Showing papers in "Ergonomics in 2015"
TL;DR: This work provides a general overview of the current state of affairs regarding the understanding, measurement and application of MWL in the design of complex systems over the last three decades, and discusses contemporary challenges for applied research.
Abstract: Mental workload (MWL) is one of the most widely used concepts in ergonomics and human factors and represents a topic of increasing importance. Since modern technology in many working environments imposes ever more cognitive demands upon operators while physical demands diminish, understanding how MWL impinges on performance is increasingly critical. Yet, MWL is also one of the most nebulous concepts, with numerous definitions and dimensions associated with it. Moreover, MWL research has had a tendency to focus on complex, often safety-critical systems (e.g. transport, process control). Here we provide a general overview of the current state of affairs regarding the understanding, measurement and application of MWL in the design of complex systems over the last three decades. We conclude by discussing contemporary challenges for applied research, such as the interaction between cognitive workload and physical workload, and the quantification of workload ‘redlines’ which specify when operators are approachi...
578 citations
TL;DR: A sociotechnical model of workplace safety with concentric layers of the work system, socio-organisational context and the external environment is developed and the future challenges that are identified through the model are highlighted.
Abstract: Traditional efforts to deal with the enormous problem of workplace safety have proved insufficient, as they have tended to neglect the broader sociotechnical environment that surrounds workers. Here, we advocate a sociotechnical systems approach that describes the complex multi-level system factors that contribute to workplace safety. From the literature on sociotechnical systems, complex systems and safety, we develop a sociotechnical model of workplace safety with concentric layers of the work system, socio-organisational context and the external environment. The future challenges that are identified through the model are highlighted.
216 citations
TL;DR: Study results suggest that text messaging, which is one of the most frequently used app categories of smartphone, could be a main contributing factor to the occurrence of neck pain of heavy smartphone users.
Abstract: Repetitive or prolonged head flexion posture while using a smartphone is known as one of risk factors for pain symptoms in the neck. To quantitatively assess the amount and range of head flexion of smartphone users, head forward flexion angle was measured from 18 participants when they were conducing three common smartphone tasks (text messaging, web browsing, video watching) while sitting and standing in a laboratory setting. It was found that participants maintained head flexion of 33–45° (50th percentile angle) from vertical when using the smartphone. The head flexion angle was significantly larger (p < 0.05) for text messaging than for the other tasks, and significantly larger while sitting than while standing. Study results suggest that text messaging, which is one of the most frequently used app categories of smartphone, could be a main contributing factor to the occurrence of neck pain of heavy smartphone users.Practitioner Summary: In this laboratory study, the severity of head flexion of smartpho...
211 citations
TL;DR: An up-to-date review of STS methods, a set of case studies illustrating their use and an evaluation of their strengths and weaknesses are provided, as well as a ‘roadmap’ for future work.
Abstract: An important part of the application of sociotechnical systems theory (STS) is the development of methods, tools and techniques to assess human factors and ergonomics workplace requirements. We focus in this paper on describing and evaluating current STS methods for workplace safety, as well as outlining a set of six case studies covering the application of these methods to a range of safety contexts. We also describe an evaluation of the methods in terms of ratings of their ability to address a set of theoretical and practical questions (e.g. the degree to which methods capture static/dynamic aspects of tasks and interactions between system levels). The outcomes from the evaluation highlight a set of gaps relating to the coverage and applicability of current methods for STS and safety (e.g. coverage of external influences on system functioning; method usability). The final sections of the paper describe a set of future challenges, as well as some practical suggestions for tackling these.
Practitioner Summary: We provide an up-to-date review of STS methods, a set of case studies illustrating their use and an evaluation of their strengths and weaknesses. The paper concludes with a ‘roadmap’ for future work.
144 citations
TL;DR: Existing evidence shows that HFE-based healthcare system redesign has the potential to improve quality of care and patient safety, and healthcare organisations need to recognise the importance of HFE to quality of Care and patientSafety, and invest resources to integrate HFE in healthcare improvement activities.
