Changes of trunk muscle stiffness in individuals with low back pain: a systematic review with meta-analysis.

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; I2 = 48 %, p = 0.11) and erector spinae at rest (SMD = 0.37, 95% CI: 0.11 - 0.62, p < 0.01; I2 = 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.

Effect of surgery on the long-term use of opioids in patients with degenerative back disorders: a retrospective register-based study.

PURPOSE: This 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. METHODS: We 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. RESULTS: For 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)). CONCLUSIONS: Patients 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.

Normative database of response surface method for human trunk extension in isometric mode.

Recent studies show that asymmetric movements are important Low Back Disorders risk factors. Measuring the trunk strength and identifying the coupling effects in different postures can provide an objective tool to assess one's task capacity. This paper estimates the maximum performance capacity for isometric trunk extension and accompanying torques. Thirty males performed maximum voluntary isometric extension in 33 trunk postures on Sharif Lumbar Isometric Strength Tester device. Corresponding moments and angular positions were collected. Second-order full response surface models (RSM) were exploited to formulate the relationship between strengths and three trunk angles. The results of correlation coefficient, percent of standard estimation error and lack of fit reflected the adequacy of models. In conclusion, the main torque was the extension, but at the same time lateral bending and rotation torques were observed. For predicting these three torques in a specific posture and injury prevention, the second order RSM is a useful tool. The presented models can be used in the fields of ergonomics, occupational biomechanics and sport.

The risk of an incident hospital contact with a musculoskeletal disorder in Danish occupational fishers: a register-based study.

BACKGROUND: The prevalence of musculoskeletal disorders (MSDs) among occupational fishers is high, yet knowledge of the risk factors is scarce and inconsistent. The aim of this study was to investigate the risk from various work-related characteristics on incident hospital contact due to a musculoskeletal disorders and other pain disorders among Danish occupational fishers. METHODS: This register-based study comprised data from the Danish Occupational Cohort with eXposure (DOC*X) for all persons registered as occupational fishers between 1994 and 2017. Time-to-event analysis with Cox regression model was used with age as the time scale. RESULTS: Among the 15,739 fishers, 40% (n = 5,669 cases) had an incident hospital contact with an MSD during follow-up. Back disorders were the dominant complaint. Male fishers working less than 5 years or more than 15 years had higher risks of MSD (HR 2.40 (95% CI: 2.06, 2.80), HR: 2.04 (95% CI: 1.76, 2.35), respectively, than those working for over 20 years. Period effects confounded and reduced the risk from occupational seniority. CONCLUSION: Fishers occupational seniority vary in risk of MSDs across working life. Results showed a nonlinear relationship between the highest risk for fishers working less than 5 years and the lowest risk working more than 20 years as occupational fisher. More years in the workforce, a captain education, and primarily working part time significantly reduced the risk of experiencing a first MSDs for men. Healthy worker effect was documented.

Biomechanical Phenotyping of Chronic Low Back Pain: Protocol for BACPAC.

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.

Continuous assessment of trunk posture in healthcare workers assigned to wards with different MAPO index.

Healthcare professionals generally experience an above-average incidence of low back disorders (LBDs) compared with workers of other professions, and its level of risk is commonly assessed using observational methods such as the MAPO method (Movement and Assistance of Hospital Patients). In this study, we continuously monitored the trunk posture of 30 healthcare workers using a single inertial sensor to: (1) understand whether the MAPO classification is effective in adequately discriminating the risk associated with the time spent in non-neutral trunk postures and (2) characterise the variability of biomechanical exposure among workers employed in wards with the same MAPO index. The results substantially confirm the validity of the MAPO approach in discriminating among wards characterised by different levels of biomechanical exposure associated with the risk of developing LBDs. However, they also highlight the need to assess workers' exposure on an individual basis due to the high intra-group variability.Practitioner summary: Employing a quantitative measurement setup to monitor trunk posture along with an observational method (ie MAPO) can identify the existence of criticalities or the poor application of ergonomic recommendations given during the training of healthcare workers even in hospital wards characterised by little or no risk of developing low back disorders.

The Effects of Isometric Fatigue on Trunk Muscle Stiffness: Implications for Shear-Wave Elastography Measurements.

