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The objectives of this case series study were to test whether an elastic back exosuit could increase a wearer’s endurance when lifting heavy objects and to assess whether lifting more cancels out the exosuit’s risk reduction benefits. We found that 88% of participants increased their lifting repetitions while wearing an exosuit, with endurance increases ranging from 28 to 75%. We then used these empirical data with an ergonomic assessment model based on fatigue failure principles to estimate the effects on cumulative back damage (an indicator of low back disorder risk) when an exosuit is worn and more lifts are performed. Participants exhibited 27–93% lower cumulative back damage when wearing an exosuit. These results confirmed that wearing an exosuit increased participants’ lifting capacity without canceling out injury risk reduction benefits. Back exosuits may make it possible to simultaneously boost productivity and reduce musculoskeletal disorder risks, which is relevant to workers in civilian and defense sectors.

Purpose Work-related low back disorders (LBDs) are prevalent among rebar workers although their causes remain uncertain. The purpose of this study is to examine the self-reported discomfort and spinal biomechanics (muscle activity and spinal kinematics) experienced by rebar workers. Design/methodology/approach In all, 20 healthy male participants performed simulated repetitive rebar lifting tasks with three different lifting weights, using either a stoop (n = 10) or a squat (n = 10) lifting posture, until subjective fatigue was reached. During these tasks, trunk muscle activity and spinal kinematics were recorded using surface electromyography and motion sensors, respectively. Findings A mixed-model, repeated measures analysis of variance revealed that an increase in lifting weight significantly increased lower back muscle activity at L3 level but decreased fatigue and time to fatigue (endurance time) (p < 0.05). Lifting postures had no significant effect on spinal biomechanics (p < 0.05). Test results revealed that lifting different weights causes disproportional loading upon muscles, which shortens the time to reach working endurance and increases the risk of developing LBDs among rebar workers. Research limitations/implications Future research is required to: broaden the research scope to include other trades; investigate the effects of using assistive lifting devices to reduce manual handling risks posed; and develop automated human condition-based solutions to monitor trunk muscle activity and spinal kinematics. Originality/value This study fulfils an identified need to study laboratory-based simulated task conducted to investigate the risk of developing LBDs among rebar workers primarily caused by repetitive rebar lifting.

PurposeConcrete workers perform physically demanding work in awkward postures, exposing their backs to musculoskeletal disorders. Back-support exoskeletons are promising ergonomic interventions designed to reduce the risks of back disorders. However, the suitability of exoskeletons for enhancing performance of concrete workers has not been largely explored. This study aims to assess a passive back-support exoskeleton for concrete work in terms of the impact on the body, usability and benefits of the exoskeleton, and potential design modifications.Design/methodology/approachConcrete workers performed work with a passive back-support exoskeleton. Subjective and qualitative measures were employed to capture their perception of the exoskeleton, at the middle and end of the work, in terms of discomfort to their body parts, ease of use, comfort, performance and safety of the exoskeleton, and their experience using the exoskeleton. These were analyzed using descriptive statistics and thematic analysis.FindingsThe exoskeleton reduced stress on the lower back but caused discomfort to other body parts. Significant correlations were observed between perceived discomfort and usability measures. Design modifications are needed to improve the compatibility of the exoskeleton with the existing safety gears, reduce discomfort at chest and thigh, and improve ease of use of the exoskeleton.Research limitations/implicationsThe study was conducted with eight concrete workers who used the exoskeleton for four hours.Originality/valueThis study contributes to existing knowledge on human-wearable robot interaction and provides suggestions for adapting exoskeleton designs for construction work.

