Constrained Postures Research Articles

Management of Musculoskeletal Disorders; A Systematic Review

Musculoskeletal disorders pose a substantial health risk to employees in various professions worldwide, particularly those in healthcare settings. While prior research has predominantly focused on musculoskeletal issues among nurses, limited attention has been given to doctors across different specialties, including surgeons. Surgeons face unique challenges, combining intense mental focus, precision in movements, and varying physical demands. This systematic review aimed to explore the epidemiology, causes, and management of musculoskeletal disorders among surgeons and healthcare workers. PubMed/Medline and Embase were used as data sources, and articles published in English from 2010 to 2023 were reviewed following PRISMA guidelines. The analysis included seven articles, primarily employing surveys and national database analyses. The findings revealed a high prevalence of musculoskeletal symptoms among healthcare workers, particularly surgeons, who experienced significant rates of shoulder, back, and neck complaints. Physical risk factors, including constrained postures and repetitive motions, were identified as significant predictors of musculoskeletal problems. Holistic treatment approaches that consider the patient\'s lifestyle, preferences, mental health, and concurrent conditions were emphasized. Conservative therapy, assistive technology, psychiatric counseling, and coping skills were recognized as beneficial interventions. The study underscores the importance of understanding and managing musculoskeletal disorders in healthcare workers, contributing to improved evaluation and management strategies in the future. Surgeons, in particular, require attention to their unique work.

Lifting Posture Prediction With Generative Models for Improving Occupational Safety

Lifting tasks have been identified to be highly associated with work-related low back pain. Posture prediction can be used for simulating workers’ posture of lifting tasks and thus facilitate the prevention of low back pain (LBP). This study adopts two generative models, conditional variational encoder and conditional generative adversarial network, to predict lifting postures. A regular feed-forward neural network (FNN) developed upon previous studies is also investigated for comparison purposes. Ground-truth lifting posture data collected by a motion capture system is used for training and testing the models. The models are trained with datasets of different size and loss functions, and the results are compared. The conditional variational autoencoder and the regular FNN achieved comparable top performance in lifting posture prediction in terms of accuracy and posture validity. Both generative models are able to partially capture the variability of constrained postures. Overall, the results prove that using a generative model is able to predict postures with reasonable accuracy and validity (RMSE of coordinates = 0.049 m; RMSE of joint angles = 19.58 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$^\circ$</tex-math></inline-formula> ). The predicted postures can support biomechanical analysis and ergonomics assessment of a lifting task to reduce the risk of low back injuries.

English

Tailoring task is usually fostered with the adoption of constrained postures, repetitive movements, and prolonged static loading which have been identified as major ergonomic risk factors of occupation related musculoskeletal disorders (OMSD). This study was undertaken to ergonomically evaluate the work set up and determine the prevalence and predictors of OMSD among tailors in Enugu Metropolis. This exploratory cross-sectional study sampled 270 tailors in Enugu metropolis. The Nordic musculoskeletal questionnaire was used to assess OMSD, while a self-structured proforma was used to obtain their demographic details, work related variables and the ergonomic assessment of their workstation. Data obtained was analyzed descriptively and inferentially using Chi-square and logistic regression. The level of significance set at 0.05. Majority of the participants were females (73.0%) and married (72.6%). Most of the participants used seats made of wood (58.1%) and plastic (39.6%) that were neither padded (61.1%) nor had back rest (67.8%). Most of the participants (83.3%) used manual sewing machines. The prevalence of OMSD in this population was 67.0% and was more common around the upper back (43.0%), low back (36.3%) and knees (23.3%). There was a significant association between OMSD and each of age (c2 = 16.98, p = 0.002), and fatigue (c2 = 6.198, p = 0.013). However, fatigue was the only significant predictor of OMSD (&beta; = 0.858, p = 0.024). There is a high prevalence of OMSD among tailors in Enugu metropolis, associated with age and fatigue. Work should be terminated at the early onset of fatigue. Key words: Ergonomics, predictors, occupation related musculoskeletal disorders (OMSD), tailors, Enugu metropolis.

