying FDA for summarizing the set of trajectories led to massive data reduction. After standardizing movement time to t’=0 (start) and t’=1 (end), a mean trajectory function and a variance trajectory function were calculated. They represent central trend and dispersion for a movement to each target. Joint functions were calculated respectively. By further standardizing spatial position to the same start (x=y=z=0) and end position (x=y=z=1), a general functional description was proposed. The same was done for the joint movements of finger joint, wrist, elbow, and shoulder. A further implementation of FDA-methods allowed analyzing interrelationships for movements within the same joint (i.e. auto-correlation function) and between (i.e. cross-correlation function) different joints.
The capabilities and shortcomings of the approach are discussed. One is the early restriction to a set of curves for modeling movements. However, this can be overcome by a more general movement function with sets of different spatial and workplace-dependent parameters. The approach was found suitable for modeling diversity of movements and, thus, for considering movements and dynamics into workplace design. Potential practical applications are in seen connection with digital human models. The approach can be used to calculate movement spaces in contrast to single movement trajectories, to better consider and include human variability into workplace design.

Practical Relevance

An ergonomic workplace design requires the consideration of human dimensions, postures and movements. Especially movements are characterized by a vast amount of variability due to many degrees of freedom and a lot of parameters of the motion system. The goal of this approach is to provide a method to include movements and their variability into workplace design.

Overview of Human Motion Modelling Using the Example of Ingress and Egress to Automobiles

Author: Olaf Sabbah, Heiner Bubb, Klaus Bengler

Keywords: Motion capturing, motion modeling, dynamic discomfort, digital human model, inverse dynamic, ingress and egress

Summary

In this study an overview is given of research approaches done for modelling human motions while entering and exiting automobiles. The main idea is to show how human biomechanical parameters are driven by discomfort sensation during the movements. As the ingress and egress motion appears to be the most complex daily movement involving nearly all body segments and muscles, the focus is set on studying these motions.In order to optimize the motion by reducing upcoming difficulties, the first step is to analyse the general motion strategies while performing. This already can be described in a mathematical functional ansatz. The next step is to determine the according stress expressed by means of discomfort in order to derive a complete tool to model human motions.In an early phase the approaches for modelling human characteristics were due to static discomfort, assigned with the development of the software-tool for digital human modelling RAMSIS and PCMAN. Here fore the basic approach for discomfort modelling was defined by measuring an occurring local joint torque and relating it to its maximum possible torque. This approach is described as “local stress analysis” (or maximum force yield rate).For this first of all the Institute of Ergonomics of the Technische Universität München researched on force-modelling within the RAMSIS-Dynamic project on behalf of BMW and Tecmath. The maximum torques in several body joints were measured regarding all spatial directions. This is followed by maximum force measurements combined with questionnaires concerning discomfort sensation within the EU project REALMAN. This lead to a static force controlled posture prediction model (FOCOPP).Secondly the motion behaviour was analysed. Beginning with simple hand/arm movements, it shows that the motion strategies are driven by a leading body part – the hand – that permanently moves in one spatial plane. This basic result was transferred to whole body ingress movements showing its applicability as the leading body parts shift from the right foot to the pelvis and finally to the left foot depending on the ingress strategy.
Together with BMW research was done to analyse numerous ingress and egress motions to define four mains strategies and their frequency. These main strategies are also compared with findings of other scientific institution.Knowing static discomfort measures as well as the motion strategies two approaches were followed to derive dynamic discomfort. One model concept considers a predefined neutral motion corridor and adds up divergences of the actual movement out of the corridor in order to specify an objective discomfort value. The other approach is derived from the static discomfort model but now considering the dynamic effects. Here again the first attempts were successfully analysed regarding the hand/arm-system. Besides taking into account the Hill correction factor to determine more adequate maximum force values, also the d’Alembert principle was considered while setting up the joint torque equations for measuring the actual occurring torque according to the principle of inverse dynamics. This model approach once again was transferred to whole body ingress and egress motions.
Results during these specific movements indicate the posture induced discomfort is predominant – triggered by the lateral flexion of the spine – rather than the force induced discomfort. This also explains why the ingress is always considered critical to the egress movement.

Pracitcal Relevance

The comfort aspect concerning automobiles is increasingly a distinguishing characteristic, since aspects such as design and engine power of the various car manufacturers seem to become more similar. The ingress and egress, generally affect the first comfort impression of the user. Based on the findings a prototype of a mechatronic ingress and egress supporting system is designed and evaluated within a CAR@TUM project of BMW and several institutes of the Technische Universität München.Sports cars with low seating conditions show that difficulties concerning entering and exiting the automobiles occur among older drivers. Due to design aspects the possibilities to build sports cars with higher seats or narrow door sills are limited.In this context the idea of an ingress/egress supporting device aroused, helping the driver with a minimized seat movement during the most difficult movement phase of ingress and egress.As no similar supporting systems for sportive designed automobiles are known, no ballpark figures for the appropriate trajectory of the seat or even movement ranges can be derived from literature. Therefore a first test was conducted at the LfE with a simple seat manually moved with lever and an indoor crane. Here 18 test persons where questioned to their discomfort after taking a seat with and without the support, resulting in high acceptance and discomfort reduction of about 50%.
After a brief design of the required movement ranges in a simulated testing environment using a digital human model (RAMSIS) in CAD (Catia V5 R17), a real mock-up is built for repeatable and reliable results. The packaging of the mock-up represents a sports car with “variable seat kinematics”, a car seat fixed onto a robotic platform. With two degrees of freedom offered by the platform the trajectory gained during the first tests can be approximated. By changing the framework structure of the test rig the seat movement can be varied easily. The actuation of the platform is designed using two spindle drives dimensioned for a load of approximately 200 kg.The brief trajectory derived from the simulation in CAD with RAMSIS is first tested with a small number of subjects to verify the best possible seat movement in the mock-up environment, followed by the main test with an enlarged number of subject considering different body sizes and age groups. In this main test the subjects are again, as in the previous mentioned study, questioned to their discomfort during ingress and egress with and without support.
Test results show a high acceptance for the supporting system, again clearly reducing occurring discomfort. As expected car geometries, as door sill and upper a-pillar show the main limits to the seat movements, due to penetration with body parts or seat structure.The result of this study shows the possibility of reducing ingress and egress discomfort in sports cars by means of a rotating and tilting seat.

Ambulatory measurement system CUELA for long-term motion analysis at workplaces

Author: Rolf Ellegast, Ingo Hermanns, Christoph Schiefer

Keywords: ambulatory workload assessment, inertial tracking device, motion capturing, CUELA, ergonomic field analysis

Summary

At many workplaces, musculoskeletal workloads due to manual material handling, awkward postures or repetitive movements can be commonly observed. Observational methods are mainly known for workload assessment in field. The problem with these methods is that the description of risk factors (e. g. postural workloads) is too broad to provide accurate information for an appropriate assessment. Therefore, direct measurements should be preferred for more accurate and less time-consuming workload data acquisition and assessment. Since more than fifteen years the IFA (Institute for Occupational Health and Safety of the German Social Accident Insurance) is using and developing a measuring system known as CUELA (computer-assisted recording and long-term analysis of musculoskeletal load) for assessment of postural and kinetic workloads of several body parts (upper and lower extremities, trunk and head). CUELA allows for a quantification of musculoskeletal workloads even in complex work processes.The CUELA system consists of potentiometers, accelerometers and gyroscopes, which can directly be attached to the worker’s clothes, and a small portable data-logger (sampling rate 50 Hz, 168 channels), designed for field analysis at mobile workplaces. The basic CUELA system enables a motion capturing of the trunk (3D) and of the lower extremities in the sagittal plane. An extension of the CUELA system also provides a 3D motion recording of the upper limb (shoulder blade, shoulder joint, elbow, forearm and wrist), the inclination of the pelvis and the head. Further CUELA versions are optimized for the motion analysis and the estimation of energy expenditure at sedentary workplaces. These versions are mainly based on inertial measurement units.Additional to the motion analysis, foot pressure sensitive insoles allow for the synchronous registration of ground reaction forces. From the ground reaction forces, it is possible by using a biomechanical model to detect the handled load weights even during dynamic movement. CUELA enables also a synchronous application and data acquisition with other physical and physiological measurement devices: 3D force handles, force gloves, ECG, EMG and whole body vibration.For simplifying and supporting the data analysis, measurements are additionally documented on video. By synchronizing the video recording with the measured data, the load readings can be matched with the related work situation.
The CUELA software WIDAAN has been developed for visualization of measured data, the synchronized video and a 3D human model, representing the body posture determined by the measurement. For data assessment it is possible to mark any actions or situations to highlight certain work activities and have them evaluated. The WIDAAN software automatically issues a series of statistical evaluations to give a quick impression of the quantified risk factors. Body angles and postures are analyzed with reference to the literature and relevant standards (extreme body angle positions, asymmetrical posture patterns, static postures and repetitive movements). There are interfaces to biomechanical models for assessment of spinal loads.Workload profiles can be stored in an IFA database for comparative assessment and development of suitable preventive measures.The article gives an overview of the actual technical state of the CUELA system and some examples of its application at workplaces.