Abstract: Healthcare systems need to be redesigned to provide care that is safe, effective and efficient, and meets the multiple needs of patients. This systematic review examines how human factors and ergonomics (HFE) is applied to redesign healthcare work systems and processes and improve quality and safety of care. We identified 12 projects representing 23 studies and addressing different physical, cognitive and organisational HFE issues in a variety of healthcare systems and care settings. Some evidence exists for the effectiveness of HFE-based healthcare system redesign in improving process and outcome measures of quality and safety of care. We assessed risk of bias in 16 studies reporting the impact of HFE-based healthcare system redesign and found varying quality across studies. Future research should further assess the impact of HFE on quality and safety of care, and clearly define the mechanisms by which HFE-based system redesign can improve quality and safety of care.
107 citations
TL;DR: Findings indicate that Acti4 provides good estimates of time spent in different activity types during semi-standardised conditions, and for sitting, standing and walking during non- standardised conditions with normal level of movement complexity.
Abstract: This study examined the ability of the Acti4 software for identifying physical activity types from accelerometers during free-living with different levels of movement complexity compared with video observations. Nineteen aircraft cabin cleaners with ActiGraph GT3X+ accelerometer at the thigh and hip performed one semi-standardised and two non-standardised sessions (outside and inside aircraft) with different levels of movement complexity during working hours. The sensitivity for identifying different activity types was 75.4–99.4% for the semi-standardised session, 54.6–98.5% outside the aircraft and 49.9–90.2% inside the aircraft. The specificity was above 90% for all activities, except ‘moving’ inside the aircraft. These findings indicate that Acti4 provides good estimates of time spent in different activity types during semi-standardised conditions, and for sitting, standing and walking during non-standardised conditions with normal level of movement complexity. The Acti4 software may be a useful tool f...
94 citations
TL;DR: The mechanical demand on the neck muscles was estimated to increase 3–5 times during seated tablet computer use versus seated neutral posture, with the lowest demand in a high propped tablet position but few differences in other conditions.
Abstract: Tablet computer use requires substantial head and neck flexion, which is a risk factor for neck pain. The goal of this study was to evaluate the biomechanics of the head–neck system during seated tablet computer use under a variety of conditions. A physiologically relevant variable, gravitational demand (the ratio of gravitational moment due to the weight of the head to maximal muscle moment capacity), was estimated using a musculoskeletal model incorporating subject-specific size and intervertebral postures from radiographs. Gravitational demand in postures adopted during tablet computer use was 3–5 times that of the neutral posture, with the lowest demand when the tablet was in a high propped position. Moreover, the estimated gravitational demand could be correlated to head and neck postural measures (0.48 < R 2 < 0.64, p < 0.001). These findings provide quantitative data about mechanical requirements on the neck musculature during tablet computer use and are important for developing ergonomics guidelin...
84 citations
TL;DR: A short questionnaire aimed to evaluate the employees' comfort in an open-plan office and to propose optimal modifications of the office showed that intelligible conversations represent the main source of noise annoyance; moreover, overall noise level is not related to this annoyance.
Abstract: It is currently accepted that noise is one of the most important annoyance factors in open-space offices. However, noise levels measured in open spaces of the tertiary sector rarely exceed 65 dB(A). It, therefore, appears necessary to develop a tool that can be used to assess the noise environment of these offices and identify the parameters to be taken into consideration when assessing the noise annoyance. This article presents a questionnaire to be filled by people working in such environment, and a case study in different open plan offices. The majority of the 237 respondents consider that the ambient noise level in their environment is high and that intelligible conversations between their colleagues represent the main source of noise annoyance. This annoyance was significantly correlated with their evaluation of sound intensity, which could not be represented by A-weighted level measurements.
84 citations
TL;DR: The optimal AH is used to assess the extent to which current CWA-based design practices, uncovered through a survey of CWA practitioners, aligns with sociotechnical systems theory, and recommendations for a design toolkit are specified.
