Is there a u-shaped relationship between load levels and fatigue and recovery? An examination of possible mechanisms.

In a previous study, an unexpected u-shaped relationship was observed between load level and fatigue/recovery responses. Moderate load levels resulted in lower perceived discomfort, pain, and fatigue, and shorter recovery times compared to either low or high load levels. This phenomenon has been reported in other studies, but no article has examined the possible mechanisms that might explain this u-shaped relationship. In this paper, we re-examined the previously published data and found that the phenomenon does not appear to be due to the experimental artefact; the u-shape may be due to unexpectedly lower fatigue effects at moderate loads, and higher fatigue effects at lower loads. We then conducted a literature review and identified several possible physiological, perceptual, and biomechanical explanatory mechanisms. No single mechanism explains the entirety of the phenomenon. Further research is needed on the relationship between work exposures, fatigue, and recovery, and the mechanisms related to the u-shaped relationship.Practitioner summary: We examine a previously observed u-shaped relationship between load level and fatigue/recovery, where moderate force resulted in lower perceived fatigue and shorter recovery times. A u-shaped fatigue response suggests that simply minimising load levels might not be an optimal approach to reduce the risk of workplace injuries.

Examining human factors and ergonomics aspects in a manufacturing organisation's metrics system: measuring up to stakeholder needs.

This research examines the status of human factors and ergonomics (HF/E) metrics in the case context of product realisation in an electronics manufacturing company. Interactions with 100+ stakeholders over a five year period were thematically analysed for metrics-related views and content. A disconnect between engineering metrics and HF/E metrics was evident. Engineers and HF/E specialists expressed different understandings of the gap between the disciplines and how to generate HF/E metrics that would fit the organisation. Other emerging themes provided insight for metrics development including improving indicator relatability, considerations for communication of information, and barriers to implementation of metrics. The results led to seven recommendations to help guide practitioners in developing and refining HF/E metrics as part of an organisation's metrics system. This macroergonomic case study provides key points for consideration when developing HF/E focussed metrics to support organisations being more proactive with HF/E in work system design. Practitioner summary: Metrics' presence, stakeholder views on metrics, and metrics-related content in a case organisation were thematically analysed with a macroergonomics focus. Human factors and ergonomics metrics (HF/E) were disconnected from engineering metrics thus limiting the design team's ability to handle human factors in design. Factors influencing HF/E metrics creation and integration were identified, resulting in seven recommendations for developing HF/E metrics.

Examining the relationship between human factors related quality risk factors and work related musculoskeletal disorder risk factors in manufacturing.

This study addresses the relationship between human factors (HF) related quality deficits in manufacturing and work-related musculoskeletal disorder (WMSD) risk factors in production staff. A recent systematic review identified 60 HF-related quality risk factors (QRFs) in manufacturing related to product, process and workstation design stages. We investigate the extent to which these identified QRFs are also WMSD risk factors. Each QRF was examined for its relationship with WMSD using a 0 (no relationship) to 10 (strong relationship) scale rubric. The authors rated each QRF separately and then discussed and adjusted their ratings in a review session. Results showed that average median ratings were the highest for QRFs related to product design (8/10), intermediate for QRFs related to workstation design (7/10) and the lowest for QRFs related to process design (5/10). This emphasises the significant role of HF in system design in reducing both quality deficits and risk of developing WMSDs for manufacturing personnel.Practitioner summary: This study investigates whether human-related risk factors for product quality are also risk factors for work-related musculoskeletal disorders in manufacturing. Results showed a substantial relationship between quality risk factors and WMSD risk factors. This indicates the significant role of human factors in operations design in improving both system performance and human wellbeing.

Developing a simulation tool to quantify biomechanical load and quality of care in nursing.