IntroductionDisability retirement is one of the important paths of exit from paid employment and major reason for loss of working years. Knowledge on the contribution of work-related factors on occupational inequalities in cause-specific disability retirement is limited. We examined the impact of physical and psychosocial work-related factors on the occupational differences in disability retirement due to low back disorders, mental disorders, cardiovascular diseases and neurological diseases.Material and MethodsA total of 1 146 744 Finnish employees aged 30–60 years were followed from January 2005 to June 2016 for the first full disability retirement. In addition to all-cause disability retirement, we examined common non-communicable diseases such as low back disorders (sciatica and non-specific low back pain (LBP)), mental disorders, cardiovascular and neurological diseases separately. Information on pensions and occupation were obtained from national registers. Physical and psychosocial work-related factors were assessed by a gender-specific job exposure matrix. We examined the associations of occupation and exposures with disability retirement using competing risk regression model.ResultsControlling for age, physical workload and low job control were statistically significantly associated with disability retirement due to sciatica, non-specific LBP, cardiovascular and neurological diseases in both genders. For disability retirement due to mental disorders a weaker association of physical workload (women) and low job control (both genders) than for other outcomes was observed. Both men and women working in lower level non-manual and manual occupations had an elevated age-adjusted risk of all-cause and cause-specific disability retirement. The observed occupational differences in disability retirement due to sciatica and non-specific LBP were largely explained by physical workload and job control.ConclusionOur results suggest that physical workload and low job control appear to be the major reasons for excess disability retirement due to low back disorders in lower level non-manual and manual occupations.

Background Low back pain (LBP) is one of the most common musculoskeletal conditions. People with LBP often display changes of neuromuscular control and trunk mechanical properties, including trunk stiffness. Although a few individual studies have examined back muscle stiffness in individuals with LBP, a synthesis of the evidence appears to be lacking. Therefore, the aim of this systematic review with meta-analysis was to synthesize and evaluate the available literature investigating back muscle stiffness in association with LBP. Methods We conducted a systematic review of the literature according to the PRISMA guidelines. We searched Pubmed, Scopus, Web of Science and ScienceDirect for studies, that compared back muscle stiffness, measured either by ultrasound-based elastography or myotonometry, between individuals with and without LBP. Pooled data of the included studies were presented descriptively. Additionally, we performed two meta-analyses to calculate the standardized mean difference between the two groups for resting stiffness of the multifidus and erector spinae muscle. For both meta-analyses, the random effect model was used and the weight of individual studies was calculated using the inverse-variance method. The quality of the included studies was assessed using the Joanna Briggs Institute Critical Appraisal Checklist for Analytical Cross-Sectional studies. Furthermore, the certainty of evidence was evaluated using the GRADE approach. Results Nine studies were included in our systematic review. Our results suggest that individuals with LBP have higher stiffness of the multifidus (SMD = 0.48, 95% CI: 0.15 – 0.81, p < 0.01; I 2 = 48 %, p  = 0.11) and erector spinae at rest (SMD = 0.37, 95% CI: 0.11 – 0.62, p < 0.01; I 2 = 39 %, p  = 0.14) compared to asymptomatic controls. On the other hand, the evidence regarding muscle stiffness during submaximal contractions is somewhat contradictory. Conclusions Based on the findings of this systematic review we conclude that people with LBP may have higher back muscle stiffness compared to asymptomatic controls. Addressing muscle stiffness might represent an important goal of LBP treatment. Nevertheless, our findings should be interpreted with extreme caution due to a limited quality of evidence, small number of included studies and differences in measurement methodology.

PurposeThis study based exclusively on register-data provides a scientific basis for further research on the use of opioids in patients with degenerative back disorder. The main objective of this study is to investigate whether surgically treated back pain patients have the same risk of being long-term opioid users as back pain patients who did not have surgery.MethodsWe performed a retrospective register-based cohort study based on all patients diagnosed with a degenerative back disorder at the Spine Center of Southern Denmark from 2011 to 2017. The primary outcome of the study was the use of opioids two years after the patient's first hospital contact with a degenerative back condition. Fisher exact tests were used for descriptive analyses. The effect of the surgery was estimated using adjusted logistic regression analyses.ResultsFor patients who used opioids before the first hospital contact, the ratio for long-term opioid use for surgically treated patients is significantly lower than for non-surgically treated patients (OR = 0.75, 95%CI (0.66; 0.86)). For patients who did not use opioids before, the ratio for long-term opioid use for surgically treated patients does not differ from that of non-surgically treated patients (OR = 1.01, 95%CI (0.84; 1.22)).ConclusionsPatients with a degenerative back disorder who used opioids before their first visit to a specialized spine center have a lower risk of becoming long-term opioid users if they were surgically treated. Whereas for patients who did not use opioids before the first visit, surgical treatment does not influence the risk of becoming long-term opioid users.

