Postural analysis of paramedics simulating frequently performed strenuous work tasks

Paramedics who perform emergency rescue functions are highly susceptible to musculoskeletal injuries. Through an interview and survey process firefighters, many of whom are cross-trained paramedics in a consortium of 14 suburban fire departments, identified and rated tasks that were perceived to be both strenuous and frequently performed. The objective of the current study was to describe the working postures and the forces applied as firefighter/paramedics (FF/Ps) simulated specific roles within the following tasks identified by the survey: (1) transferring a patient from a bed to a stretcher using bedsheets, (2) transferring a patient from the ambulance stretcher to a hospital gurney, (3) carrying a victim down a set of stairs and around a landing using a stairchair, (4) carrying a victim down a set of stairs and around a landing using a backboard, and (5) carrying a victim down a set of stairs using a stretcher. Ten two-person teams of FF/Ps participated and were videotaped to obtain postural data for the upper and lower extremities as they performed each role in the simulated two-person tasks. Trunk postures were obtained using lumbar motion monitors. Static hand forces were estimated using a hand-held dynamometer at the most physically demanding points for each role within each task. The postural and force data were averaged across subjects performing identical roles to quantify the postures assumed by the FF/Ps at the most strenuous moments during task performance. Based on these analyses we concluded that: (1) when transferring victims from a bed to a stretcher the FF/P on the bed was able to maintain an upright and more stable posture by standing as opposed to kneeling, (2) an interface board should be used to reduce the frictional forces when transferring victims from a bed to a stretcher or from a stretcher to a gurney, thereby reducing the need to lift the victim with flexed torsos and/or shoulders, and (3) equipment and training that encourages the FF/P in the leader role to walk facing forward during victim transport, especially when descending stairs, potentially results in safer transit.     

Biomechanical evaluation of scaffolding tasks

A field study was conducted to identify tasks and activities that increase the risk of overexertion injury associated with the erection and dismantling of frame scaffolds, and to determine strategies that would prevent or reduce the worker's risk of injury. Twelve construction sites involving 29 workers were visited. The investigation identified that lifting scaffold end frames, carrying end frames, handling scaffold planks, removing cross braces, and removing guardrails are activities that increase the risk of overexertion injuries during task performance. This paper has focused on end-frame handling problems. Although the techniques used to handle end frames varied among the construction sites and subjects, six lifting and five carrying strategies were commonly used. Computer simulations of these work techniques show that considerable biomechanical stress occurs to most of the workers at their shoulders, elbows, and hips. To reduce overexertion injuries during erection and dismantling of frame scaffolds, design of an assistive device to lift scaffold end frames and modifications to the end-frame fixtures are suggested. Future research areas for the prevention of injury during scaffolding work are also proposed.     

Biomechanical evaluation of nursing tasks in a hospital setting

A field study was conducted to investigate spinal kinematics and loading in the nursing profession using objective and subjective measurements of selected nursing tasks observed in a hospital setting. Spinal loading was estimated using trunk motion dynamics measured by the lumbar motion monitor (LMM) and lower back compressive and shear forces were estimated using the three-dimensional (3D) Static Strength Prediction Program. Subjective measures included the rate of perceived physical effort and the perceived risk of low back pain. A multiple logistic regression model, reported in the literature for predicting low back injury based on defined risk groups, was tested. The study results concluded that the major risk factors for low back injury in nurses were the weight of patients handled, trunk moment, and trunk axial rotation. The activities that required long time exposure to awkward postures were perceived by nurses as a high physical effort. This study also concluded that self-reported perceived exertion could be used as a tool to identify nursing activities with a high risk of low-back injury.     

Biomechanical evaluation of lifting tasks: A microcomputer-based model

This paper discusses a static and dynamic biomechanical evaluation of sagittal lifting activities via a microcomputer model. The input to the developed model includes operator's anthropometric data, and sex. The model provides the reactive forces and torques at the various joints of the body expressed in both British and metric systems. Also, the model shows the calculated compressive force on the spine at the fifth lumber/first sacral joint (L5/S1), and both kinematic and kinetic informations are displayed. The model has a menu of five options: (1) to analyze stress imposed on the L5/S1 during a dynamic activity; (2) to determine maximum weight to be allowed during a dynamic motion; (3) to check stress on the spine (L5/S1) for specified static postures; (4) to determine maximum weight to be allowed for a static posture; or (5) to stimulate the lifting action and determine critical postures while performing lifting tasks based on static biochemical analysis.     