Nursing is a high musculoskeletal disorder (MSD) risk job with high workload demands. This study combines Digital Human Modelling (DHM) and Discrete Event Simulation (DES) to address the need for tools to better manage MSD risk. This novel approach quantifies physical-workload, work-performance, and quality-of-care, in response to varying geographical patient-bed assignments, patient-acuity levels, and nurse-patient ratios. Lumbar loads for 86 care-delivery tasks in an acute care hospital unit were used as inputs in a DES model of the care-delivery process, creating a shift-long time trace of the biomechanical load. Peak L4/L5 compression and moment were 3574 N and 111.58 Nm, respectively. This study reports trade-offs in all three experiments: (i) increasing geographical patient-bed assignment distance decreased L4/L5 compression (8.8%); (ii) increased patient-acuity decreased L4/L5 moment (4%); (iii) Increased nurse-patient ratio decreased L4/L5 compression (10%) and moment (17%). However, in all experiments, Quality of care indicators deteriorated (20, 19, and 29%, respectively).Practitioner Summary: This research has the potential to support decision-makers by developing a simulation tool that quantifies the impact of varying operational and design-policies in terms of biomechanical-load and quality of care. The demonstrator-model reports: as geographical patient-bed distance, patient-acuity levels, and nurse-patient ratios increase, biomechanical-load reduces, and quality of care deteriorates.

Applying ergonomics and human factors to congress organization in uncertain times.

Organizational Design and Management (ODAM) elements of Ergonomics and Human Factors (E/HF) apply to congress organization. Exemplary delegate and organizer E/HF experience is constrained by shifting requirements, time pressures and financial constraints. E/HF application while organizing the International Ergonomics Association's Triennial Congress in 2021 (IEA2021) is described focusing on delivery platforms considering typical and exceptional (pandemic) constraints, emphasizing ODAM E/HF principles and generalizable lessons. Post-Congress feedback from delegates, session chairs and Congress organizers reveal the Congress as experienced. Presenting virtually allowed on-demand recording access following live sessions and increased question-and-answer flexibility. Frustrations included navigating multiple platforms and insufficient communications. Stakeholders' differing expectations increased organizer workloads and delegate frustration. Maximum virtual presentation benefits require efforts to ensure integrated, human-centered platform development. Simply digitizing traditional Congress sessions ignores potential enhancements. Embracing innovations would help meet delegate communication needs via careful selection and deployment of evolving virtual meeting technologies. Organizational learning strategies can support these efforts.

Modelling the impacts of COVID-19 on nurse workload and quality of care using process simulation.

Higher acuity levels in COVID-19 patients and increased infection prevention and control routines have increased the work demands on nurses. To understand and quantify these changes, discrete event simulation (DES) was used to quantify the effects of varying the number of COVID-19 patient assignments on nurse workload and quality of care. Model testing was based on the usual nurse-patient ratio of 1:5 while varying the number of COVID-19 positive patients from 0 to 5. The model was validated by comparing outcomes to a step counter field study test with eight nurses. The DES model showed that nurse workload increased, and the quality of care deteriorated as nurses were assigned more COVID-19 positive patients. With five COVID-19 positive patients, the most demanding condition, the simulant-nurse donned and doffed personal protective equipment (PPE) 106 times a shift, totaling 6.1 hours. Direct care time was reduced to 3.4 hours (-64% change from baseline pre-pandemic case). In addition, nurses walked 10.5km (+46% increase from base pre-pandemic conditions) per shift while 75 care tasks (+242%), on average, were in the task queue. This contributed to 143 missed care tasks (+353% increase from base pre-pandemic conditions), equivalent to 9.6 hours (+311%) of missed care time and care task waiting time increased to 1.2 hours (+70%), in comparison to baseline (pre-pandemic) conditions. This process simulation approach may be used as potential decision support tools in the design and management of hospitals in-patient care settings, including pandemic planning scenarios.

An inter-method comparison of four Human Reliability Assessment models.

This paper presents a comparison of four common Human Reliability Assessment (HRA) models through a scoping literature review and sensitivity analysis. The scoping literature review identified 72 relevant studies which formed the basis of the comparison. Studies reported the four selected models have similarities in terms of the sector of origin, applied sectors, output calculation, and a lack of clear guidelines on Performance Influencing Factors (PIFs) selection and risk level allocation. The studied models have differences in the number and type of PIF inputs and Human Error Probability (HEP) calculation procedures. The One Factor At a Time (OFAT) and "combined" sensitivity analysis were conducted to examine the HRA models' responses to systematic risk level changes when each of 8 matching PIFs were systematically set to "high" and then "low" levels individually and simultaneously. The OFAT analysis showed coefficients of variation (CV) in HEP varying from 9% for skills/training up to 94% for work procedure when the PIFs are assigned to a "low" risk level individually. The combined analysis showed the median HEP value close to 97% and 1% when PIFs are assigned to" high" and "low" risk levels respectively. Although the selected HRA models were reported to be validated in high-risk domains there was no study found that validated these models in low-risk domains such as manual order picking, or manual assembly lines. The HRA models examined here are disconnected from specific system design elements which can inhibit design improvement efforts. The study outcome suggests the need for clear guidelines for PIFs selection and risk level allocation. Future research should address both the connection of error assessment to the design of the system and the features of new HRA models that affect its reliability and validity in a variety of industrial contexts.

