Quality, productivity, and economic implications of exoskeletons for occupational use: A systematic review.

The objective of this systematic review was to synthesize the current state of knowledge on the quality and productivity of workers and their work while wearing exoskeletons, as well as the economic implications of exoskeletons for occupational use. Following the PRISMA guidelines, six databases were systematically searched for relevant journal articles, written in English, and published since January 2000. Articles meeting the inclusion criteria had their quality assessed using JBI's Checklist for Quasi-Experimental Studies (Non-Randomized Experimental Studies). A total of 6,722 articles were identified and 15 articles focusing on the impact of exoskeletons on quality and productivity of exoskeleton users while performing occupational tasks were included in this study. None of the included articles evaluated the economic implications of exoskeletons for occupational use. This study revealed several quality and productivity measures (e.g., endurance time, task completion time, number of errors, number of task cycles completed) used to evaluate the impact of exoskeletons. The current state of the literature suggests that quality and productivity impacts of exoskeleton use are dependent on task characteristics that should be considered when adopting exoskeletons. Future studies should evaluate the impact of exoskeleton use in the field and on a diverse pool of workers, as well as its economic implications to better support decision-making in the adoption of exoskeletons within organizations.

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.

Evolving pipe joining methods and their association to musculoskeletal symptoms for residential plumbers.

BACKGROUND: Recently the plumbing trade has transitioned from traditional copper piping to flexible plastic piping (PEX) for residential water distribution systems. However, there has been very limited research into the ergonomic implications of the modernized processes. OBJECTIVE: This research documents the physical workload and risks of musculoskeletal disorders (MSDs) with the use of new tools and processes for joining piping. The research also identifies the factors which can facilitate or limit the use of new ergonomically beneficial tools. METHODS: This mixed methods research included workplace observations, interviews, an experiment, a survey of plumbers in residential construction and focus groups with both plumbers and plumbing contractors. RESULTS: Advantages and disadvantages of the various techniques for joining pipes showed that manual crimping has advantages (i.e., productivity and lower cost) that make it desirable for plumbing contractors. Power devices, which were not widely used, have great potential to reduce MSD risks especially if the size and weight of the tools decreases with newer technologies. A continuing barrier is the cost of power equipment. CONCLUSION: The move to provide ergonomically beneficial tools was not as rapid as the willingness to change piping materials. Productivity and costs of tools are barriers to ergonomic interventions.

Synthesis of Evidence to Support EMS Personnel's Mental Health During Disease Outbreaks: A Scoping Review.

Emergency medical services (EMS) personnel are at high risk for adverse mental health outcomes during disease outbreaks. To support the development of evidence-informed mitigation strategies, we conducted a scoping review to identify the extent of research pertaining to EMS personnel's mental health during disease outbreaks and summarized key factors associated with mental health outcomes. We systematically searched three databases for articles containing keywords within three concepts: EMS personnel, disease outbreaks, and mental health. We screened and retained original peer-reviewed articles that discussed, in English, EMS personnel's mental health during disease outbreaks. Where inferential statistics were reported, the associations between individual and work-related factors and mental health outcomes were synthesized. Twenty-five articles were eligible for data extraction. Our findings suggest that many of the contributing factors for adverse mental health outcomes are related to inadequacies in fulfilling EMS personnel's basic safety and informational needs. In preparation for future disease outbreaks, resources should be prioritized toward ensuring adequate provisions of personal protective equipment and infection prevention and control training. This scoping review serves as a launching pad for further research and intervention development.

Mental and physical health and well-being of canadian employees who were working from home during the COVID-19 pandemic.

BACKGROUND: The COVID-19 pandemic has drastically changed various aspects of our lives, including how we work. Since the start of the pandemic, numerous organizations in Canada have mandated their employees to work from home (WFH) on a full-time basis. The rapid rise in the number of remote workers and the possibility for WFH continuing in the future signifies the importance of understanding the health and well-being of employees working from home over the course of the pandemic in Canada. We present the findings of two surveys (initial and 6-month follow-up) to examine the health and well-being of WFH employees during the COVID-19 pandemic in Canada. We analyzed the changes in mental and physical health and well-being of employees who were working from home between two time points during the pandemic. METHODS: Initial survey was completed between October 2020 and December 2020 (n = 1617); follow-up survey was completed between May 2021 and June 2021 (n = 382). We calculated the frequencies for survey questions involving demographics, WFH preferences, workstation setup training, employment situation, provision of hardware technologies, provision and usage of software technologies, and organization's return to work plan. We conducted Wilcoxon signed-rank tests to analyze the within-individual changes in mental and physical health and well-being of the 382 respondents who completed both the initial and follow-up surveys. RESULTS: Our analyses showed significant changes in various aspects of employee mental and physical health and well-being. Burnout, stress, general mental health, and job insecurity levels significantly decreased between the two time periods. Work-related sedentary behaviour reduced over time; however, the average proportion of time spent sitting during work hours was more than 80% in both surveys. Employees received more help and feedback from their colleagues and experienced a better sense of community with their co-workers over time. CONCLUSION: The findings can inform workers and organizations on the changes in mental and physical health and well-being of employees working from home during the pandemic. By understanding the changes in worker health and well-being, employers can develop effective strategies and implement policies that help protect employees' health and well-being.