Abstract: Cognitive work analysis (CWA) is a framework of methods for analysing complex sociotechnical systems. However, the translation from the outputs of CWA to design is not straightforward. Sociotechnical systems theory provides values and principles for the design of sociotechnical systems which may offer a theoretically consistent basis for a design approach for use with CWA. This article explores the extent to which CWA and sociotechnical systems theory offer complementary perspectives and presents an abstraction hierarchy (AH), based on a review of literature, that describes an 'optimal' CWA and sociotechnical systems theory design system. The optimal AH is used to assess the extent to which current CWA-based design practices, uncovered through a survey of CWA practitioners, aligns with sociotechnical systems theory. Recommendations for a design approach that would support the integration of CWA and sociotechnical systems theory design values and principles are also derived.
79 citations
TL;DR: A variety of sociotechnical systems perspectives on intersections between social–organisational and technology–work process factors as they impact work system analysis, design and operation are presented.
Abstract: Theoretical and practical approaches to safety based on sociotechnical systems principles place heavy emphasis on the intersections between social–organisational and technical–work process factors. Within this perspective, work system design emphasises factors such as the joint optimisation of social and technical processes, a focus on reliable human–system performance and safety metrics as design and analysis criteria, the maintenance of a realistic and consistent set of safety objectives and policies, and regular access to the expertise and input of workers. We discuss three current approaches to the analysis and design of complex sociotechnical systems: human–systems integration, macroergonomics and safety climate. Each approach emphasises key sociotechnical systems themes, and each prescribes a more holistic perspective on work systems than do traditional theories and methods. We contrast these perspectives with historical precedents such as system safety and traditional human factors and ergonomics, and describe potential future directions for their application in research and practice.
Practitioner Summary: The identification of factors that can reliably distinguish between safe and unsafe work systems is an important concern for ergonomists and other safety professionals. This paper presents a variety of sociotechnical systems perspectives on intersections between social–organisational and technology–work process factors as they impact work system analysis, design and operation.
70 citations
TL;DR: There is currently inconsistent evidence for recommending job rotation as a strategy for preventing musculoskeletal complaints, and there are no studies on sustainable working life parameters.
Abstract: The aim of this systematic review was to summarise evidence on the effects of job rotation on musculoskeletal complaints, exposures related to musculoskeletal complaints and sustainable working life parameters. A total of 16 studies were included. No studies on sustainable working life parameters were found. The quality of the studies was assessed using a checklist; eight field studies and three laboratory studies of sufficient quality were used to summarise the following evidence: one field study showed positive results and one field study showed negative results for musculoskeletal complaints, two field studies showed positive results and two field studies showed inconsistent results for exposures, and two field studies showed inconsistent results for musculoskeletal complaints and exposures. Two laboratory studies showed inconsistent results and one laboratory study showed no changes for exposures. In conclusion, there is currently inconsistent evidence for positive or negative effects of job rotation on musculoskeletal complaints and exposures related to musculoskeletal complaints. Practitioner's Summary: Currently, there is inconsistent evidence for recommending job rotation as a strategy for preventing musculoskeletal complaints. Exposures from all involved work activities and body regions should be identified and assessed first, to determine if job rotation provides increased exposure variation and/or beneficial changes in mean exposures related to musculoskeletal complaints.
TL;DR: The potential advantages of computer-based models and simulations for understanding factors that impact sociotechnical system design and operation, particularly with respect to process and occupational safety are described.
Abstract: Accurate comprehension and analysis of complex sociotechnical systems is a daunting task. Empirically examining, or simply envisioning the structure and behaviour of such systems challenges traditional analytic and experimental approaches as well as our everyday cognitive capabilities. Computer-based models and simulations afford potentially useful means of accomplishing sociotechnical system design and analysis objectives. From a design perspective, they can provide a basis for a common mental model among stakeholders, thereby facilitating accurate comprehension of factors impacting system performance and potential effects of system modifications. From a research perspective, models and simulations afford the means to study aspects of sociotechnical system design and operation, including the potential impact of modifications to structural and dynamic system properties, in ways not feasible with traditional experimental approaches. This paper describes issues involved in the design and use of such models and simulations and describes a proposed path forward to their development and implementation.