Muscle stiffness has been implicated as a possible factor in low back pain risk. There are few studies on the effects of isometric fatigue on the shear modulus of trunk muscles. This study aimed to investigate the effects of trunk isometric fatigue on the passive and active (during low and high-level contractions) shear moduli of the erector spinae (ES) and superficial and deep multifidus (MF) muscles. We assessed passive and active shear modulus using shear-wave elastography in healthy young participants (n = 22; 11 males, 11 females), before and after an isometric trunk extension fatigue protocol. Maximal voluntary force decreased from 771.2 ± 249.8 N before fatigue to 707.3 ± 204.1 N after fatigue (-8.64%; p = 0.003). Passive shear modulus was significantly decreased after fatigue in the MF muscle (p = 0.006-0.022; Cohen's d = 0.40-46), but not the ES muscle (p = 0.867). Active shear modulus during low-level contraction was not affected by fatigue (p = 0.697-0.701), while it was decreased during high-level contraction for both muscles (p = 0.011; d = 0.29-0.34). Sex-specific analysis indicated the decrease in ES shear modulus was significant in males (p = 0.015; d = 0.31), but not in females (p = 0.140). Conversely, the shear modulus in superficial MF had a statistically significant decrease in females (p = 0.002; d = 0.74) but not in males (p = 0.368). These results have important implications for further investigations of the mechanistic interaction between physical workloads, sex, muscle stiffness (and other variables affecting trunk stability and neuromuscular control), and the development/persistence of low back pain.

An ergonomic assessment tool for evaluating the effect of back exoskeletons on injury risk.

Low back disorders (LBDs) are a leading injury in the workplace. Back exoskeletons (exos) are wearable assist devices that complement traditional ergonomic controls and reduce LBD risks by alleviating musculoskeletal overexertion. However, there are currently no ergonomic assessment tools to evaluate risk for workers wearing back exos. Exo-LiFFT, an extension of the Lifting Fatigue Failure Tool, is introduced as a means to unify the etiology of LBDs with the biomechanical function of exos. We present multiple examples demonstrating how Exo-LiFFT can assess or predict the effect of exos on LBD risk without costly, time-consuming electromyography studies. For instance, using simulated and real-world material handling data we show an exo providing a 30 Nm lumbar moment is projected to reduce cumulative back damage by ∼70% and LBD risk by ∼20%. Exo-LiFFT provides a practical, efficient ergonomic assessment tool to assist safety professionals exploring back exos as part of a comprehensive occupational health program.

Using visual aids to influence manual lifting techniques: acute effects of viewing static images on spine motion.

Purpose. This study aimed to determine whether untrained observers alter their spine as directed via static images of different lifting techniques. Methods. Ten men and eight women, who had no lifting or visual observation training, performed box lifts. Following a self-selected lifting technique trial, participants performed four experimental lifting trials (in randomized order) wherein they were instructed to execute lifts in accordance with the techniques pictured. These techniques differed by the amount of knee, trunk and spine flexion modeled. Peak lumbar flexion angles and flexion/extension velocities were quantified, and then statistically analyzed via general linear models with two within-participant factors (condition = technique; phase = lift/lower). Results. Lumbar flexion angles and flexion/extension velocities differed between conditions (p < 0.001), although the effects depended on the combination of postural characteristics pictured. A main effect of phase was observed for peak lumbar flexion velocity only (p = 0.001). No condition × phase interaction effects were detected for any dependent variables (p > 0.050). Conclusions. Acute changes in lifting mechanics can be elicited via visual observation of pictured techniques. However, if using pictures to attenuate peak lumbar flexion displacements and velocities when lifting, auxiliary instruction may be needed to direct observers' attention to the spine curvature displayed.

Chronic low back pain and sick-leave: a functional magnetic resonance study.

BACKGROUND: Chronic low back pain (CLBP) represents a problem in the occupational environment, often associated with disability, sick-leave demands, loss of productivity, anxiety, depression and high socioeconomic cost. The emergence of functional neuroimaging allowed new insights into brain structure and physiology in normality and chronic pain. While occupational related aspects are recognized as important risk factors for chronicity there have not been thus far evaluated by fMRI experiments. The overall objective of this study is to compare the neuronal correlates between groups of individuals CLBP with or without sick-leave demands. METHODS: A total of 74 individuals were divided into three groups: chronic low back pain with sick-leave demands [CLBP_L]; chronic low back pain without sick-leave demands [CLBP_NL]; individuals without pain or sick-leave demands [Control]. Functional magnetic resonance imaging was used to assess brain function during moderate acute pain stimulation task (thumb controlled pressure). RESULTS: After acute painful stimulation, a higher brain response was found in the anterior cingulate and superior and medium frontal gyrus was observed in CLBP_NL vs. CLBP_L (p <  0,001) and increased brain response in the frontal pole and paracingulate region in control vs. CLBP_L (p <  0.001) during acute pain stimulation. CONCLUSION: The modulation of acute pain participates in the mechanism propagating chronic pain perception. The lower activation in the superior frontal gyrus observed in the CLBP_L group compared to CLBP_NL, reinforces the idea of an already existing activation in this area.