A study of lifting tasks performed on laterally slanted ground surfaces

Lifting in most industrial environments is performed on a smooth, level ground surface. There are, however, many outdoor work environments (e.g. agriculture and construction) that require manual material handling activities on variable grade ground surfaces. Quantifying the biomechanical response while lifting under these conditions may provide insight into the aetiology of lifting-related injury. The aim of the current study was to quantify the effect of laterally slanted ground surfaces on the biomechanical response. Ten subjects performed both isometric weight-holding tasks and dynamic lifting exertions (both using a 40% of max load) while standing on a platform that was laterally tilted at 0, 10, 20 and 30 degrees from horizontal. As the subject performed the isometric exertions, the electromyographic (EMG) activity of trunk extensors and knee extensors were collected and during the dynamic lifting tasks the whole body kinematics were collected. The whole body kinematics data were used in a dynamic biomechanical model to calculate the time-dependent moment about L5/S1 and the time-dependent lateral forces acting on the body segments. The results of the isometric weight-holding task show a significant (p < 0.05) effect of slant angle on the normalized integrated EMG values in both the left (increase by 26%) and right (increase by 70%) trunk extensors, indicating a significant increase in the protective co-contraction response. The results of the dynamic lifting tasks revealed a consistent reduction in the peak dynamic L5/S1 moment (decreased by 9%) and an increase in the instability producing lateral forces (increased by 111%) with increasing slant angle. These results provide quantitative insight into the response of the human lifter under these adverse lifting conditions.     

Autonomous learning of sequential tasks: experiments and analyses

Presents a learning model CLARION, which is a hybrid model based on the two-level approach proposed by Sun. The model integrates neural, reinforcement, and symbolic learning methods to perform on-line, bottom-up learning (i.e., learning that neural to symbolic representations). The model utilizes procedural and declarative knowledge (in neural and symbolic representations, respectively), tapping into the synergy of the two types of processes. It was applied to deal with sequential decision tasks. Experiments and analyses of various ways are reported that shed light on the advantages of the model.     

Biomechanical aspects of occupational neck postures during dental work

A typical occupational risk factor for developing neck symptoms is prolonged flexion of the cervical spine. The present aim was to determine joint moments and muscle activity of the neck during forward flexion of the cervical spine to evaluate the load in the neck region. Three dimensional video (3-D) and surface electromyography (EMG) from the splenius muscles were recorded in two common work postures. Using a 3-D static link segment model, moments at the atlanto-occipital (A-O) joint and the seventh cervical-first thoracal (C7-T1) joint were estimated. Maximal extension moments were estimated from maximal neck extension strength. Extension moments at the C7-T1 joint were significantly higher for a highly flexed position (45% of max) compared to a moderately flexed position (32% of max), but remained unchanged at the A-O joint (40% of max). The mean RMS amplitude was 9% of maximal EMG in both positions (no bilateral differences). This difference between mechanical load and muscle load indicates that EMG may seriously underestimate the total loads of the tissue. Lateral flexion influenced the lateral flexion moment while rotation did not influence the rotation moment. The study demonstrates the importance of quantification of joint loads in occupational risk assessment of the neck.

Relevance to industry

3-D biomechanical calculations provide information on the mechanical load during work. Because EMG may underestimate total tissue load, calculations of joint moments in combination with information on muscle activity and strength are necessary to estimate different tissue loading of significance for overall risk identification.     

Identification of physically demanding tasks performed during bushfire suppression by Australian rural firefighters

PurposeTo identify and characterize the physically demanding tasks undertaken during multi-day wildfire (known as bushfire in Australia) suppression by Australian rural firefighters.MethodsDuring semi-structured group interviews, thirty-one experienced male firefighters reviewed 53 firefighting tasks that could be performed during tanker-based bushfire suppression. Participants were asked to nominate the most physically demanding tasks and then define their typical frequencies, durations, operational importance and the dominant actions and activity types in each task.ResultsSeven tasks were identified as physically demanding. They were further categorized into three hose and four handtool (e.g., rakehoe) related activities. These tasks were assessed as moderately important to critical and were thought to occur less than one up to 700 times in a four-month bushfire ‘season’. Each task’s duration was estimated to last approximately 2–30 min depending on the task. Dominant actions were carry, drag, dig/rake actions in seven, three and four of the demanding tasks, respectively. ‘Strength-endurance’ was the dominant activity type for five of the seven tasks.ConclusionSeven fireground tasks, three using a hose and four using handtools were classified as physically demanding by incumbent firefighters. The combination of hose and handtool work indicates that the tanker-based bushfire suppression tactics used by Australian rural firefighters appears to be a hybrid of structural and wildfire firefighting techniques and may require a dedicated physiological analyses before the job demands for these firefighters can be quantified.     

Comparison of lifting and bending demands of the various tasks performed by daycare workers

The objective of this study was to evaluate lifting and trunk postural demands of the tasks performed by daycare workers. Twenty-four caregivers were monitored for approximately 3.5 h. Eleven tasks were identified. Posture was monitored by a dosimeter with sensors at T1 and S1. Flexion-extension, lateral bending and torsion angles were investigated using Exposure Variation Analyses (EVA).Most of the lifting, in both weight lifted and repetitions, was performed during two tasks: “Preparation” (0.6 lifts/min) and “Changing diapers” (0.8 lifts/min).EVA allowed identifying the most demanding tasks in sagittal flexion for both amplitude and duration.The most asymmetric tasks (large lateral bending) were “Caring,” “Changing diapers” and “Cleaning”. All the tasks listed as demanding for posture or duration also had a low level of variability.RelevanceThis study was able to identify the most physically stressful tasks in terms of lifting and postural demands. These tasks should be redesigned in priority taking into account this information and the specific context of individual daycare centres to improve the work context of workers.     