Practitioner Summary: The size and complexity of real-world sociotechnical systems can present significant barriers to their design, comprehension and empirical analysis. This article describes the potential advantages of computer-based models and simulations for understanding factors that impact sociotechnical system design and operation, particularly with respect to process and occupational safety.
TL;DR: The DBQ is probably the most widely used self-report questionnaire in driver behaviour research and shows that DBQ violations and errors correlate moderately with self-reported traffic accidents.
Abstract: This article synthesises the latest information on the relationship between the Driver Behaviour Questionnaire (DBQ) and accidents. We show by means of computer simulation that correlations with accidents are necessarily small because accidents are rare events. An updated meta-analysis on the zero-order correlations between the DBQ and self-reported accidents yielded an overall r of .13 (fixed-effect and random-effects models) for violations (57,480 participants; 67 samples) and .09 (fixed-effect and random-effects models) for errors (66,028 participants; 56 samples). An analysis of a previously published DBQ dataset (975 participants) showed that by aggregating across four measurement occasions, the correlation coefficient with self-reported accidents increased from .14 to .24 for violations and from .11 to .19 for errors. Our meta-analysis also showed that DBQ violations (r = .24; 6353 participants; 20 samples) but not DBQ errors (r = - .08; 1086 participants; 16 samples) correlated with recorded vehicle speed. Practitioner Summary: The DBQ is probably the most widely used self-report questionnaire in driver behaviour research. This study shows that DBQ violations and errors correlate moderately with self-reported traffic accidents.
TL;DR: D dwell time percentages to six areas of interest (AOIs), of six participants cycling on four different roads, were analysed both frame-by-frame and in a ‘fixation- by-fixation’ manner, finding a high correlation indicates that the results are very similar.
Abstract: Although analysing software for eye-tracking data has significantly improved in the past decades, the analysis of gaze behaviour recorded with head-mounted devices is still challenging and time-consuming. Therefore, new methods have to be tested to reduce the analysis workload while maintaining accuracy and reliability. In this article, dwell time percentages to six areas of interest (AOIs), of six participants cycling on four different roads, were analysed both frame-by-frame and in a 'fixation-by-fixation' manner. The fixation-based method is similar to the classic frame-by-frame method but instead of assigning frames, fixations are assigned to one of the AOIs. Although some considerable differences were found between the two methods, a Pearson correlation of 0.930 points out a good validity of the fixation-by-fixation method. For the analysis of gaze behaviour over an extended period of time, the fixation-based approach is a valuable and time-saving alternative for the classic frame-by-frame analysis.
TL;DR: This study classifies the foot shapes of Taiwanese using 3D foot scanning data from 2000 males and 1000 females into three different foot shapes for males and females, respectively to provide very useful information for gender-specific shoe last design and footwear production.
Abstract: This study classifies the foot shapes of Taiwanese using 3D foot scanning data from 2000 males and 1000 females. Nine foot dimensions relative to foot length and absolute measures in the common foot length categories were applied to compare the gender differences. Using foot breadth in % foot length (% FL), ball of foot length in % FL and arch height in % FL as feature parameters, three foot shape types for males and females can be classified. Significant gender differences were found in seven of the nine foot dimensions. Females had greater ball of foot length than males (0.2% FL). When comparing feet of the same foot length, males had greater breadth, girth and height dimensions than females, except for toe height. In addition, ethnic differences in foot shape were also observed. The findings can provide very useful information for building gender-specific shoe lasts and designing footwear insoles.
TL;DR: A threshold for an acceptable level of response time and accuracy contingent upon time pressure imposed and display size presented is presented, which generates a lower boundary threshold for display screen size for this order of task demand.