Factors associated with early opioid dispensing compared with NSAID and muscle relaxant dispensing after a work-related low back injury.

OBJECTIVES: The objective of this historical cohort study was to determine the claimant and prescriber factors associated with receiving opioids at first postinjury dispense compared with non-steroidal anti-inflammatory drugs (NSAIDs) and skeletal muscle relaxants (SMRs) in a sample of workers' compensation claimants with low back pain (LBP) claims between 1998 and 2009 in British Columbia, Canada. METHODS: Administrative workers' compensation, prescription and healthcare data were linked. The association between claimant factors (sociodemographics, occupation, diagnosis, comorbidities, pre-injury prescriptions and healthcare) and prescriber factors (sex, birth year, specialty) with drug class(es) at first dispense (opioids vs NSAIDs/SMRs) was examined with multilevel multinomial logistic regression. RESULTS: Increasing days supplied with opioids in the previous year was associated with increased odds of receiving opioids only (1-14 days OR 1.62, 95% CI 1.51 to 1.75; ≥15 days OR 5.12, 95% CI 4.65 to 5.64) and opioids with NSAIDs/SMRs (1-14 days OR 1.49, 95% CI 1.39 to 1.60; ≥15 days OR 2.82, 95% CI 2.56 to 3.12). Other significant claimant factors included: pre-injury dispenses for NSAIDs, SMRs, antidepressants, anticonvulsants and sedative-hypnotics/anxiolytics; International Statistical Classification of Diseases and Related Health Problems, 9th Revision diagnosis; various pre-existing comorbidities; prior physician visits and hospitalisations; and year of injury, age, sex, health authority and occupation. Prescribers accounted for 25%-36% of the variability in the drug class(es) received, but prescriber sex, specialty and birth year did not explain observed between-prescriber variation. CONCLUSIONS: During this period in the opioid crisis, early postinjury dispensing was multifactorial, with several claimant factors associated with receiving opioids at first prescription. Prescriber variation in drug class choice appears particularly important, but was not explained by basic prescriber characteristics.

Effectiveness of a lumbopelvic monitor and feedback device to change postural behaviour: the ELF cluster randomised controlled trial.

OBJECTIVES: The aim of this clustered, randomised controlled trial was to assess the effectiveness of a lumbopelvic postural feedback device for changing postural behaviour in a group of healthcare workers. We hypothesised that workers exposed to auditory postural feedback would reduce the number of times forward bending posture is adopted at work. METHODS: This was a participant and assessor blinded, randomised, sham-controlled trial with blocked cluster random allocation. We recruited healthcare workers from aged care institutions. Healthcare sites were randomly allocated to the feedback or sham group (SG). A postural monitoring and feedback device was used to monitor and record lumbopelvic forward bending posture, and provided audio feedback whenever the user sustained lumbopelvic forward bending posture that exceeded predefined thresholds. The primary outcome measure was postural behaviour (exceeding thresholds). We used a robust variant of repeated measures mixed-effect model for assessing within-group and between-group differences in postural behaviour. RESULTS: We recruited 19 sites, and 130 healthcare workers participated. There were no within-group changes on the number of times postural threshold was exceeded at 1-week follow-up (feedback group: -0.7, 95% CI -2.61 to 0.72; SG -0.3, -1.65 to 0.98), and no differences (0.05, 95% CI -1.83 to 1.94) between SG and feedback group. CONCLUSIONS: Findings from this trial indicate that audio feedback provided by a postural monitor device did not reduce the number of times healthcare workers exceeded the postural threshold. TRIAL REGISTRATION NUMBER: ACTRN12616000449437.

Occupational lifting predicts hospital admission due to low back pain in a cohort of airport baggage handlers.

PURPOSE: To examine if occupational lifting assessed as cumulative years as a baggage handler is associated with first-time hospital diagnosis or treatment for low back disorders. METHODS: This study is based on the Copenhagen Airport Cohort consisting of male baggage handlers performing heavy lifting every day and a reference group of unskilled men from the greater Copenhagen area during the period 1990-2012. We followed the cohort in the National Patient Register and Civil Registration System to obtain information on diagnoses, surgery, mortality, and migration. The outcomes were first-time hospital diagnosis or surgery for (1) lumbar disc herniation or (2) low back pain (LBP). RESULTS: Baggage handlers (N = 3473) had a higher incidence rate of LBP, but not of lumbar disc herniation, compared to the reference group (N = 65,702). Baggage handlers with longer employment had a higher incidence of LBP compared to baggage handlers with shorter employment. The linear association of cumulative years as a baggage handler on LBP was significantly increased with an incidence rate ratio of 1.16 (95% CI 1.07-1.25) for a 5-year increase of employment as baggage handler. CONCLUSIONS: In this large cohort study, we found an increased incidence of LBP among baggage handlers compared to the reference group with indications of a dose-response relationship between years of employment and the outcome. For baggage handlers working on the apron, the incidence was particularly increased before introduction of technical lifting equipment, suggesting that preventive measures to reduce cumulative work load may have a positive effect.

