Defining a systems framework for characterizing physical work demands with wearable sensors

Measuring the physical demands of work is important in understanding the relationship between exposure to these job demands and their impact on the safety, health, and well-being of working people. However, work is changing and our knowledge of job demands should also evolve in anticipation of these changes. New opportunities exist for noninvasive long-term measures of physical demands through wearable motion sensors, including inertial measurement units, heart rate monitors, and muscle activity monitors. Inertial measurement units combine accelerometers, gyroscopes, and magnetometers to provide continuous measurement of a segment's motion and the ability to estimate orientation in 3-dimensional space. There is a need for a system-thinking perspective on how and when to apply these wearable sensors within the context of research and practice surrounding the measurement of physical job demands. In this paper, a framework is presented for measuring the physical work demands that can guide designers, researchers, and users to integrate and implement these advanced sensor technologies in a way that is relevant to the decision-making needs for physical demand assessment. We (i) present a literature review of the way physical demands are currently being measured, (ii) present a framework that extends the International Classification of Functioning to guide how technology can measure the facets of work, (iii) provide a background on wearable motion sensing, and (iv) define 3 categories of decision-making that influence the questions that we can ask and measures that are needed. By forming questions within these categories at each level of the framework, this approach encourages thinking about the systems-level problems inherent in the workplace and how they manifest at different scales. Applying this framework provides a systems approach to guide study designs and methodological approaches to study how work is changing and how it impacts worker safety, health, and well-being.

Determining the effects of AR/VR HMD design parameters (mass and inertia) on cervical spine joint torques

This study aimed to determine gravitational and dynamic torques and muscle activity of the neck across a series of design parameters of head mounted displays (mass, center of mass, and counterweights) associated with virtual and augmented reality (VR/AR). Twenty young adult participants completed five movement types (Slow and Fast Flexion/Extension and Rotation, and Search) while wearing a custom-designed prototype headset that varied the three design parameters: display mass (0, 200, 500, and 750 g), distance of the display's center of mass in front of the eyes (approximately 1, 3, and 5 cm anteriorly), and counterweights of 0, 166, 332, and 500 g to balance the display mass of 500 g at 7 cm. Inverse dynamics of a link segment model of the head and headset provided estimates of the torques about the joint between the skull and the occiput-first cervical vertebrae (OC1) and joint between the C7 and T1 vertebrae (C7). Surface electromyography (EMG) measured bilateral muscle activity of the splenius and upper trapezius muscles. Adding 750 g of display mass nearly doubled root mean square joint torques across all movement types. Increasing the distance of the display mass in front of the eyes by 4 cm increased torques about OC1 for the Slow and Fast Rotation and Search movements by approximately 20%. Adding a counterweight decreased torques about OC1 during the rotation and search tasks but did not decrease the torques experienced in the lower cervical spine (C7). For the flexion/extension axis, the magnitude of the dynamic torque component was 20% or less of the total torque experienced whereas for the rotation axis the magnitude of the dynamic torque component was greater than 50% of the total torque. Surface EMG root mean square values significantly varied across movement types with the fast rotation having the largest values; however, they did not vary significantly across the headset configurations.

Artificial intelligence and the work-health interface: A research agenda for a technologically transforming world of work

The labor market is undergoing a rapid artificial intelligence (AI) revolution. There is currently limited empirical scholarship that focuses on how AI adoption affects employment opportunities and work environments in ways that shape worker health, safety, well-being and equity. In this article, we present an agenda to guide research examining the implications of AI on the intersection between work and health. To build the agenda, a full day meeting was organized and attended by 50 participants including researchers from diverse disciplines and applied stakeholders. Facilitated meeting discussions aimed to set research priorities related to workplace AI applications and its impact on the health of workers, including critical research questions, methodological approaches, data needs, and resource requirements. Discussions also aimed to identify groups of workers and working contexts that may benefit from AI adoption as well as those that may be disadvantaged by AI. Discussions were synthesized into four research agenda areas: (1) examining the impact of stronger AI on human workers; (2) advancing responsible and healthy AI; (3) informing AI policy for worker health, safety, well-being, and equitable employment; and (4) understanding and addressing worker and employer knowledge needs regarding AI applications. The agenda provides a roadmap for researchers to build a critical evidence base on the impact of AI on workers and workplaces, and will ensure that worker health, safety, well-being, and equity are at the forefront of workplace AI system design and adoption.

Evaluation of vertical and multi-axial suspension seats for reducing vertical-dominant and multi-axial whole body vibration and associated neck and low back joint torque and muscle activity

The primary aim of this laboratory-based human subject study was to evaluate the biomechanical loading associated with mining vehicles' multi-axial whole body vibration (WBV) by comparing joint torque and muscle activity in the neck and low back during three vibration conditions: mining vehicles' multi-axial, on-road vehicles' vertical-dominant, and no vibration. Moreover, the secondary aim was to determine the efficacy of a vertical passive air suspension and a prototype multi-axial active suspension seat in reducing WBV exposures and associated biomechanical loading measures. The peak joint torque and muscle activity in the neck and low back were higher when exposed to multi-axial vibration compared to the vertical-dominant or no vibration condition. When comparing the two suspension seats, there were limited differences in WBV, joint torque, and muscle activity. These results indicate that there is a need to develop more effective engineering controls to lower exposures to multi-axial WBV and related biomechanical loading. Practitioner Summary: This study found that mining vehicles' multi-axial WBV can increase biomechanical loading in the neck and back more so than on-road vehicles' vertical-dominant WBV. While a newly-developed multi-axial active suspension seat slightly reduced the overall WBV exposures, the results indicate that more effective engineering controls should be developed. Abbreviation: APDF: amplitude probability density function; Aw: weighted average vibration; BMI: body mass index; C7: The 7th cervical vertebra; EMG: electromyography; ES: erector spinae; IRB: institutional review board; ISO: International Organization for Standardization; L5/S1: the fifth lumbar vertebra (L5)/the first sacral vertebra(S1); MSDs: musculoskeletal disorders; MVC: maximum voluntary contraction; PSD: power spectral density; RVC: reference voluntary contraction; SCM: sternocleidomastoid; SD: standard deviation; SPL: splenius capitis; TRAP: trapezius; VDV: vibration dose value; WBV: whole body vibration.

Evaluating the impact of writing surface and configuration on muscle activation level during a handwriting task: An exploratory study

BACKGROUND: Tablets are ubiquitous in workplaces and schools. However, there have been limited studies investigating the effect tablets have on the body during digital writing activities. OBJECTIVE: This study investigated the biomechanical impact of writing interface design (paper, whiteboard, and tablet) and orientation (horizontal, 45°, and vertical) on tablet users. METHODS: Fourteen adults (7 male, 7 female) participated in a study during which they performed simple writing tasks. Surface electromyography (sEMG) sensors were used to measure upper extremity muscle activation. RESULTS: Results indicate that the effects of writing surface type were most pronounced in forearm muscle activation. Specifically, in the extensor carpi radialis (ECR), where muscle activity was lower on the tablet PC surface. The effects of writing configuration were prominent in the shoulder and forearm. The activation of the flexor carpi ulnaris (FCU) and trapezius muscles was significantly lower in the 45° configuration. An exception to the efficacy of this configuration was the anterior deltoid muscle, which exhibited the lowest muscle activity in the horizontal orientation. CONCLUSIONS: Tablet surface and the 45° configuration resulted in the lowest muscle activation levels. Future studies should include longer experiment duration to investigate the effects of continuous writing.

Work and worker health in the post-pandemic world: a public health perspective

The COVID-19 pandemic has highlighted the importance of work in shaping population health and wellbeing. This Viewpoint applies a multilevel systems framework to assist in understanding the diverse and complex interactions of forces affecting worker health and wellbeing, and how trending changes in employment and working conditions have been accelerated by the pandemic. Government agencies concerned with population health and wellbeing, and economic activity must expand their capacity to monitor, evaluate, and respond to these trends. In addition, integrated enterprise and workplace-based approaches that consider the interactions among these multidimensional drivers will build organisation and worker resilience to navigate the continual changes in work and worker safety, health, and wellbeing in a post-pandemic world.