Working in the digital economy: A systematic review of the impact of work from home arrangements on personal and organizational performance and productivity.

Work-from-home has become an increasingly adopted practice globally. Given the emergence of the COVID-19 pandemic, such arrangements have risen substantially in a short timeframe. Work-from-home has been associated with several physical and mental health outcomes. This relationship has been supported by previous research; however, these health and safety issues often receive little resources and attention from business perspectives compared to organizational and worker performance and productivity. Therefore, aligning work-from-home practices with business goals may help catalyze awareness from decision makers and serve to effectively implement work-from-home policies. We conducted a review to synthesize current knowledge on the impact of work-from-home arrangements on personal and organizational performance and productivity. Four large databases including Scopus, PubMed, PsychInfo, and Business Source Complete were systematically searched. Through a two-step screening process, we selected and extracted data from 37 relevant articles. Key search terms surrounded two core concepts: work-from-home and productivity/performance. Of the articles published prior to the COVID-19 pandemic, 79% (n = 19) demonstrated that work-from-home increased productivity and performance whereas 21% (n = 5) showed mixed or no effects. Of the articles published during the pandemic, 23% (n = 3) showed positive effects, 38% (n = 5) revealed mixed results, and 38% (n = 5) showed negative effects. Findings suggest that non-mandatory work-from-home arrangements can have positive impacts on productivity and performance. When work-from-home becomes mandatory and full-time, or external factors (i.e., COVID-19 pandemic) are at play, the overall impacts are less positive and can be detrimental to productivity and performance. Results will help foster an understanding of the impact of work-from-home on productivity and performance and inform the development of organizational strategies to create an effective, resilient, and inclusive work-from-home workplace by helping to effectively implement work-from-home policies that are aligned with business goals.

Organizational strategies to address posttraumatic stress injuries among Canadian paramedics.

BACKGROUND: Paramedics are a high-risk occupational group for posttraumatic stress injuries (PTSI), and increasingly, evidence suggests that organizational factors play a significant role. While several resources for paramedic services to address PTSI exist, there is limited knowledge as to which PTSI-related programs and practices are implemented and how they are perceived in the workplace. OBJECTIVES: This research aimed to explore key informants' perspectives on existing and desired organizational-wide initiatives for, as well as the challenges and potential solutions to, the primary prevention, early detection and intervention, and disability management of PTSI in Canadian paramedic services. METHODS: Semi-structured interviews were conducted with 12 key informants from jurisdictions across Canada who have over five years of work experience in prehospital care. Interviews were audio-recorded, transcribed, and analyzed using thematic analysis. RESULTS: Eight recurrent organizational elements (themes) for addressing PTSI emerged: psychologically safe and healthy work culture; consistent supervisor support, mental health training and awareness, opportunities for recovery and maintaining resiliency, recognition of PTSI and its diverse risk factors, access to a variety of support initiatives for PTSI, communication during medical leave, and meaningful work accommodations. CONCLUSIONS: While organizational-wide initiatives were in place for the primary prevention, early detection and intervention, and disability management of PTSI, systemic challenges with coordination, resource allocation, and worker engagement were also identified. These challenges prevented paramedic services from optimally addressing PTSI in their workplace. Integrating considerations from the eight organizational elements to address PTSI into broader existing management systems may have merit in overcoming the systemic challenges.

Exploring the need for and application of human factors and ergonomics in ambulance design: Overcoming the barriers with technical standards.