Chronic low back pain and sick-leave: a functional magnetic resonance study

Abstract Background Chronic low back pain (CLBP) represents a problem in the occupational environment, often associated with disability, sick-leave demands, loss of productivity, anxiety, depression and high socioeconomic cost. The emergence of functional neuroimaging allowed new insights into brain structure and physiology in normality and chronic pain. While occupational related aspects are recognized as important risk factors for chronicity there have not been thus far evaluated by fMRI experiments. The overall objective of this study is to compare the neuronal correlates between groups of individuals CLBP with or without sick-leave demands. Methods A total of 74 individuals were divided into three groups: chronic low back pain with sick-leave demands [CLBP_L]; chronic low back pain without sick-leave demands [CLBP_NL]; individuals without pain or sick-leave demands [Control]. Functional magnetic resonance imaging was used to assess brain function during moderate acute pain stimulation task (thumb controlled pressure). Results After acute painful stimulation, a higher brain response was found in the anterior cingulate and superior and medium frontal gyrus was observed in CLBP_NL vs. CLBP_L ( p < 0,001) and increased brain response in the frontal pole and paracingulate region in control vs. CLBP_L ( p < 0.001) during acute pain stimulation. Conclusion The modulation of acute pain participates in the mechanism propagating chronic pain perception. The lower activation in the superior frontal gyrus observed in the CLBP_L group compared to CLBP_NL, reinforces the idea of an already existing activation in this area.(AU)

Spine loading during laboratory-simulated fireground operations - inter-individual variation and method of load quantification.

Spine loading data are needed to design low-back health-preserving ergonomic interventions for firefighters. Study objectives were to quantify spine loads during simulated fireground operations using simple (polynomial) and advanced (EMG-assisted musculoskeletal model) methods and to describe the variation in spine loads between performers (N = 20). Spine compression forces differed by as much as 5.5 times bodyweight between individuals performing identical tasks. Anteroposterior and mediolateral shear forces varied by as much 3.2 and 2.1 times bodyweight between individuals performing the same tasks, respectively. Large variations in spine load magnitudes were documented regardless of whether simple or advanced quantification methods were used. Results suggest that low-back loading demands on the fireground would vary widely depending on the physical characteristics of individual firefighters, movement strategies employed, and tasks performed. Thus, personalised ergonomic interventions are warranted to regulate spine loading and load tolerance in firefighters. Practitioner summary: Even when performing the same work, the associated spine loading demands will vary widely across people due to differences in their body sizes, shapes, and movement strategies. Therefore, personalised interventions are needed to regulate spine loading and load tolerance in workers (e.g. obesity prevention, physical capacity-building exercise, and movement [re]training).

Recurrent back pain during working life and exit from paid employment: a 28-year follow-up of the Whitehall II Study.

OBJECTIVES: To examine the impact of recurrent, as compared with single, reports of back pain on exit from paid employment over decades of follow-up. METHODS: The study sample was from the British Whitehall II Study cohort (n=8665, 69% men, aged 35-55 at baseline), who had provided information about their reports of back pain between 1985 and 1994. Data about exit from paid employment (health-related and non-health related exit, unemployment and other exit) were collected between 1995 and 2013. Repeated measures logistic regression models were fitted to examine the associations, and adjust for covariates. RESULTS: Recurrent pain was reported by 18% of participants, while 26% reported pain on an occasion and 56% did not report pain. Report of back pain on an occasion was not associated with health-related job exit, whereas recurrent pain was associated with such an exit (OR 1.51; 95% CI 1.15 to 1.99), when compared with those who did not report pain. These associations were somewhat stronger among middle-grade and lower-grade employees, while these associations were not seen among higher-grade employees. Differences in associations by age and psychosocial working conditions were small. CONCLUSIONS: These results highlight the need for early detection of recurrent back pain to prevent exit out of paid employment for health reasons. As the risk varies by occupational grade, this emphasises the importance of identification of high-risk groups and finding ways to address their modifiable risk factors.

Influence of age on lifting capacity among manual materials handlers.