Abstract Objective Biomechanics represents the common final output through which all biopsychosocial constructs of back pain must pass, making it a rich target for phenotyping. To exploit this feature, several sites within the NIH Back Pain Consortium (BACPAC) have developed biomechanics measurement and phenotyping tools. The overall aims of this article were to: 1) provide a narrative review of biomechanics as a phenotyping tool; 2) describe the diverse array of tools and outcome measures that exist within BACPAC; and 3) highlight how leveraging these technologies with the other data collected within BACPAC could elucidate the relationship between biomechanics and other metrics used to characterize low back pain (LBP). Methods The narrative review highlights how biomechanical outcomes can discriminate between those with and without LBP, as well as among levels of severity of LBP. It also addresses how biomechanical outcomes track with functional improvements in LBP. Additionally, we present the clinical use case for biomechanical outcome measures that can be met via emerging technologies. Results To answer the need for measuring biomechanical performance, our “Results” section describes the spectrum of technologies that have been developed and are being used within BACPAC. Conclusion and Future Directions The outcome measures collected by these technologies will be an integral part of longitudinal and cross-sectional studies conducted in BACPAC. Linking these measures with other biopsychosocial data collected within BACPAC increases our potential to use biomechanics as a tool for understanding the mechanisms of LBP, phenotyping unique LBP subgroups, and matching these individuals with an appropriate treatment paradigm.

Obesity has been associated to increase the risk of low back disorders. Previous musculoskeletal models simulating the effect of body weight on intervertebral joint loads have assumed identical body postures for obese and normal-weight individuals during a given physical activity. Our recent kinematic-measurement studies, however, indicate that obese individuals adapt different body postures (segmental orientations) than normal-weight ones when performing load-reaching activities. The present study, therefore, used a subject- and kinematics-specific musculoskeletal modeling approach to compare spinal loads of nine normal-weight and nine obese individuals each performing twelve static two-handed load-reaching activities at different hand heights, anterior distances, and asymmetry angles (total of 12 tasks × 18 subjects = 216 model simulations). Each model incorporated personalized muscle architectures, body mass distributions, and full-body kinematics for each subject and task. Results indicated that even when accounting for subject-specific body kinematics obese individuals experienced significantly larger (by ∼38% in average) L5-S1 compression (2305 ± 468 N versus 1674 ± 337 N) and shear (508 ± 111 N versus 705 ± 150 N) loads during all reaching activities (p < 0.05 for all hand positions). This average difference of ∼38% was similar to the results obtained from previous modeling investigations that neglected kinematics differences between the two weight groups. Moreover, there was no significant interaction effect between body weight and hand position on the spinal loads; indicating that the effect of body weight on L5-S1 loads was not dependent on the position of hands. Postural differences alone appear, hence, ineffective in compensating the greater spinal loads that obese people experience during reaching activities.

Purpose To investigate the prevalence of low back pain among Finnish firefighters and to examine whether sleep disturbances predict membership of low back pain trajectories. Methods In this prospective study, 360 actively working firefighters responded to a questionnaire in 1996, 1999 and 2009. The outcome variables were radiating and local low back pain during the preceding year. Using logistic regression modeling, the likelihood of membership of pain trajectories was predicted by sleep disturbances at baseline. Results During the 13-year follow-up, the prevalence of radiating low back pain increased from 16 to 29 % ( p  < 0.0001) and that of local low back pain from 28 to 40 % ( p  < 0.001). The following trajectories were identified: “pain free,” “recovering,” “new pain,” “fluctuating” and “chronic.” More than one-fifth of the participants belonged to the new pain trajectory as regards both pain types, 6 % of the participants belonged to the chronic radiating and 12 % to the chronic local low back pain trajectory. Those with sleep disturbances at baseline had a 2.4-fold risk (adjusted OR 2.4; 95 % CI 1.2–4.7) of belonging to the new pain or chronic radiating pain cluster compared to pain-free participants. Conclusions This is the first prospective study to show that low back symptoms are common and persistent among firefighters and that sleep disturbances strongly predict membership of a radiating pain trajectory. Occupational health and safety personnel, as well as the firefighters themselves, should recognize sleep problems early enough in order to prevent back pain and its development into chronic pain.