A comparison of work-rest models using a "breakpoint" analysis raises questions.

OCCUPATIONAL APPLICATIONSDesigning sustainable cyclic work requires attention to both the workload amplitude as well as the duty cycle, the fraction of the work cycle with active workload, that therefore also defines the recovery phase of the cycle. A number of different approaches and models have been developed to calculate the required recovery time for a given load and duty cycle. We present a comparison of three types of models at the "breakpoint" that defines the boundary of load amplitude and duty cycle where fatigue begins to accumulate faster than recovery allows within the work cycle. This comparison shows considerable variation between models of the "allowable" load or duty cycle depending on the method used. Practitioners should thus be cautious applying these models indiscriminately in job design as their results can vary substantially. In particular, differences between the tasks used for model formulation and application may compromise validity, and model application in a given context should be verified before broad application.

TECHNICAL ABSTRACTRationale: There is a need for tools to help design sustainable work in which muscular capacity and other human resources can recover at least as quickly as they are used. Purpose: In this brief report, three different approaches presented in the literature to determining work-rest schedules in cyclic work are compared. Methods: First, a set of five different muscular endurance models coupled with a recovery time model were considered, both with and without a dynamic work correction factor. Second, we examined a model of "resumption time", and third a psychophysically-based model of maximum duty cycle was included. These models were compared using the concept of a "breakpoint" in fatigue accumulation­the point at which a given load amplitude and duty cycle combination begins to cause accumulation of fatigue in each cycle and from which there is inadequate time to recover. Results: While the five endurance time models all behaved similarly, both with and without the static-to-dynamic correction factor applied, the three different types of modeling approaches provided substantially different response patterns. The psychophysically based model provided the most protective guideline among the models compared. Conclusion: These models should be applied with caution to particular work scenarios. Further research is needed to test accuracy and effectiveness when applying such models to a range of task scenarios to establish safe workloads and loading times in the design of repetitive work.

Examining the fatigue-quality relationship in manufacturing.

A recent systematic review identified 73 empirical studies that linked human factors (HF) with manufacturing quality. Human fatigue was noted as a frequent (n = 26) issue in the HF-quality relationship - a finding that warrants closer examination. We extend this review by investigating the relationship between fatigue and manufacturing quality by identifying how fatigue has been conceptualized and measured, and we attempted to quantify their relationship. From the original database, 12 of 26 relevant studies (46%) indicated that physical fatigue was the primary contributor to observed quality deficits. There was a positive relationship between fatigue and quality deficits, with fatigue accounting up to 42% of the variance. More studies are needed to improve the resolution, specificity, and power of these analyses. This study sheds light on the role of HF and human fatigue effects on manufacturing quality with macroergonomic implications for embedding HF aspects into design and quality assurance processes.

Using system dynamics modelling to show the effect of nurse workload on nurses' health and quality of care.

The objective of the current study is to explore System Dynamics modelling to quantify and understand the effects of nursing workload on nurse burnout, absenteeism, and quality of patient care. A literature search was performed to identify the causal relationships between factors related to the problem and build a conceptual causal loop diagram. Each of these factors was then operationalised and a simulation model was built using quantitative empirical data from the literature, supplemented with expert input. The model results showed that long nurse shifts and work weeks double nurse fatigue levels, while increasing burnout by up to 6 times, absenteeism by up to 5 times, and medical errors for the patients increasing by up to 150%. The study demonstrates a novel application of System Dynamics in healthcare to examine the impact of management strategies and healthcare system design on nurses' wellbeing and on care quality. Practitioner summary: System Dynamics Modelling allows for the integration of available scientific evidence and expertise to reveal the relationship between nurse workload, burnout and care quality in terms of medical errors. Such models can reveal possible responses from proposed policy or system design changes that could not be quantified with conventional approaches. Abbreviations: HF: human factors; SD: system dynamics; CLD: causal loop diagram; OFAT: one factor at a time.

