Miguel L. Lourenço

Horizontal and Vertical Handheld Pointing Devices Comparison for Increasing Human Systems Integration at the Design Stage

In addition to postural and biomechanical aspects related to usage of handheld pointing devices it is also important to perform usability assessment. The paper reports on an experimental study comparing two computer pointing devices, a standard horizontal PC mouse and a vertical device (for neutral pronation of the forearm), both commercially available. The standardized tasks implemented by software and performed by 20 experienced computer mouse users included pointing, dragging and steering. The usability parameters of effectiveness and efficiency were calculated and the participants subjectively assessed their discomfort, effort and ease of use in relation to each device in each task. Efficiency and effectiveness were higher for the horizontal device. Assessments of discomfort, effort and ease of use across the different tasks also supported the consideration of preference for the horizontal device in detriment of the vertical model. The results suggest that designing hybrid configurations may configure a better compromise.

Working conditions under multiple exposures: A cross-sectional study of private sector administrative workers.

BACKGROUND Office workers are increasingly exposed to physical and psychosocial risk factors. OBJECTIVE To assess the association between environmental, physical and organizational working conditions and the physical and psychosocial well-being of a sample of private sector office workers. METHODS Musculoskeletal pain was collected from a body map and the Disabilities of the Arms, Shoulders and Hands questionnaire. The short version of the Copenhagen Psychosocial Questionnaire enabled collecting information on six job related satisfaction and dissatisfaction subscales. A checklist for ergonomics in computer work guided the analysis of ergonomic factors and measurements were taken to characterize environmental conditions. Association between exposures and outcomes was calculated using IBM SPSS Statistics 20 software. RESULTS Significant moderate positive association was found between dissatisfaction with job psychological demands and musculoskeletal pain in the upper body (0.40; p= 0.05), as well as between postural ergonomic mismatches and dissatisfaction with job insecurity towards the future (0.42; p= 0.04). A significant moderate negative association (-0,47; p= 0.02) was found as well between satisfaction with job social support and with leadership quality and location of the work station in an open-plan office as opposed to smaller office rooms. CONCLUSIONS The results show how raising awareness of the risk factors encountered in contemporary office work is still necessary to promote widespread improvement of working conditions, from both a physical and a psychosocial perspective.

Improving occupational health by modelling indoor pollutant distribution

Purpose Indoor environments are characterized by several pollutant sources. Some of these can be sufficiently characterized through the prediction of the airflow and pollutant distribution patterns. The purpose of this study was to simulate, analyze and compare different locations of known pollutant source inside a ventilated room. Design/methodology/approach Computational fluid dynamics modelling approach was used to analyze the prediction of the airflow and pollutant distribution patterns for different locations of known pollutant source inside a ventilated room by mixing ventilation. Findings Distinct areas of poor air quality, perfectly identified by concentration fields, were given. The indoor air quality obtained by the different simulated conditions was analyzed and compared. Research limitations/implications Pollutant concentration was not measured in the validation experiments (qualitative validation based on the velocity fields). Practical implications Once the contaminant concentration fields are calculated based on the source location, the model is very useful to choose the best place to install any pollutant indoor equipment to preserve breathing zones. Originality/value Providing an effective indoor air quality assessment to prevent exposure risk. The results would be useful for making decisions to optimize the design procedure, such as establish the best location to install polluting equipment, occupied areas and their interdependence with ventilation systems. In addition, this tool also helps to choose the best location and correct set point adjustment for the pollutant sensors.

S-EMG of Forearm Muscles Activity in Conventional PC Mouse Use

Prevalence of static muscular activity is believed to represent a higher risk for musculoskeletal health than dynamic muscular activity. PC mouse usage is a kind of activity where static muscle activation levels, while low in general, can indicate potential for musculoskeletal disorders. The study reported in this paper proposes a forearm four muscle approach to evaluation of muscular activity during mouse use, describing the rationale for selection of the muscles monitored. Additionally, signal processing is also characterized in the paper. The paper also presents results of surface electromyography assessment of 20 participants interacting with a conventional type of PC mouse. Analysis of the electromyographic signals was performed via a procedure of Amplitude Probability Distribution Function (APDF) calculation for the 90th, 50th and 10th percentiles. Average APDF90 values of muscular activity as a percentage of Maximum Voluntary Contraction found were between 7% and 21%.

