Non-neutral Trunk Postures Research Articles

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.

Trunk Posture during Manual Materials Handling of Beer Kegs.

Craft brewing is a rapidly growing industry in the U.S. Most craft breweries are small businesses with few resources for robotic or other mechanical-assisted equipment, requiring work to be performed manually by employees. Craft brewery workers frequently handle stainless steel half-barrel kegs, which weigh between 13.5 kg (29.7 lbs.) empty and 72.8 kg (161.5 lbs.) full. Moving kegs may be associated with low back pain and even injury. In the present study, researchers performed a quantitative assessment of trunk postures using an inertial measurement unit (IMU)-based kinematic measurement system while workers lifted kegs at a craft brewery. Results of this field-based study indicated that during keg handling, craft brewery workers exhibited awkward and non-neutral trunk postures. Based on the results of the posture data, design recommendations were identified to reduce the hazardous exposure for musculoskeletal disorders among craft brewery workers.

Biomechanical Evaluation of Passive Back-Support Exoskeletons in a Precision Manual Assembly Task: "Expected" Effects on Trunk Muscle Activity, Perceived Exertion, and Task Performance.

To assess the efficacy of two different passive back-support exoskeleton (BSE) designs, in terms of trunk muscle activity, perceived low-back exertion, and task performance. BSEs have the potential to be an effective intervention for reducing low-back physical demands, yet little is known about the impacts of different designs in work scenarios requiring varying degrees of symmetric and asymmetric trunk bending during manual assembly tasks. Eighteen participants (gender balanced) completed lab-based simulations of a precision manual assembly task using a "grooved pegboard." This was done in 26 different conditions (20 unsupported; 6 supported, via a chair), which differed in vertical height, horizontal distance, and orientation. Using both BSEs reduced metrics of trunk muscle activity in many task conditions (≤47% reductions when using BackX™ and ≤24% reductions when using Laevo™). Such reductions, though, were more pronounced in the conditions closer to the mid-sagittal plane and differed between the two BSEs tested. Minimal effects on task completion times or ratings of perceived exertion were found for both BSEs. Our findings suggest that using passive BSEs can be beneficial for quasi-static manual assembly tasks, yet their beneficial effects can be task specific and specific to BSE design approaches. Further work is needed, though, to better characterize this task specificity and to assess the generalizability of different BSE design approaches in terms of physical demands, perceived exertion, and task performance. These results can help guide the choice and application of passive BSE designs for diverse work scenarios involving nonneutral trunk postures.

Physical ergonomic hazards in highway tunnel construction: Overview from the Construction Occupational Health Program

This report provides an overview of physical ergonomic exposures in highway construction work across trades and major operations. For each operation, the observational method “PATH” (Posture, Activity, Tools and Handling) was used to estimate the percentage of time that workers spent in specific tasks and with exposure to awkward postures and load handling. The observations were carried out on 73 different days, typically for about 4 h per day, covering 120 construction workers in 5 different trades: laborers, carpenters, ironworkers, plasterers, and tilers. Non-neutral trunk postures (forward or sideways flexion or twisting) were frequently observed, representing over 40% of observations for all trades except laborers (28%). Kneeling and squatting were common in all operations, especially tiling and underground utility relocation work. Handling loads was frequent, especially for plasterers and tilers, with a range of load weights but most often under 15 pounds. The results of this study provide quantitative evidence that workers in highway tunnel construction operations are exposed to ergonomic factors known to present significant health hazards. Numerous opportunities exist for the development and implementation of ergonomic interventions to protect the health and safety of construction workers.

Quantitative Ergonomics Exposure Assessment for Floor Coverers in the Greater Boston Area

Floor Coverers have a high prevalence of knee related injuries. The objective of this study is to quantify whole body ergonomics exposure for Floor Coverers in the greater Boston area. A total of 6213 observations (about 100 hours) were made on 49 Floor Coverers by 7 trained observers in 8 construction sites. Awkward leg postures were common. “Kneeling/Crawling” was observed 61.2% of the time. Non-neutral trunk postures were observed frequently. “Severe Flexion” was observed 36.6% of the time, “Mild Flexion” 12.9%. “Manual Material Handling” was observed most frequently during “Hardwood Floor” (36.1%). Hand tools were used more frequently (32.6%) than power tools (5.2%). “Severe Trunk Flexion” did not always lead to heavy trunk load with kneeling postures. Leg postures should be considered before trunk postures were converted to trunk loads. Awkward leg postures are a big problem for Floor Coverers. A majority of the tasks happened near or on the ground.

