Jan Dul

A strategy for human factors/ergonomics: developing the discipline and profession

Human factors/ergonomics (HFE) has great potential to contribute to the design of all kinds of systems with people (work systems, product/service systems), but faces challenges in the readiness of its market and in the supply of high-quality applications. HFE has a unique combination of three fundamental characteristics: (1) it takes a systems approach (2) it is design driven and (3) it focuses on two closely related outcomes: performance and well-being. In order to contribute to future system design, HFE must demonstrate its value more successfully to the main stakeholders of system design. HFE already has a strong value proposition (mainly well-being) and interactivity with the stakeholder group of ‘system actors’ (employees and product/service users). However, the value proposition (mainly performance) and relationships with the stakeholder groups of ‘system experts’ (experts fromtechnical and social sciences involved in system design), and ‘system decision makers’ (managers and other decision makers involved in system design, purchase, implementation and use), who have a strong power to influence system design, need to be developed. Therefore, the first main strategic direction is to strengthen the demand for high-quality HFE by increasing awareness among powerful stakeholders of the value of high-quality HFE by communicating with stakeholders, by building partnerships and by educating stakeholders. The second main strategic direction is to strengthen the application of high-quality HFE by promoting the education of HFE specialists, by ensuring high-quality standards of HFE applications and HFE specialists, and by promoting HFE research excellence at universities and other organisations. This strategy requires cooperation between the HFE community at large, consisting of the International Ergonomics Association (IEA), local (national and regional) HFE societies, and HFE specialists. We propose a joint world-wide HFE development plan, in which the IEA takes a leadership role. Practitioner Summary: Human factors/ergonomics (HFE) has much to offer by addressing major business and societal challenges regarding work and product/service systems. HFE potential, however, is underexploited. This paper presents a strategy for the HFE community to strengthen demand and application of high-quality HFE, emphasising its key elements: systems approach, design driven, and performance and well-being goals.

Muscular synergism. II: A minimum-fatigue criterion for load sharing between synergistic muscles

P6new physiological criterion for muscular load sharing is developed. The criterion is based on the assumption that the endurance time of muscular contractions is maximized, hence muscular fatigue is minimized. The optimization problem is cast in the form of a linearly constrained, non-linear MINIMAX optimization. The new method predicts that: (1) there is synergistic muscle action, (2) muscle force increases non-linearly with external force (load), (3) relatively more force is allocated to muscles that have a large maximum force (large muscles), (4) relatively more force is allocated to muscles with a high percentage of slow-twitch fibers (muscles that are fatigue-resistant), (5) the load sharing does not depend on the moment arm of the muscles (although the absolute force levels do depend on this variable). The predicted load sharing between two cat muscles during standing and walking is in good agreement with direct force measurement data from the literature.

Ergonomics contributions to company strategies

Managers usually associate ergonomics with occupational health and safety and related legislation, not with business performance. In many companies, these decision makers seem not to be positively motivated to apply ergonomics for reasons of improving health and safety. In order to strengthen the position of ergonomics and ergonomists in the business and management world, we discuss company strategies and business goals to which ergonomics could contribute. Conceptual models are presented and examples are given to illustrate: (1) the present situation in which ergonomics is not part of regular planning and control cycles in organizations to ensure business performance; and (2) the desired situation in which ergonomics is an integrated part of strategy formulation and implementation. In order to realize the desired situation, considerable changes must take place within the ergonomics research, education and practice community by moving from a health ergonomics paradigm to a business ergonomics paradigm, without losing the health and safety goals.

Dutch Musculoskeletal Questionnaire: description and basic qualities

A questionnaire (‘Dutch Musculoskeletal Questionnaire’, DMQ) for the analysis of musculoskeletal workload and associated potential hazardous working conditions as well as musculoskeletal symptoms in worker populations is described and its qualities are explored using a database of 1575 workers in various occupations who completed the questionnaire. The 63 questions on musculoskeletal workload and associated potentially hazardous working conditions can be categorized into seven indices (force, dynamic and static load, repetitive load, climatic factors, vibration and ergonomic environmental factors). Together with four separate questions on standing, sitting, walking and uncomfortable postures, the indices constitute a brief overview of the main findings on musculoskeletal workload and associated potentially hazardous working conditions. Homogeneity of the indices is satisfactory. The divergent validity of the indices is fair when compared with an index of psychosocial working conditions and discomfort during exposure to physical loads. Worker groups with contrasting musculoskeletal loads can be differentiated on the basis of the indices and other factors. With respect to the concurrent validity, it appears that most indices and factors show significant associations with low back and/or neck shoulder symptoms. This questionnaire can be used as a simple and quick inventory for occupational health services to identify worker groups in which a more thorough ergonomic analysis is indicated.

Muscular synergism—I. On criteria for load sharing between synergistic muscles

The use of optimization techniques to predict individual muscle forces in redundant biomechanical systems implies the formulation of a criterion for load sharing between the muscles. In part I of this paper, the characteristics and performance of several linear and non-linear criteria reported in the literature have been compared for static-isometric knee flexion. The results show that linear criteria inherently predict discrete muscle action (orderly recruitment of muscles) whereas non-linear criteria can predict synergistic action. All criteria predict that relatively more force is allocated to muscles with large moment arms. When muscle stresses (or ratios of muscle force to maximum muscle force) are used as the decision variables in the objective function, then relatively more force is allocated to muscles with large maximum possible force as well. Future formulations of the optimization should consider the differences in fiber type composition among the muscles. Such an approach is presented in part II of the paper.

