Liberty Mutual Research Institute for Safety
Recent publications
The availability of electrical light has altered modern light exposure, affecting the synchronization process (‘entrainment’) of the circadian clock to the natural light–dark cycle. The discrepancy between the natural light–dark cycle and self-selected light exposure has raised the question whether humans entrain to sun time (as most organisms do) vs. social time. None of the studies addressing this question have been conducted in the US in a large-scale, nationally representative sample. In this brief report, we aimed at estimating the relationship between individual chronotype (the result of the entrainment process) and longitude position in a time zone, using 12 years (2003–2014) of pooled diary data (n = 50,753) from the American Time Use Survey (ATUS). Chronotype was estimated based on mid-sleep time on weekends (MSFWe), a proxy that was previously shown to replicate known age and sex differences in chronotype in the ATUS. Longitude position was derived from state-level information (e.g., average state border outline). Regression results showed a progressive delay in MSFWe from east to west within three of the four US continental time zones (delay per degree of longitude): Eastern, 1.8 min; Central, 1.2 min; Mountain, 2.4 min (all p < .01). The findings suggest that humans entrain to sun time, leading to an increasing discrepancy between social time and biological time (“circadian misalignment”) towards the west of a time zone. Such a misalignment induced by where people live within a time zone may affect a large share of the population, with implications for health and safety.
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.
Purpose An increasing number of workers in the US have chronic health conditions that limit their ability to work, and few worksite interventions have been tested to improve worker coping and problem solving at work. The purpose of this study was to evaluate a worksite-based health self-management program designed to improve workplace function among workers with chronic health conditions. Methods We conducted a randomized, controlled trial of a worksite self-management program (“Manage at Work”) ( #NCT01978392) for workers with chronic health conditions (N = 119; 82% female, ages 20–69). Most workers were recruited from the health care or light manufacturing industry sectors. Workers attended a 5-session, facilitated psychoeducational program using concepts of health self-management, self-efficacy, ergonomics, and communication. Changes on outcomes of work engagement, work limitation, job satisfaction, work fatigue, work self-efficacy, days absent, and turnover intention at 6-month follow-up were compared to wait-list controls. Results The most prevalent chronic health conditions were musculoskeletal pain, headaches, vision problems, gastrointestinal disorders, respiratory disorders, and mental health disorders. The self-management program showed greater improvement in work engagement and turnover intent at 6-month follow-up, but there was no evidence of a parallel reduction in perceived work limitation. Trends for improved outcomes of work self-efficacy, job satisfaction, and work fatigue in the intervention group did not reach statistical significance in a group x time interaction test. Conclusions Offering a worksite self-management program to workers with chronic health conditions may be a feasible and beneficial strategy to engage and retain skilled workers who are risking disability. Clinical trial registration: #NCT01978392.
Utilizing a longitudinal approach, this study examined mechanisms explaining how safety climate is associated with truck drivers’ safety behavior and outcomes. The present study also examined the top-down process of how organization-level safety climate (i.e., top management referenced) is related to group-level safety climate (i.e., supervisor referenced). Two waves (matched N = 481) of safety climate and safety behavior data (with a 2-year interval) were obtained from a large US trucking company. Days lost due to road injuries were assessed 6 months after time 2. Autoregressive, cross-lagged, and prospective effects were examined. Safety climate scores and safety behavior were moderately stable across a 2-year period. Both organization- and group-level safety climate scores were positively associated with safety behavior. The top-down association between time 1 organization-level safety climate and time 2 group-level safety climate was supported. Safety behavior mediated the relationship between group-level safety climate and future lost days due to injury. Contrary to suggestions of some prior research, the present study shows that safety climate measures may have lasting ability to predict safety behavior/outcomes in the trucking industry. In particular, the present study supported a hierarchical model in which organization-level safety climate influences safety outcomes through its influence on group-level climate. The top-down model connotes that top management efforts to instill a strong positive safety climate to affect workers’ driving behavior operate through management’s influence on the actions of the workers’ immediate supervisor.