A cross-sectional survey of musculoskeletal disorder hazard exposures and self-reported discomfort among on-shore wind turbine service technicians

Background Servicing and maintaining wind turbines may expose wind turbine technicians (wind techs) to musculoskeletal disorder (MSD) hazards. We aimed to characterise MSD hazard exposures and identify work elements that should be prioritised for MSD prevention efforts. Methods A cross-sectional online survey methodology gathered data from 144 wind techs based on a convenience, non-probability sampling approach. The survey was developed using resources from the Ontario MSD Prevention Guideline, where cognitive interviewing yielded wind tech specific modifications. Results Climbing was the most physically demanding task, followed by torqueing/tensioning and manual materials handling (MMH). However, working in awkward and constrained postures emerged as the task most likely to cause or aggravate discomfort. Conclusions Injecting ergonomic and human factors principles into wind turbine design should be a high priority. Re-engineering tools like torque tensioning devices may reduce MSD hazard exposures associated with tasks including torqueing/tensioning and MMH. Practitioner Summary We know little about musculoskeletal disorder (MSD) hazards associated with green jobs. By surveying wind turbine technicians, we learned that MSD hazards exists, and can be addressed by better considering human factors/ergonomics principles in the design of wind turbines and the tools required for service and maintenance operations. Abbreviations: MSD: musculoskeletal disorder; MMH: manual materials handling; Wind techs: wind turbine technicians; CRE-MSD: centre of research expertise for the prevention of musculoskeletal disorders; CanWEA: Canadiarn wind energy association; HFE: human factors/ergonomics; ASME: American Society of Mechanical Engineers; CSA: Canadian Standards Association

Postural Strategies of Bus Drivers During a Regular Work Shift in Urban Area: A Pilot Study

Bus drivers are forced to adopt constrained postures for a long time on a daily basis. This may cause discomfort and, in the long term, represent a co-factor for the onset of musculoskeletal disorders (MSDs), particularly in the low back. Objective measurements of biomechanical variables associated to sitting posture may be useful to better estimate the risk of MSD and, in this context, in recent times in chair movements (ICM) have been shown to represent a reliable tool to characterize sitting postural strategies. This study aimed to evaluate postural strategies of bus drivers during actual long-term driving session in urban area, through the analysis of ICM trend with shift time. Seven professional drivers were tested during regular 6-hours work-shift divided in 50 min point-to-point routes, interspersed by 10 minutes breaks at each last stop. Body-seat interface pressures were collected using a pressure sensitive mat and subjective discomfort rating was evaluated using a 2-parts questionnaire. The results show that, during the whole shift, most drivers report a constant increase in perceived discomfort and a correspondent increase in the overall number of ICM. However, it was interesting to observe that considering a single point-to-point route (i.e. the maximum amount of time in which the drivers must remain seated continuously) the number of ICM increase at the beginning of the period but then decrease significantly, probably when the optimal position to minimize discomfort is reached.

An evaluation of off-axis manual forces and upper extremity joint moments during unilateral pushing and pulling exertions

This study quantified changes in off-axis manual force production and upper extremity joint moments during sub-maximal one-handed push and pull tasks. Off-axis forces in the up/down and left/right directions were quantified in the presence or absence of constraints placed upon the direction of manual force application and/or arm posture. Resultant off-axis forces of 13.1% and 9.4% were produced for pulls and pushes, respectively. Off-axis forces during pulling were oriented downwards and to the right and were associated with a decreased should flexion moment when posture was constrained. Off-axis forces in the up/down direction were minimized with increased on-axis force level. Off-axis forces during pushing tended to be oriented to the left and were associated with increased elbow flexion moment when off-axis forces were allowed. By not accounting for these off-axis forces, we may not be accurately reflecting actionable muscle- and joint-level loading characteristics derived from biomechanically-based proactive ergonomics assessment approaches.Practitioner Summary: Constrained arm postures and directions of manual force application influence the production of off-axis forces. As inaccurate estimation of true manual forces can markedly influence actionable outcomes of proactive ergonomic assessments, this study suggests that simplification of these estimates is insufficient and potentially misleading.