Ergonomic risk factors, such as excessive physical effort, awkward postures or repetitive movements, were the leading causes of injuries amongst EMS workers in the United States, of which 90% were attributed to lifting, carrying, or transferring a patient and/or equipment. Although the essential tasks of patient handling, transport, and care cannot be eliminated, the design of ambulances and associated equipment is modifiable. Our aims were to identify the extent of Human Factors and Ergonomic (HFE) considerations in existing ambulance design standards/regulations, and describe how HFE and the standards/regulations were applied in the EMS system. Through an extensive environmental scan of jurisdictionally relevant standards/regulations and key informant interviews, our findings demonstrated that existing standards/regulations had limited considerations for HFE. As a result, HFE principles continue to be considered reactively through retrofit rather than proactively in upstream design. We recommend that performance-based HFE requirements be integrated directly into ambulance design standards.

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.

Musculoskeletal symptoms associated with workplace physical exposures estimated by a job exposure matrix and by self-report.

BACKGROUND: A job-exposure matrix (JEM) is an efficient method to assign physical workplace exposures based on job titles. JEMs offer the possibility of linking work exposures to outcome data from national health registers that contain job titles. The French CONSTANCES JEM was constructed from self-reported physical work exposures of asymptomatic workers participating in a large general population study. We validated this general population JEM by testing its ability to demonstrate exposure-outcome associations for musculoskeletal disorders (MSD) symptoms. METHODS: The CONSTANCES JEM was evaluated by assigning exposure estimates to a validation sample of new participants in the CONSTANCES study (final n = 38 730). We used weighted Kappas to compare the level of agreement between JEM-assigned and self-reported exposures across job codes for each of the 27 physical exposure variables. We computed prevalence ratios and 95% confidence intervals using Poisson regression models adjusted for age and sex for pain at six body locations associated with work exposures estimated via individual self-report and by the JEM. RESULTS: Agreement between individual self-reported and JEM-assigned exposures ranged from κ = 0.16 to 0.71; generally, the level of agreement was fair to good. We observed consistent and significant associations between pain and both self-reported and JEM-assigned exposures at all body locations. CONCLUSIONS: The CONSTANCES JEM replicated known associations between physical risk factors and prevalent MSD symptoms. Physical exposure JEMs can reduce some types of information bias, and open new avenues of research in the prevention of MSDs and other health conditions related to workplace physical activities.

Applying two general population job exposure matrices to predict incident carpal tunnel syndrome: A cross-national approach to improve estimation of workplace physical exposures.

Objectives A job exposure matrix (JEM) is a tool to estimate workers' exposure to occupational physical risk factors. We evaluated the performance of two general population JEM (CONSTANCES and O*NET) to detect known exposure-disease relationships in an American prospective cohort study. We compared exposure estimates from three data sources and explored whether combining exposures from these two JEM, or combining exposure from each JEM with individual-level measures, improved prediction of carpal tunnel syndrome (CTS). Methods Using Cox proportional hazard models, we evaluated relationships between physical work exposure and incident CTS of 2393 workers using JEM-assigned and individual-level measure exposure information. We compared exposure estimates using Spearman's rank correlation and Cohen's kappa. We compared combined exposure models to single source exposure models by using binomial logistic regression and examined differences based on model fit and performance. Results The O*NET JEM [hazard ratio (HR) range 1.3-2.01] demonstrated generally similar exposure-disease associations as individual-level measures (HR range 1.00-1.42); we found fewer associations with the CONSTANCES JEM (HR range 1.08-2.05). Comparisons between the three sources showed stronger correlations and agreement at the job versus worker level. Combined models improved goodness-of-fit and had lower Akaike information criterion (AIC) values compared to single-source models. Conclusions JEM can be applied cross nationally and there is potential to combine complementary exposure methods to improve estimation of workplace physical exposures in the prediction of CTS. More investigations are needed to explore exposure-disease associations in other samples and combinations of exposure data from different methods.

Modeling the Effect of the 2018 Revised ACGIH® Hand Activity Threshold Limit Value® (TLV) at Reducing Risk for Carpal Tunnel Syndrome.