Abstract: We examined the systematic effects of display size on task performance as derived from a standard perceptual and cognitive test battery. Specifically, three experiments examined the influence of varying viewing conditions on response speed, response accuracy and subjective workload at four differing screen sizes under three different levels of time pressure. Results indicated a ubiquitous effect for time pressure on all facets of response while display size effects were contingent upon the nature of the viewing condition. Thus, performance decrement and workload elevation were evident only with the smallest display size under the two most restrictive levels of time pressure. This outcome generates a lower boundary threshold for display screen size for this order of task demand. Extrapolations to the design and implementation of all display sizes and forms of cognitive and psychomotor demand are considered.
TL;DR: With increasing duration and intensity of occupational WBV exposure, primarily musculoskeletal or neurological disorders of the spine occur, and an international review of compensation criteria, trends and prevention efforts is reviewed.
Abstract: Workers with whole-body vibration (WBV) exposure are likely to report non-specific health complaints. Health and safety providers may not recognise such occupational injuries and may be unfamiliar with appropriate exposure assessment and prevention. This is a review of clinical studies, medical evidence, differential diagnostic evaluation protocols, surveillance programmes, national and international standards, and interventions recommendations utilising PubMed and other online resources. In summary, several studies show a clear trend: with increasing duration and intensity of occupational WBV exposure, primarily musculoskeletal or neurological disorders of the spine occur. Other organ damage has also been reported. In some European Union countries, spinal injury caused by WBV is recognised as an occupational disease and may be compensable. The WBV-related injury diagnosis includes a review of the work history, exposure assessment and differential diagnostic evaluation. WBV health surveillance should asse...
TL;DR: An algorithm to estimate core temperature (Tc) from non-invasive measures of HR was validated and shows promise for use in real-time monitoring of encapsulated first responders.
Abstract: First responders often wear personal protective equipment (PPE) for protection from on-the-job hazards. While PPE ensembles offer individuals protection, they limit one's ability to thermoregulate, and can place the wearer in danger of heat exhaustion and higher cardiac stress. Automatically monitoring thermal–work strain is one means to manage these risks, but measuring core body temperature (Tc) has proved problematic. An algorithm that estimates Tc from sequential measures of heart rate (HR) was compared to the observed Tc from 27 US soldiers participating in three different chemical/biological training events (45–90 min duration) while wearing PPE. Hotter participants (higher Tc) averaged (HRs) of 140 bpm and reached Tc around 39°C. Overall the algorithm had a small bias (0.02°C) and root mean square error (0.21°C). Limits of agreement (LoA ± 0.48°C) were similar to comparisons of Tc measured by oesophageal and rectal probes. The algorithm shows promise for use in real-time monitoring of encapsulated ...
TL;DR: Cumulative whole-body vibration exposure, physical load factors and adverse psychosocial environment at the workplace, as well as individual-related psychological distress, were significant predictors of the occurrence of NSP in the professional drivers.
Abstract: In a three-year follow-up study, the occurrence of neck and shoulder pain (NSP) in terms of frequency, duration and intensity was investigated in a population of 537 male professional drivers. Over the follow-up period, the cumulative incidences for neck and shoulder pain were 31.9% and 21.4%, respectively. After adjustment for potential confounders, a measure of cumulative whole-body vibration exposure was significantly associated with all NSP outcomes. Lifting loads and work with hands above shoulder level were significantly related to shoulder outcomes, while driving with trunk bent or twisted was associated with neck pain. Limited job decision, low social support and job dissatisfaction were significant predictors of neck outcomes. Psychological distress was associated with all NSP outcomes. The findings of this cohort study suggest that NSP outcomes are of multifactorial origin in driving occupations.Practitioner Summary: This prospective cohort study highlighted the multifactorial nature of neck and...
TL;DR: The results suggest that motor variability drops when repetitive movements are performed at increased paces, which may in the long run lead to undesirable outcomes such as muscle fatigue or overuse.