An evaluation of backpack harness systems in non-neutral torso postures

Much of the research on backpack design has been focused on spinal loading/biomechanics while the wearer is in a neutral/upright trunk posture, such as those employed by outdoor enthusiasts and schoolchildren. This research has led to some important harness design improvements that reduce trunk muscle exertions, fatigue and improve overall comfort. There are number of occupations, however, wherein workers wear back-mounted packs/devices (e.g. air tanks) while working in non-neutral trunk postures. The objective of the current study was to evaluate the effects of these non-neutral postures on biomechanical loading and then reconsider the backpack system design recommendations. Fifteen participants were asked to support a 18.2 kg load on their back while assuming static forward flexed postures of the torso (15°, 30°, 45°, and 60° of sagittal bend). The mass on the back was attached to the participant through two different harness mechanisms: a basic harness design (as seen on college student backpacks) and a more advanced design containing lateral stiffness rods and a weight-bearing hip belt (as seen on backpacks for hikers). While performing these static, posture maintenance tasks, the activation levels of the bilateral trapezius, erector spinae, and rectus abdominis were collected. Participants also provided subjective ratings of comfort. The results showed that there was a significant interaction between harness type and forward flexion angle for the trapezius and the erector spinae muscles. The normalized EMG for the trapezius muscles showed a 14% and 11% reduction in muscle activity at 15° and 30°, respectively, with the advanced design but these positive effects of the advanced design were not found at the greater flexion angles. Likewise the erector spinae muscles showed a 24% and 14% reduction in muscle activity at 15° and 30°, respectively, with the advanced design harness but these effects of the advanced design were not found at the greater forward flexion angles. The level of forward flexion angle affected the rectus abdominis muscle activity, but neither the harness type main effect nor the interaction of harness type and forward flexion angle was significant. The subjective survey results agreed with the EMG results and showed the advanced design harness was generally more comfortable with respect to the shoulder and low back areas. Collectively, the subjective and objective results show a significant improvement with the advanced harness system but also note an interesting interaction with degree of sagittal flexion, indicating a diminished effectiveness of the design improvements at forward flexed postures. Design criteria for harness systems in these forward flexed postures are discussed.

Biomechanical assessment of massage therapists

This study was undertaken to investigate the biomechanical demands on the low back of Massage Therapists performing typical massage therapy techniques and the nature of the associated cumulative exposure. Ten Massage Therapists performed a standardized relaxation back massage that incorporated a series of basic massage therapy techniques used in standard treatments. The 44-minute massage treatment was videotaped and a posture-matching approach was used to determine 3D peak and cumulative loads on the low back. Although the resultant peak low back loads would be considered safe in relation to current published compression and shear guidelines, the cumulative loading values were well within the ranges considered disconcerting in other health care and industrial workers. The therapists were found to assume non-neutral trunk, neck and arm postures for a significant portion of the massage, which could place these professionals at risk of cumulative musculoskeletal disorders.

Task content and physical ergonomic risk factors in construction ironwork

Construction ironwork (CI) has been identified as a trade wherein the exposures to ergonomic risk factors are high. In this study, quantitative exposure assessments for seven specific ironwork tasks selected from the four main specialties of CI—machinery moving/rigging, ornamental, reinforcing, structural—were performed. A total of 13,821 observations were made using the work-sampling, specialty-task-activity-based analysis method called PATH (posture, activity, tools, and handling) and a taxonomy developed specifically for CI. The PATH data provided specialty-task-activity estimates of the percentage of time ironworkers spent in specified postures of the trunk, arms, and legs, and also gave estimated frequencies of manual materials handling activities as well as 11 other predefined activities. Depending on the specialty-task-activity performed, results showed that ironworkers spent anywhere from 13% to 48% of their work time in non-neutral trunk postures; worked with one or both arms at or above shoulder level 6–21% of the time; and stood on uneven/unstable work surfaces 3–53% of the time. The type of activity performed was consistently found to be a major predictor of the frequency of work time spent in non-neutral postures for the trunk, legs, and arms. Relevance to industry These results can be used to target hazardous activities in CI such as rebar and structural ironwork and confirms the need for specialty-task-activity-specific information within each construction trade on exposures and worker activities so that the most appropriate ergonomic interventions can be designed and implemented.

Quantification of ergonomic hazards for ironworkers performing concrete reinforcement tasks during heavy highway construction.