Recent studies have shown the 2001 American Conference of Governmental Industrial Hygienists (ACGIH®) Threshold Limit Value (TLV®) for Hand Activity was not sufficiently protective for workers at risk of carpal tunnel syndrome (CTS). These studies led to a revision of the TLV and Action Limit. This study compares the effect of applying the 2018 TLV vs. the 2001 TLV to predict incident CTS within a large occupational pooled cohort study (n = 4,321 workers). Time from study enrollment to first occurrence of CTS was modeled using Cox proportional hazard regression. Adjusted and unadjusted hazard ratios for incident CTS were calculated using three exposure categories: below the Action Limit, between the Action Limit and TLV, and above the TLV. Workers exposed above the 2001 Action Limit demonstrated significant excess risk of carpal tunnel syndrome, while the 2018 TLV demonstrated significant excess risk only above the TLV. Of 186 total cases of CTS, 52 cases occurred among workers exposed above the 2001 TLV vs. 100 among those exposed above the 2018 value. Eliminating exposures above the 2001 TLV might have prevented 11.2% of all cases of CTS seen in our pooled cohort, vs. 25.1% of cases potentially prevented by keeping exposures below the 2018 value. The 2018 revision of the TLV better protects workers from CTS, a recognized occupational health indicator important to public health. A significant number of workers are currently exposed to forceful repetitive hand activity above these guidelines. Public health professionals should promulgate these new guidelines and encourage employers to reduce hand intensive exposures to prevent CTS and other musculoskeletal disorders.

Cross-national comparison of two general population job exposure matrices for physical work exposures.

OBJECTIVES: Job exposure matrices (JEMs) are increasingly used to estimate physical workplace exposures. We conducted a cross-national comparison of exposure estimates from two general population JEMs to aid the interpretation of exposure-outcome associations across countries and to explore the feasibility of cross-national application of JEMs to provide workplace physical exposure estimates. METHODS: We compared physical exposure estimates from two general population JEMs created from the FrenchCohorte des consultants des Centres d'examens de santé study (27 exposure variables) and the American Occupational Information Network database (21 exposure variables). These exposure variables were related to physical demands or ergonomic risk factors for musculoskeletal disorders. We used a crosswalk to match French Profession et Catégorie Sociale job codes with American Standard Occupational Classification job codes and calculated Spearman's correlations and Cohen's kappa values for exposure variable pairs between these French and American JEMs. We defined a priori 50 matched French and American JEM variable pairs that measured similar exposures. RESULTS: All variable pairs measuring similar physical exposures demonstrated positive correlations. Among the 50 matched pairs, 33 showed high correlation (ρ≥0.70) and 46 showed at least moderate agreement (κ≥0.41). Exposures expected to be mutually exclusive (manual work vs office work) showed strongly negative correlations. CONCLUSIONS: French and American general population physical exposure JEMs were related, sharing moderate to high association and moderate to substantial agreement between the majority of variable pairs measuring similar exposures. These findings will inform cross-national comparisons of study results and support some uses of general population JEMs outside their countries of origin.

The CONSTANCES job exposure matrix based on self-reported exposure to physical risk factors: development and evaluation.

OBJECTIVES: Job exposure matrices (JEMs) can be constructed from expert-rated assessments, direct measurement and self-reports. This paper describes the construction of a general population JEM based on self-reported physical exposures, its ability to create homogeneous exposure groups (HEG) and the use of different exposure metrics to express job-level estimates. METHODS: The JEM was constructed from physical exposure data obtained from the Cohorte des consultants des Centres d'examens de santé (CONSTANCES). Using data from 35 526 eligible participants, the JEM consisted of 27 physical risk factors from 407 job codes. We determined whether the JEM created HEG by performing non-parametric multivariate analysis of variance (NPMANOVA). We compared three exposure metrics (mean, bias-corrected mean, median) by calculating within-job and between-job variances, and by residual plots between each metric and individual reported exposure. RESULTS: NPMANOVA showed significantly higher between-job than within-job variance among the 27 risk factors (F(253,21964)=61.33, p<0.0001, r2=41.1%). The bias-corrected mean produced more favourable HEG as we observed higher between-job variance and more explained variance than either means or medians. When compared with individual reported exposures, the bias-corrected mean led to near-zero mean differences and lower variance than other exposure metrics. CONCLUSIONS: CONSTANCES JEM using self-reported data yielded HEGs, and can thus classify individual participants based on job title. The bias-corrected mean metric may better reflect the shape of the underlying exposure distribution. This JEM opens new possibilities for using unbiased exposure estimates to study the effects of workplace physical exposures on a variety of health conditions within a large general population study.

The Multisystem Effects of Simulated Agricultural Whole Body Vibration on Acute Sensorimotor, Physical, and Cognitive Performance.