Abstract: Increased movement variability has been suggested to reduce the risk of developing musculoskeletal disorders caused by repetitive work. This study investigated the effects of work pace on arm movement variability in a standardised repetitive pipetting task performed by 35 healthy women. During pipetting at slow and fast paces differing by 15%, movements of arm, hand and pipette were tracked in 3D, and used to derive shoulder and elbow joint angles. The size of cycle-to-cycle motor variability was quantified using standard deviations of several kinematics properties, while the structure of variability was quantified using indices of sample entropy and recurrence quantification analysis. When pace increased, both the size and structure of motor variability in the shoulder and elbow decreased. These results suggest that motor variability drops when repetitive movements are performed at increased paces, which may in the long run lead to undesirable outcomes such as muscle fatigue or overuse.
TL;DR: A novel Firefighting Activities Station, which simulates four common fireground tasks, is presented for use with an environmental chamber in a controlled laboratory setting and physiological responses more closely replicate those from live-fire activities than a traditional treadmill protocol.
Abstract: For decades, research to quantify the effects of firefighting activities and personal protective equipment on physiology and biomechanics has been conducted in a variety of testing environments. It is unknown if these different environments provide similar information and comparable responses. A novel Firefighting Activities Station, which simulates four common fireground tasks, is presented for use with an environmental chamber in a controlled laboratory setting. Nineteen firefighters completed three different exercise protocols following common research practices. Simulated firefighting activities conducted in an environmental chamber or live-fire structures elicited similar physiological responses (max heart rate: 190.1 vs 188.0 bpm, core temperature response: 0.047°C/min vs 0.043°C/min) and accelerometry counts. However, the response to a treadmill protocol commonly used in laboratory settings resulted in significantly lower heart rate (178.4 vs 188.0 bpm), core temperature response (0.037°C/min vs 0.043°C/min) and physical activity counts compared with firefighting activities in the burn building. Practitioner Summary: We introduce a new approach for simulating realistic firefighting activities in a controlled laboratory environment for ergonomics assessment of fire service equipment and personnel. Physiological responses to this proposed protocol more closely replicate those from live-fire activities than a traditional treadmill protocol and are simple to replicate and standardise.
TL;DR: This study applies a PE approach to redesigning the family-centred rounds (FCR) process to improve family engagement and broadens PE application from designing individual tasks in specific jobs to address physical ergonomic issues to designing complex healthcare processes to address cognitive and organisational ergonomic Issues.
Abstract: Participatory ergonomics (PE) can promote the application of human factors and ergonomics (HFE) principles to healthcare system redesign. This study applied a PE approach to redesigning the family-centred rounds (FCR) process to improve family engagement. Various FCR stakeholders (e.g. patients and families, physicians, nurses, hospital management) were involved in different stages of the PE process. HFE principles were integrated in both the content (e.g. shared mental model, usability, workload consideration, systems approach) and process (e.g. top management commitment, stakeholder participation, communication and feedback, learning and training, project management) of FCR redesign. We describe activities of the PE process (e.g. formation and meetings of the redesign team, data collection activities, intervention development, intervention implementation) and present data on PE process evaluation. To demonstrate the value of PE-based FCR redesign, future research should document its impact on FCR proces...
TL;DR: This is the first empirical investigation providing objective evidence that firefighters’ sleep is restricted during wildfire suppression, and sleep location, shift length and shift start time should be targeted when designing appropriate controls to manage fatigue-related risk and preserve firefighters' health and safety during wildfire events.