Background: Early magnetic resonance imaging (eMRI) for nonspecific low back pain (LBP) not adherent to clinical guidelines is linked with prolonged work disability. Although the prevalence of eMRI for occupational LBP varies substantially among states, it is unknown whether the risk of prolonged disability associated with eMRI varies according to individual and area-level characteristics. The aim was to explore whether the known risk of increased length of disability (LOD) associated with eMRI scanning not adherent to guidelines for occupational LBP varies according to patient and area-level characteristics, and the potential reasons for any observed variations. Methods: A retrospective cohort of 59,360 LBP cases from 49 states, filed between 2002 and 2008, and examined LOD as the outcome. LBP cases with at least 1 day of work disability were identified by reviewing indemnity service records and medical bills using a comprehensive list of codes from the International Classification of Diseases, Ninth Edition (ICD-9) indicating LBP or nonspecific back pain, excluding medically complicated cases. Results: We found significant between-state variations in the negative impact of eMRI on LOD ranging from 3.4 days in Tennessee to 14.8 days in New Hampshire. Higher negative impact of eMRI on LOD was mainly associated with female gender, state workers' compensation (WC) policy not limiting initial treating provider choice, higher state orthopedic surgeon density, and lower state MRI facility density. Conclusion: State WC policies regulating selection of healthcare provider and structural factors affecting quality of medical care modify the impact of eMRI not adherent to guidelines. Targeted healthcare and work disability prevention interventions may improve work disability outcomes in patients with occupational LBP.
Purpose: Insurance company case managers can play a critical role in the rehabilitation process of people with musculoskeletal disorders sustained following minor motor vehicle crash injury due to their interaction with multiple stakeholders and their role in approving various services. This study aimed to identify factors that case managers perceive as predictive of recovery in people with musculoskeletal disorders after minor motor vehicle crash injury. Materials and methods: To explore the perspectives of cases managers in Australia and the United States, semi-structured interviews explored factors that case managers thought provided an early indication of likely recovery outcomes in people with musculoskeletal disorders after minor motor vehicle crash injury. A framework analysis was applied and factors were displayed within the ICF-framework. Results: Case managers (n = 40) demonstrated a broad, detailed understanding of biopsychosocial and contextual issues influencing recovery. They emphasized the importance of the injured worker’s expressed affect and motivation, style of communication, the role of lawyers, the worker’s family and friends, as well as cultural and geographic influences. The overarching themes perceived as having a major influence on recovery outcomes were general health, pain processing and response, work situation, and compensation entitlement. Conclusions: Case managers’ broad and detailed perceptions about recovery may provide additional, valuable perspectives for professionals involved in the rehabilitation process of people with musculoskeletal disorders after minor motor vehicle crash injury. Further research needs to be conducted to explore the effects of case manager involvement in the process of recovery. • Implications for rehabilitation • Insurance Case Managers identified multiple factors including affect and motivation, style of communication, the role of lawyers, family and friends, cultural and geographic variation provide opportunities for more effective treatment of people with musculoskeletal disorders related to minor motor vehicle collisions. These managers’ perceptions about recovery may be informative to and provide opportunities for health professionals involved in the rehabilitation of people with musculoskeletal disorders related to minor motor vehicle collisions. • While the Insurance Case Managers involved in this research did not use formalized assessment techniques, tools and assessment protocols could be developed jointly between for the needs of Insurance Case Managers and other stakeholders to tackle recovery of people with musculoskeletal disorders related to minor motor vehicle collision.
Background: Muscle co-contraction is an accepted clinical measure to quantify the effects of aging on neuromuscular control and movement efficiency. However, evidence of increased muscle co-contraction in old compared to young adults remains inconclusive. Research question: Are there differences in lower-limb agonist/antagonist muscle co-contractions in young and old adults, and males and females, during walking and stair use? Methods: In a retrospective study, we analyzed data from 20 healthy young and 19 healthy old adults during walking, stair ascent, and stair descent at self-selected speeds, including marker trajectories, ground reaction force, and electromyography activity. We calculated muscle co-contraction at the knee (vastus lateralis vs. biceps femoris) and ankle (tibialis anterior vs. medial gastrocnemius) using the ratio of the common area under a muscle pairs' filtered and normalized electromyography curves to the sum of the areas under each muscle in that pair. Results: Old compared to young adults displayed 18%-22% greater knee muscle co-contractions during the entire cycle of stair use activities. We found greater (17%-29%) knee muscle co-contractions in old compared to young adults during the swing phase of walking and stair use. We found no difference in ankle muscle co-contractions between the two age groups during all three activities. We found no difference in muscle co-contraction between males and females at the knee and ankle joints for all three activities. Significance: Based on our findings, we recommend clinical evaluation to quantify the effects of aging through muscle co-contraction to include the knee joint during dynamic activities like walking and stair use, and independent evaluation of the stance and swing phases.