Assessing human factors and ergonomics capability in organisations - the Human Factors Integration Toolset.

This paper presents the development of a tool that allows an organisation to assess its level of human factors (HF) and ergonomics integration and maturity within the organisation. The Human Factors Integration Toolset (available at: https://www.researchgate.net/project/Human-Factors-Integration-Toolset ) has been developed and validated through a series of workshops with 45 participants from industry and academia and through industry partnered field-testing. HF maturity is assessed across five levels in 16 organisational functions based on any of 31 discrete elements contributing to HF. Summing element scores in a function determines a percent of ideal HF for the function. Industry stakeholders engaged in field-testing found the tool helped to establish the status of HF in the organisation, plan projects to further develop HF capabilities, and initiate discussions on HF for performance and well-being. Improvement suggestions included adding an IT function, refining the language for non-HF specialists, including knowledge work and creating a digital version to improve usability. Practitioner summary: A tool scoring HF capability in 16 organisation functions has been developed collaboratively. Industry stakeholders expressed a need for the tool and provided validation of tool design decisions. Field-testing improved tool usability and showed that beyond scoring HF capability, the tool created opportunities for discussions of HF-related improvement possibilities. Abbreviations: HF: human factors; HFIT: Human Factors Integration Toolset.

Predicting the effect of nurse-patient ratio on nurse workload and care quality using discrete event simulation.

AIM: A novel nurse-focused discrete event simulation modelling approach was tested to predict nurse workload and care quality. BACKGROUND: It can be challenging for hospital managers to quantify the impact of changing operational policy and technical design such as nurse-patient ratios on nurse workload and care quality. Planning tools are needed-discrete event simulation is a potential solution. METHOD: Using discrete event simulation, a demonstrator "Simulated Care Delivery Unit" model was created to predict the effects of varying nurse-patient ratios. Modelling inputs included the following: patient care data (GRASP systems data), inpatient unit floor plan and operating logic. Model outputs included the following: nurse workload in terms of task-in-queue, cumulative distance walked and Care quality in terms of task in queue time, missed care. RESULTS: The model demonstrated that as NPR increases, care quality deteriorated (120% missed care; 20% task-in-queue time) and nursing workload increased (120% task-in-queue; 110% cumulative walking distance). CONCLUSIONS: DES has the potential to be used to inform operational policy and technical design decisions, in terms of impacts on nurse workload and care quality. IMPLICATIONS FOR NURSING MANAGEMENT: This research offers the ability to quantify the impacts of proposed policy changes and technical design decisions, and provide a more cost-effective and safe alternative to the current trial and error methodologies.

Modelling endurance and resumption times for repetitive one-hand pushing.

This study's objective was to develop models of endurance time (ET), as a function of load level (LL), and of resumption time (RT) after loading as a function of both LL and loading time (LT) for repeated loadings. Ten male participants with experience in construction work each performed 15 different one-handed repetaed pushing tasks at shoulder height with varied exerted force and duration. These data were used to create regression models predicting ET and RT. It is concluded that power law relationships are most appropriate to use when modelling ET and RT. While the data the equations are based on are limited regarding number of participants, gender, postures, magnitude and type of exerted force, the paper suggests how this kind of modelling can be used in job design and in further research. Practitioner Summary: Adequate muscular recovery during work-shifts is important to create sustainable jobs. This paper describes mathematical modelling and presents models for endurance times and resumption times (an aspect of recovery need), based on data from an empirical study. The models can be used to help manage fatigue levels in job design.

'Power base' tactics for workplace change - an interview study with industrial engineers and ergonomists.

The work activities of industrial engineers (IEs) and ergonomists drive workplace changes. The purpose of this study is to compare the work practices of the two professions and examine (1) how IEs and ergonomists gain influence over workplace changes and (2) whether there are prevailing types of intentional interaction behaviours called Power bases (PB) present in the interaction tactics they employ. The study identified key behavioural strategies used by the interviewees to successfully influence workplace changes; these were then mapped to their corresponding PB. Results showed that IEs and ergonomists were successfully influencing workplace changes using several tactics across the spectrum of PB, with the exception of Reward and Coercion. The study concludes with a list of recommended workplace change agent tactics, and proposes that a PB 'analytical lens' can serve to increase the budding ergonomists' critical and analytical skills when considering possible workplace change tactics. Practitioner Summary: This interview study examines how workplace ergonomics change agents, represented by the two professions: industrial engineers and ergonomists, perceive and exercise their capacity to influence workplace change. Key behavioural tactics that interviewees have found successful are reported, alongside effects on short- and long-term relations with other workplace-influencing stakeholders.