Self-recordings of upper arm elevation during cleaning \u2013 comparison between analyses using a simplified reference posture and a standard reference posture

BackgroundTo reduce ergonomic risk factors in terms of awkward and constrained postures and high velocities, it is important to perform adequate risk assessments. Technical methods provide objective measures of physical workload. These methods have so far mainly been used by researchers. However, if written instructions how to apply the sensors and how to adopt the reference posture are provided, together with triaxial accelerometers, it may be possible for employees to record their own physical workload. The exposure in terms of e.g. upper arm elevations could then easily be assessed for all workers in a workplace. The main aims of this study were: 1) to compare analyses for self-recording of upper arm elevation during work using a simplified reference posture versus using a standard reference posture, and 2) to compare the two reference postures.MethodsTwenty-eight cleaners attached an accelerometer to their dominant upper arm and adopted a simplified reference according to a written instruction. They were thereafter instructed by a researcher to adopt a standard reference. Upper arm elevations were recorded for 2 or 3 days. Each recording was analysed twice; relative to the simplified reference posture and relative to the standard reference posture. The group means of the differences in recorded upper arm elevations between simplified and standard reference analyses were assessed using Wilcoxon signed ranks test. Furthermore, we calculated the group mean of the differences between the simplified reference posture and the standard reference posture.ResultsFor arm elevation during work (50th percentile), the group mean of the differences between the two analyses was 0.2° (range -7 – 10°). The group mean of the differences between the two references was 9° (range 1 – 21°). The subjects were able to follow the instructions in the protocol and performed self-recording of upper arm elevation and velocity.ConclusionsThe small difference between the two analyses indicates that recordings performed by employees themselves are comparable, on a group level, with those performed by researchers. Self-recordings in combination with action levels would provide employers with a method for risk assessment as a solid basis for prevention of work-related musculoskeletal disorders.

Validity of a small low-cost triaxial accelerometer with integrated logger for uncomplicated measurements of postures and movements of head, upper back and upper arms

Repetitive work and work in constrained postures are risk factors for developing musculoskeletal disorders. Low-cost, user-friendly technical methods to quantify these risks are needed. The aims were to validate inclination angles and velocities of one model of the new generation of accelerometers with integrated data loggers against a previously validated one, and to compare meaurements when using a plain reference posture with that of a standardized one. All mean (n = 12 subjects) angular RMS-differences in 4 work tasks and 4 body parts were <2.5° and all mean median angular velocity differences <5.0 °/s. The mean correlation between the inclination signal-pairs was 0.996. This model of the new generation of triaxial accelerometers proved to be comparable to the validated accelerometer using a data logger. This makes it well-suited, for both researchers and practitioners, to measure postures and movements during work. Further work is needed for validation of the plain reference posture for upper arms.

The Impact of Ergonomically Designed Workstations on Shoulder EMG Activity during Carpet Weaving.

The present study aimed to evaluate the biomechanical exposure to the trapezius muscle activity in female weavers for a prolonged period in the workstation A (suggested by previous studies) and workstation B (proposed by the present study). Electromyography data were collected from nine females during four hours for each ergonomically designed workstation at the Ergonomics Laboratory, Hamadan, Iran. The design criteria for ergonomically designed workstations were: 1) weaving height (20 and 3 cm above elbow height for workstations A and B, respectively), and 2) seat type (10° and 0° forwardsloping seat for workstations A and B, respectively). The amplitude probability distribution function (APDF) analysis showed that the left and right upper trapezius muscle activity was almost similar at each workstation. Trapezius muscle activity in the workstation A was signifi-cantly greater than workstations B (P<0.001). In general, use of workstation B leads to significantly reduced muscle activity levels in the upper trapezius as compared to workstation A in weavers. Despite the positive impact of workstation B in reducing trapezius muscle activity, it seems that constrained postures of the upper arm during weaving may be associated with musculoskeletal symptoms.

Constrained postures and spatial S-R compatibility as measured by the Simon effect.

Whereas working under constrained postures is known to influence the worker's perceived comfort and health, little is known in regard to its influence on performance. Employing an Auditory Simon task while varying posture, we investigated the relationship between constrained postures and cognitive processes in three experiments. In Experiment 1 and 2, participants operated a rocker switch or a control knob with one hand either in front or in the back of their body and while either sitting or kneeling. Perceived musculoskeletal exertion was gathered with a questionnaire. Results of the first two experiments showed differently perceived comfort and a minor effect of constrained posture on cognitive performance. However, results indicated that spatial coding in the back compares to either a virtual turn of the observer towards the control device (front-device coding) or along the observer's hand (effector coding). To clarify this issue the rocker switch was operated with one or two hands in Experiment 3, showing a comparable coding only in the one-hand condition and indicating evidence for the effector-coding hypothesis in the back.