Abstract: This study examined firefighters' sleep quantity and quality throughout multi-day wildfire suppression, and assessed the impact of sleep location, shift length, shift start time and incident severity on these variables. For 4 weeks, 40 volunteer firefighters' sleep was assessed using wrist actigraphy. Analyses revealed that the quantity of sleep obtained on fire days was restricted, and pre- and post-sleep fatigue ratings were higher, compared to non-fire days. On fire days, total sleep time was less when: (i) sleep location was in a tent or vehicle, (ii) shifts were greater than 14 h and (iii) shifts started between 05:00 and 06:00 h. This is the first empirical investigation providing objective evidence that firefighters' sleep is restricted during wildfire suppression. Furthermore, sleep location, shift length and shift start time should be targeted when designing appropriate controls to manage fatigue-related risk and preserve firefighters' health and safety during wildfire events. Practitioner Summary: During multi-day wildfire suppression, firefighters' sleep quantity was restricted, and pre- and post-sleep fatigue ratings were higher, compared to non-fire days. Furthermore, total sleep time was less when: (i) sleep occurred in a tent/vehicle, (ii) shifts were >14 h and (iii) shifts started between 05:00 and 06:00 h.
TL;DR: Lumbar extensor muscle fatigue generates more in-phase lumbar–pelvic coordination patterns and elevated spinal loading during lifting, which may indicate higher risk of back injury.
Abstract: Lumbar muscle fatigue is a potential risk factor for the development of low back pain. In this study, we investigated the influence of lumbar extensor muscle fatigue on lumbar–pelvic coordination patterns during weightlifting. Each of the 15 male subjects performed five repetitions of weightlifting tasks both before and after a lumbar extensor muscle fatiguing protocol. Lumbar muscle electromyography was collected to assess fatigue. Trunk kinematics was recorded to calculate lumbar–pelvic continuous relative phase (CRP) and CRP variability. Results showed that fatigue significantly reduced the average lumbar–pelvic CRP value (from 0.33 to 0.29 rad) during weightlifting. The average CRP variability reduced from 0.17 to 0.15 rad, yet this change ws statistically not significant. Further analyses also discovered elevated spinal loading during weightlifting after the development of lumbar extensor muscle fatigue. Our results suggest that frequently experienced lumbar extensor muscle fatigue should be avoided ...
TL;DR: This parametric modelling approach is useful for reliable prediction of the body shape of a specific child with a few given predictors such as stature, body mass index and age.
Abstract: A statistical body shape model (SBSM) for children was developed for generating a child body shape with desired anthropometric parameters. A standardised template mesh was fit to whole-body laser scan data from 137 children aged 3–11 years. The mesh coordinates along with a set of surface landmarks and 27 manually measured anthropometric variables were analysed using principal component (PC) analysis. PC scores were associated with anthropometric predictors such as stature, body mass index (BMI) and ratio of erect sitting height to stature (SHS) using a regression model. When the original scan data were compared with the predictions of the SBSM using each subject's stature, BMI and SHS, the mean absolute error was 10.4 ± 5.8 mm, and 95th percentile error was 24.0 ± 18.5 mm. The model, publicly available online, will have utility for a wide range of applications.Practitioner Summary: A statistical body shape model for children helps to account for inter-individual variability in body shapes as well as anth...
TL;DR: The ability to predict back injury was not high, suggesting that there is more complexity to the relationship between exposure, movement competency, training, fitness and injury than is explained with the variables tested here.
Abstract: Elite police work has bursts of intense physically demanding work requiring high levels of fitness, or capacity, and movement competency; which are assumed to increase one's injury resilience. The purpose of this study was to follow members of an elite police force (N = 53) to test whether back injuries (N = 14) could be predicted from measures of fitness and movement quality. Measures of torso endurance, relative and absolute strength, hip ROM and movement quality using the Functional Movement Screen(TM) and other dynamic movement tests were obtained from every officer at baseline. When variables were grouped and considered holistically, rather than individually, back injury could be predicted. Seven variables best predicted those who would suffer a back injury (64% sensitivity and 95% specificity for an overall concordance of 87%). Overall, the ability to predict back injury was not high, suggesting that there is more complexity to this relationship than is explained with the variables tested here. Practitioner Summary: Members of elite police forces have exposure to intense physically demanding work. Increased levels of fitness and movement competency have been assumed to increase injury resilience. However, complexity in the interactions between exposure, movement competency, training, fitness and injury may occlude the true relationship between these variables.