Background: Exposure to whole body vibration (WBV) is common in construction, agriculture, mining, and transportation. There is strong epidemiological evidence linking WBV with adverse health outcomes in the long-term, including low back pain. Fortunately, WBV exposure guidelines to prevent long-term musculoskeletal disorders and discomfort exist. In the shorter-term, it has been speculated that occupational levels of WBV may lead to increased risk of vehicle accidents and falls during egress; however, the acute effects of different vibration intensities remain poorly understood and it is uncertain whether established standards protect the worker from injurious short-term effects. Objective: The aim of this study was to investigate the acute sensorimotor, physical, and cognitive effects of occupationally-relevant, simulated whole body vibration (WBV) at levels equivalent to international standard guideline thresholds for long-term discomfort and musculoskeletal disorder risk. Method: Eighteen participants were recruited to perform four, 60-min conditions: (i) Control-no vibration, (ii) Low vibration-equivalent to the exposure action value, (iii) Shock-transient impacts at 1-min intervals superimposed on the Low condition, and (iv) High vibration-equivalent to the exposure limit value. Whole body vibration was simulated using data based on field-collected accelerations experienced by rural workers while operating an all-terrain vehicle. This vibration signal was manipulated to achieve required intensities for each condition and simulated with a 6 degree-of-freedom hexapod platform. Before and after each condition, we collected: rating of perceived body discomfort, rating of perceived headache, postural sway, blink frequency, King-Devick test, and psychomotor vigilance task. Pre- and post-condition data in each condition were submitted to either a paired t-test (parametric) or Wilcoxon signed-rank test (non-parametric). To determine differences between conditions, each condition's post-condition data was normalized to its pre-condition value and entered as the dependent variable in a repeated measures analysis of variance. Results: All conditions, including Control, led to increased upper body discomfort when compared to pre-exposure baseline. The Low condition led to increased discomfort in seven body locations, headache (91% increase from baseline; t = -2.44, P = 0.03), and postural imbalance (53% increase from baseline; t = -2.88, P = 0.01), but the effect on cognitive functioning was less clear. Shock condition led to whole body discomfort, specifically at nine upper body and lower body locations. The High condition led to increased whole body discomfort at all 10 body locations, headache (154% increase from baseline; t = -2.91, P = 0.01), postural imbalance (61% increase from baseline; t = -2.57, P = 0.02), and decrements in vigilance (mean reaction time: 6% increase from baseline, t = -3.27, P = 0.005; Number of lapses: 100% increase from baseline, S = -42.5, P = 0.002). Conclusion: Although the number of pre-post condition effects increased with higher vibration intensity, these effects were not significantly different from sitting without vibration. Therefore, current guideline thresholds might not protect the worker from acute WBV effects. However, further research is needed to discern these effects from other sources of WBV. Based on this study, future WBV interventions and action controls should not only address vibration reduction, but also consider potential effects from prolonged sitting.

The combined fatigue effects of sequential exposure to seated whole body vibration and physical, mental, or concurrent work demands.

Many occupations in agriculture, construction, transportation, and forestry are non-routine, involving non-cyclical tasks, both discretionary and non-discretionary work breaks, and a mix of work activities. Workers in these industries are exposed to seated whole body vibration (WBV) and tasks consisting of physical, mental, or a combination of demands. Risk assessment tools for non-routinized jobs have emerged but there remains a need to understand the combined effects of different work demands to improve risk assessment methods and ultimately inform ergonomists and workers on optimum work arrangement and scheduling strategies. The objective of this study was to investigate fatigue-related human responses of WBV sequentially combined with physical, mental, or concurrent physical and mental demands. Sixteen healthy participants performed four conditions on four separate days: (1) physically demanding work, (2) mentally demanding work, (3) concurrent work, and (4) control quiet sitting. For each condition, participants performed two 15-minute bouts of the experimental task, separated by 30-minutes of simulated WBV based on realistic all-terrain vehicle (ATV) riding data. A test battery of fatigue measures consisting of biomechanical, physiological, cognitive, and sensorimotor measurements were collected at four interval periods: pre-session, after the first bout of the experimental task and before WBV, after WBV and before the second bout of the experimental task, and post-session. Nine measures demonstrated statistically significant time effects during the control condition; 11, 7, and 12 measures were significant in the physical, mental, and concurrent conditions, respectively. Overall, the effects of seated WBV in combination with different tasks are not additive but possibly synergistic or antagonistic. There appears to be a beneficial effect of seated ATV operation as a means of increasing task variation; but since excessive WBV may independently pose a health risk in the longer-term, these beneficial results may not be sensible as a long-term solution.