Issues about home computer workstations and primary school children in Hong Kong: A pilot study

All around the world, there is a rising trend of computer use among young children especially at home; yet the computer furniture is usually not designed specifically for children's use. In Hong Kong, this creates an even greater problem as most people live in very small apartments in high-rise buildings. Most of the past research literature is focused on computer use in children in the school environment and not about the home setting. The present pilot study aimed to examine ergonomic issues in children's use of computers at home in Hong Kong, which has some unique home environmental issues. Fifteen children (six male, nine female) aged 8-11 years and their parents were recruited by convenience sampling. Participants were asked to provide information on their computer use habits and related musculoskeletal symptoms. Participants were photographed when sitting at the computer workstation in their usual postures and joint angles were measured. The participants used computers frequently for less than two hours daily and the majority shared their workstations with other family members. Computer furniture was designed more for adult use and a mismatch of furniture and body size was found. Ergonomic issues included inappropriate positioning of the display screen, keyboard, and mouse, as well as lack of forearm support and suitable backrest. These led to awkward or constrained postures while some postural problems may be habitual. Three participants reported neck and shoulder discomfort in the past 12 months and 4 reported computer-related discomfort. Inappropriate computer workstation settings may have adverse effects on children's postures. More research on workstation setup at home, where children may use their computers the most, is needed.

Continuous assessment of back and upper arm postures by long-term inclinometry in carpet weavers

Awkward back and shoulder postures have been suggested to be a cause of back and shoulder discomfort in carpet weavers. This study aimed at continuous assessment of the upper arm and back postures and estimation of biomechanical load subtasks using inclinometers during 4 h.Median of trunk flexion angle in weavers was 18° and 13° during knotting and compacting subtasks, respectively. The weavers worked with arms elevated greater than 45° for %4.5 of the work time. The average cumulative compression load for males and females were estimated at 22 MN-S and 13 MN-S, respectively.In addition to poor workstation design, constrained posture of the trunk and low elevation and velocity for both arms may be the main risk factors for developing fatigue and disorders in the back and shoulder regions among carpet weavers. Therefore, any ergonomic interventions should be focused on reducing trunk flexion and the constrained postures of weavers.

Estimating maximum and psychophysically acceptable hand forces using a biomechanical weakest link approach

Accurate estimation of occupational performance capability facilitates better job (re-) design by informing workplace parties about the potential mismatches between job demands and the capability of their labour force. However, estimating occupational performance requires consideration of multiple factors that may govern capacity. In this paper, a novel model is described that uses a stochastic algorithm to estimate how variability in underlying biomechanical constraints affects hand force capability. In addition, the model estimates psychophysically acceptable hand force capacity thresholds by applying a biomechanical weakest link approach. Model estimates were tested against experimentally determined maximal and psychophysically determined hand forces in two exertion directions in constrained postures. The model underestimated maximum hand force capacity relative to measured maximum hand force by 30% and 35% during downward pressing and horizontal pulling, respectively. These values are consistent with those observed using previous two-dimensional models. Psychophysically acceptable hand forces were also underestimated by 29% during both pressing and pulling. Since the psychophysical estimates were scaled as a percentage of the estimated maximum capacity, this suggests that the underestimation in both predictions may be corrected by improving estimates of maximum hand force. Psychophysically acceptable forces were observed to be partially governed by demands at the biomechanical weakest link.