Practical Relevance

Work-related musculoskeletal disorders are associated with high direct and indirect costs in Germany and lead the sick leave statistic each year. The knowledge of work-related risk factors for the musculoskeletal system is essential for the derivation of precise ergonomic measures. In this context the measurement of physical workloads directly at workplaces is essential.

Effect of Sharpness and Insertion Force on Time Requirements and Electromyographic Activity for Snap-Fit Assembly

Author: Hamed Salmanzadeh, Marianela Diaz Meyer, Verena Bopp, Kurt Landau, Ralph Bruder

Keywords: delicate objects, sharpness, snap fastener, insertion force, insertion time, EMG

Summary

Snap-fit assembly has become more important in the automotive industry and within its subcontractors, as well as, in the consumer goods industry. The reason for this development is particularly related to the increased economic benefits that occur through the accelerated assembly task. Snap-fasteners, however, require a high degree of precision during assembly and optimization of the hand-finger coordination in order to allow sufficient grasp stability when handling, aligning and inserting. Due to characteristics such as sharpness, slipperiness and flexibility, snap-fits are considered to be a type of delicate objects. These characteristics of snap-fits can lead to complaints and cause impairments on the skin of the finger, increase muscle strain and even increase the absence due to inability to work. The ergonomic and micro-economic aspects of snap-fit assembly have not been sufficiently studied.This study investigates the influence of grasp- and contact-characteristics of snap-fits on the assembly time, on the surface electromyographic activity of the shoulder, arm and hand musculature, as well as, on the subjective skin sensation of the thumb. An adjustable apparatus, fixed to a force plate, was used to insert two types of head geometry of snap fasteners (sharp-edged and even). The apparatus was adjusted for two predetermined insertion forces (20N and 70N). This resulted in the combination of four experimental variants. The insertion times and the actual measured forces of all participants for each of these four experimental conditions were recorded via a force plate (Kiag Swiss, Type 9261A). Simultaneously, the activity of six muscles (M. flexor digitorum superficialis, M. extensor digitorum, M. biceps brachii, M. triceps brachii, M. erector spinae and thenar muscles) in the right upper extremity and trunk was recorded with a surface electromyography. 12 male students aged 19 to 30 participated in this study.
The results of the statistical analysis showed that the insertion time was significant longer for sharp-edged snap-fits than for even snap-fits. This effect was higher for higher predetermined insertion forces. Fasteners with sharp-edged head geometry produced also a higher displeasing perception on the finger pad during the insertion operation. Although the force measuring apparatus was adjusted for equal predetermined insertion forces for both head geometries, the actual measured insertion forces were higher for sharp-edged snap-fits. The increased actual measured insertion forces are associated with the increased muscular strain of the Triceps and Thenar muscles (EMG), which, in both cases, was higher for the insertion of sharp-edged snap-fits. Recommendations for the improvement of ergonomic aspects and productivity during snap-fit assembly were proposed.

Practical relevance

The investigation of ergonomic and micro-economic factors related to the snap-fit assembly, and the further improvement in an early stage of the design process of snap fasteners, should contribute to an increment in log-term productivity, as well, as a reduction of musculoskeletal disorders and repetitive strain injuries.

Vol. 3 - 2010

Age diversity and group effectiveness – The moderating role of team climate

Author: Birgit Claudia Ries, Stefan Diestel, Jürgen Wegge, Klaus-Helmut Schmidt

Keywords: Demographic change, age heterogeneity, group efficiency, innovation, burnout, team climate

Summary

As a result of demographic change, age heterogeneity in the working population increases. Motivated by this development, a series of field studies on the effects of increasing age heterogeneity on different indicators of team efficiency was performed (van Knippenberg et al. 2004; Wegge & Schmidt 2009). These studies mainly take two theories into consideration, which differ in the prediction of the effects of increasing age heterogeneity on team performance and well-being: The Theory of Social Categorization (Tajfel & Turner 1986) assumes impairing effects on indicators of team efficiency due to increasing age heterogeneity. On the other hand, more recent models of information processing and decision making in teams (Kerschreiter et al. 2003) expect effects promoting efficiency as a consequence of increasing age heterogeneity. Empirical findings of available field studies provide evidence for both theoretical notions, provoking the question as to which specific boundary conditions the predicted and observed effects are linked to. Taking a look at the theoretical notions on processes by means of which age heterogeneity influences teams efficiency positively or negatively, it is possible to deduce the assumption that team climate has a significant influence on the direction of the relationship between age heterogeneity and team efficiency. The present study examines the moderator effect of team climate on the relationship between age heterogeneity and team efficiency in a field study including 66 work teams from the administrative area. The examination took place as a part of the ADIGU-Project (“Age heterogeneity as a determinant of innovation, team performance and health”), which is part of the DFG priority program “Age differentiated working systems”. Age heterogeneity was measured by computing the standard deviation, following an advice of Harrison and Klein (2007). Team climate was measured via a scale by Moltzen and van Dick (2002), referring to the team climate inventory by Brodbeck et al. (2001). As an indicator of team efficiency, innovative performance was recorded using a scale by Janssen (2001). In order to prevent distorting influences of common method variance, answering this scale was performed by team members as well as their superiors. As an indicator of team efficiency on the level of experience, burnout was recorded using the scale of “emotional exhaustion” in the German translation of the Maslach-Burnout-Inventory (Maslach & Jackson 1986) by Büssing and Perrar (1992). Testing the expected moderator effect of the team climate was accomplished via hierarchically moderated regression analyses. Results confirm the expected moderator effect: In teams showing a good team climate, increasing age heterogeneity leads to increments in innovative performance as well as to a decrease of burnout; while in teams with a bad team climate, age heterogeneity contributes to a decrease of innovative performance as well to an increasing degree of burnout.

Practical Relevance

The results of the present study concur with the theoretical notion of age heterogeneity causing promoting or impairing processes within a team – depending on its team climate. Thus, against the background of increasing age heterogeneity, establishing a good team climate represents a central executive task.

Age-, gender- and tenure-diversity in administrative teams: Do faultlines explain more variance in team conflicts and burnout compared to traditional diversity indicators?

Author: Cristiane Breu, Jürgen Wegge, Klaus-Helmut Schmidt

Keywords: Age diversity, gender diversity, tenure diversity, faultlines, conflicts in teams, burnout

Summary

Group work becomes more and more accepted and implemented in organizations (Kerr & Tindale, 2004; Kozlowski & Ilgen, 2006, Wegge & Schmidt, 2007). Therefore, psychological research is interested to broaden the knowledge of factors which influence the work and performance of groups. A factor that has been often examined in prior studies is the demographic composition of teams (Bell, 2007, Bezrukova et al., 2009; Thatcher et al., 2003; van Knippenberg & Shippers, 2007; Wegge, 2003). Jehn et al. (2008) distinguish between two types of theories underlying research on team composition: Alignment theories and dispersion theories of group composition. By now, diversity research is mainly based on dispersion theories which focus on the distribution of a single individual demographic characteristic (e.g., age) within a group and its impact on different outcomes. One disadvantage of this approach is that it considers only the degree to which a group differs on one demographic characteristic while often ignoring other attributes (e.g., gender, tenure) and important interdependences among them. In short, it can be argued that this analysis strategy doesn’t fit the multidimensionality of the diversity concept in general and, therefore, fails to reflect adequately also the complexity of the related phenomena.
The main goal of this research is to examine a new approach that attempts covering the complexity of diversity in teams more appropriately by (a) including more than one attribute at the same time and by (b) analysing the alignment of multiple characteristics between team members: The diversity faultline approach. The faultline theory was firstly introduced by Lau and Murnighan (1998) in analogy to the geological phenomenon of faults. They define faultlines as “hypothetical dividing lines that may split a group into subgroups based on one or more attributes“ (Lau & Murnighan, 1998, p. 328). Faultlines are characterized by a faultline strength (FS) and a faultline distance (FD) which can be combined into a faultlineindex (Fau). While faultline strength reflects the extent of demographic attributes that align within a group or how clearly a group splits into two homogeneous subgroups, faultline distance captures how conceptual different these subgroups are. The faultlineindex, as an overall dimension, desribes how clean and deep a split (faultline) within a team is.
Lau and Murnighan proposed that faultlines indicate higher levels of conflicts in groups. According to the social identity theory (Tajfel & Turner, 1986) group members tend to build subgoups with individuals they perceive as similar to themselves and rate the ingroup more positive than an outgroup. This can cause conflicts between the different subgroups which can influence the performance of the whole group. Today, research on the relationship between faultlines and conflicts in teams is inconsistent as this relationship was found to be both positive and negative (see for example Thatcher et al., 2003; Lau & Murnighan, 2005; Bezrukova et al., 2002; Li & Hambrick, 2005; Molleman, 2005). An important reason for the inconsistent data can be the lack of field studies analysing faultlines and their impact on team effectivity in real existing groups. Moreover, the faultlineindex – what is theoretically the best measure for faultlines – was not used consistently in prior studies. There are also only few studies that have investigated the relations of faultlines on psychological well-being and health although there is evidence that conflicts have an impact on these factors (see Ries, Diestel, Wegge & Schmidt, in press). Therefore this article analyses if the calculation of group faultlines is useful for the prediction of emotional and cognitive conflicts as well as burnout in teams. We assume that through the consideration of multiple attributes of team composition incremental variance of faultlines compared with traditional heterogeneity indicators (standard deviation and Blau-index) should be found.
Using existing data of the ADIGU-project (Age heterogeneity as a determinant of innovation, group performance and health; see; Ries et al., in print; Schmidt & Wegge, 2009; Wegge, Roth, Neubach, Schmidt & Kanfer, 2008; Wegge, Roth & Schmidt, 2008) from 232 employees working in 58 natural work groups, we calculated faultlines based on the attributes age, sex and tenure of team members. To measure faultlines we used two algorithms developed by Thatcher et al. (2003) and Bezrukova et al. (2009). Both measurement methods were adapted from multivariate statistical cluster analysis (e.g. Jobson, 1992; Morrison, 1967; Sharma, 1996). To restrict the complexity of calculation and prevent effects of group size, we controlled this factor and only used group with four members and limited the number of possible subgroups to two. Outcome variables were emotional and cognitive conflicts and self-reported burnout.
We calculated three different stepwise multiple regression to test if faultlines explain incremental variance compared to traditional diversity indicators in predicting outcome variables. In the first step, we always controlled for age and gender. In the second step, we included the three traditional diversity scores: standard deviations of age and tenure and the Blau-index of gender. In the third step, we added the faultlineindex. The results support the assumption that stronger faultlines lead to statistically significant more cognitive conflicts in teams (β=.40 and p<.05) and marginally also to more burnout (β =.34 and p<.09). However, no significant effects were found for emotional conflicts. Based on these findings, it can be concluded that the faultline concept is indeed fruitful and extends traditional research on team composition. Futures studies should examine other important variables like performance or satisfaction of workgroups as outcomes.