The effects of a new seat suspension system on whole body vibration exposure and driver low back pain and disability: Results from a randomized controlled trial in truck drivers

Through a randomized controlled trial, we evaluated the effects of an electro-magnetic active seat suspension that reduces exposure of a long-haul truck driver to whole body vibration (WBV) on low back pain (LBP) and disability. Among 276 drivers recruited from six trucking terminals of a major US trucking company, 135 eligible drivers were assigned to either having an Active Seat (Intervention: n = 70) - the BoseRide® electro-magnetic active seat - or Passive Seat (reference: n = 65) - a new version of their current seat (passive air suspension seat) - installed in their truck via block (terminal) randomization. Low back pain (LBP) severity, on a 0-10 scale and the Oswestry LBP Disability Index were collected before and 3-, 6-, 12-, 18-, and 24-months post seat installation. LBP severity and LBP disability scores were significantly lower post seat installation in both groups. At 3 months, LBP severity decreased -1.4 [95% CI: -2.1 to -0.7: n = 46] for drivers in the Active Seat arm, and -1.5 [95% CI: -2.3 to -0.8: n = 41] for drivers in the Passive Seat arm. In a subset of drivers, WBV exposures were collected before and after the seat installation. WBV exposures significantly decreased post seat installation for Active Seat (p < 0.01) but not for Passive Seat (p = 0.15). While the new seat-suspension technology reduced WBV exposures, LBP appeared to be improved by multiple factors. These results were limited by the secondary prevention approach and the longer-term loss to follow up due to large rates of driver turnover typical for the industry.

Associations Between Work-Related Factors and Psychological Distress Among Construction Workers

OBJECTIVE

Identify work-related factors associated with the mental health and well-being of construction workers.

METHODS

We completed eight key informant interviews, six worker focus groups, and a survey, informed by the interviews and focus groups, of 259 construction workers on five construction sites. Negative binomial regressions examined associations between psychological distress and work-related factors including safety climate, work-to-family conflict, psychological demands, social support, harassment, and job security.

RESULTS

Three themes emerged from the interviews and focus groups, job demands and structure, social support and workplace relations, and job precarity. From the survey higher psychological demands, higher work-to-family conflict, lower supervisor support, higher discrimination, and higher likelihood of losing a job were associated with higher psychological distress. When combined into a single model job demands and work-to-family conflict remained significant.

CONCLUSIONS

Work-related factors were associated with high levels of distress.

Muscle co-contractions are greater in older adults during walking at self-selected speeds over uneven compared to even surfaces

Falls in the aging population are a major public health concern. Outdoor falls in community-dwelling older adults are often triggered by uneven pedestrian walkways. Our understanding of the motor control adaptations to walk over an uneven surface, and the effects of aging on these adaptations is sparse. Here, we study changes in muscle co-contraction, a clinically accepted measure of motor control, due to changes in walking surfaces typically encountered in the outdoor built environment. We address the following research questions: 1) are there walking surface and sex-based differences in muscle co-contractions between young and older adults? and 2) is muscle co-contraction associated with age? We calculated muscle co-contractions from 13 young and 17 older adults during walking at self-selected speeds over even and uneven brick walkways. Muscle co-contraction at the ankle joint was determined from the tibialis anterior and lateral gastrocnemius muscle pair, and at the knee joint from the rectus femoris and semitendinosus muscle pair. Older adults displayed 8-13% greater ankle muscle co-contractions during walking over uneven compared to even surfaces. We found 55-61% (entire gait) and 73-75% (stance phase) greater ankle muscle co-contractions in older females compared to older males during walking over even and uneven surfaces. We found 31-43% greater knee muscle co-contractions in older females compared to older males during the swing phase of walking over even and uneven surfaces. This study underscores the need for determining muscle co-contractions from even and uneven surfaces for quantifying motor control deficits due to aging or neuromuscular disorders.

Working Conditions Influencing Drivers' Safety and Well-Being in the Transportation Industry: "On Board" Program

The conditions of work for professional drivers can contribute to adverse health and well-being outcomes. Fatigue can result from irregular shift scheduling, stress may arise due to the intense job demands, back pain may be due to prolonged sitting and exposure to vibration, and a poor diet can be attributed to limited time for breaks and rest. This study aimed to identify working conditions and health outcomes in a bussing company by conducting focus groups and key informant interviews to inform a Total Worker Health^® organizational intervention. Our thematic analysis identified three primary themes: lack of trust between drivers and supervisors, the scheduling of shifts and routes, and difficulty performing positive health behaviors. These findings demonstrate the value of using participatory methods with key stakeholders to determine the unique working conditions and pathways that may be most critical to impacting safety, health, and well-being in an organization.

Development and application of an innovative instrument to assess work environment factors for injury prevention in the food service industry

BACKGROUND

With the growth the food service industry and associated high injury and illness rates, there is a need to assess workplace factors that contribute to injury prevention.

OBJECTIVE

The objective of this report is to describe the development, application, and utility of a new instrument to evaluate ergonomics and safety for food service workers.

METHODS

Starting with a similar tool developed for use in healthcare, a new tool was designed through a collaborative, participatory process with the stakeholders from a collaborating food service company. The new instrument enables the identification and assessment of key safety and health factors through a focused walkthrough of the physical work environment, and structured interviews exploring the organizational work environment. The researchers applied the instrument at 10 of the partnering company's worksites.

RESULTS

The instrument identified factors related to both the physical work environment and organizational and contextual environment (e.g., vendor-client relationships) impacting worker safety and health.

CONCLUSIONS

Modern assessment approaches should address both the physical and organizational aspects of the work environment, and consider the context complexities in which the worksites and the industry operate.

Building Capacity for Integrated Occupational Safety, Health, and Well-Being Initiatives Using Guidelines for Total Worker Health® Approaches

OBJECTIVES

To describe the process used to build capacity for wider dissemination of a Total Worker Health® (TWH) model using the infrastructure of a health and well-being vendor organization.

METHODS

A multiple-case study mixed-methods design was used to learn from a year-long investigation of the experiences by participating organizations.

RESULTS

Increased capacity for TWH solutions was observed as evidenced by the participation, plans of action, and experience ratings of the participating organizations. The planning process was feasible and acceptable, although the challenges of dealing with the COVID-19 pandemic only afforded two of the three worksites to deliver a comprehensive written action plan.

CONCLUSIONS

A suite of services including guidelines, trainings, and technical assistance is feasible to support planning, acceptable to the companies that participated, and supports employers in applying the TWH knowledge base into practice.

The future of research on work, safety, health and wellbeing: A guiding conceptual framework

Work plays a central role in health. A conceptual model can help frame research priorities and questions to explore determinants of workers' safety, health, and wellbeing. A previous conceptual model focused on the workplace setting to emphasize the role of conditions of work in shaping workers' safety, health and wellbeing. These conditions of work include physical, organizational, and psychosocial factors. This manuscript presents and discusses an updated and expanded conceptual model, placing the workplace and the conditions of work within the broader context of socio-political-economic environments and consequent trends in employment and labor force patterns. Social, political and economic trends, such as growing reliance on technology, climate change, and globalization, have significant implications for workers' day-to-day experiences. These structural forces in turn shape employment and labor patterns, with implications for the availability and quality of jobs; the nature of relationships between employers and workers; and the benefits and protections available to workers. Understanding these patterns will be critical for anticipating the consequences of future changes in the conditions of work, and ultimately help inform decision-making around policies and practices intended to protect and promote worker safety, health, and wellbeing. This model provides a structure for anticipating research needs in response to the changing nature of work, including the formation of research priorities, the need for expanded research methods and measures, and attention to diverse populations of enterprises and workers. This approach anticipates changes in the way work is structured, managed, and experienced by workers and can effectively inform policies and practices needed to protect and promote worker safety, health and wellbeing.

Associations between a safety prequalification survey and worker safety experiences on commercial construction sites

BACKGROUND

While assessment of subcontractors' safety performance during project bidding processes are common in commercial construction, the validation of organizational surveys used in these processes is largely absent.

METHODS

As part of a larger research project called Assessment of Contractor Safety (ACES), we designed and tested through a cross-sectional study, a 63-item organizational survey assessing subcontractors' leading indicators of safety performance. We administered the ACES Survey to 43 subcontractors on 24 construction sites. Concurrently, we captured the safety climate of 1426 workers on these sites through worker surveys, as well as injury rates, for the duration of the project.

RESULTS

At the worksite level, higher average ACES scores were associated with higher worker safety climate scores (P < .01) and lower rates of injury involving days away (P < .001). Within subcontracting companies, no associations were observed between ACES and worker safety climate scores and injuries.