Research Methodologies in the Ergonomic Development and Evaluation of PC Mice

Framing research within a methodology supports the planning which guides the research process. The process design defines a plan where research strategies aim collection of data and respective methods of analysis, in order to provide answers to research questions. This paper describes the research process conducted in the experimental and design work conducive to the doctoral dissertation by Lourenco [1] focusing on the development and ergonomic analysis of new PC mice. This research was framed within positivism, associated to exact sciences, adopting a structured research methodology, enabling enhanced replicability. The aim of this paper is report on research methodology, in particular in what concerns the intertwined research methodologies and associated research questions involved in the development and ergonomic evaluation of PC mice. The taxonomy of research approaches proposed by Jarvinen [2] is the basis for the classification of the research methodology presented.

Development of a New Ergonomic Computer Mouse

Developing a new computer pointing device abiding to the requirements set out in ergonomics literature necessitates joining contributions from several areas including the systematization recommended for product design projects, ergonomic recommendations and principles and guidelines applicable to hand tools as well as anthropometric considerations. The development of new geometries for computer pointing devices constitutes a complex process as these are simultaneously hand tools, enabling the interaction with the computer, and at the same time, meant for use by people from both sexes and practically all ages, as its use today is practically ubiquitous. The paper reports on a study aimed at developing an innovative PC mouse geometry supported by literature review and an adequate design methodology. In particular, reducing forearm pronation was set as a goal for the new design.

A Pilot Naturalistic Study of PC Mouse Usability

An uncontrolled study took place in course settings with 30 3rd year undergraduates. Standard graphical tasks were generated from dedicated software. Subjects used their own and other subjects’ pointing devices. Pointing efficiency was calculated within each 2 to 4 subjects group. Hypothetically, subjects would not experience improved efficiency in pointing and dragging tasks when switching to other devices from their own device. The other devices might share the archetype of the owned device, but differ in dimensions and shape details, or activation thresholds. Reasons are suggested for cases where the hypothesis is not verified in the results. Literature review and prior experimental results tentatively explains the subjects’ improvement in efficiency when changing to unfamiliar pointing devices. Familiarity with the tasks and improved fitness with borrowed device are potential motivators for efficiency gains observed that do not comply with the hypothesis. A snapshot of PC mice used by students is provided.

Psychosocial and ergonomic survey of office and field jobs in a utility company

Introduction. The effect of different kinds of work on the psychosocial assessment of workers under the same management and organizational environment is investigated. Methods. A voluntary assessment in a utility company was carried out using the short version of the Copenhagen psychosocial questionnaire (CoPsoQ) on two occasions, 1.5 years apart. Initially, 25 office workers (11 men and 14 women) participated, while 14 of those workers (8 women and 6 men) participated in the second assessment together with 32 field workers. The sewage, water treatment and maintenance workers, totaling 32 men, also participated in a field ergonomics assessment using the Washington State Department of Labor and Industries field work ergonomic checklist. Results. The longitudinal outlook was fairly stable, with sustained severe scores in many CoPsoQ subscales and intensification of severity of workers’ control over work and esteem for men. A significantly higher esteem score resulted for field rather than office workers. Workers subjected to foul odors showed similar severity of psychosocial factors. Discussion. For most psychosocial dimensions, the organizational design and management system in place, as well as the overall cultural environment in which it operates, create a much stronger and more decisive impact than job-specific factors.

Psychometric Analysis of Scales for Usability Evaluation of Pointing Devices

Usability evaluation involves measuring user performance (effectiveness and efficiency) and registering the user’s perception of satisfaction related aspects. The paper reports on a method for assessing the satisfaction component, in computer handheld pointing devices, through a series of ratings related to three dimensions: comfort (discomfort), ease of use (per task performed) and effort (gripping, pointing, clicking). Cronbach’s alpha is obtained as an estimate of the reliability of the assessment method made up of the multiple attribute evaluation of discomfort, ease of use and effort, based on Likert scales. Results revealed high values of internal consistency within each subjective dimension. Increased internal consistency would be obtained by removing the shoulder discomfort attribute from the discomfort evaluation questionnaire, and gripping and clicking attributes from the effort evaluation questionnaire. These divergences indicate that participants perceived these attributes as fundamentally different from the rest of the attributes within the evaluation dimensions.