Practical Relevance

Knowledge about the effects of faultlines in teams can be used for changing group composition systematically. With this knowledge it is possible to control team processes indirectly and to influence team effectiveness. It was found that faultlines based on age, sex and organizational tenure mainly promote cognitive conflicts in teams. Hence, such faultlines have a strong potential for both preventing and inducing cognitive team conflicts.

Author: Anja Philipp und Heinz Schüpbach

Keywords: Teacher, age, professional life-span, emotion regulation, episodic analysis

Summary

Demanding situations and disturbances in class are almost inevitable in teaching - and they may evoke intense emotions. How teachers regulate their emotions in such demanding situations is crucial for their well-being.
According to Carstensen's Socioemotional Selectivity Theory (e.g. Carstensen et al. 2003), positive experiences become more important with increasing age and emotion regulation strategies are important for achieving such positive emotional states. Older persons are in general very experienced in dealing with emotionally demanding situations and have a variety of different strategies available which they even use more efficiently than younger people (Blanchard-Fields 2007). However, especially for teachers also other results have to be taken into account. Schaarschmidt (2005) shows on the one hand that older teachers use inefficient strategies quite frequently to deal with the demands of their profession. Younger and less experienced teachers, on the other hand, also struggle with the emotional demands of their profession, and tend to establish problematic strategies already during their first five years as teachers (Schaarschmidt & Kieschke 2007). It can, thus, be postulated that younger teachers at the beginning of their professional career as well as older teachers struggle with the emotional demands of their profession, which might bring about states of discrepancy between their spontaneously felt emotions (e.g. anger) and the emotions they consider appropriate for the demanding situation (positive, friendly, supportive). Therefore, they are more likely experiencing a state of emotional dissonance and thus, have to regulate their emotions more intensely than their middle-aged colleagues.
A quasi-experimental study with 205 secondary school teachers was conducted to investigate this. Two typical emotionally demanding situations (episode A: „Girl plays with her MP3-player and talks to her neighbor. She was then sent out of class. But she does not calm down and disturbs the class from outside the room“; episode B: „boy arrives much too late and instead of sitting down quietly he starts to chat with his neighbours and increasingly disturbs the entire class with his noise”) had been identified. These were then re-enacted with students from an 8^th grade of a secondary school and recorded as episodes on video. In order to assess emotion regulation over the course of the episodes, as Beal et al. 2005 stipulate, each episode was cut into two to three separate scenes. After each scene, teachers were asked to fill in a short questionnaire on emotion regulation aspects.
First, emotion regulation indeed showed the expected pattern of changes over the professional life-span. Over the course of the two episodes, teachers with more than 20 years in the teaching profession felt a stronger discrepancy between the positive emotional state they find appropriate in the situation and the emotions they had actually felt (so called emotional dissonance) than their middle-aged colleagues. The results also show that older teachers regulate their emotions more intensely and use a broader variety of strategies than their middle-aged colleagues. They tend to conciliate their spontaneously felt emotions and the emotion they perceive as appropriate in the situation (so called deep acting) significantly more strongly over the course of all episodes than their middle-aged colleagues. Over the course of episode B, older teachers also expressed an emotion they did not feel because they acknowledge this as part of their job (so called faking in good faith) more strongly than their middle-aged colleagues. This also applies to younger teachers, although this difference is less pronounced and not consistently significant.
Second, results also show that the emotion regulation changed over the course of the episodes with little changes between the episodes, indicating that emotion regulation has a situation-specific aspect. Overall, the teachers tried to constantly conciliate their spontaneously felt emotions and the emotion they perceive as appropriate in the situation (by deep acting) over the course of the two episodes. Strategies of expressing an emotion they did not actually feel either because they acknowledged this as part of their professional role and as necessary for achieving their task (so called faking in good faith) or because they were afraid of possible consequences (so called faking in good faith) decreased. Especially the more experienced and to a lesser degree also the inexperienced teachers seem to struggle more with the emotional demands of their profession. These sensible phases (being exposed to the emotional demands for a long time or adaptation to a new field) bring about feelings of emotional dissonance that especially the older try to down-regulate this by using different strategies of emotion regulation more intensely than their middle-aged colleagues. The younger teachers, on the other hand, preferably engage in deep acting.

Practical Relevance

The development of an intervention is necessary to maintain a health-beneficial emotion regulation in the face of obstacles. It should address older teachers as well as their young colleagues who experience more emotional dissonance in emotionally demanding situations. Implications for the design of such an intervention will be discussed.

Changes in attitudes towards work activity as a function of age - first results of a longitudinal study conducted in two automobile manufacturing companies

Author: Sarah Schiekirka, José-Alonso Enríquez-Díaz und Ekkehart Frieling

Keywords: longitudinal study, automobile industry, age, work ability, attitudes

Summary

The demographic change confronts our society with a growing number of older people due to decreased birth rates and an increasing life expectancy. This shift will have a massive impact on all levels of society. This is of direct relevance to employers responsible for sustaining the lifelong work ability of workers, especially for jobs with high physical demands often found in the automotive industry, for instance in assembly lines.
However, these jobs are of central importance in the work process of the automotive and component supply industry. They are characterized by low levels of automation, are highly personnel-intensive and under great competitive pressure in the global arena. Although cars are assembled under similar production related conditions worldwide, differences between the age cohorts working in the assembly lines, as well as the organization work type, exist. Assembly plants that have been built during the last two decades in Asia, South America and Eastern Europe, for instance, mostly employ young and efficient blue collar workers. The same applies to established Japanese automotive plants, which take part in determining the competition in the international market.
Thus, there is high competitive pressure for German automobile manufacturers to maintain their competitiveness with generally older assembly line workers. To design new assembly line concepts, elements of the Toyota Production System are adopted with slight modifications (Neuhaus 2008). Toyota employs mostly young blue collars, although Japan is facing the challenges of demographic change as well. However, due to a different remuneration and employment system Toyota can easily relocate older employees into other divisions as well as component supply subsidiaries. Assembly line workers in Germany are on average 40 years old, having worked in the company for an average of 20 years, and thus have vested rights.
As a result of these new production concepts, older workers are exposed to work conditions, which may be described as follows: In the series assembly, the cycle time varies between 60 and 120 sec., work is structured in a two- or three-shift system, ineffective work steps are reduced (e.g. retrieval of work elements, delivery of material and “unnecessary” movements). The implementation of job rotation aims at reducing the associated workload consequences for the workers.
In the following study two longitudinal and cross-section data sets from two automobile manufacturing companies were compared. It will be demonstrated how the working conditions in assembly lines have changed over the last two to three years from the employees’ point of view, how employees perceive these changes and what kind of improvements may be derived. The differences in age cohorts are particularly relevant for finding specific improvement measures for older and younger people.
The samples of both companies are relatively homogenous concerning age structure, gender composition, qualifications, professional activities and seniority. This homogeneity is a good basis for comparing the perception of the different work conditions in the plants, i.e. the differences in the survey results can be mainly attributed to working conditions. Rationalization processes which are found in both plants cause an increased pressure concerning time and performance for employees. The results of our study show an age-related decrease in subjective work ability, an increase in physical complaints, uncertainty due to potential job loss and increased irritation. The results differ in the two plants and are due to different work patterns. In factory B, group work is only marginally existent, whereas in plant A, it is strictly organized, e.g. with a fixed time for group discussions. The assembly processes are partially automated, so that technical troubleshooting may occur several times a day. The employees thus have the possibility to solve problems themselves or in collaboration with a specialist. On the assembly line in plant B, comparable work promoting employee learning is very rare. A systematic analysis of job rotation (Weichel et al. 2010) in company B revealed that physically demanding activities are mostly performed by younger rather than by older employees. This self-selection by workers or by the foreman leads to the fact that physical symptoms not necessarily increase with higher age. However, for this “special” distribution of tasks sufficient young staff is needed which could be a problem in the future due to the demographic change. Therefore the working conditions have to be changed according to ergonomic and psychological criteria.
The longitudinal data show clearly that with increasing age underchallenge by work requirements declines and overload rises. Possible reasons can be that younger age cohorts are better qualified than older employees; they feel less challenged by the highly standardized activities and can handle the increasing pressure better. The crisis of the automotive industry has induced an intensive search for the right management concepts which also has an impact on working conditions in production. The frequent changes of supervisor, the adoption of Japanese organizational concepts and their implementation, the search for more efficient production conditions which limit opportunities for participation and cause a fear of job loss, lead to an understandable uncertainty among employees.