The User Experience (UX) research team at Liberty Mutual Insurance has implemented a new method of taking notes and sharing notes with the team, Sketch notes. The purpose of Sketch notes is to accurately convey meaning at a glance and facilitate visual memory during collaborative analysis and insight-driven workshop activities. Sketch notes are a condensed visual map of what recruited participants share with the product team in an interview session or a usability test. In the first section, we explain why note-taking is an important part of the work of user researchers. Next, we review the note-taking methods that we use at Liberty Mutual and their advantages and drawbacks. In the third section, we introduce Sketch notes and explain how both the literature and its successful deployment at Liberty Mutual Insurance support this approach.
ASM Failure Analysis Case Histories: Processing Errors and Defects documents more than 110 cases of structural and/or functional failure attributed to manufacturing defects associated with primary and secondary processes, including melting, casting, forging, forming, and heat treating. Cases also examine failures stemming from cleaning, finishing, coating, and plating defects, as well as failures due to machining, injection molding, welding, and brazing errors. The cases describe the investigation, identify the primary cause, and include remedial solutions. These case histories have been compiled from a wide variety of ASM International publication types, including ASM Handbook volumes, conference proceedings, technical books, journals, and magazines.
Purpose To examine factors associated with Functional Capacity Evaluation (FCE) results in patients with painful musculoskeletal conditions, with focus on social factors across multiple countries. Methods International cross-sectional study was performed within care as usual. Simple and multiple multilevel linear regression analyses which considered measurement's dependency within clinicians and country were conducted: FCE characteristics and biopsychosocial variables from patients and clinicians as independent variables; and FCE results (floor-to-waist lift, six-minute walk, and handgrip strength) as dependent variables. Results Data were collected for 372 patients, 54 clinicians, 18 facilities and 8 countries. Patients' height and reported pain intensity were consistently associated with every FCE result. Patients' sex, height, reported pain intensity, effort during FCE, social isolation, and disability, clinician's observed physical effort, and whether FCE test was prematurely ended were associated with lift. Patient's height, Body Mass Index, post-test heart-rate, reported pain intensity and effort during FCE, days off work, and whether FCE test was prematurely ended were associated with walk. Patient's age, sex, height, affected body area, reported pain intensity and catastrophizing, and physical work demands were associated with handgrip. Final regression models explained 38‒65% of total variance. Clinician and country random effects composed 1-39% of total residual variance in these models. Conclusion Biopsychosocial factors were associated with every FCE result across multiple countries; specifically, patients' height, reported pain intensity, clinician, and measurement country. Social factors, which had been under-researched, were consistently associated with FCE performances. Patients' FCE results should be considered from a biopsychosocial perspective, including different social contexts.
The original version of this article unfortunately contained a mistake in the Table 2. The data under column head "Left handgrip strength (n = 336)" was erroneously omitted during the production process. The corrected Table 2 is given below.
In this article we investigate the performance of robust scan statistics based on moving medians, as test statistics for detecting a local change in population mean, for one and two dimensional data. When a local change in the population mean has not occurred and outliers are not present in the data, we derive approximations for the tail probabilities of fixed window scan statistics based on moving medians. The performance of the proposed robust scan statistics are evaluated and compared to, via power calculations, the performance of scan statistics based on moving sums, that have been previously investigated in the statistical literature. Numerical results based on a simulation study, for independent and identically distributed (iid) normal observations with known variance, indicate that in presence of outliers the scan statistic based on moving medians outperform the scan statistic based on moving sums, in terms of achieving more accurately the specified probability of type I error. The performance of a multiple window scan statistic based on moving medians for detecting a local change in population mean, for one and two dimensional normal data in presence of outliers, when the size of the window where a change has occurred is unknown has been investigated as well.
