Enhancing the impact of ergonomics interventions

The aim of this paper was to provide recommendations for ergonomists involved in project design and evaluation. Twelve research and consultancy projects involving ergonomics interventions in a variety of settings in The Netherlands were analysed to identify factors important to success. Projects included participatory and non-participatory cases. Eight factors were identified for successful project design and for demonstrating project effectiveness.     

Early traces of usability as a science and as a profession

Shackel’s paper [Shackel, B., 1991. Usability – context, framework, definition, design and evaluation. In: Shcakel, B., Richardson, S. (Eds.), Human Factors for Informatics Usability. Cambridge University Press, Cambridge, UK] is reviewed in an attempt to assess his contribution to the development of usability as a science and as a profession. Usability related research is first situated in the period around 1990. The contributions to usability as a science then are addressed via Professor Shackel’s definition and evaluation of usability. Finally, his contribution toward usability as a profession is acknowledged via his view of usability in the light of wider business goals.     

Culture,politics and ergonomics

The beginning of a new century is an appropriate moment to consider the role of ergonomics in relation to the problems facing society. To help solve these serious global problems, ergonomics needs to be open to new disciplines, particularly those in the social sciences. Also, it may be difficult to generalize research on human-centred sociotechnical design without taking into account national characteristics, economics and political constraints. Currently there is more interest than ever in what ergonomics has to offer, but to deliver its promise requires a much broader approach than is usual. By adopting such new approaches one may help solve both the problems of the overdeveloped post-industrial societies and those of the societies of the Third World, where a new approach to work and economics may provide an improved chance for development given the recent changes in global economic policy.     

Improving engineering design- contributions of cognitive ergonomics

Engineering design is analysed in terms of design problem-solving. Engineering designers of differing productivity hardly differ in mental abilities, especially their tested intelligence. However, they differ in their strategies concerning the analysis of requirements and of the problem, in their search for general principles solving the relevant problem, and in the procedures used for developing specific solutions. Experimental and interview results stress that the interrelationship of thinking and sketching, as well as other kinds of an early low-cost prototyping are of crucial importance for the efficiency of the problem-solving procedure and the result. Possibilities for assisting design problem-solving and to improve the training of designers are discussed.     

The effect of tool handle shape on hand muscle load and pinch force in a simulated dental scaling task

Work-related upper extremity musculoskeletal disorders, including carpal tunnel syndrome, are prevalent among dentists and dental hygienists. An important risk factor for developing these disorders is forceful pinching which occurs during periodontal work such as dental scaling. Ergonomically designed dental scaling instruments may help reduce the prevalence of carpal tunnel syndrome among dental practitioners. In this study, eight custom-designed dental scaling instruments with different handle shapes were used by 24 dentists and dental hygienists to perform a simulated tooth scaling task. The muscle activity of two extensors and two flexors in the forearm was recorded with electromyography while thumb pinch force was measured by pressure sensors. The results demonstrated that the instrument handle with a tapered, round shape and a 10 mm diameter required the least muscle load and pinch force when performing simulated periodontal work. The results from this study can guide dentists and dental hygienists in selection of dental scaling instruments.     

Marketing ergonomics to industrial designers

Conventional tungsten–filament brake lamps have a relatively slow rise time. It takes approximately 250 ms for them to reach 90% of their asymptotic luminous intensity. This slowness of response can cause important delays of warning information to following drivers. We have designed a simple and relatively inexpensive circuit that produces a faster warning signal using a conventional lamp. As we have reported previously, this device reduces reaction times to the onset of brake lamps by about 115 ms. The present study evaluated the benefits of a 115 ms reduction in driver brake reaction time. Two approaches were used. In the first approach we calculated the reductions in effective stopping distance assuming a range of initial speeds. The results indicate, for example, that if the initial speed is 100 km/h. the reduction in the effective stopping distance is 3–2 m. In the second approach we calculated the reductions in the proportions of very long reaction times, assuming a normal distribution of reaction times that is shifted by 115 ms. For the distribution without the device we assumed a mean of 1·25 s and a standard deviation of 0·46 s. The results indicate, for example, that decreasing the mean by 115 ms yields a 55% reduction in the frequency of reaction times that are longer than 2·5 s.     