Practical Relevance

The demographic change confronts the automotive industry with a growing number of older employees. This has become a new challenge when it comes to jobs with high physical demands which are often found in the automotive industry. By comparing longitudinal questionnaire data, collected at assembly lines of two automobile manufacturing companies, the effects of these operating conditions on workers of different ages are analyzed and practical instructions are derived.

Author: Holger Rademacher, Andrea Sinn-Behrendt, Ralph Bruder und Kurt Landau

Keywords: Physical capabilities, age-differentiated work design, musculoskeletal disorders, capability-adapted assignment of employees, age management

Summary

Effective age-differentiated design of workplaces in production systems as part of a sustainable concept for age management in industrial enterprises is based on the analysis and assessment of (physical) work-related exposures in order to prepare specific measures of workload optimisation. To be able to assess exposures in an age-differentiated manner in terms of prevention of work-related (musculoskeletal) disorders, evidence-based knowledge about the characteristics of (physical) capabilities that are necessary to fulfil the specific work task is required.
The question whether the age of workers, who are confronted with physical exposures that are typical for a certain production system, is a key factor for ergonomic work design has not been answered sufficiently by present scientific studies. Therefore the authors are conducting field studies in companies of automotive industry, which are part of a six-year research project (funded by the German Research Foundation DFG). They incorporate analyses of age dependency of specific physical capabilities in order to receive an age-differentiated picture of the characteristics of these capabilities that is valid for the particular worker population. Our research aims at investigating workplaces and employees from manufacturing or assembly areas. Hence, we are focusing on predominantly physical work. The hypothesis for the capability study is that there are significant relationships between industry-relevant capabilities to cope with physical work-related exposures and the workers’ age. Another hypothesis is, that in German automotive industry workplaces exist, which are “age-critical” concerning their exposure characteristics.
In a field study in cooperation with a major German vehicle manufacturer to date 73 male workers from 20 to 57 years in age have been examined on site in production area of the plant. The data collection is continued at present in order to collect data from 160 male workers in total. Furthermore, follow-up studies are intended.
There are two major age groups regarded in this study: the “younger workers” at the age of 20 to 35 years (separated into three subgroups) as well as the “older workers” aged between 45 and 65 years (separated into two subgroups).
The necessary data for an age-differentiated evaluation of industry-relevant physical worker capabilities is collected during a three-hour test procedure developed by the authors. It consists of three parts and every part takes about one hour. The most important part of the test procedure are physical, work-specific tests. More than 400 workplace analyses conducted by the authors in several automotive companies served as basis for the selection of work exposures that have to be represented.
The results of seven tests to the status of industry-relevant capabilities of 71 workers are presented. Age group effects on characteristics of 10 out of 19 test variables can be identified in six of the seven tests regarded here. But in most cases solely the comparison “younger (20-35 years) vs. older (45-57 years) workers” is significant. Only in four test variables the differentiation into “smaller” age groups provides statistically relevant differences. In three of those four cases solely between two of the five defined age groups. Overall, the older workers of the sample indeed show “weaker” results compared to the younger workers, but there are no dramatic drops found in the scores of the older workers.
Some limitations of the study are, that present data is not from a longitudinal study and therefore susceptible to bias caused by selection effects. Moreover, an impact on the results caused by motivation of the subjects during the test procedure is possible. Furthermore, the question arises whether those subjects who are - because of their actual or past jobs – the most “familiar” with the physical exposures (reproduced in the tests) achieve different results. Such a comparison of exposure biography and test results may give additional information. During the research project data about exposure biography of the subjects is recorded, but the data currently available is not sufficient for a statistical analysis.
The present results of the field study about industry-relevant physical capabilities indicate the existence of age dependencies with practical relevance. Especially in manual materials handling and awkward static body postures capability differences between the age groups have been found. These should be considered with regard to age-differentiated work design. The manual materials handling tests as well as the tests about static postures represent by no means extreme levels of exposure that would only be found scarcely in practice. Rather medium load weights or for example awkward postures in combination with tasks located in a vehicle’s interior may be a serious problem for the group of older workers.
Concrete design recommendations cannot be derived with the test data in its current form and size, but within the research project of the authors an integration of the test variables (presented here) and additional data is planned in order to prepare capability ratings that consider all relevant information. These capability ratings will be done by trained occupational physicians. The ratings will focus on 20 industry-relevant capabilities (e. g. capability to work with one or both arms above head level).
After completion of the ratings of employee capabilities and a comparison between age group specific capability profiles and demand profiles based on workplace analyses age-related bottlenecks and their characteristics can be determined. With the help of these bottlenecks age-related exposure limits will be calculated. These limits are used to develop a screening method for age-differentiated workload analysis. This screening of existing or planned workplaces makes it possible to detect age-related design deficits and to formulate preliminary guidelines for age-differentiated ergonomic work design. But these guidelines have to be well-founded with longitudinal analyses. In the end, components of an assistance system for age management in industrial enterprises will be available.

Practical Relevance

The current study provides results of a field study of age-related differences in industry-relevant physical capabilities of workers. These results are an important basis for age-differentiated ergonomic work design against the background of the demographic change.

Process model elements adjusted to abilities for the generation of age-differentiated strain profiles

Author: Mathias Keil, Ralph Hensel und Birgit Spanner-Ulmer

Keywords: Stress-strain concept, strain profiles, age differentiated task-arrays, age-based product and process design, ability-adjusted process model elements

Summary

Introduction

Regarding the ergonomic goal of realising user-friendly and efficient working systems and processes, companies face the challenge of increasing their productivity in the context of an aging staff.

State of the Art

The centre of the design of age-based working systems is the necessity of designing the elements of the working system in a way that occurring deficits of the human performance might get compensated as far as possible. According to the stress-strain concept, the level and duration of the stress determine, depending on the individual abilities of the human being, his/her strain. Hence, due to possible age-based ability changes, it can be assumed that elderly staff members are more strained than younger staff members when carrying out the same work.
The look at the entrepreneurial practice shows that the design of working systems in terms of elderly staff members partly fails to meet the ergonomic objectives. The design of less wasteful and value-adding product processes ends in a performance compression causing an increase in efficiency by raising the stress of the staff. Due to the highly standardised processes, the abolition of hidden short breaks as well as of changes in the movement and posture lead to a higher strain, especially of elderly people.
In this report a line of research will be presented that should help to prospectively evaluate strain situations regarding the age-related performance changes. The goal is to generate age-based working systems by means of measures in human resource management, technology and organisation.

Practical Relevance

The companies accept the challenge of the demographic change in the entrepreneurial practice by measures like job-rotation, workplace design or by installing adapted workplaces. But the realisation of these measures effects according to experience and in terms of age effects is not enough scientifically funded. With the system of ability-adjusted process model elements, which will be developed in this research project, age-differentiated working processes on the basis of balanced, age-differentiated strain profiles can be shaped. Therewith an important contribution for the prospective planning and design of age-differentiated working systems even in the early phases of the product development process will be made.

Simulation-supported balancing of assembly systems according to an aging workforce

Author: Gert Zülch und Martin Waldherr

Keywords: Demographic change, aging workforce, assembly line balancing, simulation of assembly systems, personnel-oriented simulation