BACKGROUND: Recommended weight limit for manual materials handlers has to be decided based on the individual characteristics of the person and age is one of the major variable affecting maximal lifting capacity. But there is limited information on pattern of change in lifting capacity with age. OBJECTIVE: To determine the influence of age on the maximum acceptable weight of lift among manual materials handlers. METHODS: Two hundred and seventeen male construction workers were grouped into four age quotas- 19-28, 29-38, 39-48 and 49-58 years. Lifting capacity was determined using progressive isoinertial lifting evaluation, adopting semi-squat technique of lifting at two levels: waist and shoulder. RESULTS: A statistically significant increase in the maximum acceptable weight was observed from first to second age group followed by a gradual decline. The percentage of decline from second to third age group was 11.89% and 14.34% and from third to fourth age group was 5.60% and 19.90% for waist and shoulder level respectively. CONCLUSION: Pattern of change in lifting capacity with age among manual materials handlers has been investigated in this study. Lifting capacity was found to be the greatest in 29-38 year age group, therefore prescribing recommended weight limit uniformly for all the workers may not be the best practice.

Mechanical lifting energy consumption in work activities designed by means of the "revised NIOSH lifting equation".

The aims of the present work were: to calculate lifting energy consumption (LEC) in work activities designed to have a growing lifting index (LI) by means of revised NIOSH lifting equation; to evaluate the relationship between LEC and forces at the L5-S1 joint. The kinematic and kinetic data of 20 workers were recorded during the execution of lifting tasks in three conditions. We computed kinetic, potential and mechanical energy and the corresponding LEC by considering three different centers of mass of: 1) the load (CoML); 2) the multi-segment upper body model and load together (CoMUpp+L); 3) the whole body and load together (CoMTot). We also estimated compression and shear forces. Results shows that LEC calculated for CoMUpp+L and CoMTot grew significantly with the LI and that all the lifting condition pairs are discriminated. The correlation analysis highlighted a relationship between LEC and forces that determine injuries at the L5-S1 joint.

Postural habits and weight of backpacks of Portuguese adolescents: Are they associated with scoliosis and low back pain?

BACKGROUND: The adoption of incorrect postures or carrying overweight backpacks may contribute to the development of musculoskeletal disorders in school children. OBJECTIVE: This study evaluated the weight of backpacks and the postural habits adopted in schools by Portuguese adolescents, and their association with scoliosis and low back pain (LBP). METHOD: The sample comprised 966 Portuguese students, aged between 10 and 16 years. The instruments included a questionnaire to characterize the presence of LBP and the postural habits adopted by students, the weighing of backpacks and a scoliometer to evaluate scoliosis. RESULTS: No association was observed between assuming incorrect postures and carrying overweight backpacks, in students with scoliosis. Students who adopted incorrect sitting postures had 1.77 times the risk (95% CI: 1.32-2.36; p < 0.001) of developing LBP; those positioned incorrectly whilst watching TV and playing games had 1.44 times the risk (95% CI: 1.08-1.90; p = 0.012) of developing LBP; and those standing incorrectly had 2.39 the risk (95% CI: 1.52-3.78; p < 0.001) of developing LBP. CONCLUSIONS: The results revealed that students who sat with the spine positioned wrongly, as well as those who were standing incorrectly, were more likely to present with LBP.

Evaluation of Lumbar Spine Load by Computational Method in Order to Acknowledge Low-back Disorders as Occupational Diseases.

AIM: The aim of the study was to develop a computational module for the prediction of compressive force on the L4/L5 disc suitable for use in field settings. METHOD: The value of compressive force is intended to be used as a proxy measure of the mechanical burden of low-back when performing work activities. The compressive force predicted by the module in a particular worker should be compared with the NIOSH limit value of 3,400 N for the assessment of lumbar spine load during manual lifting tasks. Exceeding the limit will be considered as the fulfilment of "hygienic criterion" that should be met to acknowledge low-back disorder as an occupational disease. To develop the computational module we used the ergonomic software TECNOMATIX Classic Jack taking into account the anthropometric parameters of a worker and ergonomic parameters of his/her work activity. RESULTS: We calculated compressive forces on the L4/L5 disc in about 1,300 simulated combinations of various factors influencing compressive force. Parameters which turned out to be crucial for the compression of L4/L5 disc were included in the computational algorithm. CONCLUSION: Our study was primarily aimed at the assessment of lumbar disorders as occupational diseases. Moreover, the study can contribute to the recommendation of preventive measures to decrease health risks in occupations associated with the overload of low-back region. The graphic maps generated by the computational module enable a fast and exact analysis of particular job.