CONCLUSIONS

These results suggest the overall and collective importance of the construction project and its worksite in mediating worker experiences, perhaps somewhat independent of the individual subcontractor level.

An Integrative Total Worker Health Framework for Keeping Workers Safe and Healthy During the COVID-19 Pandemic

OBJECTIVE

The aim was to recommend an integrated Total Worker Health (TWH) approach which embraces core human factors and ergonomic principles, supporting worker safety, health, and well-being during the COVID-19 pandemic.

BACKGROUND

COVID-19 has resulted in unprecedented challenges to workplace safety and health for workers and managers in essential businesses, including healthcare workers, grocery stores, delivery services, warehouses, and distribution centers. Essential workers need protection, accurate information, and a supportive work environment with an unwavering focus on effective infection control.

METHOD

The investigators reviewed emerging workplace recommendations for reducing workers' exposures to the novel coronavirus and the challenges to workers in protecting their health. Using a theoretical framework and guidelines for integrating safety and health management systems into an organization for TWH, the investigators adapted the framework's key characteristics to meet the specific worker safety and health issues for effective infection control, providing supports for increasing psychological demands while ensuring a safe work environment.

RESULTS

The recommended approach includes six key characteristics: focusing on working conditions for infection control and supportive environments for increased psychological demands; utilizing participatory approaches involving workers in identifying daily challenges and unique solutions; employing comprehensive and collaborative efforts to increase system efficiencies; committing as leaders to supporting workers through action and communications; adhering to ethical and legal standards; and using data to guide actions and evaluate progress.

CONCLUSION

Applying an integrative TWH approach for worker safety, health, and well-being provides a framework to help managers systematically organize and protect themselves, essential workers, and the public during the COVID-19 pandemic.

APPLICATION

By using the systems approach provided by the six implementation characteristics, employers of essential workers can organize their own efforts to improve system performance and worker well-being during these unprecedented times.

Designing a Participatory Total Worker Health® Organizational Intervention for Commercial Construction Subcontractors to Improve Worker Safety, Health, and Well-Being: The "ARM for Subs" Trial

Background: Evidence supports organizational interventions as being effective for improving worker safety, health and well-being; however, there is a paucity of evidence-based interventions for subcontracting companies in commercial construction. Methods: A theory-driven approach supplemented by formative research through key stakeholder interviews and focus groups and an iterative vetting process with stakeholders, resulted in the development of an intervention for subcontractors in the commercial construction industry. We piloted the intervention in one subcontracting commercial construction company. We used these findings to adapt and finalize the intervention design to be tested in a future large-scale trial. Results: There were several key findings from the formative research, including challenges faced by companies and assets that should be considered in the intervention design. This resulted in a communication infrastructure company-based, continual improvement, participatory intervention design, consisting of a needs assessment and report, committee-led prioritization, action planning and implementation, and worker communication/feedback cycle. The pilot contributed to the final intervention design with modifications made with respect to timing, implementation support, capacity building, adaptability and sustainability. Conclusions: The use of a theory-driven participatory approach to developing an integrated organizational intervention for commercial construction subcontracting companies was important and necessary. It allowed us to consider the empirical evidence and relevant theories and tailor these to meet the needs of our target population. This study gives pragmatic insight into the early development of a complex intervention, with practical experience of how we adapted our intervention at each stage. This intervention will be tested in a future randomized trial.

A database of human gait performance on irregular and uneven surfaces collected by wearable sensors

Gait analysis has traditionally relied on laborious and lab-based methods. Data from wearable sensors, such as Inertial Measurement Units (IMU), can be analyzed with machine learning to perform gait analysis in real-world environments. This database provides data from thirty participants (fifteen males and fifteen females, 23.5 ± 4.2 years, 169.3 ± 21.5 cm, 70.9 ± 13.9 kg) who wore six IMUs while walking on nine outdoor surfaces with self-selected speed (16.4 ± 4.2 seconds per trial). This is the first publicly available database focused on capturing gait patterns of typical real-world environments, such as grade (up-, down-, and cross-slopes), regularity (paved, uneven stone, grass), and stair negotiation (up and down). As such, the database contains data with only subtle differences between conditions, allowing for the development of robust analysis techniques capable of detecting small, but significant changes in gait mechanics. With analysis code provided, we anticipate that this database will provide a foundation for research that explores machine learning applications for mobile sensing and real-time recognition of subtle gait adaptations.

Machine learning algorithms can classify outdoor terrain types during running using accelerometry data

BACKGROUND

Running is a popular physical activity that benefits health; however, running surface characteristics may influence loading impact and injury risk. Machine learning algorithms could automatically identify running surface from wearable motion sensors to quantify running exposures, and perhaps loading and injury risk for a runner.

RESEARCH QUESTION

(1) How accurately can machine learning algorithms identify surface type from three-dimensional accelerometer sensors? (2) Does the sensor count (single or two-sensor setup) affect model accuracy?

METHODS

Twenty-nine healthy adults (23.3 ± 3.6 years, 1.8 ± 0.1 m, and 63.6 ± 8.5 kg) participated in this study. Participants ran on three different surfaces (concrete, synthetic, woodchip) while fit with two three-dimensional accelerometers (lower-back and right tibia). Summary features (n = 208) were extracted from the accelerometer signals. Feature-based Gradient Boosting (GB) and signal-based deep learning Convolutional Neural Network (CNN) models were developed. Models were trained on 90% of the data and tested on the remaining 10%. The process was repeated five times, with data randomly shuffled between train-test splits, to quantify model performance variability.

RESULTS

All models and configurations achieved greater than 90% average accuracy. The highest performing models were the two-sensor GB and tibia-sensor CNN (average accuracy of 97.0 ± 0.7 and 96.1 ± 2.6%, respectively).

SIGNIFICANCE

Machine learning algorithms trained on running data from a single- or dual-sensor accelerometer setup can accurately distinguish between surfaces types. Automatic identification of surfaces encountered during running activities could help runners and coaches better monitor training load, improve performance, and reduce injury rates.

A training intervention to improve frontline construction leaders' safety leadership practices and overall jobsite safety climate

INTRODUCTION

The 2.5 h Foundations for Safety Leadership (FSL) training program teaches construction supervisors the leadership skills they need to strengthen jobsite safety climate and reduce adverse safety-related outcomes.

METHODS

Using a quasi-experimental prospective switching replications study design, we examined (1) if FSL-trained jobsite safety leaders would report improved understanding and practice of the FSL leadership skills, safety practices and crew reporting of safety related conditions, and (2) if their crew perceived a change in (a) their supervisors' practices, (b) their own safety practices and reporting of safety-related conditions, and (c) overall jobsite safety climate. Twenty construction sub-contracting companies were recruited and randomly assigned to either an early or lagged-control training group. Participating supervisors and workers completed surveys at multiple time points before and after the FSL training. We used linear mixed modeling to test changes over time.

RESULTS

Only supervisors in the early group reported a statistically significant improvement in their understanding and practice of the leadership skills as well as safety practices from before to 2- and 4-weeks post-training. Overall, no significant change was detected in crew-reported outcomes from before to after their supervisors' participated in the FSL training.

CONCLUSIONS

These results provide evidence that the FSL training can, at least in the short-term, improve construction frontline leaders' jobsite leadership skills. Future research could include an evaluation of FSL refresher activities and a longer-term follow-up. Practical applications: The Foundations for Safety Leadership (FSL) program fills an identified need for construction frontline supervisors to learn and practice critical safety leadership skills on the jobsite. It has already reached over 60,000 leaders and has the potential to reach over 100,000 each year during either an OSHA 30-h or a stand-alone course.

Whole-body vibration and back pain-related work absence among heavy equipment vehicle mining operators

Objective

To determine the association between several whole-body vibration (WBV) exposure estimates and back pain-related work absence.

Methods

Exposures (based on the weighted daily root mean square acceleration, A(8); the daily vibration dose value, VDV(8); and the daily equivalent static compression dose, Sed(8)) of 2302 workers during 4 years were estimated using each worker’s monthly vehicle operation records and WBV measurements from 11 different types of heavy equipment vehicles in a large coal mine. Company payroll data provided work absence during the concurrent 4 years of exposure. Cox regression models estimated the associations between the different WBV metrics and time to first work absence related to back pain. An adjusted R2 statistic provided a measure of model fit.