Summary

In many Western countries, it has become common practice of companies to withdraw elderly workers from work before reaching the statutory retirement age. Mostly, the reasons for such a process are job cuts or specifically replacing older workers with younger and presumably more efficient workers. Due to the demographic change this will no longer be possible to the same extent in the future.
Furthermore, the trend for shorter cycle times can be observed, which in general younger workers can better cope with compared to elderly ones. These trends need to be taken into account during the long-term planning of production systems. As a consequence, questions regarding performance equitable employment possibilities for elderly workers arise.
The sweeping judgement that elderly workers are generally more inefficient than younger ones cannot be confirmed, but with respect to biologic- and functional-oriented approaches human performance at work is subject to certain differentiated changes. This may lead to a reduced output from elderly workers in some situations, which, however, can be compensated, at least in part, through their accumulation of competencies. Thus, production enterprises should acknowledge these performance changes, both for individuals and for personnel groups.
This paper will discuss a planning procedure and simulation approach for looking into the future of an assembly system under the precondition of an aging workforce. In order to prognosticate future development, simulation models based on quantitative assumptions can be used to examine the impact of age-related performance changes. Due to their specific interpretation of human-influenced factors, personnel-oriented simulation is particularly well suited for this purpose. Furthermore, a combination of planning and simulation tools will be presented to support the evaluation and re-structuring of a so-called age-robust assembly system. The idea is to apply new methods which strongly consider the strengths and weaknesses of aging workers as early as in the planning phase of a work system. If this turns out to be successful, most cost-intensive improvements of an existing system at a later stage can be avoided.
There are specific planning procedures for assembly systems; the underlying methods, however, do not sufficiently consider the skill development of aging workers. Considering age-related differences in skills and changes thereof, however, is the key to designing an age-robust assembly system.
The paper will show that performance losses in certain areas can be compensated with organisational changes and must not necessarily lead to a bottleneck in the entire work system. In contrast, the goal of harmonious personnel utilization can positively influence the employment of workers with changed performance capabilities. Supported by this knowledge a new methodology for planning assembly systems considering the aging of workers will be discussed.
This procedure is based on a genetic algorithm, which is used to build up an initial set of several initial solutions. After that, this set of solutions will iteratively be developed over multiple generations. Using a simulation procedure, the generated solutions are evaluated with regards to several target criteria. The best solutions are then transferred to the next generation. In the following generations the planning solutions are again modified by mutation and selection. This process is continued until a predefined termination condition has been reached.
A pilot study in the automotive industry was performed in order to illustrate the application of this procedure. Its results reveal that – at least in this case – planning of an age-robust assembly system is feasible.

Practical relevance

Especially small and medium-size enterprises will be affected by demographic changes. The employment and use of an aging workforce will be essential for the success of an enterprise. The presented the simulation-aided planning procedures help to forecast trends and to develop age-robust planning solutions.

Age-specific health-effects of physical stressors and autonomy in elderly care

Author: Andreas Müller, Matthias Weigl, Bettina Lampert, Jürgen Glaser und Peter Angerer

Keywords: Age, stress, demand-control, health, elderly care, work design

Summary

There is an increasing need for age-specific work design that focuses on well-being of employees (e.g. Wegge et al, 2008). Models of stress at work, like the Job Demand-Control (JDC) model, can be a starting point for such an age-specific work design. The JDC model identifies two dimensions of work characteristics: Job demands refer to the strain of employees. Job control refers the possibility of an employee to make individual decisions on their work activities. According to the JDC model, high job demands will increase and high job control will reduce strain and health risks. Moreover it is assumed that health risks will especially occur when high job demands are associated with low job control, and that increased control will reduce the detrimental effects of high demands (buffer-hypothesis). There is good empirical evidence of the JDC model, however age-specific effects are rarely tested (see de Lange et al, 2003).
According to the JDC model, our study tested the effects of physical stressors (in terms of job demands) and of autonomy (in terms of job control) on the health of caregivers. Physical stressors are relevant because caregivers are often required to lift, to move or to transfer patients or clients, and to work in uncomfortable positions. Moreover it is known that physical functions decrease as a function of chronological age. Thus it can be assumed that especially elder employees will have health risks due to physical stressors. Autonomy is assumed to be one of the most important resources for health and well being at work in general. Moreover there are first hints that autonomy enables individual strategies for successful ageing at work, like compensation strategies (Abraham & Hansson, 1995; Wegge et al 2008). In line with the buffer-hypothesis we also tested, if autonomy can reduce health risks of caregivers due to physical stressors. Accordingly with our previous considerations, especially older employees should benefit from this buffer effect.
1.848 caregivers working in 111 nursing homes for elderly completed a questionnaire in the course of an employee survey. 86% were female. The mean age was 40.5 years. To enable statistical control demographical data about professional tenure (in years) and type of contract was collected. Additionally smoking behaviour and exercise frequency during leisure time was assessed with two questions. Physical stressors and autonomy were assessed with two scales of the hospital work analysis tool (TAA). Physical and mental health was assessed with the SF-12 Health Survey. The SF-12 norms of physical health decrease with age. Therefore we decided to assess deviations beyond the 25^th percentile of the respective age norm as outcome variable. Multivariate hierarchical logistic regression with stepwise inclusion of 1) sociodemographic factors, 2) health behaviour and 3) working conditions (physical stressors and autonomy) was used for statistical analyses. As for standard moderated regression, we tested in a last step for incremental effects of the two way interaction between physical stressors and autonomy. Beside an analysis of the total sample we also did separate analyses of three age groups (≤ 30, 31-50 und 51-67 years).
Results point to a diminished health status of especially younger caregivers. Physical stressors in daily care contributed significantly to an increasing risk of diminished physical as well as mental health, especially of caregivers > 50 years. Autonomy significantly reduced the risk of diminished mental health. Here, no consistent differences between age groups were observed. The study did not support the buffer-hypothesis: No significant effects of the interaction between physical stressors and autonomy on health were observed. Interestingly the variance explained by the working conditions over and above the control variables was the highest in the age group > 50 years. This result suggests that the impact of work conditions on health may increase with age. At the same time the study also shows that age-specific work design in the field of care should not solely focus on older caregivers. This is because especially younger employees report a diminished health status. Moreover, risk and protective effects of the analysed working conditions were observed over all age groups.

Results are critically discussed in terms of possible healthy worker effects, common method bias, and actuality of the SF-12 norms.

Practical Relevance

In the future care can only be provided in a sufficient manner when employed caregivers will remain healthy and capable in their jobs. The present study provides valuable information for age-specific work design in the field of elderly care.

Do older learners benefit from new media? Design and evaluation of an e-learning Behavior Modeling Training for different age-groups

Author: Sonja Bausch, Karlheinz Sonntag, Ralf Stegmaier und Katrin Noefer

Keywords: Behavior Modeling Training, e-learning, age, training, learning

Summary

As companies and employees frequently face new challenges in their work environment, training is a central issue of personnel development. E-learning is getting more important because it has a relatively short development phase and is accessible anywhere at any time. Although knowing about its importance, studies showed that especially older employees participate less in training and development programs than their younger co-workers (Maurer et al. 2003; Sonntag & Stegmaier 2010).
The time and self-management program ZEuS is an e-learning tool based on the principles of Behavior Modeling Training, BMT, (Bandura 1977). In BMT, observational learning occurs through highlighting key learning points, observing a successfully acting model, practicing learned behavior and getting performance feedback. In the 2.5 hours lasting program the BMT principles were realized in three modules with introductions, video-based modelings and interactive tasks. Although research showed that BMT is an effective learning method suited for older learners as well (Callahan et al. 2003), age-differentiated effects have not been studied so far. Therefore, we systematically developed an e-BMT applying multimedia design principles and considering especially older learners’ training needs. In this study, we firstly proved whether the e-BMT led to a substantial learning and transfer effort. Secondly, we tested if different age-groups do learn equally successful. Thirdly, we hypothesized that age-congruence between trainee and observed model should foster the learning effort through increased similarity and identification which in other studies had a positive influence on taking over another opinion or on health behavior (Bandura 1977; Fox & Bailenson 2009; Hilmert et al. 2006). We varied the program showing a young, a middle-aged, or an older learning model (25, 40, 55 years). Trainees themselves were classified in three age-groups and randomly assigned to one of the three model variations. Instead of the evolving 9 groups, we contrasted age-congruence vs. age-incongruence to reduce the complexity of our study design. A differentiated picture of training success was gained through evaluating learning success before and immediately after the training and again 45 days later and with different instruments: We tested the declarative knowledge at three times (pre, post and follow-up), the skill performance before and immediately after the training (pre and post) and the time and self-management behavior before and delayed after the training (pre and follow-up). With the resulting 2x3x2-design and the factors time, learners’ age-group and age-congruence, we conducted an analysis of variance (ANOVA) with repeated measures, to test the effects.
Out of 583 trainees who started the program, 285 trainees, aged 18 to 76 years finished the pre and the post test. 93 trainees observed an age-congruent and 192 an age-incongruent model. 147 remaining trainees additionally answered the follow-up test. A positive main effect of time for all four measures (short term and delayed measured declarative knowledge, task performance and behavior) showed the impact of training on learning outcomes. As hypothesized, we found no time x age-group interaction for delayed measures of declarative knowledge, task performance and time and self-management behavior, indicating, that the age-group does not influence these learning outcomes. Other than expected, time x age-group showed a significant interaction on declarative knowledge in a pre-post comparison. Referring to the age-congruence variation, we found an effect of time x age-congruence for task performance and for time and self-management behavior. In the age-congruence condition learners’ task performance and their time and self-management behavior improved more than it did in the incongruence-condition. In contrast, we found no significant interaction of time x age-congruence with respect to declarative knowledge. Results suggest that the e-learning program ZEuS led to substantial learning and, moreover, that an e-learning program based on BMT and software economical principles can be a suitable learning environment for older learners as well. As a practical implication, e-learning could be designed more often based on BMT principles. As all age-groups benefited from the training, especially older learners could be encouraged to learn with new media to reduce existing barriers. With the enhancing effect of age-congruence between learner and model, BMT could be designed more effectively. Because the age-congruence effect held only for the transfer measures, further research is needed to gain more information about the influences of age-congruence and training outcome measures in learning processes.