TL;DR: This three-year case study and the theory derived demonstrate how ergonomists changed their focus to align with design and business goals to integrate HF into the design process.
Abstract: The ‘design for human factors’ grounded theory explains ‘how’ human factors (HF) went from a reactive, after-injury programme in safety, to being proactively integrated into each step of the production design process. In this longitudinal case study collaboration with engineers and HF Specialists in a large electronics manufacturer, qualitative data (e.g. meetings, interviews, observations and reflections) were analysed using a grounded theory methodology. The central tenet in the theory is that when HF Specialists acclimated to the engineering process, language and tools, and strategically aligned HF to the design and business goals of the organisation, HF became a means to improve business performance. This led to engineers ‘pulling’ HF Specialists onto their team. HF targets were adopted into engineering tools to communicate HF concerns quantitatively, drive continuous improvement, visibly demonstrate change and lead to benchmarking. Senior management held engineers accountable for HF as a key performa...
TL;DR: A time-varying multi-muscle co-activation function that considers electromyographic (EMG) signals as input is proposed that provides a measure of time- varying co- activation between more than two muscles.
Abstract: Low-back disorders (LBDs) are the most common and costly musculoskeletal problem. Muscle co-activation, a mechanism that stabilises the spine, is adopted by the central nervous system to provide added protection and avoid LBDs. However, during high-risk lifting tasks, the compressive load on the spine grows owing to increased co-activation. The aim of this study was to develop a method for the sample-by-sample monitoring of the co-activation of more than two muscles, and to compare this method with agonist-antagonist methods. We propose a time-varying multi-muscle co-activation function that considers electromyographic (EMG) signals as input. EMG data of 10 healthy subjects were recorded while they manually lifted loads at three progressively heavier conditions. The repeated measures ANOVA revealed a significant effect of lifting condition on our co-activation index. Heavier conditions resulted in higher muscle co-activation values. Significant correlations were found between the time-varying multi-muscle co-activation index and other agonist-antagonist methods. Practitioner Summary: We have developed a method to quantify muscle co-activation during the execution of a lifting task. To do this we used surface electromyography. Our algorithm provides a measure of time-varying co-activation between more than two muscles.
TL;DR: The results show that practitioners place particular importance on the support the methods provide in making decisions regarding changes in work systems and how applicable they are to different types of jobs.
Abstract: Most observational methods for musculoskeletal disorder risk assessment have been developed by researchers to be applied in specific situations, and practitioners could find difficulties in their use in real-work conditions The main objective of this study was to identify the factors which have an influence on how useful the observational techniques are perceived to be by practitioners and to what extent these factors influence their perception A survey was conducted on practitioners regarding the problems normally encountered when implementing these methods, as well as the perceived overall utility of these techniques The results show that practitioners place particular importance on the support the methods provide in making decisions regarding changes in work systems and how applicable they are to different types of jobs The results of this study can serve as guide to researchers for the development of new assessment techniques that are more useful and applicable in real-work situations
TL;DR: A methodology for using finite element methods to model a seat–body system to predict seat transmissibility has been demonstrated and can be developed to explore how seating dynamics interact with human biodynamics.
Abstract: The transmissibility of seat depends on the dynamics of both the seat and the human body, and shows how the amplification and attenuation of vibration varies with the frequency of vibration. A systematic methodology was developed for finite element (FE) modelling of the dynamic interaction between a seat and the human body and predicting the transmissibility of a seat. A seat model was developed to improve computational efficiency before models of the seat pan and backrest were calibrated separately using load–deflection and dynamic stiffness measurements, joined to form the complete seat model, and integrated with the model of a manikin for further calibration. The calibrated seat model was combined with a human body model to predict the transmissibility of the seat. By combining a calibrated seat model with a calibrated human body model, and defining appropriate contacts between the two models, the vibration transmissibility with a seat–occupant system can be predicted.