Exploring the Relationship of Task Performance and Physical and Cognitive Fatigue During a Daylong Light Precision Task.

OBJECTIVE: Our aim was to explore the relationship between fatigue and operation system performance during a simulated light precision task over an 8-hr period using a battery of physical (central and peripheral) and cognitive measures. BACKGROUND: Fatigue may play an important role in the relationship between poor ergonomics and deficits in quality and productivity. However, well-controlled laboratory studies in this area have several limitations, including the lack of work relevance of fatigue exposures and lack of both physical and cognitive measures. There remains a need to understand the relationship between physical and cognitive fatigue and task performance at exposure levels relevant to realistic production or light precision work. METHOD: Errors and fatigue measures were tracked over the course of a micropipetting task. Fatigue responses from 10 measures and errors in pipetting technique, precision, and targeting were submitted to principal component analysis to descriptively analyze features and patterns. RESULTS: Fatigue responses and error rates contributed to three principal components (PCs), accounting for 50.9% of total variance. Fatigue responses grouped within the three PCs reflected central and peripheral upper extremity fatigue, postural sway, and changes in oculomotor behavior. CONCLUSION: In an 8-hr light precision task, error rates shared similar patterns to both physical and cognitive fatigue responses, and/or increases in arousal level. APPLICATION: The findings provide insight toward the relationship between fatigue and operation system performance (e.g., errors). This study contributes to a body of literature documenting task errors and fatigue, reflecting physical (both central and peripheral) and cognitive processes.

Fatigue Detection Using Phase-Space Warping.

A novel application of phase-space warping (PSW) method to detect fatigue in the musculoskeletal system is presented. Experimental kinematic, force, and physiological signals are used to produce a fatigue metric. The metric is produced using time-delay embedding and PSW methods. The results showed that by using force and kinematic signals, an overall estimate of the muscle group state can be achieved. Further, when using electromyography (EMG) signals the fatigue metric can be used as a tool to evaluate muscles activation and load sharing patterns for individual muscles. The presented method will allow for fatigue evolution measurement outside a laboratory environment, which open doors to applications such as tracking the physical state of players during competition, workers in a plant, and patients undergoing in-home rehabilitation.

Responsive upper limb and cognitive fatigue measures during light precision work: an 8-hour simulated micro-pipetting study.

Many contemporary occupations are characterised by long periods of low loads. These lower force levels, which are relevant to the development of work-related musculoskeletal disorders, are usually not the focus of fatigue studies. In studies that did measure fatigue in light manual or precision work, within and between measurement responses were inconsistent. The aim of this study was to identify fatigue measures that were responsive at lower force levels (<10% MVC) over the course of an 8-h period. A complementary set of fatigue measures, reflecting both neuromuscular and cognitive mechanisms, was measured during a light precision micro-pipetting task performed by 11 participants. Nine measures were found to be significantly responsive over the 8-h period, including: ratings of perceived fatigue, postural tremor, blink frequency and critical flicker fusion frequency threshold. Common field measures, specifically electromyography RMS amplitude and maximum voluntary contractions, did not lead to extraordinary time effects. Practitioner summary: The findings provide insight towards the responsiveness of a complementary set of field usable fatigue measures at low work intensities Although commonly used measures did not reveal significant increases in fatigue, nine alternative measures were significantly responsive over the 8-h period.

Sensitivity, reliability and the effects of diurnal variation on a test battery of field usable upper limb fatigue measures.

Fatigue has been linked to deficits in production quality and productivity and, if of long duration, work-related musculoskeletal disorders. It may thus be a useful risk indicator and design and evaluation tool. However, there is limited information on the test-retest reliability, the sensitivity and the effects of diurnal fluctuation on field usable fatigue measures. This study reports on an evaluation of 11 measurement tools and their 14 parameters. Eight measures were found to have test-retest ICC values greater than 0.8. Four measures were particularly responsive during an intermittent fatiguing condition. However, two responsive measures demonstrated rhythmic behaviour, with significant time effects from 08:00 to mid-afternoon and early evening. Action tremor, muscle mechanomyography and perceived fatigue were found to be most reliable and most responsive; but additional analytical considerations might be required when interpreting daylong responses of MMG and action tremor. Practitioner Summary: This paper presents findings from test-retest and daylong reliability and responsiveness evaluations of 11 fatigue measures. This paper suggests that action tremor, muscle mechanomyography and perceived fatigue were most reliable and most responsive. However, mechanomyography and action tremor may be susceptible to diurnal changes.