A usability comparison of PDA-based quizzes and paper-and-pencil quizzes

In the last few years, schools and universities have incorporated personal digital assistants (PDAs) into their teaching curricula in an attempt to enhance students’ learning experience and reduce instructors’ workload. One of the most common uses of PDAs in the classroom is as a test administrator. This study compared the usability effectiveness, efficiency, and satisfaction of a PDA-based quiz application to that of standard paper-and-pencil quizzes in a university course. Effectiveness was measured as students’ quiz scores and through a mental workload questionnaire; efficiency was the time it took students to complete each quiz; and satisfaction was evaluated using a subjective user satisfaction questionnaire. The study showed the PDA-based quiz to be more efficient, that is, students completed it in less time than they needed to complete the paper-and-pencil quiz. No differences in effectiveness and satisfaction were found between the two quiz types. Computer anxiety was not affected by the quiz type. For these reasons, as well as other advantages to both students (e.g., real-time scoring) and teachers (e.g., less time spent on grading), PDAs are an attractive test administration option for schools and universities.     

The development of a theoretical framework and design tool for process usability assessment

The purpose of usability engineering is to facilitate the deployment of new products by decreasing development costs and improving the quality of systems. This paper will discuss the development and delivery of a unique, theoretically based software tool that provides engineers and designers with easy access to the most recent advances in human-machine interface design. This research combines several theoretical views of the interaction process into a hybrid model. Based on this model, a software tool was produced that allows engineers to model the human interaction process within their design. The system then provides feedback on the interaction process through items such as: the amount of mental effort required by a user, the degree to which the system conforms to human capabilities, the expected time to complete the interaction, where potential human error may occur, as well as potential misunderstandings or points of confusion to the users. The designer may then use this information to improve the design of the system. Validation of this technique indicates that the hybrid model produces accurate predictions of usability attributes and that the technique transfers from the laboratory to the real world.     

The evaluation of an innovative intelligent thermostat interface: universal usability and age differences

Usability trials were carried out with a simulation of an early version of an intelligent thermostat interface. The multimodal interaction dialog took place in speech, sound, graphics and touch. Usability of new concepts of interaction was assessed. Most user behavior and problems of use were equal for old and young subjects (between 25 and 73 years of age). Relative high usability was observed with the new interaction styles, in particular with the task-based dialog and with the suggestions given by the thermostat. Even the oldest subjects could accomplish complicated programming. Age-dependent differences in usability were found for certain interface details, such as finding a hidden menu item. The summarized typical "modern" interaction details, which caused problems, were significantly less usable for the older cohort (over 59 years of age), compared to the young (under 46 years of age). Electronic Publication     

The effects of tool handle shape on hand performance,usability and discomfort using masons' trowels

The effects of five new different handle shapes on hand performance capabilities, usability and discomfort, and also the relationship between these variables were evaluated in the context of masonry work and using masons’ trowels as an exemplar hand tool. The prototype handles were designed to provide different patterns of grip so that they could be suited to the hand/tool interaction in particular hand areas. The results showed significant effect of tool handle shape on the hand grip effort, usability, and hand and finger discomfort assessments, but not on the time to complete the masonry task. The hand grip effort and usability were negatively correlated with subjective assessment of hand and finger discomfort, so that a lower level of hand and finger discomfort corresponded to higher hand grip exertion and usability. These findings provide a better insight into the performance and usability issues when using hand tools which can be applied by tool manufacturers to improve industrial hand tool design.Relevance to industryThese findings present a unique insight into the handle design for industrial hand tool use and support the general conclusion that objective measurements should be supplemented by qualitative subjective assessments to provide a more holistic approach where specific and additional details about the hand tool design characteristics are incorporated from the workers' perspective.     

The influence of target torque and torque build-up time on physical stress in right angle nutrunner operation

This study used a computer-controlled electric right angle nutrunner to investigate the relative effects of different power hand tool and process parameters on operator muscular exertions, handle stability and subjective ratings of perceived exertion. Target torque (25, 40 and 55 Nm), torque build-up time (35, 150, 300, 500 and 900 ms), and workstation orientation (horizontal and vertical) were studied. Dependent variables included EMG activity of the finger flexors, biceps, and triceps, handle velocity and displacement, work done on the tool-hand system and power involved in doing work, subjective ratings of perceived exertion, and task acceptance. Six inexperienced subjects (three females and three males) participated. Ten replications were performed for each combination of experimental conditions. The consequences of increasing the torque reaction force were greater handle instability and perceived exertion. The effect of torque buildup time on handle kinematics, muscular activity and perceived exertion was not monotonic. Among five build-up times tested, the hand was most unstable (greater peak handle velocity and power against the operator) for a 150 ms buildup time. Greater peak handle displacement, total work against the operator and average EMG were observed for 150 and 300 ms build-up times than for other build-up time conditions. Integrated EMG and EMG latency significantly increased as build-up time increased. Average EMG latency between the onset of EMG burst and the onset of torque build-up was 40 ms for a 35 ms build-up time and 330 ms for a 900 ms build-up time. Subjective ratings of perceived exertion were the least when torque build-up time was 35 ms, however greater peak torque variance was associated with this condition.     