Human factors: spanning the gap between OM and HRM

Purpose – The purpose of this paper is to examine the claim that the application of human factors (HF) knowledge can improve both human well‐being and operations system (OS) performance.Design/methodology/approach – A systematic review was conducted using a general and two specialist databases to identify empirical studies addressing both human and OS effects in examining manufacturing OS design aspects.Findings – A total of 45 empirical studies were found, addressing both the human and system effects of OS (re)design. Of those studies providing clear directional effects, 95 percent showed a convergence between human effects and system effects (+, + or −,−), 5 percent showed a divergence of human and system effects (+,− or −,+). System effects included quality, productivity, implementation performance of new technologies, and also more “intangible” effects in terms of improved communication and co‐operation. Human effects included employee health, attitudes, physical workload, and “quality of working life...

Work environments for employee creativity

Innovative organisations need creative employees who generate new ideas for product or process innovation. This paper presents a conceptual framework for the effect of personal, social-organisational and physical factors on employee creativity. Based on this framework, an instrument to analyse the extent to which the work environment enhances creativity is developed. This instrument was applied to a sample of 409 employees and support was found for the hypothesis that a creative work environment enhances creative performance. This paper illustrates how the instrument can be used in companies to select and implement improvements. Statement of Relevance:The ergonomics discipline addresses the work environment mainly for improving health and safety and sometimes productivity and quality. This paper opens a new area for ergonomics: designing work environments for enhancing employee creativity in order to strengthen an organisations capability for product and process innovation and, consequently, its competitiveness.

A participatory ergonomics approach to reduce mental and physical workload

A step-by-step approach to better work, aimed at reducing mental and physical workload in office work, is evaluated. This approach is based on a strong commitment of the management in the enterprise, and on as much direct worker participation as possible. After every step the workers proposed how to continue and a steering group led by the management decided on this proposal. The workers identified the problems, developed ideas for improvement, tested improvements and chose them. As a result, most workplaces were adjusted and more than half of the subjects took organizational measures. The approach was considered worthwhile, despite the fact that it is time consuming because it took about one year to arrive at better working conditions. Relevance to industry. Reduction of physical and mental workload is often pursued in industry. In this paper an approach is described which has been successful in implementing improvements aimed at reduction of mental and physical workload. A step-by-step approach to better work, aimed at reducing mental and physical workload in office work, is evaluated. This approach is based on a strong commitment of the management in the enterprise, and on as much direct worker participation as possible. After every step the workers proposed how to continue and a steering group led by the management decided on this proposal. The workers identified the problems, developed ideas for improvement, tested improvements and chose them. As a result, most workplaces were adjusted and more than half of the subjects took organizational measures. The approach was considered worthwhile, despite the fact that it is time consuming because it took about one year to arrive at better working conditions.

A kinematic model of the human ankle

The spatial gross motion of the foot with respect to the shank is modelled as rotations about two fixed ankle axes: the upper ankle rotation axis (plantar flexion/dorsiflexion) and the subtalar rotation axis (inversion/eversion). The positions of the axes are determined by externally visible bony landmarks of the lower leg, and are measured for a living subject. The model input data are the plantar flexion/dorsiflexion and inversion/eversion rotation angles; the model output is a 4 X 4 transformation matrix which quantitatively describes the relative position of a foot coordinate system with respect to a shank coordinate system.

Recommended maximum holding times for prevention of discomfort of static standing postures

The aim of the present study was threefold; (1) to analyze the influence of posture on the maximum holding time (MHT), (2) to study the possibility of classifying postures on the basis of MHT, and (3) to develop ergonomic recommendations for the MHT of categories of postures. For these purposes data concerning the MHT of 19 symmetric standing postures from 7 experimental studies from the literature were analyzed. All postures were defined by the position of the hands with respect to the feet. For each posture the mean MHT over all available data was calculated. The results show that for the 19 postures this mean MHT ranges from 2 to 35 minutes. For a given posture the variation in MHT between different studies is large. It seems that in particular the type of task (boring versus interesting) performed while maintaining the posture has a great influence on the MHT. On the basis of the mean MHT postures were classified into three classes. Comfortable postures are defined as postures that have a MHT of more than 10 minutes and are recommended not to be maintained more than 2 minutes. Moderate postures have a MHT of 5-10 minutes and are recommended to be maintained for less than 1 minute. Uncomfortable postures, having a MHT up to 5 minutes, are not acceptable. It is estimated that with theses recommendations a discomfort of more than 2 (weak discomfort) on the Borg 10-point rating scale (up to maximum discomfort) is prevented for at least 50% of the population, and a discomfort of more than 5 (strong discomfort) is prevented for at least 95% of the population. The recommended holding time valid for each class corresponds with the lowest recommended holding time of that class. Therefore the recommendations are safe for all postures. Our classification of postures corresponds well with classifications based on biomechanical and anthropometric data and is more strict than the OWAS-classification. The maximum holding time (MHT) was categorically studied to analyze its influence on postures, classify postures based on MHT and to develop ergonomic recommendations for MHT. Postures were based on the mean MHT. Comfortable postures have more than 10 minutes MHT and recommended not to be maintained for more than 2 minutes. Moderate postures have 5-10 minutes MHT and were recommended to be maintained for less than 1 minute. Uncomfortable postures with a 5-minute MHT were not accepted. These recommendations have prevented discomfort of more than 2 (weak discomfort) on the Borg 10-point rating scale for at least 50% of the population, and a discomfort of more than 5 (strong discomfort) was prevented for at least 95% of the population.