Practical Relevance

The study shows how multimedia design principles can be applied and also older learners’ training needs can be considered to successfully develop an e-learning program for different age groups. Age-congruence between model and learner can be used to increase the effectiveness of behavior modeling trainings. Additionally, findings demonstrate the importance to measure long term training success in addition to short term success.

Age-differentiated Investigation of Visualization Techniques Supporting the direct Manipulation of Complex Net Plans

Author: Nicole Jochems, Sebastian Vetter, Jennifer Bützler, Christopher M. Schlick

Keywords: Human-Computer Interaction, Aging users, Visualization, Project management

Summary

Demographic change demands new concepts for the support of computer work by aging employees. The use of the computer is often especially straining for older workers due to a lack of training, experience and age-specific changes in performance. The decrease in sensory as well as motor performance is well known and frequently leads to usability problems during computer work. Thus, there is a compelling need to support elderly computer users. Different aspects concerning the design of software and hardware should be investigated to assist elderly computer users adequately. Particular the amount and the structure of information presented on a screen describe one important starting-point to support aging users. This is due to the fact that large graphical structure such as net plans in project management software may require scrolling actions which are often very difficult for aging users. The approach of age-differentiated adaptation of the human computer interface followed here is focused on compensating age specific changes in performance, thereby especially supporting aging computer users. The adaptation of the human computer interface is exemplarily carried out with project management software. Work with network plans places coordinative communicative demands on the user while also requiring complex cognitive processes. The goal of our experimental study was to compare different visualizations of net plans in regard to age-specific and individual aspects. Three visualization variants - (1) Overview map, (2) Detail window and (3) Zoom-function - were contrasted with a control layout by performing typical project management tasks. In the first visualization variant “Overview map” an additional window with structural information of the entire net plan is shown on the top of the screen. This so called overview map shows the details of the net plan (working area) together with an overview of the entire information space. The overview map and the detail window (working area) are tightly coupled so that structural as well as visual changes in the original net plan in the working area are immediately reflected in the overview map. In the second visualization variant “Detail window” the content information of the net plan is reduced, thus the total net plan can be shown in the working area. No additional scrolling is needed. Activated by a “touch” on a net plan element additional information is fade in. Accordingly the complete information of the activity, the duration, the start / end time are presented on the top of the screen. In the third visualization variant “Zoom-function” the content information are also reduced and fade in by touching a net plan element. Thus no scrolling activities are needed here, too. The information of the activity is presented on the current position of the activity. Both the detail information as well as the overview information can be shown simultaneously in the working area. In our experimental study these visualization variants were investigated with 90 subjects between 20 and 75 years. The processing of typical project management tasks, such as the creation and deletion of net plan elements as well as the modification of content information or the linking of two net plan elements have to completed by the participants. The data were analyzed with regard to execution time, error rate and mental workload. The results show that the best performance in terms of short execution time and less mental workload results from the visualization variant “Zoom-function”. The results confirm that human-computer interaction can be designed more efficient, more effective and less mentally demanding through the use of ergonomic visualization variants. This is of particular interest for aging computer users who, as was shown, often have great difficulties with conventional layout design and scrolling.

Practical Relevance

Currently there are two main developments in our society – demographic change as well as automation of working processes. In particular, computer work is interesting due to the increasing level of technological complexity of software and the overall reserved attitude of aging employees toward technology. As a result, using a computer intensively often creates a barrier for aging workers due to a lack of training, experience and age specific changes in performance. Particular the amount and the structure of information presented on a screen describe one important starting-point to support aging users.

Adaptation to visumotor transformations with indirect view in early and late working age

Author: Mathias Hegele und Herbert Heuer

Keywords: aging workforce, pointing movements, indirect vision, visuomotor transformation

Summary

Modern technology places increasing demands on the sensorimotor skills of employees. In particular there is an increasing number of working tasks that comprise transformed movements with indirect vision, as in controlling the position of a cursor on a computer monitor by means of a mouse or in minimally-invasive surgery using endoscopic tools. In order to operate devices like this, humans have to learn to deal with visuomotor transformations. Findings from applied research suggest that there may be particular problems to produce transformed movements with indirect vision at higher working age. Basic research showed age-specific changes in the control and adaptation of simple movements; these changes might partly vary as a function of the transformation rule that translates body movements into movements of a tool. The research reported here focused on two questions:

(1) Is adaptation to a novel visuomotor transformation already affected at pre-retirement age? If so, are the processes subserving adaptation affected differently by aging?

In order to assess the locus of age-related impairments within perceptuo-motor control, we distinguish three processes each contributing to visuo-motor adaptation: closed-loop control, open-loop control via an internal model, and strategic corrections of an otherwise spontaneously executed movement. Our results show that strategic adjustments based on explicit knowledge of the transformation are selectively impaired already at pre-retirement age whereas the implicit development of an internal model remains unaffected by aging. When age groups are matched by explicit knowledge, age-related impairments of adaptation largely disappear.

(2) Are age-related changes different for different types of visuomotor transformations?

Based on the vector-coding hypothesis according to which goal-directed reaching movements are planned in terms of amplitude and direction of a vector that connects movement’s start and end position, we compared adaptation to visuomotor gains and visuomotor rotations. Results show that there is no categorical difference between rotation and gain adaptation as both show age-related impairments in the more cognitive component of visuomotor adpatation, i.e., in strategic corrections based on explicit knowledge of the respective transformation.

However, rotations had to be of sufficient size and the gain change had to vary as a function of movement direction (making it more difficult to adapt to).

All in all, our findings suggest that the difficulty of the novel visuomotor trans- formation and, related to this, the involvement of explicit knowledge in adaptation is critical for age-related changes to show up, whereas the nature of the adaptation task at hand, no matter if rotation or gain adaptation, does not modulate the observed effects of aging on visuomotor adaptation.

Practical Relevance

Age-related changes in adjustment to novel relationships between body and goal-directed tool movements can manifest in various mechanisms of sensorimotor control, all of which subserve visuomotor adaptation. Knowledge regarding which mechanisms are insensitive to aging and which mechanisms are affected by age allow for age-differentiated training schemes and might contribute to the design of human-machine-interfaces.

Vol. 4 - 2010

Human stature, health and workplace design. An ethical dilemma

Author: Roland Kadefors

Keywords: Stature, workplace design, work postures, health, discrimination

Summary

A study was undertaken in an automotive assembly plant in order to find out if short or long stature of operators implied a higher risk to acquire musculoskeletal disorders due to extreme work postures. The study was initiated since a female applicant had challenged a decision of the company to deny her employment on the basis of a stature criterion (<163 cm or >195 cm), applied by the company on the basis of health concerns. The study concluded that there was an elevated risk in operators shorter than 160-165 cm to acquire problems in the neck, shoulders or low back due to exposure to work in awkward postures.

Practical relevance

Automotive assembly implies high postural load, particularly on operators of short stature. A conflict may appear between health concerns and employability of women on these grounds.

Regarding the posture of the trunk in the assessment of whole-body vibration

Author: Martin Fritz, Klaus Schäfer

Keywords: body postures, inclination of the trunk, simulation, upright sitting, whole-body vibrations

Summary

During typical work processes the drivers of container-bridge cranes are forced to sit with a forward bended upper trunk in order to control the motions of the container or the correct fixation of the container at the load-grappling device. The drivers of fork-lift trucks incline the upper trunk to the side in order to look forward beside the lifting mast or they twist to one side during revising. It is generally assumed that these inclined postures result in a higher health risk than vibration exposure in the upright sitting posture. Thus the aim of the present study was to assess the forces transmitted in the lumbar spine and to compare the effects of the different postures.

The spine forces were computed by means of a biomechanical model simulating the human vibration properties in standing and sitting positions. The model consists of 29 rigid bodies with 102 degrees-of-freedom. The different sitting postures of the drivers were imitated by inclining the segments of the model trunk gradually forward or to the side or by rotating around the longitudinal axis of the trunk. Hereby the maximal forward inclination of the chest amounted to 56° and the lateral inclination amounted to 9°. By the rotation the left shoulder was shifted 0.085 m backward in relation to the right shoulder and the left hand was hold beside the left hip.

The accelerations were measured in three directions on the seat of a container-bridge crane and a fork-lift truck during typical work processes. In the model the accelerations were transmitted over the feet, the hands, and the buttocks to the trunk. With the acceleration as input the forces acting in the lumbar motion segments L3-L4 and L5-S1 were simulated for eight exposure segments (duration 4.5 min) selected from the work processes. In order to simplify the comparison of the effects of the different postures the temporal mean values of the forces and the ranges, the differences between the minimal and maximal compressive or shear forces in each exposure segment were evaluated.

The bent forward postures result in an increase of the temporal mean values of the compressive forces and of the shear forces in the dorsoventral direction compared with the upright sitting posture. Most of the computed ranges of these forces are smaller in the bent forward postures. In the lateral inclined posture the compressive forces and the shear forces in the left-to-right direction are enhanced. By the shear forces a lateral displacement of the upper motion segments is prevented. The ranges of the compressive and shear forces show a non-uniform tendency in relation to the lateral inclination. The main effect of the twisted posture is the increase of the ranges of the shear forces.

The quantitative relationship between the mean values of the spine forces and the inclination of the chest was approximated by regression functions. Sufficient results were attained by linear equations between the resultant forces, representing the forces in the corresponding motion segments, and the angle of the forward or lateral inclination. The angle dependent increase of the spine forces are the result of the increased muscle forces which stabilize the inclined trunk.