A study was conducted to assess the ergonomic hazards of ironwork job tasks associated with concrete reinforcement work at a large highway construction site. PATH (posture, activity, tools, and handling) analysis, a work-sampling method, was used to provide task-based estimates of the percentage of time ironworkers spent in specified postures of the trunk, arms, and legs; performed activities; used tools; and handled loads. A total of 2128 PATH observations were made of 17 ironworkers performing 5 job tasks: (1) ground-level reinforcement bar (rebar) construction, (2) wall rebar construction, (3) ventilation rebar construction, (4) preparation work, and (5) supervising. Nonneutral trunk postures were observed frequently (exceeding 30%) and manual material handling (MMH) was the most commonly observed activity (exceeding 20%) for all job tasks except supervising. The percentage of time workers spent in specific postures, activities performed, tool use, and MMH activities differed significantly between the five main job tasks, even when supervising was excluded from the analysis. It was concluded that ironworkers are exposed to significant ergonomic hazards when performing concrete reinforcing tasks, and that opportunities exist for the implementation of ergonomic interventions. Further, the results of this study can be used to target specific hazardous tasks for ergonomic interventions and confirms the need to use a task-based exposure assessment strategy to properly assess ergonomic risk profiles for nonstructured jobs such as construction.

LOW BACK PAIN IN PORT MACHINERY OPERATORS

The occurrence of several types of low back pain (LBP) was investigated by a standardized questionnaire in a group of 219 port machinery operators exposed to whole-body vibration (WBV) and postural load and in a control group of 85 maintenance workers employed at the same transport company. The group of port machinery operators included 85 straddle carrier drivers, 88 fork-lift truck drivers, and 46 crane operators. The vector sum of the frequency-weighted r.m.s. acceleration of vibration measured on the seatpan of port vehicles and machines averaged 0·90 m/s2 for fork-lift trucks, 0·48 m/s2 for straddle carriers, 0·53 m/s2 for mobile cranes, and 0·22 m/s2 for overhead cranes. The 12-month prevalence of low back symptoms (LBP, sciatic pain, treated LBP, sick leave due to LBP) was significantly greater in the fork-lift truck drivers than in the controls and the other two groups of port machinery operators. After adjusting for potential confounders, the prevalence of low back symptoms was found to increase with the increase of WBV exposure expressed as duration of exposure (driving years), equivalent vibration magnitude (m/s2), or cumulative vibration exposure (yr m2/s4). An excess risk for lumbar disc herniation was observed in the port machinery operators with prolonged driving experience. In both the controls and the port machinery operators, low back complaints were strongly associated with perceived postural load assessed in terms of frequency and/or duration of awkward postures at work. Multivariate analysis showed that vibration exposure and postural load were independent predictors of LBP. Even though the cross-sectional design of the present study does not permit firm conclusions on the relationship between WBV exposure and low back disorders, the findings of this investigation provide additional epidemiological evidence that seated WBV exposure combined with non-neutral trunk postures, as while driving, is associated with an increased risk of long-term adverse health effects on the lower back.

Evaluation of Personal and work Parameters on Ability to Maintain Non-Neutral Trunk Postures

Work-related musculoskeletal disorders affect millions of workers and run up enormous costs by affecting both worker well-being and by production loss. Jobs that require static trunk flexion create biomechanical loads on the muscles and soft-tissue of the lower back, and may contribute to disability caused by low back pain. This paper presents the preliminary results from a laboratory study to identify personal and work factors that determine endurance limits for maintaining non-neutral trunk postures. Subjective and objective measures of performance were recorded using a visual analog scale for discomfort, time of distracting discomfort (TDD), total endurance time (TET) in each posture, and surface electromyography. Endurance time dropped significantly between 15 and 30° of flexion. Older subjects outperformed the younger subjects in TET. Perceived discomfort increased monotonically as a function of trunk flexion angle, with younger subjects perceiving greater discomfort than the older population.

PATH: A work sampling-based approach to ergonomic job analysis for construction and other non-repetitive work

A high prevalence and incidence of work-related musculoskeletal disorders have been reported in construction work. Unlike industrial production-line activity, construction work, as well as work in many other occupations (e.g. agriculture, mining), is non-repetitive in nature; job tasks are non-cyclic, or consist of long or irregular cycles. PATH (Posture, Activity, Tools and Handling), a work sampling-based approach, was developed to characterize the ergonomic hazards of construction and other non-repetitive work. The posture codes in the PATH method are based on the Ovako Work Posture Analysing System (OWAS), with other codes included for describing worker activity, tool use, loads handled and grasp type. For heavy highway construction, observations are stratified by construction stage and operation, using a taxonomy developed specifically for this purpose. Observers can code the physical characteristics of the job reliably after about 30 h of training. A pilot study of six construction laborers during four road construction operations suggests that laborers spend large proportions of time in nonneutral trunk postures and spend approximately 20% of their time performing manual material handling tasks. These results demonstrate how the PATH method can be used to identify specific construction operations and tasks that are ergonomically hazardous.

An analysis of scanning postures among grocery cashiers and its relationship to checkstand design.