A framework for evaluating the usability of mobile phones based on multi-level, hierarchical model of usability factors

As a mobile phone has various advanced functionalities or features, usability issues are increasingly challenging. Due to the particular characteristics of a mobile phone, typical usability evaluation methods and heuristics, most of which are relevant to a software system, might not effectively be applied to a mobile phone. Another point to consider is that usability evaluation activities should help designers find usability problems easily and produce better design solutions. To support usability practitioners of the mobile phone industry, we propose a framework for evaluating the usability of a mobile phone, based on a multi-level, hierarchical model of usability factors, in an analytic way. The model was developed on the basis of a set of collected usability problems and our previous study on a conceptual framework for identifying usability impact factors. It has multi-abstraction levels, each of which considers the usability of a mobile phone from a particular perspective. As there are goal-means relationships between adjacent levels, a range of usability issues can be interpreted in a holistic as well as diagnostic way. Another advantage is that it supports two different types of evaluation approaches: task-based and interface-based. To support both evaluation approaches, we developed four sets of checklists, each of which is concerned, respectively, with task-based evaluation and three different interface types: Logical User Interface (LUI), Physical User Interface (PUI) and Graphical User Interface (GUI). The proposed framework specifies an approach to quantifying usability so that several usability aspects are collectively measured to give a single score with the use of the checklists. A small case study was conducted in order to examine the applicability of the framework and to identify the aspects of the framework to be improved. It showed that it could be a useful tool for evaluating the usability of a mobile phone. Based on the case study, we improved the framework in order that usability practitioners can use it more easily and consistently.     

Towards a comprehensive Functional Capacity Evaluation for hand function

The aim of this study was to develop a more efficient (i.e. shortened) protocol for hand function capacity evaluation and to test the agreement of the protocol compared to the original protocol. 643 Healthy subjects performed tests for hand function. Agreement between two shortened protocols was compared with an existing protocol. The original protocol was performed once and the proposed shortened protocol differed in the number of trials which were reduced by statistical elimination. Agreement was determined with Intraclass Correlation Coefficients (ICC) and Limits of Agreement (LoA). Excellent ICCs (≥0.91) were observed in all proposed protocols except for the one trial purdue pegboard test protocol. For all tests of hand function, shorter protocols are valid to determine hand function. For Tip Pinch Strength testing, Palmar Pinch Strength testing and the Purdue Pegboard test, a two-trial protocol is recommended, because the LoA were considerable, which could affect decision-making with regards to hand capacity. For the Hand Grip strength test, the Key Pinch Strength test and the Complete Minnesota Dexterity Test, a one-trial protocol is recommended, because the LoA were acceptable. It was concluded that for healthy subjects, this shorter protocol is a reliable measure. Further testing of the short form hand FCE protocols should be completed on patients with disabling conditions prior to widespread use of these protocols among clinical samples.     

Design aids for designers: an effective role for ergonomics

The paper describes, with examples taken from the mining industry, the role of ergonomics in providing design aids for designers. The examples cover: (a) The provision of ergonomics design guidelines for families of machines; (b) The use of subjective assessment by expert panels to evaluate alternative solutions to development proposals; (c) The development of a computer-based simulation which produces multiple activity charts for the evaluation of the performance potential of new coal face designs. It is suggested that ergonomics specifically directed to the provision of design aids for designers may be one of the most fruitful approaches available to ensure a wider implementation of ergonomics knowledge and practice.     

A test battery related to ergonomics of protective clothing

Specialised protective clothing, such as that worn by firefighters, is usually tested only to standards which give requirements for the materials used (e.g. EN469). However, this testing often neglects the effect the manufacturing process of the garment has on the material properties, the effects of clothing design, sizing and fit, as well as the interaction of the clothing with other components of the standard gear for the profession. Such effects can only be tested by looking at the protective gear as a whole. This paper deals with methods to do additional testing on protective garments with firefighter clothing as example. In other words, methods which go beyond EN469. Human subject tests for physiological load, heat protection, ergonomic design, loss of performance, rain/moisture protection and conspicuity/visibility of the clothing are described and proposed for evaluation of protective clothing in general and for further development of standards on firefighters' clothing.     