Physical workload in neck, shoulders and wrists/hands in dental hygienists during a work-day

Physical workload was recorded by electromyography, inclinometry and goniometry for twelve female dental hygienists during authentic work. Their work was, in relation to other types of work, characterised by pronounced head flexion (90th percentile 46°), high loads on the forearm extensor muscles (90th percentile 23% and 18% of maximal EMG (MVE), for the right and left sides, respectively), average loads on trapezius muscles (90th percentile 15% and 14% MVE), average arm elevation (99th percentile 83° and 72°) and average wrist flexion and velocities (50th percentiles 17° of extension and 7.3°/s, for the right side). Manual scaling and machinery (use of ultrasonic scaling and hand-pieces) showed higher loads on the trapezius muscles, regarding muscular rest, as well as the 10th and 50th percentiles, than the other tasks, and for the forearm extensor muscles, an almost complete lack of muscular rest (0.1% time), and much higher loads regarding the 10th and 50th percentiles. Further, more pronounced head flexion and lower head and upper arm velocities were found, indicating more constrained postures for the neck and shoulders for the manual scaling and machinery. Use of ultrasonic scaler reduced the 50th percentile loads on the right forearm extensor muscles, but had no effect on the fraction of muscular rest and on the 10th percentile load. These findings are consistent with the high prevalences of musculoskeletal disorders among dental hygienists.

Investigating reduced bag weight as an effective risk mediator for mason tenders

Masonry workers face some of the highest physical demands in the construction industry where large bags of masonry material weighing 42.7 kg are commonly handled by mason tenders who mix the mortar, distribute mortar and bricks/blocks, and erect/dismantle scaffolding throughout the day. The objective of this study was to determine the effectiveness of using half-weight bags (21.4 kg) on reducing the biomechanical loading, physiological response, and perceived exertions. Ten male subjects performed asymmetric lifting tasks simulating unloading bags from a pallet. Muscle activity, trunk kinematics, heart rate, blood pressure and subjective rating data were collected. Spine loads were predicted from a well-validated EMG-assisted model. Bag weight, lift type, bag height at origin, and asymmetry at destination significantly impacted the spine loads. While there was a 50% reduction in bag weight, the peak loads for the half-weight bags were only 25% less than the more available full-weight bags (a reduction of about 320 N of shear and 1000 N of compression). Lifts allowing movement of the feet reduced the loads by about 22% in shear and 27% in compression compared to constrained postures. Interestingly, cumulative spine loads were greater for the lighter bags than the heavy bags (∼40%). The subjective ratings of exertion and risk were significantly lower for the lighter bags. Relevance to Industry The reduction in peak spine loading for the half-weight bags, particularly at the higher heights and when the feet were allowed to move could significantly reduce the injuries of masonry workers. However, there were trade-offs with cumulative loads that may minimize the reduced risk. Overall, given the limited amount of time lifting bags, the reduction of peak loads

Use of Self-Selected Postures to Regulate Multi-Joint Stiffness During Unconstrained Tasks

BackgroundThe human motor system is highly redundant, having more kinematic degrees of freedom than necessary to complete a given task. Understanding how kinematic redundancies are utilized in different tasks remains a fundamental question in motor control. One possibility is that they can be used to tune the mechanical properties of a limb to the specific requirements of a task. For example, many tasks such as tool usage compromise arm stability along specific directions. These tasks only can be completed if the nervous system adapts the mechanical properties of the arm such that the arm, coupled to the tool, remains stable. The purpose of this study was to determine if posture selection is a critical component of endpoint stiffness regulation during unconstrained tasks.Methodology/Principal FindingsThree-dimensional (3D) estimates of endpoint stiffness were used to quantify limb mechanics. Most previous studies examining endpoint stiffness adaptation were completed in 2D using constrained postures to maintain a non-redundant mapping between joint angles and hand location. Our hypothesis was that during unconstrained conditions, subjects would select arm postures that matched endpoint stiffness to the functional requirements of the task. The hypothesis was tested during endpoint tracking tasks in which subjects interacted with unstable haptic environments, simulated using a 3D robotic manipulator. We found that arm posture had a significant effect on endpoint tracking accuracy and that subjects selected postures that improved tracking performance. For environments in which arm posture had a large effect on tracking accuracy, the self-selected postures oriented the direction of maximal endpoint stiffness towards the direction of the unstable haptic environment.Conclusions/SignificanceThese results demonstrate how changes in arm posture can have a dramatic effect on task performance and suggest that postural selection is a fundamental mechanism by which kinematic redundancies can be exploited to regulate arm stiffness in unconstrained tasks.