Results

All estimated metrics of WBV exposures were positively and significantly associated with back pain-related absence. HRs varied from 2.03 to 12.39 for every 0.21 m/s2 increase in the A(8)-based exposures; from 1.03 to 1.18 for every 1.72 m/s1.75 increase in VDV(8)-based exposures; and from 1.04 to 1.07 for every 0.06 MPa increase in Sed(8)-based exposures. Models using the estimated VDV(8) metric for the z axis fit the data best as measured by the R2 statistic.

Conclusion

Higher WBV exposures were associated with back pain-related absences in this population, which appears after a few years of follow-up. Introducing controls to lower exposure levels may help reduce back pain-related work absences.

Effect of walking surface, late-cueing, physiological characteristics of aging, and gait parameters on turn style preference in healthy, older adults

Turning while walking is a crucial component of locomotion, often performed on irregular surfaces with little planning time. Turns can be difficult for some older adults due to physiological age-related changes. Two different turning strategies have been identified in the literature. During step turns, which are biomechanically stable, the body rotates about the outside limb, while for spin turns, generally performed with closer foot-to-foot distance, the inside limb is the main pivot point. Turning strategy preferences of older adults under challenging conditions remains unclear. The aim of this study was to determine how turning strategy preference in healthy older adults is modulated by surface features, cueing time, physiological characteristics of aging, and gait parameters. Seventeen healthy older adults (71.5 ± 4.2 years) performed 90° turns for two surfaces (flat, uneven) and two cue conditions (pre-planned, late-cue). Gait parameters were identified from kinematic data. Measures of lower-limb strength, balance, and reaction-time were also recorded. Generalized linear (logistic) regression mixed-effects models examined the effect of (1) surface and cuing, (2) physiological characteristics of ageing, and (3) gait parameters on turn strategy preference. Step turns were preferred when the condition was pre-planned (p < 0.001) (model 1) and when the gait parameters of stride regularity and maximum acceleration decreased (p = 0.010 and p = 0.039, respectively) (model 3). Differences in turn strategy selection under dynamic conditions ought to be evaluated in future fall-risk research and rehabilitation utilizing real-world activity monitoring.

The Effect of Workforce Mobility on Intervention Effectiveness Estimates

Background

Little is known about how mobile populations of workers may influence the ability to implement, measure, and evaluate health and safety interventions delivered at worksites.

Methods

A simulation study is used to objectively measure both precision and relative bias of six different analytic methods as a function of the amount of mobility observed in the workforce. Those six methods are then used to reanalyze a previously conducted cluster-randomized control trial involving a highly mobile workforce in the construction industry.

Results

As workforce mobility increases, relative bias in treatment effects derived from standard models to analyze cluster-randomized trials also increases. Controlling for amount of time exposed to the intervention can greatly reduce this bias. Analyzing only subsets of workers who exhibit the least amount of mobility can result in decreased precision of treatment effect estimates. We demonstrate a 59% increase in the treatment effect size from the reanalysis of the previously conducted trial.

Conclusions

When evaluating organizational interventions implemented at specific worksites by measuring perceptions and outcomes of workers present at those sites, researchers should consider the effects that the mobility of the workforce may have on the estimated treatment effects. The choice of analytic method can greatly affect both precision and accuracy of estimates.

Improving Working Conditions to Promote Worker Safety, Health, and Wellbeing for Low-Wage Workers: The Workplace Organizational Health Study

This paper addresses a significant gap in the literature by describing a study that tests the feasibility and efficacy of an organizational intervention to improve working conditions, safety, and wellbeing for low-wage food service workers. The Workplace Organizational Health Study tests the hypothesis that an intervention targeting the work organization and environment will result in improvements in workers' musculoskeletal disorders and wellbeing. This ongoing study is being conducted in collaboration with a large food service company. Formative evaluation was used to prioritize outcomes, assess working conditions, and define essential intervention elements. The theory-driven intervention is being evaluated in a proof-of-concept trial, conducted to demonstrate feasibility and potential efficacy using a cluster randomized design. Ten worksites were randomly assigned to intervention or control conditions. The 13-month intervention uses a comprehensive systems approach to improve workplace policies and practices. Using principles of participatory engagement, the intervention targets safety and ergonomics; work intensity; and job enrichment. The evaluation will provide a preliminary assessment of estimates of the intervention effect on targeted outcomes and inform understanding of the intervention implementation across worksites. This study is expected to provide insights on methods to improve working conditions in support of the safety and wellbeing of low-wage workers.

Testing the associations between leading and lagging indicators in a contractor safety pre-qualification database

BACKGROUND

Safety prequalification assessing contractors' safety management systems and safety programs lack validation in predicting construction worker injuries.

METHODS

Safety assessments of leading indicators from 2198 construction contractors, including Safety Management Systems (SMS), Safety Programs (e.g., falls, hearing protection), and Special Elements (drug testing, return to work) scales as well as the history of citations from the Occupational Safety and Health Administration (OSHA) were compared to contractors' lagging indicators of recordable injury case rates (RC) and rates of injuries involving days away, restricted, or transferred (DART).

RESULTS

Increased SMS scores were related to lower injury rates. Each one-point increase in SMS values was associated with 34% reduced odds of a recordable case rate greater than zero (Odds ratio (OR): 0.66, 95% Confidence Interval (CI): (0.57, 0.79)), and a 9% reduced recordable case rate, if one occurs (Risk Ratio (RR): 0.91, 95% CI: (0.88, 0.94)). A one-point increase in SMS was associated with 28% reduced odds of a DART (OR = 0.72, 95%CI (0.56, 0.91)), and 9% reduced DART rate, if one occurs (RR = 0.91, 95%CI (0.87, 0.95)). Safety programs did not show consistent associations with injury outcomes. Having additional Special Elements related to drug and alcohol programs was associated with lower injury rates while the Special Element related to return to work showed no consistent associations with injury. Having more OSHA Citations was associated with lower injury rates for companies with injuries.

CONCLUSIONS

These results support pre-qualification methods based on SMS and suggest the need for safety management systems in contractors.

Paradoxical Impact of a Patient-Handling Intervention on Injury Rate Disparity Among Hospital Workers

OBJECTIVES

To test whether a comprehensive safe patient-handling intervention, which successfully reduced overall injury rates among hospital workers in a prior study, was differentially effective for higher-wage workers (nurses) versus low-wage workers (patient care associates [PCAs]).

METHODS

Data were from a cohort of nurses and PCAs at 2 large hospitals in Boston, Massachusetts. One hospital received the intervention in 2013; the other did not. Using longitudinal survey data from 2012 and 2014 plus longitudinal administrative injury and payroll data, we tested for socioeconomic differences in changes in self-reported safe patient-handling practices, and for socioeconomic differences in changes in injury rates using administrative data.

RESULTS

After the intervention, improvements in self-reported patient-handling practices were equivalent for PCAs and for nurses. However, in administrative data, lifting and exertion injuries decreased among nurses (rate ratio [RR] = 0.64; 95% confidence interval [CI] = 0.41, 1.00) but not PCAs (RR = 1.10; 95% CI = 0.74,1.63; P for occupation × intervention interaction = 0.02).

CONCLUSIONS

Although the population-level injury rate decreased after the intervention, most improvements were among higher-wage workers, widening the socioeconomic gap in injury and exemplifying the inequality paradox. Results have implications for public health intervention development, implementation, and analysis.

The Gap Between Tools and Best Practice: An Analysis of Safety Prequalification Surveys in the Construction Industry

This study characterizes safety prequalification surveys currently in use in the construction industry to identify approaches that include leading indicators of worker safety performance. We collected prequalification surveys available in the public domain from internet searches, construction company websites, published literature, and construction industry partners. We utilized a conceptual framework, based on safety theory and best practices, to categorize survey questions. Fifty-two prequalification surveys were identified containing 112 unique questions. Most included questions related to lagging indicators (83 percent), safety management leadership (75 percent), and worker training (60 percent). Safety management system elements such as hazard prevention and control, program evaluation and improvement, and coordination and communication were notably absent in 90 percent of the surveys. There was little consistency in the surveys available concerning leading indicators of safety. Only a small number of surveys currently in use incorporate all the elements of best practices associated with robust safety management systems.

Concussion History and Cognitive Function in a Large Cohort of Adolescent Athletes

BACKGROUND

The incidence of reported concussions in the adolescent population is increasing, yet research on the effects of concussions in this population is minimal and inconclusive.