The relationships between the ranges of the resultant forces and the inclination angles could not be sufficiently approximated by regression equations. The differences between the ranges result from the inclination related changes of the vibration properties of the human body. With the inclination angle the transfer functions between the spine forces and the vibration accelerations change their frequency dependences. These changes combined with the different frequency spectra of the measured vibration accelerations result in the variation of the force ranges.

Practical Relevance

The typical postures of the trunk of container bridge drivers or fork-lift truck drivers result in higher forces transmitted in the motion segments of the lumbar spine than it is given by the upright sitting posture. This effect must be considered in the risk analysis of workplaces with whole-body vibration.

Analysis of lifting and carrying activities in the furniture removal trade focusing on the stress on the lumbar spine

Author: Claus Backhaus, Stefan Baars, Karl-Heinz Jubt, Christian Felten, Jörg Hedtmann

Keywords: Furniture remover, removal, carrying, manual handling, lumbar load, spine

Summary

Furniture removers are apparently stressed by the manual handling of heavy loads. Although removers belong to the professions which are most frequently affected by disability due to the diseases of the lumbar spine, there is a lack of data on the workload. The following study aims to analyse the working situation of these employees and quantifies the musculoskeletal workload to evaluate the lumbar stress with established estimation methods from the occupational safety and health sector.

In order to analyse the work situation, 21 enterprises of the furniture removal trade were questioned concerning occupational safety and health activities. 23 removals were observed to measure the handled weights and the distance of carrying. From this data the average weights, distances and times of carrying were calculated for different groups of employees.

The workload was evaluated with the “Leitmerkmalmethode” (LMM - Key Item Method). LMM calculates a number which indicates one of four risk categories considering the handled weight, working posture, frequency or duration and the context of lifting or carrying. For 5 removals the body posture of an employee was continuously captured by using the biomechanical motion analysing system CUELA. To analyse this data, the amount of time of working in different trunk positions and OWAS-Categories (Ovako working posture analysing system) was defined. Additionally the lumbar load dose for one working shift was calculated by using the “Mainz-Dortmunder Dosismodell” (Mainz-Dortmunder Dose Model).

The average size of an enterprise is 20 employees. 11 of 23 companies have performed a risk analysis to identify and prevent work related hazards. 5 companies offer occupational medical examinations to the employees. Lifting and carrying devices like carrying straps, dollies or sack barrows are available in each enterprise. A team of furniture removers typically consists of one loader who is responsible for stowing and securing the furniture on the truck and one or two removers which mainly carry the load. If necessary the team will be supplemented by a cabinetmaker who assembles or disassembles the furniture. Temporarily, both the loader and the cabinetmaker help to carry the furniture.

We averaged a weight of 16.3 kg for the handled load. The average walking distance from the habitation to the truck is 25.5 m. The removers are the most exposed workers in the furniture remover team due to the carrying of heavy weights. As an average, they walk a total distance of 3.3 km and move a total weight of 2.1 t in each working shift.

Applying the LMM, the evaluation of the removers’ workload leads to risk category 2 which indicates an increased work stress that could lead to an overload for low resilient people.

CUELA indicates an average time of 45.5 minutes for working with flexed back and 22.9 minutes for working with lateral flexed or rotated back. For less than 2 minutes the employees worked in a lateral flexed and rotated trunk position. The OWAS analysis shows similar results: For 43.8 minutes the subject works in OWAS-category 2, for 11.8 minutes in OWAS-category 3 and for only 1 minute in OWAS-category 4. The MDD lumbar load doses range from 3.6 to 9.2 kNh per shift.

In the international literature there is a lack of information about data for the workload of furniture removers. As expected the results confirm a high workload for the removers for the manual handling of heavy loads. In the enterprises the supply of lifting and carrying devices is always good but is insufficiently used in practice. This suggests deficits in the information and the sensitising of the employees and the management. The implementation of legal standards for occupational safety and health also needs to be improved. The employees’ individual activities to reduce work related stress generally aim at minimizing cardiovascular strain which could, in some circumstances, even lead to an increase of the musculoskeletal strain. The main problems are the handling of heavy loads (≥ 40 kg) by only one employee and the long carrying distances.

Practical Relevance

The results of the study document and quantify data in order to evaluate the workload e. g. for the declaratory proceedings of occupational diseases and allow the prevention of lumbar disorders of furniture removers.

German Questionnaires for Evaluating Usability

Author: Kathrin Figl

Keywords: Usability, EN ISO 9241-110, Human Computer Interaction, Software Evaluation, Questionnaires, Isometrics, Isonorm 9241/10

Summary

Software usability is a highly relevant issue in the ergonomics of information systems, as these systems are prevalent in today’s workplace. Accurate evaluation methods are crucial for the construction of usable software that helps users to achieve their goals in an effective, efficient and satisfying way. For this purpose, usability engineers frequently employ usability questionnaires in practice. Usability questionnaires are economic in their administration and scoring, and they allow for accurate subjective assessments of users with a standardized method. In German, there exist two widely used questionnaires, Isonorm 9241/10 and Isometrics, which both evaluate software in accordance with the 7 criteria of the EN ISO 9241-110 (suitability for the task, suitability for learning, suitability for individualization, conformity with user expectations, self-descriptiveness, controllability and error tolerance). Both questionnaires offer scales for each usability criterion, but they differ in the amount of items (35 items in the Isonorm questionnaire, in comparison to 75 items in the Isometrics questionnaire), the wording of the items and the answering format. Although previous research has analyzed these questionnaires separately, little research has been devoted to improving our understanding of how these questionnaires differ and whether their results are comparable. To fill this gap, our study seeks to compare these two questionnaires regarding test theoretical criteria. Additionally, we investigate whether users prefer one questionnaire to another. Concerning test theoretical criteria, differences in objectivity are unlikely, as the administration and scoring of both questionnaires are detailed in the manuals. Still, differences in validity and reliability need further inquiry. To this end, we conducted an experiment in which we used the two questionnaires to evaluate two standard software packages. In the controlled two-group design, a total of 50 participants took part. The experiment was conducted via laptops, and the total duration was an average of 50 minutes per user. First, we acquainted the participants with one of the two statistical software packages in a usability test comprised of 14 tasks. To complete those tasks, the participants had to carry out different statistical procedures on a small data set, to eliminate input errors and to use the help functions. The tasks and instructions were constructed in a way to give participants an overview of as many different facets of the software as possible. Then, participants filled out both usability questionnaires. We used different scramblings to avoid order effects. Regarding the content validity of the questionnaires, the results showed a high agreement between usability measurements of the two questionnaires. According to an analysis of variance, the factor “questionnaire” did not have a significant influence on the usability measurement. For instance, results from both questionnaires showed that users rated one of the software packages better on the scale for controllability. Additionally, the scales of the questionnaires showed medium to high correlations. In general, participants who spent more time on the tasks rated the usability lower, which demonstrated the criterion-related validity of both questionnaires. Moreover, both questionnaires offer satisfying reliability, and there were only a few negatively worded items that would heighten reliability if excluded. According to individual preferences, half of the users thought that Isonorm was more enjoyable to answer, the other half preferred Isometrics; therefore, we cannot decisively conclude which questionnaire was more popular among users. However, participants needed more extensive knowledge of the software system to answer some items of Isometrics than to answer the items of Isonorm. As a typical example, to answer some items in the Isometrics questionnaire of the scale of “conformity with user expectations”, the users needed long-term experience with the software. In summary, our test-theoretical analyses indicate that the use of both questionnaires leads to similar results. Because we used only two different software packages in this experiment, one must generalize our findings with caution, and further research is necessary to validate our results. A possible direction for future inquiry emerges from our study. Since our data showed high intercorrelations between different usability scales in both questionnaires, a study that uses higher sample sizes might examine whether different usability criteria are measurable independently from each other or whether they can be explained with one general usability factor. In conclusion, based on our findings, both questionnaires can be recommended equally for research and practice from a test theoretical point of view.

Practical Relevance

The fact that different usability questionnaires are used in practice as well as in research begs the question of whether and to what extent evaluation results stemming from different questionnaires are comparable. The present work seeks to investigate this issue by comparing two widely used German usability questionnaires, Isonorm 9241/10 and Isometrics. From a practical perspective, the knowledge gained as a result of the present study can provide advice for practitioners and users, who have low test-theoretical backgrounds, to choose a questionnaire.

Development of an Instrument for Stress-related Job Analysis for Hospital Physicians

Author: Monika Keller, Eva Bamberg, Maren Böhmert, Albert Nienhaus

Keywords: job analysis, stressors, resources, hospital physicians

Summary

Empirical studies have revealed a variety of work-related stressors of hospital physicians, such as long working hours, time pressure, stressors in the interaction with patients as well as social stressors with colleagues and supervisors. These stressors affect hospital physicians' health and the quality of patient care. In order to improve the working conditions in hospitals, an instrument for stress-related job analysis for hospital physicians was developed. Accordingly, the instrument was developed as a self-report survey questionnaire.

The questionnaire's conceptual framework is an extended model of transactional stress that differentiates between situational and personal stressors and resources (Lazarus & Launier 1981; Bamberg et al. 2003). This conceptual framework allows integrating further occupational stress theories, such as action theory.