Mounting evidence suggests that musculoskeletal disorders are prevalent among US retail food workers. Cashiers who use electronic scanners appear to be at especially high risk for upper extremity musculoskeletal disorders. Checkstand design has been implicated as a contributor to musculoskeletal injury among cashiers because workstation design can significantly impact working posture. The present study examines working posture among two groups of cashiers to determine if checkstand design is associated with substantial differences in posture and movement during scanning. The work activities of twenty grocery cashiers using one of two checkstand designs (front-facing and right-hand takeaway) were examined. Videotapes of cashiers performing scanning tasks were observed and associated postures and movements were visually coded. The right-hand takeaway design was associated with a significantly higher percentage of non-neutral trunk postures than the front-facing design. However, there were no significant differences in shoulder posture, grasp, or scanning motion associated with checkstand/scanner design. Factors that appeared to affect cashier work posture during scanning included stature, order size, and product type. Although improving the checkstand design may reduce the occurrence of certain awkward postures and static muscle loading conditions among cashiers, the success of these interventions is likely to be limited unless follow-up programmes are instituted to ensure that cashiers are able to use these designs effectively. Furthermore, fundamental changes in cashier work may be required to fully eliminate hazards for musculoskeletal disorders from this job.

Sources of variance in exposure to nonneutral trunk postures in varying work situations.

The purpose of this study was to estimate the different components of variance in exposure to nonneutral trunk postures. The percentages of worktime spent in trunk flexion and trunk rotation or lateroflexion during 10-min observation periods were used as primary measures in analyses of variance to separate the total variance in its components. For two occupational groups six observation periods were selected per worker, and for four other groups 10 periods were used. Most of the 35 subjects were not restricted to one workplace, and they performed dynamic work while being observed. The variance within workers contributed around 80% to the total variability of exposure to both unfavorable postures. These results indicate that it is difficult to achieve an unbiased estimate of exposure to postural stress for individual workers who perform dynamic tasks in varying work situations. The results indicate that it is difficult to achieve an unbiased estimate of exposure to postural stress for individual workers who perform dynamic tasks in varying work situations. Measurement strategy for exposure assessment requires many repeated observations per worker.

The orthostatic factor in textile workers

This report provides an overview of physical ergonomic exposures in highway construction work across trades and major operations. For each operation, the observational method “PATH” (Posture, Activity, Tools and Handling) was used to estimate the percentage of time that workers spent in specific tasks and with exposure to awkward postures and load handling. The observations were carried out on 73 different days, typically for about 4 h per day, covering 120 construction workers in 5 different trades: laborers, carpenters, ironworkers, plasterers, and tilers. Non-neutral trunk postures (forward or sideways flexion or twisting) were frequently observed, representing over 40% of observations for all trades except laborers (28%). Kneeling and squatting were common in all operations, especially tiling and underground utility relocation work. Handling loads was frequent, especially for plasterers and tilers, with a range of load weights but most often under 15 pounds. The results of this study provide quantitative evidence that workers in highway tunnel construction operations are exposed to ergonomic factors known to present significant health hazards. Numerous opportunities exist for the development and implementation of ergonomic interventions to protect the health and safety of construction workers.

Back disorders and nonneutral trunk postures of automobile assembly workers.

A case-referent study was conducted in an automobile assembly plant to evaluate the health effect of trunk postures, such as bending and twisting, that deviate from anatomically neutral. Cases of back disorders were all those of workers who reported back pain to the medical department in a ten-month period and met the severity criteria of an interview. The referents were randomly selected workers free of back pain according to medical department records, an interview, and an examination. For each of the final 95 cases and 124 referents, the job was analyzed for postural and lifting requirements with a video recording and software analysis system by analysts blinded to the case/referent status. Back disorders were associated with mild trunk flexion [odds ratio (OR) 4.9, 95% confidence interval (95% CI) 1.4-17.4], severe trunk flexion (OR 5.7, 95% CI 1.6-20.4), and trunk twist or lateral bend (OR 5.9, 95% CI 1.6-21.4). The risk increased with exposure to multiple postures and increasing duration of exposure.

Trunk Posture and Back Pain: Identification and Control of Occupational Risk Factors

Abstract Awkward trunk posture during work can be caused by a number of controllable factors, including poor work station layout, inappropriate design of tools and equipment, and/or incorrect work methods. If not eliminated, these postures can cause fatigue and contribute to the development of pain and disorders in the lower back. A computer-aided system was developed to evaluate trunk posture during work by measuring the time spent in neutral and non-neutral postures. This system was used to assess postural risk factors in a case-referent study of back disorders in an automobile assembly plant. The use of non-neutral trunk postures, such as forward flexion, lateral bending, and axial twisting, was associated with reports of back pain. The results of this study suggest that job redesign and/or other methods for controlling non-neutral posture be implemented to reduce the risk of back pain on industrial jobs. A general approach to work station design, based on a mechanical model of the human skeletal system, is described. This model is used to develop specific job-design guidelines to prevent awkward trunk posture.