Purpose Worker’s expectations for return to working have been found to relate to return-to-work (RTW) outcomes; however, it is unclear if this varies depending upon the expected time to RTW. To advance the understanding of the relationship between expectations and RTW, we set out to answer the following research questions: Are shorter estimated times to RTW more accurate than estimates that are longer of duration? In addition, we sought to determine if there was a point in time that coincides with RTW estimates no longer being reliably related to time to RTW. Methods We utilized workers’ compensation data from a large, United States-based insurance company. Injured workers’ (N = 15,221) expectations for returning to work were compared with the termination of their total temporary indemnity payments. A linear regression model was used to determine if shorter lengths of expected time to RTW were more accurate. Quantile regression modelling was used to determine if there was point at which the expected time to RTW no longer reliably relates to the actual time to RTW. Results Findings indicated a positive relationship such that as the number of expected days to RTW increased, the number of days of difference (estimate error) between the actual time to RTW and the expected time to RTW also increased (β = 0.34, P < .001). The results of the quantile regression modelling indicated that for all quantiles estimated, with the exception of the quantile for estimates of 360 days, the relationship between the actual time to RTW and the expected time to RTW were statistically significant (P < .05). However, for RTW estimates of more than 14 days the relationship began decreasing in strength. Conclusion Results indicate that injured workers’ expectations for RTW can be used for RTW forecasting purposes. However, it is the case that RTW events in the near future can be forecasted with higher accuracy than those that are more distant, and that in general, injured workers will underestimate how long it will take them to RTW.
Driver support systems are intended to enhance driver performance and improve transportation safety. Even though these systems afford safety advantages, they challenge the traditional role of drivers in operating vehicles. Driver acceptance, therefore, is essential for the adoption of new in-vehicle technologies into the transportation system. In this study, a model of driver acceptance of driver support systems was developed. A conceptual driver acceptance model, including several components, was proposed based on a review of current literature. An empirical study was subsequently carried out using an online survey approach. The study collected data on participants' perceptions of two driver support systems (a fatigue monitoring system and an adaptive cruise control system combined with a lane-keeping system) in terms of attitude, perceived usefulness, and other components of driver acceptance. Results identified five components of driver acceptance (attitude, perceived usefulness, endorsement, compatibility, and affordability). The results also confirmed several mediating effects. The developed model was able to explain 85% of the variability in driver acceptance. The model provides an improved understanding how driver acceptance is formed, including which factors affect driver acceptance and how they affect it. The model can also help automakers and researchers to assess the design and estimate the potential use of a driver support system. The model could also be highly beneficial in developing a questionnaire to assess driver acceptance.
Functional capacity evaluations (FCE) are clinical instruments that use a battery of standardised performance tests to evaluate an individual’s ability to perform work-related activities. Several studies have investigated the potential biopsychosocial factors associated with FCE results to gain a better understanding of FCE results. Such studies have provided evidence for significant associations between FCE performance with primarily biological and psychological factors, while social factors have only been scarcely described. Despite its relevance in patients undergoing FCE, it is currently unclear which social factors are significantly associated with FCE performance. We conducted a systematic review to provide an overview of the association between social factors and performance of FCE tests in adults with chronic musculoskeletal pain.
Lumbar passive tissue elongation is a potential risk factor for the development of low back pain. In this study, we explored the effect of lumbar passive tissue elongation on lumbar-pelvic coordination pattern during trunk flexion/extension task. Thirteen participants performed 5 trials of trunk flexion/extension task both before and after a lumbar passive tissue elongation protocol. Trunk kinematics were recorded to calculate lumbar–pelvic continuous relative phase (CRP) and CRP variability. Results showed that passive tissue elongation significantly decreased the mean lumbar-pelvic CRP and CRP variability. Our results indicate that prolonged experienced lumbar passive tissue elongation should be avoided in an occupational environment.
Background: The amount of time between key points in the work disability and workers' compensation process, referred to as lag times, have been shown to relate to work disability outcomes but little research has examined how this finding may differ based on the diagnosis associated with the cause of work disability. Objective: To examine whether relationships between lag times in the work disability process and disability duration vary by diagnosis in a sample of workers' compensation claims. Methods: Using workers' compensation claims, Analysis of Covariance was used to estimate differences in disability duration across three lag times (days from the date of injury to: reporting the injury, seeking medical care, and starting lost work time paid by the workers' compensation insurer) and injury diagnosis groups (Work-related Musculoskeletal Disorders (WRMSD) and fractures). Results: WRMSD tended to have longer lag times than fractures, whereas disability duration tended to be longer for fractures than WRMSD. Overall, shorter lag times were associated with shorter disability duration, but the relationships varied across diagnosis groups, and greater variation in disability duration was observed for WRMSD compared to fractures. Conclusions: The findings suggest the importance of responding to work-related injuries by reporting the injury, receiving medical care, and taking time off of work if necessary, in a timely fashion.
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70 members
Helen Wellman
  • Center for Injury Epidemiology
Raymond W McGorry
  • Center for Physical Ergonomics
Yueng-Hsiang Huang
  • Center for Behavioral Science
Boston, United States