An empirical approach for evaluating the usability of model-driven tools

MDD tools are very useful to draw conceptual models and to automate code generation. Even though this would bring many benefits, wide adoption of MDD tools is not yet a reality. Various research activities are being undertaken to find why and to provide the required solutions. However, insufficient research has been done on a key factor for the acceptance of MDD tools: usability. With the help of end-users, this paper presents a framework to evaluate the usability of MDD tools. The framework will be used as a basis for a family of experiments to get clear insights into the barriers to usability that prevent MDD tools from being widely adopted in industry. To illustrate the applicability of our framework, we instantiated it for performing a usability evaluation of a tool named INTEGRANOVA. Furthermore, we compared the outcome of the study with another usability evaluation technique based on ergonomic criteria.     

A usability evaluation toolkit for In-Vehicle Information Systems (IVISs)

Usability must be defined specifically for the context of use of the particular system under investigation. This specific context of use should also be used to guide the definition of specific usability criteria and the selection of appropriate evaluation methods. There are four principles which can guide the selection of evaluation methods, relating to the information required in the evaluation, the stage at which to apply methods, the resources required and the people involved in the evaluation. This paper presents a framework for the evaluation of usability in the context of In-Vehicle Information Systems (IVISs). This framework guides designers through defining usability criteria for an evaluation, selecting appropriate evaluation methods and applying those methods. These stages form an iterative process of design–evaluation–redesign with the overall aim of improving the usability of IVISs and enhancing the driving experience, without compromising the safety of the driver.     

Participatory ergonomics in design processes: the role of boundary objects

The aim of this paper is to introduce the concept of boundary objects in order to better understand the role of objects in participatory ergonomics (PE) design processes. The research question is: What characterizes boundary objects in PE processes? Based on two case studies, we identify eight characteristics of boundary objects and their use, which make them particularly useful in PE design processes. These characteristics go beyond the object itself and extend into the context of their use. We argue that the selection of boundary objects in PE processes is of great importance, since different objects enable workers’ participation and collaborative design in different ways. The framework developed may serve to provide criteria to guide practitioners and intervention researchers in the selection of objects to facilitate a PE process. The paper concludes with a list of recommendations for ergonomic practitioners that are based on the framework.     

Snap-on-handles for a non-powered hacksaw: An ergonomics evaluation,redesign and testing

In this study, we investigated how experienced and inexperienced subjects handle a box when it could be approached from any of its sides. Subjects moved a box (11 kg) either to a high (HS) or a low surface (LS). Wrist movements and grip force were synchronised and recorded, respectively, by electrogoniometers and an instrumented box. All subjects adopted a lateral-and-bottom grip, with parts of the hands simultaneously placed on the side and bottom of the box. This grip allowed the 50th percentile of wrist movements to be within safe limits, particularly in the sagittal plane. Low force was associated with lowering the box to LS and equally distributed but greater force when lifting to HS. Larger ulnar deviation was recorded when the box was lifted to HS. Only peak of wrist extension differentiated experienced from inexperienced subjects, with experienced presenting larger wrist extension. Alternative box designs are suggested to improve handling in real settings. PRACTITIONER SUMMARY: Understanding worker preferences for box lifting behaviour can contribute to the development of new designs that facilitate the adoption of more efficient postures while reducing the risk of upper-limb musculoskeletal disorders and promoting safer manual material handling.     

User-oriented evaluation of mechanical single-channel axial pipettes

Hand tools should be designed so that they are comfortable to use, fit the hand and are user-oriented. Six different manual, single-channel axial pipettes were evaluated for such objective outcomes as muscular activity, wrist postures and efficiency, as well as for subjective outcomes concerning self-assessed features of pipette usability and musculoskeletal strain. Ten experienced laboratory employees volunteered for the study. The results showed that light and short pipettes with better tool comfort resulted in reduced muscular activity and perceived musculoskeletal strain when they were compared with a long and heavy pipette. There were no differences in the efficiency between the different pipettes. Combining both the objective and subjective measures enabled a broader evaluation of product usability. The results of this study can be used both in product development and as information on which to base the purchase of new pipettes for laboratory work.