Experimental evaluation of a computational shoulder musculoskeletal model

Background Many evaluations of shoulder biomechanical models have focused on static exertions in constrained postures, but few have considered tasks that are more complex. This study examines model performance in load delivery tasks for a range of target locations. Methods The study evaluated an optimization-based muscle force prediction model used to assess dynamic load transfer tasks. Model predictions were compared with experimental electromyographic data for two task phases: (1) static hold and (2) dynamic reach. Findings Predictions correlated positively over all subjects with electromyographic data for prime movers (deltoid [ r = 0.53]; infraspinatus [ r = 0.63]; biceps [ r = 0.61]), though variations in the correlation existed across subjects and tasks. Conversely, the model predicted electromyographic activity of secondary muscles somewhat less accurately. The model also predicted inactivity for electromyographic inactive muscles. Interpretation The model provides important insights into activity levels muscles that most actively respond to external moments during manual load transfer tasks.

Increasing the degree of automation in a production system: Consequences for the physical workload

In spite of the continuous development of production systems work-related musculoskeletal disorders is still a large problem. One reason might be the difficulties in quantifying the ergonomic effects of interventions. In this paper ergonomic consequences of technical and organisational changes were quantified in a plant for producing slats for parquet flooring. Muscle activity, work postures and movements were assessed for neck/shoulders and upper limb by direct technical measurements at three generations of production lines. The physical workload for 31 operators at the manual, semi-automated and automated line was derived based on all existing work tasks. The work was characterised by moderate muscular loads, the 50th percentiles being 1.2–3.8%MVE for the neck/shoulder muscles, high repetitiveness and constant movements of the hands and a high prevalence of neck/shoulder disorders. There were statistically significant differences considering exposure levels between the work tasks within each line as well as between the lines. The semi-automated line implied reduced muscular load for all muscles registered but more constrained work postures. The automated line, on the other hand, required higher skills, offered less constrained postures, lower loads and repetitiveness for the hands as well as frequent changes between different physical load levels. Relevance to industry When designing or redesigning production systems, technical solutions are often used to obtain ‘beneficial’ ergonomic conditions, implying a strive for low physical workloads. However, there is a risk that this might lead to more constrained physical activities. Possibilities for job enlargement must be thoroughly utilised.

Standing, sitting and associated working conditions in the Quebec population in 1998

Working posture is an important determinant of musculoskeletal and vascular health. Knowledge of the context and type of postures is necessary in order to examine their associations with health-related outcomes. This study describes self-reported usual working postures in a population and their associations with other working conditions and demographic variables. The 1998 Quebec Health and Social Survey is a population-based survey of 11,986 private households in the province of Québec. It contained a self-administered questionnaire, including an extensive occupational health section. The analyses in this study were limited to respondents with paid employment who had at least 6 months seniority in their current job, comprising 9,425 subjects. The overall prevalence of usual work in a standing posture is 58%; it is more common among men, workers under 25 years, those in the two lowest educational quintiles and those with incomes under $20,000 CAN. Only one person in six who works standing reports being able to sit at will. Women and men differ in the types of usual standing and sitting postures at work. Those who work standing and/or who work in more constrained postures are more likely to be exposed to other physical work demands, such as handling heavy loads, repetitive work, forceful exertion and low job decision latitude. The association between decision latitude and constrained postures is an important link between psychosocial and physical stressors in the workplace. In epidemiological studies, exposure covariation and interactions should be considered in the generation and interpretation of the associations between work postures and musculoskeletal disorders.

Laptop Configurations in Offices: Effects on Posture and Discomfort

This study investigates a variety of laptop configurations and their effects on posture and discomfort. There are several benefits to using laptops in an office setting. They conserve space and allow greater computing flexibility in meetings or business travel. One potential drawback of laptops is that the keyboard and monitor cannot be adjusted independently, which may lead to constrained postures and musculoskeletal discomfort. In this study, 14 users experienced six laptop configurations. The configurations varied in terms of laptop placement and the kinds of external peripherals (e.g. external monitor) that were used in conjunction with the laptop. Past findings showing increased neck flexion and discomfort with laptop use were replicated. However, the addition of peripheral devices to laptops seems to mitigate the problems previously associated with their use.