PURPOSE

To assess the association between concussion and performance on a cognitive test battery.

STUDY DESIGN

Cross-sectional study; Level of evidence, 3.

METHODS

Using multivariate models, the authors assessed the association between concussion and performance on a cognitive test battery among 5616 high school and junior high school athletes. The researchers utilized a global cognitive score and scores for 5 domains: verbal memory, visual memory, visual motor, reaction time, and impulse control. Each cognitive score was converted to a z score with the mean and SD of the nonconcussed population. Results from each model were then interpreted as change in the standardized unit score. In the models, concussion was evaluated as ever having a concussion, number of concussions, time since last concussion, and age at first concussion.

RESULTS

Ever having a concussion was associated with a mean decrease of 0.11 standardized units (95% CI, -0.20 to -0.01) on the global cognitive score and lower scores in all cognitive domains. Each additional concussion was associated with lower scores on global cognitive function (effect estimate, -0.06; 95% CI, -0.11 to -0.02), verbal memory, visual memory, and impulse control. Concussion in early childhood was associated with lower global cognition (effect estimate, -0.05; 95% CI, -0.08 to -0.01), visual memory, and motor visual scores as compared with concussions in later childhood. The associations between time since last concussion and cognitive test scores were nonlinear, and on all tests, lower scores were observed even ≥1 year after the concussion.

CONCLUSION

On the basis of objective performance metrics for cognitive function, concussions had a more persistent effect on cognitive function than previously thought. The age at which an individual has his or her first concussion may be an important factor in determining long-lasting cognitive effects.

A Cluster Randomized Controlled Trial of a Total Worker Health® Intervention on Commercial Construction Sites

This study evaluated the efficacy of an integrated Total Worker Health^® program, “All the Right Moves”, designed to target the conditions of work and workers’ health behaviors through an ergonomics program combined with a worksite-based health promotion Health Week intervention. A matched-pair cluster randomized controlled trial was conducted on ten worksites (five intervention (n = 324); five control sites (n = 283)). Worker surveys were collected at all sites pre- and post- exposure at one- and six-months. Linear and logistic regression models evaluated the effect of the intervention on pain and injury, dietary and physical activity behaviors, smoking, ergonomic practices, and work limitations. Worker focus groups and manager interviews supplemented the evaluation. After controlling for matched intervention and control pairs as well as covariates, at one-month following the ergonomics program we observed a significant improvement in ergonomic practices (B = 0.20, p = 0.002), and a reduction in incidences of pain and injury (OR = 0.58, p = 0.012) in the intervention group. At six months, we observed differences in favor of the intervention group for a reduction in physically demanding work (B = −0.25, p = 0.008), increased recreational physical activity (B = 35.2, p = 0.026) and higher consumption of fruits and vegetables (B = 0.87, p = 0.008). Process evaluation revealed barriers to intervention implementation fidelity and uptake, including a fissured multiemployer worksite, the itinerant nature of workers, competing production pressures, management support, and inclement weather. The All the Right Moves program had a positive impact at the individual level on the worksites with the program. For the longer term, the multi-organizational structure in the construction work environment needs to be considered to facilitate more upstream, long-term changes.

A Randomized Controlled Trial of a Truck Seat Intervention: Part 1-Assessment of Whole Body Vibration Exposures

Full-time vehicle and heavy equipment operators often have a high prevalence of musculoskeletal disorders, especially low back pain (LBP). In occupations requiring vehicles or heavy equipment operation, exposure to whole body vibration (WBV) has been consistently associated with LBP. LBP is the most common cause of work-related disability and continues to be the leading cause of morbidity and lost productivity in the US workforce. Using a parallel randomized controlled trial design, over a 12-month period, this study evaluated two different seating interventions designed to reduce WBV exposures. Forty professional truck drivers were initially recruited and randomly assigned to one of two groups: (i) a passive suspension/control group-20 drivers who received a new, industry-standard air-suspension seat, and (ii) an intervention group-20 drivers who received an active-suspension seat, which has been shown to reduce vertical WBV exposures by up to 50% compared to passive seats. WBV exposures from the truck seat and floor were collected during driver's full shifts (6-18 h) before (pre-intervention) and after the intervention (0, 3, 6, and 12 months post-intervention) per International Standards Organization (ISO) 2631-1 and 2631-5 WBV standards. After subject dropout and turnover, 16 truck drivers remained in each group. The pre-intervention WBV data showed that there were no differences in the daily equivalent time-weighted average WBV exposures [A(8)], vibration dose values [VDV(8)], and static spinal compression doses [Sed(8)] between the two groups (P's > 0.36). After the new seats were installed, the A(8) values showed that the active suspension/intervention group experienced much greater reduction in the vertical (z) axis [~50%; P = <0.0001; Cohen's d effect size (95% CI) = 1.80 (1.12, 2.48)] exposures when compared to in the passive suspension/control group [~20%; P = 0.23; 0.33 (-0.36, 1.02)]. The post-intervention z-axis VDV(8) and Sed(8) WBV exposure measures were not different between the two seat groups [VDV(8), P = 0.33; 0.35 (-0.32, 1.03); Sed(8), P = 0.61; 0.08 (-0.59, 0.76)]. These study findings indicate that, relative to the current industry-standard, passive air-suspension seats which are ubiquitous in all semi-trucks today, the active suspension seat dramatically reduced average continuous [A(8)] WBV exposures but not periodic, cumulative impulsive exposures [VDV(8) and Sed(8)].

A Randomized Controlled Trial of a Truck Seat Intervention: Part 2-Associations Between Whole-Body Vibration Exposures and Health Outcomes

This randomized controlled trial study was conducted to determine whether two different seating interventions would reduce exposure to whole-body vibration (WBV) and improve associated health outcomes. Forty professional truck drivers were randomly assigned to two groups: (i) a control group of 20 drivers who received a new, industry-standard air-suspension seat, and (ii) an intervention group of 20 drivers who received an active-suspension seat. This study collected regional body pain (10-point scale), low back disability [Oswestry Disability Index (ODI)], physical and mental health [the Short Form 12-item Health Survey (SF-12)], and work limitations [Work Limitation Questionnaire (WLQ)] before and 3, 6, and 12 months after the seating intervention. WBV exposures were also collected during the same time periods. Due to dropouts at the 12-month time period, only data up to 6 months post-intervention were included in the analyses. The post-intervention A(8) WBV exposures were lower in both groups with a more substantial WBV exposure reduction (~50%) in the intervention group compared to the control group (~26%). There was little to no change in the impulsive exposures [VDV(8) and Sed(8)] post-intervention and no differences between the two groups. The self-reported musculoskeletal health outcomes showed that intervention group experienced a greater reduction in the low back pain (LBP) and other musculoskeletal outcomes than the control group. The LBP reduction in the intervention group was clinically meaningful (>25%); however, none of the changes in pain reached statistical significance (P's > 0.22). The SF-12 health scores demonstrated that the intervention group's physical health improved after the intervention (P's < 0.06) while the control group experience little to no improvement (P's > 0.11). The WLQ scores showed that the intervention group generally experienced reduced (improved) work limitation over time whereas the control group showed inconsistent changes in work limitation scores. These study findings indicate that reducing truck drivers' exposure to WBV through seating intervention can lead to improvements in LBP and other health outcomes.

Correctness of Self-Reported Task Durations: A Systematic Review

Objectives

Duration of tasks in a job is an essential interest in occupational epidemiology. Such duration is frequently measured using self-reports, which may, however, be associated with both bias and random errors. The present systematic literature review examines the correctness of self-reported durations of tasks, i.e. the extent to which they differ from more valid reference data due to either systematic or random errors, and factors influencing this correctness, with particular emphasis on the assessment of exposures of relevance to musculoskeletal disorders.

Methods

The search for relevant studies included the databases ISI Web of Science, MEDLINE, EBSCO HOST, Proquest, and Psycnet.