Psychological evaluation and design of work tasks: two examples

Abstract

Practical experience with flexible production automation has provoked rising demands for human oriented job design. Prospective evaluation of work tasks based on status-quo analyses with the psychological instrument VERA, developed for the assessment of the available scope of action in fulfilling the task, has led to design proposals concerning technical and organizational aspects as well as questions of training and retraining. Procedure and results are shown by presenting two case studies dealing with a small flexible manufacturing system and a planned ‘production island’.     

Vision at work visual defect and the visual demand of tasks

Several related studies of visual tasks in a large communications undertaking have revealed much defect of vision and many sources of visual fatigue and inefficiency. The nature of visual fatigue is described briefly and a programme to facilitate visual tasks is outlined.     

Hybrid work stealing of locality-flexible and cancelable tasks for the APGAS library

Since large parallel machines are typically clusters of multicore nodes, parallel programs should be able to deal with both shared memory and distributed memory. This paper proposes a hybrid work stealing scheme, which combines the lifeline-based variant of distributed task pools with the node-internal load balancing of Java’s Fork/Join framework. We implemented our scheme by extending the APGAS library for Java, which is a branch of the X10 project. APGAS programmers can now spawn locality-flexible tasks with a new asyncAny construct. These tasks are transparently mapped to any resource in the overall system, so that the load is balanced over both nodes and cores. Unprocessed asyncAny-tasks can also be cancelled. In performance measurements with up to 144 workers on up to 12 nodes, we observed near linear speedups for four benchmarks and a low overhead for cancellation-related bookkeeping.     

A comparison of risk assessment of single and combination manual handling tasks: 3. Biomechanical measures

Anecdotal evidence suggests organisations experience difficulty assessing the risk in manual handling tasks. One reason for this difficulty may be that many common tasks are a combination of lift, lower, push, pull and carry tasks. No prior reports of attempts to assess the risk in combination tasks using biomechanical measures could be found. The aim of the study was to compare the risks assessed in single manual handling tasks with those in combination tasks. Nine male and nine female students performed combination and single handling tasks. The force applied by subjects to a box was recorded and, together with kinematic data on subject posture collected via video, used in a twodimensional dynamic model to estimate the lumbar compression force and lumbar shear force. The hand force, peak lumbar compression force and peak lumbar shear force for each combination task were each compared with the same variable for the single tasks which comprised the combination, using repeated measured analysis of variance with specific contrasts. In at least one of the twelve comparisons performed for each dependent variable, the combination task value was significantly different to the single task value. It is concluded that the risk in combination manual handling tasks can not be accurately assessed by using estimates based on biomechanical measures of single tasks.     

Ergonomic evaluation of work table for waste sorting tasks using digital human modelling

Waste sorting facilities rely heavily on plentiful human labour, and the lack of adequately designed work systems leads to musculoskeletal disorders among the workers. The present research explores the ergonomic design aspects of a cost-effective intervention, a work table for waste sorting in developing countries. This study evaluates the appropriate range of work height for the sorting tasks and proper location of hoppers to drop the sorted items. The ergonomic assessment was conducted by simulating postures involved in sorting tasks in a virtual environment and performing a biomechanical evaluation of the static postures by digital human modelling. Thirty male subjects from Indian population simulated the postures of sorting tasks. The compressive force at L4/L5 intervertebral disc, shoulder flexion moment, shoulder abduction moment, and elbow flexion moment were taken as the indicative parameters of the subject's physical workload. The appropriate table height was marginally lower than the elbow height of the subject and within 4 cm. The preferred hopper position was on the floor adjacent to the worker compared with the hopper on the top of the table.     

A two-phase mathematical-programming heuristic for flexible assignment of activities and tasks to work shifts

In the service industry, workers perform work shifts and are assigned to interruptible activities and uninterruptible tasks during their shifts. The work shifts of regular employees are often established several weeks in advance of the operations when the activity and task demands are still uncertain. Just a few days before the operations when these demands are unveiled with more certainty, the planned schedules can be slightly modified and on-call temporary employees can be scheduled to satisfy the demands as best as possible. As acceptable modifications, extending the planned shifts and moving workers’ meal breaks are considered. In this paper, we are interested in the scheduling problem encountered in this second step, which also involves assigning activities and tasks to the scheduled work shifts. To produce good-quality solutions in fast computational times for large-sized instances, we develop a two-phase heuristic. In the first phase, an approximate mixed-integer programming model is used to suggest temporary shifts and extensions to regular shifts and to schedule and assign tasks. In the second phase, a column-generation heuristic embedded in a rolling horizon procedure determines the final shifts and assigns activities to them. Computational results obtained on randomly generated instances are reported to evaluate the validity of the proposed solution method.