Young consumers' considerations of healthy working conditions in purchasing decisions: a qualitative examination.

Research has suggested that products manufactured under healthy work conditions (HWC) may provide a marketing advantage to companies. This paper explores young consumers' considerations of HWC in purchasing decisions using data from qualitative interviews with a sample of 21 university students. The results suggest that interviewees frequently considered the working conditions of those who produced the products they purchased. Participants reported a willingness to pay 17.5% more on a $100 product if it were produced under HWC compared to not. Their ability and willingness to act on this issue was, however, hampered by  a lack of credible information about working conditions in production, the limited availability of HWC goods and a presumed higher price of HWC goods. While caution should be applied when generalising from this targetable market segment to a general population, these results provide actionable direction for companies interested in using a HWC brand image to gain a strategic sales advantage. Practitioner Summary: This interview study shows that young consumers are interested in, and willing to pay a premium for, goods made under healthy working conditions (HWC). Reported barriers to acting on this impulse include a lack of credible information on working conditions. Ergonomics can help provide a strategic marketing advantage for companies.

Prevention of musculoskeletal disorders within management systems: A scoping review of practices, approaches, and techniques.

The purpose of this study was to identify and summarize the current research evidence on approaches to preventing musculoskeletal disorders (MSD) within Occupational Health and Safety Management Systems (OHSMS). Databases in business, engineering, and health and safety were searched and 718 potentially relevant publications were identified and examined for their relevance. Twenty-one papers met the selection criteria and were subjected to thematic analysis. There was very little literature describing the integration of MSD risk assessment and prevention into management systems. This lack of information may isolate MSD prevention, leading to difficulties in preventing these disorders at an organizational level. The findings of this review argue for further research to integrate MSD prevention into management systems and to evaluate the effectiveness of the approach.

How compatible are participatory ergonomics programs with occupational health and safety management systems?

OBJECTIVES: Musculoskeletal disorders (MSD) are a major cause of pain, disability, and costs. Prevention of MSD at work is frequently described in terms of implementing an ergonomics program, often a participatory ergonomics (PE) program. Most other workplace injury prevention activities take place under the umbrella of a formal or informal occupational health and safety management system (OHSMS). This study assesses the similarities and differences between OHSMS and PE as such knowledge could help improve MSD prevention activities. Methods Using the internationally recognized Occupational Health and Safety Assessment Series (OHSAS 18001), 21 OHSMS elements were extracted. In order to define PE operationally, we identified the 20 most frequently cited papers on PE and extracted content relevant to each of the OHSAS 18001 elements. RESULTS: The PE literature provided a substantial amount of detail on five elements: (i) hazard identification, risk assessment and determining controls; (ii) resources, roles, responsibility, accountability, and authority; (iii) competence, training and awareness; (iv) participation and consultation; and (v) performance measurement and monitoring. However, of the 21 OHSAS elements, the PE literature was silent on 8 and provided few details on 8 others. CONCLUSIONS: The PE literature did not speak to many elements described in OHSMS and even when it did, the language used was often different. This may negatively affect the effectiveness and sustainability of PE initiatives within organizations. It is expected that paying attention to the approaches and language used in management system frameworks could make prevention of MSD activities more effective and sustainable.

Fatigue and recovery during and after static loading.

Subjectively assessed endurance time (ET), resumption time (RT) and perceived discomfort, pain or fatigue (PD), and objectively measured maximum force-exerting capacity were investigated for varying loads and durations of a pushing task with two repeated trials. Beyond the main results quantifying how the load scenario affected ET, RT and PD, three additional results are of note: (1) although the maximum pushing force did not change between trials, shorter ET, longer RT and higher PD indicated accumulation of fatigue in Trial 2; (2) the PD ratings showed a trend with a linear increase during loading and a curvilinear decrease during recovery; and (3) the RT and the load level for different relative loading times were found to have an unexpected U-shaped relationship, indicating lowest fatigue at the intermediate load level. These results can be used to model a more sustainable and productive work-recovery ratio.