Results

Thirty-two articles were identified; of which, 23 examined occupational tasks and 9 examined non-occupational tasks. Agreement between self-reports and a more correct reference was reported for, in total, 182 tasks. Average proportional errors were, for most tasks, between -50% (i.e. underestimations) and +100%, with a dominance of overestimations; 22% of all results considered overestimations of 100% or more. For 15% of the 182 reported tasks, the mean difference between the self-reported and the reference duration value was <5%, and 20% of the 182 mean differences were between 5 and 20%. In general, respondents were able to correctly distinguish tasks of a longer duration from shorter tasks, even though the actual durations were not correct. A number of factors associated with the task per se appeared to influence agreement between self-reports and reference data, including type of task, true task duration, task pattern across time (continuous versus discontinuous), and whether the addressed task is composed of subtasks. The musculoskeletal health status of the respondent did not have a clear effect on the ability to correctly report task durations. Studies differed in key design characteristics and detail of information reported, which hampers a formal aggregation of results.

Conclusions

The correctness of self-reported task durations is, at the best, moderate at the individual level, and this may present a significant problem when using self-reports in task-based assessment of individual job exposures. However, average self-reports at the group level appear reasonably correct and may thus be a viable method in studies addressing, for instance, the relative occurrence of tasks in a production system. Due to the disparity of studies, definite conclusions on the quantitative effect on agreement of different modifiers are not justified, and we encourage future studies specifically devoted to understanding and controlling sources of bias in self-reported task durations. We also encourage studies developing decision support for when to apply or avoid self-reports to measure task durations, depending on study purpose and occupational setting.

Predicting Forearm Physical Exposures During Computer Work Using Self-Reports, Software-Recorded Computer Usage Patterns, and Anthropometric and Workstation Measurements

Objectives

Alternative techniques to assess physical exposures, such as prediction models, could facilitate more efficient epidemiological assessments in future large cohort studies examining physical exposures in relation to work-related musculoskeletal symptoms. The aim of this study was to evaluate two types of models that predict arm-wrist-hand physical exposures (i.e. muscle activity, wrist postures and kinematics, and keyboard and mouse forces) during computer use, which only differed with respect to the candidate predicting variables; (i) a full set of predicting variables, including self-reported factors, software-recorded computer usage patterns, and worksite measurements of anthropometrics and workstation set-up (full models); and (ii) a practical set of predicting variables, only including the self-reported factors and software-recorded computer usage patterns, that are relatively easy to assess (practical models).

Methods

Prediction models were build using data from a field study among 117 office workers who were symptom-free at the time of measurement. Arm-wrist-hand physical exposures were measured for approximately two hours while workers performed their own computer work. Each worker's anthropometry and workstation set-up were measured by an experimenter, computer usage patterns were recorded using software and self-reported factors (including individual factors, job characteristics, computer work behaviours, psychosocial factors, workstation set-up characteristics, and leisure-time activities) were collected by an online questionnaire. We determined the predictive quality of the models in terms of R2 and root mean squared (RMS) values and exposure classification agreement to low-, medium-, and high-exposure categories (in the practical model only).

Results

The full models had R2 values that ranged from 0.16 to 0.80, whereas for the practical models values ranged from 0.05 to 0.43. Interquartile ranges were not that different for the two models, indicating that only for some physical exposures the full models performed better. Relative RMS errors ranged between 5% and 19% for the full models, and between 10% and 19% for the practical model. When the predicted physical exposures were classified into low, medium, and high, classification agreement ranged from 26% to 71%.

Conclusion

The full prediction models, based on self-reported factors, software-recorded computer usage patterns, and additional measurements of anthropometrics and workstation set-up, show a better predictive quality as compared to the practical models based on self-reported factors and recorded computer usage patterns only. However, predictive quality varied largely across different arm-wrist-hand exposure parameters. Future exploration of the relation between predicted physical exposure and symptoms is therefore only recommended for physical exposures that can be reasonably well predicted.

Late-cueing of gait tasks on an uneven brick surface impacts coordination and center of mass control in older adults

BACKGROUND

Changing directions while walking (turning gait), often with little planning time, is essential to navigating irregular surfaces in the built-environment. It is unclear how older adults reorient their bodies under these constraints and whether adaptations are related to declines in physiological characteristics.

RESEARCH QUESTION

The aims of this study were to (1) investigate whether surface irregularity, late-cueing, and age negatively affect coordination, kinematics, and center of mass (COM) movement during 90° turning gait and (2) determine if adaptations correlate with declines in strength, balance, and reaction-time.

METHODS

Eighteen young (18-35 years) and sixteen older (65+ years) healthy adults participated in the study. Retro-reflective marker and trunk-accelerometry data were used to compute upper-body segmental reorientation timing, upper-body kinematics, and COM movement characteristics. Balance scores, lower-limb strength, and choice-reaction-times were also recorded.

RESULTS

Young and older adults maintained a cranial-caudal (head, shoulders, pelvis) reorientation sequence (p ≤ 0.018), lowered head pitch (uneven surface; young p = 0.035 and old p < 0.001), increased maximum COM acceleration (uneven surface and late-cueing; p ≤ 0.002), and decreased COM smoothness (uneven surface; p < 0.001). Young adults increased shoulder roll (uneven surface and late-cueing; p ≤ 0.008). Reduced stride regularity (late-cueing) was observed in older (p < 0.001), compared to young (p = 0.017), adults. Declines in strength (p ≤ 0.040) and balance (p = 0.018) were correlated with gait adaptations of older adults.

SIGNIFICANCE

Late-cueing on an uneven surface is challenging for older adults. These challenges are exacerbated by strength and balance deficits.

Evaluation of commercially available seat suspensions to reduce whole body vibration exposures in mining heavy equipment vehicle operators

As mining vehicle operators are exposed to high level of Whole body vibration (WBV) for prolonged periods of time, approaches to reduce this exposure are needed for the specific types of exposures in mining. Although various engineering controls (i.e. seat suspension systems) have been developed to address WBV, there has been lack of research to systematically evaluate these systems in reducing WBV exposures in mining heavy equipment vehicle settings. Therefore, this laboratory-based study evaluated the efficacy of different combinations of fore-aft (x-axis), lateral (y-axis), and vertical (z-axis) suspensions in reducing WBV exposures. The results showed that the active vertical suspension more effectively reduced the vertical vibration (∼50%; p's < 0.0001) as compared to the passive vertical suspension (10%; p's < 0.11). The passive fore-aft (x-axis) and lateral (y-axis) suspension systems did not attenuate the corresponding axis vibration (p's > 0.06) and sometimes amplified the floor vibration, especially when the non-vertical vibration was predominant (p's < 0.02). These results indicate that there is a critical need to develop more effective engineering controls including better seat suspensions to address non-vertical WBV exposures, especially because these non-vertical WBV exposures can increase risks for adverse health effects including musculoskeletal loading, discomfort, and impaired visual acuity.

Outcomes of safe patient handling and mobilization programs: A meta-analysis

BACKGROUND

Variability in patient care settings and the range of patient handling tasks present challenges in developing and evaluating safe patient handling and mobilization (SPHM) programs.

OBJECTIVE

We performed a systematic meta-analysis of SPHM program evaluations.

METHODS

Systematic literature review identified published SPHM program evaluations. Injury Rate Ratios (IRR), pre- to post-intervention, were used to estimate intervention effects and to examine the influence of patient care level, program components, and follow-up time using meta-regression.

RESULTS

27 articles reported evaluations from 44 sites. Combined effect estimate for all SPHM programs was 0.44 (95% CI 0.36, 0.54), reflecting substantial injury reductions after program implementation. While specific program components were not associated with greater effectiveness, longer follow-up duration was associated with greater injury rate reduction (p = 0.01) and intervention effects varied by level of care (p = 0.01), with the greatest effect in intensive care unit interventions (IRR 0.14; 95% CI 0.07, 0.30).

CONCLUSIONS

SPHM programs appear to be highly effective in reducing injuries. More research is needed to identify the most effective interventions for different patient care levels.

The relationship between organizational policies and practices and work limitations among hospital patient care workers

OBJECTIVE

We examined relationships between organizational policies and practices (OPPs) (safety practices, ergonomic practices, and people-oriented culture) and work limitations in a sample of hospital workers.

METHODS

We used the 6-item Work Limitations Questionnaire (WLQ) to assess workers' perceptions of health-related work limitations. Self-reported OPPs and the WLQ were collected from workers in Boston, Massachusetts (n = 1277). We conducted random-intercept multi-level logistic regression models for each OPP using stepwise selection of covariates.

RESULTS

As the unit-average ergonomic practice score increased by one, the odds of a worker reporting work limitations decreased by approximately 39% (P-value = 0.018), adjusted for job title, age, and body mass index. A similar relationship existed for people-oriented culture (P-value = 0.038). The association between safety practices and work limitations was similar, but not statistically significant.