The questionnaire for hospital physicians focuses on work-related stressors and resources. It comprises situational stressors, such as time pressure, uncertainty and frustration about how work needs to be done as well as long working hours and shifts. Furthermore, stressors in the interaction with patients are included, i.e. social stressors with patients and relatives and emotional dissonance. The questionnaire also contains situational resources like autonomy, options for skill development, participation and environmental conditions in hospitals. In addition, it includes scales about the social environment at work, such as supervisor and coworker support as well as respect and appreciation.

The questionnaire is based on the German Instrument for Stress-related Job Analysis (ISTA; Semmer 1984). Items were adapted from the ISTA, the Frankfurt Emotion Work Scales (Zapf et al. 2003b), a social support scale (Frese 1989) and a questionnaire on work climate (v. Rosenstiel et al. 1983; v. Rosenstiel et al. 1992). For a number of stressors and resources no validated scales that met the hospital physicians' working conditions were available. Hence, new items had to be developed.

The questionnaire was developed in multiple steps. First, the current situation of hospital physicians was analysed in 12 interviews and 3 job observations with a heterogeneous group of hospital physicians. Based on these preliminary analyses, a first draft of the questionnaire was developed and further revised in 13 interviews with hospital physicians. Subsequently, 45 hospital physicians were consulted in a pilot survey which resulted in a first version of the instrument for stress-related job analysis for hospital physicians. This version contained 27 scales with 158 items.

In the main study an online survey with 702 hospital physicians was conducted. Explorative factor analyses − principal component analyses with promax rotation − revealed that most of the theoretically derived scales were confirmed. Only few of the newly developed items loaded on different factors. Two new factors emerged.

In the next steps, the questionnaire was shortened. First, the number of items in the scales was reduced on several criteria, i.e. internal consistencies, item-total correlations and face validity. Subsequently, entire scales were deleted from the questionnaire. Selection criteria for that were based on zero order correlations and multiple regression analyses with different outcome variables on health, well-being and personal accomplishment.

Finally, the questionnaire included 23 scales with 84 items. A first examination of the scales showed satisfactory results for the descriptive statistics, internal consistencies and item-total correlations. Nevertheless, another survey should be conducted to validate the questionnaire.

In conclusion, the instrument for stress-related job analysis for hospital physicians is a questionnaire which is based on occupational stress conceptual framework and which contains a variety of stressors and resources related to the working conditions of hospital physicians. All scales are correlated with negative health outcomes and/or personal accomplishment. The development of an instrument especially for hospital physicians gives differentiated insight on specific working conditions in hospitals and allows comparing the work situation across medical specialties, hospitals and departments.

Practical Relevance

The newly developed questionnaire gives hospitals the opportunity to identify problematic working conditions for hospital physicians. Based on the results of a sound job analysis interventions can target the specific challenges in hospitals and improve the working conditions for hospital physicians.

Does the impact of learning-promoting job design depend on employee’s age?

Author: Falk Richter

Keywords: Ageing, competence development, work ability, learning-promoting job design, age-differentiated job design

Summary

Although meta-analyses show zero correlations between age and job performance on average (McEvoy & Cascio 1989; Ng & Feldman 2008; Sturman 2003; Waldman & Avolio 1986) negative stereotypes and prejudices toward older employees are still very popular (Krings & Kluge 2008).

Of course there are personal performance characeristics related to fluid intelligence that decrement with age: speed of information processing, reaction time (increasing) and cognitive flexibility. But there are also performance characteristics related to crystallized intelligence and personality that are widely seen as stable or growing over job biography: knowledge, experience, handling of complexity, conscientiousness and social skills (Baltes & Baltes 1989; Lindenberger & Staudinger 2006; Lehr 2000; Naegele 1992).

Meta-analyses on correlations between age and job performance refer to a great variety of coefficients (e.g. McEvoy & Cascio 1989: -0.44 to +0.66) – indicating the influence of moderator variables. Although meta-analyses could not show evidence for moderator effects there are many references confirming the importance of job characteristics such as autonomy and skill variety for competence-related personal characteristics (for an overview: Baitsch 1998; Bergmann 2000).

Current literature often focuses primarely on differences between young and old people indicating different work tasks and design of work places for younger and older employees (e.g. Kanfer & Ackerman 2004; Sonntag & Stegmaier 2007). But: Should work tasks really be designed differentiated for people of different ages? Especially: Does age influence the relation between learning-promoting job design and job-related competence of employees?

This study has another focus and other assumptions: It is expected that the impact of learning-promoting job design on competence is stronger than the impact of age. Furthermore it is assumed that learning-promoting job design is positively related to indicators of competence and work ability for younger as well as for older employees.

For that purpose a sample of 904 employees from different sectors (banks, insurance, industry, education, consulting, health services) was asked to assess characteristics of work tasks (decision latitude, variety of demands, transparency and feedback) as well as competence-related personal characteristics (individual demands on job design, developmental objectives, learning activities, professional, methodical and social competence, self-efficacy, involvement and work ability). The influence of learning-promoting job design vs. age and possible moderating effects of age were calculated using moderated hierarchical regression analysis (Aiken & West 1992).

Results refer to a significant positive impact of job design on all considered personal characteristics. The effect of job design on competence-related personal characteristics is higher than the effect of age – except for developmental objectives. Age is significantly negatively related to individual demands on job design, developmental objectives, learning activities, professional competence and work ability. Age is significantly positively related to methodical competence, self-efficacy and involvement. There is no significant influence of age on social skills. There is also no moderating effect of age concerning the relation between learning-promoting job design and competence. Learning-promoting job design is significantly positively related to competence-related personal characteristics even if employees are younger or older.

Special attention must be given to the negative correlation between age and developmental objectives. Developmental objectives are related to future situations apart from current work tasks. On the one hand with higher age formerly aspired positions may already be reached and objectives far from career may become more important (Carstensen 2006). Otherwise less ambitious objectives may also result from resignation because of less developmental opportunities and less support for older employees (Baron & Stamov-Roßnagel 2010).

The results of this study are highly topical because of actual transitions to flexible work associated with inadequate conditions for learning at the job especially in the growing field of temporary work (DGB-Index Gute Arbeit 2008; Pietrzyk 2004). But also in other fields that are not related to precarious jobs a renaissance of elements of tayloristic job design is observable because of increasing competition (Deuse, Schallow & Sackermann 2009; Frieling, Buch & Wieselhuber 2006).

Practical relevance

Considering the results of this study an age-differentiated job design regarding aspects as job control and job variety is not indicated for preservation and development of employee’s work ability and competence. Independently of employee’s age a learning-promoting job design should be focused to handle the challenges of demographic change at work.

Working time of the ageing workforce. Lessons learned from the KRONOS research project

Author: Peter Knauth, Dorothee Karl, Kathrin Elmerich

Keywords: demographic change, shift work, part-time work, optional working time, long-term accounts

Summary

Under the DFG-sponsored KRONOS research project, working-time models for the ageing workforce were developed, implemented, and evaluated in six German companies from the automobile, steel, pharmaceutical and chemical industries. This paper presents a summary of the lessons learned from a total of ten sub-projects in each of the following working-time design field.

a) Number of working hours per day, week or year

Uniformly reducing the daily working hours of all older employees does not make sense as personal health and work ability vary very widely among individuals in the older age groups.

b) Adequate rest periods

Older employees tend to rate the recovery value of breaks less highly than younger workers. This appears to corroborate the demand for more breaks for elderly persons.

c) Shift work

Shift systems designed to conform to ergonomic recommendations (fast forward rotation) tend to have a more favourable effect on work ability (WAI) than traditional shift systems that rotate backwards once a week. As the night shift is the most critical of all as far as sleep, tiredness, performance, and health are concerned, it makes sense to reduce the number of night shifts per person and year. One way to reduce night shift manning levels is to reschedule certain activities from the night to the morning and afternoon shifts.

d) Employee influence on working-time design

Models that permit employees to switch between various weekly or annual working times in the course of their active life are meaningful and attractive not only to older workers but also to younger employees who might wish for more leisure time.

e) Long-term time accounts

From the ergonomic point of view, sabbaticals that promote regeneration make more sense than models under which employees work very many hours of overtime to enable them to retire early later on, when their health may already have been impaired. Options to pay into and withdraw from long-term time accounts must be tailored to the needs of the target groups.

f) Beginning and end of the daily working time

If the morning shift begins too early (before 6 a.m.), this will have a negative impact on the quality of sleep before the morning shift as well as on a person's tiredness and reaction time during it.

Practical Relevance

An important outcome was, that there is no such thing as an “ideal” working-time model for an ageing workforce because, first there is a great inter-individual scatter in the work ability and the working-time preferences of the employees and second companies follow different objectives with regard to operating hours and adaptation to demographic change. This is why working-time models need to be tailor-made.

Factors of essential importance for the success of ageing-appropriate working-time models include:

1. giving consideration to ergonomic recommendations,

2. giving employees an opportunity to influence the design of their working time

3. ensuring favourable framework conditions (e.g. managerial attitudes, adequate participatory strategies of introduction), and

4. integrating all constituent projects into a corporate master strategy to deal with demographic change.