CONCLUSIONS

This study demonstrated the importance of workplace OPPs. OPPs that promote positive and supportive environments and that foster improvements in ergonomics may help reduce work limitations.

Aging may negatively impact movement smoothness during stair negotiation

Stairs represent a barrier to safe locomotion for some older adults, potentially leading to the adoption of a cautious gait strategy that may lack fluidity. This strategy may be characterized as unsmooth; however, stair negotiation smoothness has yet to be quantified. The aims of this study were to assess age- and task-related differences in head and body center of mass (COM) acceleration patterns and smoothness during stair negotiation and to determine if smoothness was associated with the timed "Up and Go" (TUG) test of functional movement. Motion data from nineteen older and twenty young adults performing stair ascent, stair descent, and overground straight walking trials were analyzed and used to compute smoothness based on the log-normalized dimensionless jerk (LDJ) and the velocity spectral arc length (SPARC) metrics. The associations between TUG and smoothness measures were evaluated using Pearson's correlation coefficient (r). Stair tasks increased head and body COM acceleration pattern differences across groups, compared to walking (p < 0.05). LDJ smoothness for the head and body COM decreased in older adults during stair descent, compared to young adults (p ≤ 0.015) and worsened with increasing TUG for all tasks (-0.60 ≤ r ≤ -0.43). SPARC smoothness of the head and body COM increased in older adults, regardless of task (p < 0.001), while correlations showed improved SPARC smoothness with increasing TUG for some tasks (0.33 ≤ r ≤ 0.40). The LDJ outperforms SPARC in identifying age-related stair negotiation adaptations and is associated with performance on a clinical test of gait.

Tablet form factors and swipe gesture designs affect thumb biomechanics and performance during two-handed use

Tablet computers' hardware and software designs may affect upper extremity muscle activity and postures. This study investigated the hypothesis that forearm muscle activity as well as wrist and thumb postures differ during simple gestures across different tablet form factors and touchscreen locations. Sixteen adult (8 female, 8 male) participants completed 320 tablet gestures across four swipe locations, with various tablet sizes (8″ and 10"), tablet orientations (portrait and landscape), swipe orientations (vertical and horizontal), and swipe directions (medial and radial). Three-dimensional motion analysis and surface electromyography measured wrist and thumb postures and forearm muscle activity, respectively. Postures and muscle activity varied significantly across the four swipe locations (p < .0001). Overall, swipe location closest to the palm allowed users to swipe with a more neutral thumb and wrist posture and required less forearm muscle activity. Greater thumb extension and abduction along with greater wrist extension and ulnar deviation was required to reach the target as the target moved farther from the palm. Extensor Carpi Radialis, Extensor Carpi Ulnaris, Flexor Carpi Ulnaris, Extensor Policis Brevis, and Abductor Pollicis Longus muscle activity also increased significantly with greater thumb reach (p < 001). Larger tablet size induced greater Extensor Carpi Radialis, Extensor Carpi Ulnaris, Flexor Carpi Ulnaris, Flexor Carpi Radialis, and Abductor Pollicis Longus muscle activity (p < .0001). The study results demonstrate the importance of swipe locations and suggest that the tablet interface design can be improved to induce more neutral thumb and wrist posture along with lower forearm muscle load.

The effect of a multi-axis suspension on whole body vibration exposures and physical stress in the neck and low back in agricultural tractor applications

Whole body vibration (WBV) exposures are often predominant in the fore-aft (x) or lateral (y) axis among off-road agricultural vehicles. However, as the current industry standard seats are designed to reduce mainly vertical (z) axis WBV exposures, they may be less effective in reducing drivers' exposure to multi-axial WBV. Therefore, this laboratory-based study aimed to determine the differences between a single-axial (vertical) and multi-axial (vertical + lateral) suspension seat in reducing WBV exposures, head acceleration, self-reported discomfort, and muscle activity (electromyography) of the major muscle of the low back, neck and shoulders. The results showed that the multi-axial suspension seat had significantly lower WBV exposures compared to the single-axial suspension seats (p' < 0.04). Similarly, the multi-axial suspension seat had lower head acceleration and muscle activity of the neck, shoulder, and low back compared to the single-axial suspension seat; some but not all of the differences were statistically significant. These results indicate that the multi-axial suspension seat may reduce the lateral WBV exposures and associated muscular loading in the neck and low back in agricultural vehicle operators.

Gait adaptations of older adults on an uneven brick surface can be predicted by age-related physiological changes in strength

BACKGROUND

Outdoor falls in community-dwelling older adults are often triggered by uneven pedestrian walkways. It remains unclear how older adults adapt to uneven surfaces typically encountered in the outdoor built-environment and whether these adaptations are associated to age-related physiological changes.

RESEARCH QUESTION

The aims of this study were to (1) compare gait parameters over uneven and flat brick walkways, (2) evaluate the differences between older and young adults for these two surfaces, and (3) assess if physiological characteristics could predict adaptations in older adults.

METHODS

Balance, strength, reaction-time, full-body marker positions, and acceleration signals from a trunk-mounted inertial measurement unit were collected in seventeen older (71.5 ± 4.2 years) and eighteen young (27.0 ± 4.7 years) healthy adults to compute lower-limb joint kinematics, spatio-temporal parameters, dynamic stability, and accelerometry-derived metrics (symmetry, consistency, and smoothness).

RESULTS

Both groups increased hip flexion at foot-strike, while decreasing ankle dorsiflexion, margin of stability, symmetry, and consistency on the uneven, compared to flat, surface. Older, compared to young, adults showed a larger increase in knee flexion at foot-strike and a larger decrease in smoothness on the uneven surface. Only young adults decreased hip abduction on the uneven surface. Strength, not balance nor reaction-time, was the main predictor of hip abduction in older adults on both surfaces.

SIGNIFICANCE

While older adults may be especially vulnerable, uneven surfaces negatively impact gait, irrespective of age, and could represent a risk to all pedestrians.

Prevalence of Work-Related Musculoskeletal Disorders Among Surgeons and Interventionalists: A Systematic Review and Meta-analysis

Importance

Physicians in procedural specialties are at high risk for work-related musculoskeletal disorders (MSDs). This has been called "an impending epidemic" in the context of the looming workforce shortage; however, prevalence estimates vary by study.

Objectives

To estimate the prevalence of work-related MSDs among at-risk physicians and to evaluate the scope of preventive efforts.

Data Sources and Study Selection

Systematic search in MEDLINE (Ovid), Embase (Elsevier), Web of Science, PubMed (National Center for Biotechnology Information), and 2 clinical trial registries, without language restriction, for studies reporting on the prevalence and prevention of work-related MSDs among at-risk physicians published until December 2016. The Meta-analysis of Observational Studies in Epidemiology (MOOSE) guidelines for meta-analyses and systematic reviews of observational studies were used. At-risk physicians were defined as surgeons and medical interventionalists. Studies reporting on specific disorders or pain assessed with validated instruments were included.

Data Extraction and Synthesis

Study characteristics; disease prevalence for the neck, shoulder, back, and upper extremity; and measures of resulting disability were recorded. Study estimates were pooled using random-effects meta-analytic models.

Main Outcomes and Measures

Career prevalence of injuries and 12-month prevalence of pain.

Results

Among 21 articles (5828 physicians [mean age, 46.0 years; 78.5% male; 12.8 years in practice; 14.4 hours performing procedures per week]) included in this systematic review and meta-analysis, pooled crude prevalence estimates of the most common work-related MSDs were degenerative cervical spine disease in 17% (457 of 2406 physicians) (95% CI, 12%-25%), rotator cuff pathology in 18% (300 of 1513 physicians) (95% CI, 13%-25%), degenerative lumbar spine disease in 19% (544 of 2449 physicians) (95% CI, 5%-16%), and carpal tunnel syndrome in 9% (256 of 2449 physicians) (95% CI, 5%-16%). From 1997 to 2015, the prevalence of degenerative cervical spine disease and degenerative lumbar spine disease increased by 18.3% and 27%, respectively. Pooled prevalence estimates for pain ranged from 35% to 60% and differed by assessment instrument. Of those with a work-related MSD, 12% (277 of 2319 physicians) (95% CI, 7%-18%) required a leave of absence, practice restriction or modification, or early retirement. Heterogeneity was considerable for all crude analyses (mean I2 = 93.5%) but was lower for sensitivity analyses (mean I2 = 72.3%). Interventions focused on products and behaviors. Twelve at-risk specialties described a gross lack of awareness and an unmet need for ergonomics education.

Conclusions and Relevance

Prevalence estimates of work-related MSDs among at-risk physicians appear to be high. Further research is needed to develop and validate an evidence-based applied ergonomics program aimed at preventing these disorders in this population.

Machine learning algorithms based on signals from a single wearable inertial sensor can detect surface- and age-related differences in walking

The aim of this study was to investigate if a machine learning algorithm utilizing triaxial accelerometer, gyroscope, and magnetometer data from an inertial motion unit (IMU) could detect surface- and age-related differences in walking. Seventeen older (71.5 ± 4.2 years) and eighteen young (27.0 ± 4.7 years) healthy adults walked over flat and uneven brick surfaces wearing an inertial measurement unit (IMU) over the L5 vertebra. IMU data were binned into smaller data segments using 4-s sliding windows with 1-s step lengths. Ninety percent of the data were used as training inputs and the remaining ten percent were saved for testing. A deep learning network with long short-term memory units was used for training (fully supervised), prediction, and implementation. Four models were trained using the following inputs: all nine channels from every sensor in the IMU (fully trained model), accelerometer signals alone, gyroscope signals alone, and magnetometer signals alone. The fully trained models for surface and age outperformed all other models (area under the receiver operator curve, AUC = 0.97 and 0.96, respectively; p ≤ .045). The fully trained models for surface and age had high accuracy (96.3, 94.7%), precision (96.4, 95.2%), recall (96.3, 94.7%), and f1-score (96.3, 94.6%). These results demonstrate that processing the signals of a single IMU device with machine-learning algorithms enables the detection of surface conditions and age-group status from an individual's walking behavior which, with further learning, may be utilized to facilitate identifying and intervening on fall risk.

Evaluating biomechanics of user-selected sitting and standing computer workstation

A standing computer workstation has now become a popular modern work place intervention to reduce sedentary behavior at work. However, user's interaction related to a standing computer workstation and its differences with a sitting workstation need to be understood to assist in developing recommendations for use and set up. The study compared the differences in upper extremity posture and muscle activity between user-selected sitting and standing workstation setups. Twenty participants (10 females, 10 males) volunteered for the study. 3-D posture, surface electromyography, and user-reported discomfort were measured while completing simulated tasks with each participant's self-selected workstation setups. Sitting computer workstation associated with more non-neutral shoulder postures and greater shoulder muscle activity, while standing computer workstation induced greater wrist adduction angle and greater extensor carpi radialis muscle activity. Sitting computer workstation also associated with greater shoulder abduction postural variation (90th-10th percentile) while standing computer workstation associated with greater variation for should rotation and wrist extension. Users reported similar overall discomfort levels within the first 10 min of work but had more than twice as much discomfort while standing than sitting after 45 min; with most discomfort reported in the low back for standing and shoulder for sitting. These different measures provide understanding in users' different interactions with sitting and standing and by alternating between the two configurations in short bouts may be a way of changing the loading pattern on the upper extremity.

Continuous ambulatory hand force monitoring during manual materials handling using instrumented force shoes and an inertial motion capture suit

Hand forces (HFs) are commonly measured during biomechanical assessment of manual materials handling; however, it is often a challenge to directly measure HFs in field studies. Therefore, in a previous study we proposed a HF estimation method based on ground reaction forces (GRFs) and body segment accelerations and tested it with laboratory equipment: GFRs were measured with force plates (FPs) and segment accelerations were measured using optical motion capture (OMC). In the current study, we evaluated the HF estimation method based on an ambulatory measurement system, consisting of inertial motion capture (IMC) and instrumented force shoes (FSs). Sixteen participants lifted and carried a 10-kg crate from ground level while 3D full-body kinematics were measured using OMC and IMC, and 3D GRFs were measured using FPs and FSs. We estimated 3D hand force vectors based on: (1) FP+OMC, (2) FP+IMC and (3) FS+IMC. We calculated the root-mean-square differences (RMSDs) between the estimated HFs to reference HFs calculated based on crate kinematics and the GRFs of a FP that the crate was lifted from. Averaged over subjects and across 3D force directions, the HF RMSD ranged between 10-15N when using the laboratory equipment (FP + OMC), 11-18N when using the IMC instead of OMC data (FP+IMC), and 17-21N when using the FSs in combination with IMC (FS + IMC). This error is regarded acceptable for the assessment of spinal loading during manual lifting, as it would results in less than 5% error in peak moment estimates.

Nurses' but not supervisors' safety practices are linked with job satisfaction

AIMS

To test the associations of safety practices as reported by nurses and their respective unit supervisors with job satisfaction.

BACKGROUND

Psychosocial workplace factors are associated with job satisfaction; however, it is unknown whether nurses and supervisors accounts of safety practices are differentially linked to this outcome.

METHODS

Cross-sectional study design including nurses (n = 1052) nested in 94 units in two hospitals in Boston (MA, USA). Safety practices refer to the identification and control of occupational hazards at the unit. Safety practices were measured aggregating nurses' responses per unit, and supervisory levels. Individual's job satisfaction for each nurse was the response variable.

RESULTS

Supervisors assessed safety practices more favourably than their unit nursing staff. Adjusted random intercept logistic regressions showed that the odds of higher job satisfaction were higher for nurses at units with better safety practices (OR: 1.67, 95% CI: 1.04, 2.68) compared with nurses at units that averaged lower safety practices. Supervisors' reports of safety practices were not correlated with the job satisfaction of their staff.

CONCLUSIONS

Adequate safety practices might be a relevant managerial role that enhances job satisfaction among nurses.

IMPLICATIONS FOR NURSING MANAGEMENT

Nursing supervisors should calibrate their safety assessments with their nursing staff to improve nurses' job satisfaction.

A research framework for the development and implementation of interventions preventing work-related musculoskeletal disorders

Objectives Work-related musculoskeletal disorders (MSD) are highly prevalent and put a large burden on (working) society. Primary prevention of work-related MSD focuses often on physical risk factors (such as manual lifting and awkward postures) but has not been too successful in reducing the MSD burden. This may partly be caused by insufficient knowledge of etiological mechanisms and/or a lack of adequately feasible interventions (theory failure and program failure, respectively), possibly due to limited integration of research disciplines. A research framework could link research disciplines thereby strengthening the development and implementation of preventive interventions. Our objective was to define and describe such a framework for multi-disciplinary research on work-related MSD prevention. Methods We described a framework for MSD prevention research, partly based on frameworks from other research fields (ie, sports injury prevention and public health). Results The framework is composed of a repeated sequence of six steps comprising the assessment of (i) incidence and severity of MSD, (ii) risk factors for MSD, and (iii) underlying mechanisms; and the (iv) development, (v) evaluation, and (vi) implementation of preventive intervention(s). Conclusions In the present framework for optimal work-related MSD prevention, research disciplines are linked. This framework can thereby help to improve theories and strengthen the development and implementation of prevention strategies for work-related MSD.

An Inspection Tool and Process to Identify Modifiable Aspects of Acute Care Hospital Patient Care Units to Prevent Work-Related Musculoskeletal Disorders

A dearth of practical resources is available for evaluating ergonomic risk factors in dynamic health care work environments. Of particular need are tools for inspecting patient care environments for hazards. The goal of this study was to describe the development and application of an inspection tool and a process for identifying hazards inherent in the modifiable aspects of the physical environment to reduce injury risk to hospital workers. Through an iterative and participatory process, the tool and inspection process were developed with three purposes in mind: (a) create a framework for the inspection of physical work environments and physical conditions of work associated with injury risk (hazards), (b) document the physical conditions, and (c) provide feedback to decision makers. The tool and process were used by an ergonomics researcher on four patient care units as part of the Be Well, Work Well Total Worker Health® intervention. The resulting inspection process provided a structured method for recognizing hazards in the dynamic modifiable physical work environment and reporting both observations and recommendations to decision makers. The development and implementation of the inspection tool provided guidance to modify the physical work environment by implementing ergonomic solutions. The tool allowed the organization to plan and prioritize ergonomic hazard abatement (e.g. resource allocation and tracking trends). Within a Total Worker Health® framework, this tool can measure work practices which can then be used to inform organizational programs and policies within a health care setting.