An evaluation of methods assessing the physical demands of manual lifting in scaffolding

Four methods assessing the physical demands of manual lifting were compared. The scaffolding job was evaluated and three distinct scaffolding tasks were ranked using: (1) the revised NIOSH lifting equation (NIOSH method), (2) lifting guidelines for the Dutch construction industry (Arbouw method), (3) rapid appraisal of the NIOSH lifting equation (practitioners' method), and (4) systematic observations. For the three first-mentioned methods the same dataset was used; observation took place in a different setting in the same company. At job level, all methods indicated that ergonomic interventions are required to protect scaffolders from an increased risk for low back pain. The NIOSH, Arbouw and practitioners' method resulted in a similar ranking order of tasks (transport>construction>dismantlement). In contrast, the observational method gave transport the lowest ranking. The underlying cause was probably that the observational method is more sensitive to durations of tasks and lifting within tasks than the three other methods.     

Exploring physical exposures and identifying high-risk work tasks within the floor layer trade

Introduction

Floor layers have high rates of musculoskeletal disorders yet few studies have examined their work exposures. This study used observational methods to describe physical exposures within floor laying tasks.

Methods

We analyzed 45 videos from 32 floor layers using Multimedia-Video Task Analysis software to determine the time in task, forces, postures, and repetitive hand movements for installation of four common flooring materials. We used the WISHA checklists to define exposure thresholds.

Results

Most workers (91%) met the caution threshold for one or more exposures. Workers showed high exposures in multiple body parts with variability in exposures across tasks and for different materials. Prolonged exposures were seen for kneeling, poor neck and low back postures, and intermittent but frequent hand grip forces.

Conclusions

Floor layers experience prolonged awkward postures and high force physical exposures in multiple body parts, which probably contribute to their high rates of musculoskeletal disorders.     

Rethinking scaffolding in the information age

This paper addresses the use of scaffolding in learning contexts that incorporate technologically based novel problems. We suggest that in computer contexts extended conceptualisations of scaffolding are needed in order to gain greater insights into teaching and learning processes. Our work has revealed that traditional forms of scaffolding, based on the “expert’s” view of how the problem should be solved, need to be modified in order to accommodate the child’s perspective and that three different types of scaffolding which we refer to as cognitive, technical and affective can be conceptualized. This paper discusses the ways in which the performance of pairs of children is enhanced in such scaffolding contexts, to include more examples of metastrategic processes and strategies for problem-solving, than when the pairs are left to spontaneously solve the problems. This study provides additional support that cognitive, affective and technical scaffolding are beneficial for learning and that children are able to support each others learning via sharing strategies and articulating the reasons behind them to each other.     

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.     

The effects of scaffolding metacognitive activities in small groups

This study examined the effects of scaffolds on triads’ metacognitive activities in complex open learning environments. In an experimental design, two experimental groups receiving scaffolds were compared with a control group. The experimental groups differed in the form of scaffolding messages used: structuring scaffolds vs. problematizing scaffolds. We analyzed the effects of scaffolding and the different forms of scaffolds on the amount of metacognitive activities of triads on the interpersonal plane. The results show that scaffolding has a significant effect on stimulating metacognitive activities; triads receiving scaffolds performed significantly more metacognitive activities on the interpersonal plane. Additionally, scaffolding also has a significant development effect; triads continue to show more metacognitive activities after the scaffolding is ceased. Finally, no significant differences between the two forms of scaffolding were found: triads receiving problematizing scaffolds did not showed more metacognitive activities during or after the scaffolding compared to triads receiving structuring scaffolds.     

A mobile learning system for scaffolding bird watching learning

Abstract This paper develops a mobile learning system for scaffolding students learning about bird-watching. The aim is to construct an outdoor mobile-learning activity using up-to-date wireless technology. The proposed Bird-Watching Learning (BWL) system is designed using a wireless mobile ad-hoc network. In the BWL system, each learner has a PDA (Personal Digital Assistant) with a Wi-Fi-based (IEEE 802.11b) wireless network card. The BWL system offers a mobile learning system which supports the students learning through scaffolding. The aim of a formative evaluation was twofold: to explore the possible roles and scaffolding aids that the mobile learning device offers for bird-watching activities and to investigate whether student learning benefited from the mobility, portability, and individualisation of the mobile learning device.     

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.     

The role of scaffolding and motivation in CSCL

Recent findings from research into Computer-Supported Collaborative Learning (CSCL) have indicated that not all learners are able to successfully learn in online collaborative settings. Given that most online settings are characterised by minimal guidance, which require learners to be more autonomous and self-directed, CSCL may provide conditions more conducive to learners comfortable with greater autonomy. Using quasi-experimental research, this paper examines the impact of a redesign of an authentic CSCL environment, based upon principles of Problem-Based Learning, which aimed to provide a more explicit scaffolding of the learning phases for students. It was hypothesised that learners in a redesigned ‘Optima’ environment would reach higher levels of knowledge construction due to clearer scaffolding. Furthermore, it was expected that the redesign would produce a more equal spread in contributions to discourse for learners with different motivational profiles.     

Human responses to augmented virtual scaffolding models

This study investigated the effect of adding real planks, in virtual scaffolding models of elevation, on human performance in a surround-screen virtual reality (SSVR) system. Twenty-four construction workers and 24 inexperienced controls performed walking tasks on real and virtual planks at three virtual heights (0, 6 m, 12 m) and two scaffolding-platform-width conditions (30, 60 cm). Gait patterns, walking instability measurements and cardiovascular reactivity were assessed. The results showed differences in human responses to real vs. virtual planks in walking patterns, instability score and heart-rate inter-beat intervals; it appeared that adding real planks in the SSVR virtual scaffolding model enhanced the quality of SSVR as a human – environment interface research tool. In addition, there were significant differences in performance between construction workers and the control group. The inexperienced participants were more unstable as compared to construction workers. Both groups increased their stride length with repetitions of the task, indicating a possibly confidence- or habit-related learning effect. The practical implications of this study are in the adoption of augmented virtual models of elevated construction environments for injury prevention research, and the development of programme for balance-control training to reduce the risk of falls at elevation before workers enter a construction job.     

Design and implementation of a participatory ergonomics program for machine sewing tasks

A participatory ergonomics program was designed and implemented to control and reduce workers' compensation costs within an automobile products manufacturing company. Pareto analysis identified a substantial number of musculoskeletal disorders (MSD) associated with manual, machine sewing of canvas automobile accessory products. This case study will discuss the elements of the participatory ergonomics program, describe its implementation, highlight intervention measures, and present program results. Specifically, during the period of 1993 to 1996, the participatory ergonomics program played a significant part in reducing the number of MSD claims by approximately 85%, and contributed to an overall reduction in workers' compensation incurred loss costs by approximately 42%.     

Musculoskeletal disorder risk as a function of vehicle rotation angle during assembly tasks

Musculoskeletal disorders (MSD) are costly and common problem in automotive manufacturing. The research goal was to quantify MSD exposure as a function of vehicle rotation angle and region during assembly tasks. The study was conducted at the Center for Occupational Health in Automotive Manufacturing (COHAM) Laboratory. Twelve subjects participated in the study. The vehicle was divided into seven regions, (3 interior, 2 underbody and 2 engine regions) representative of work areas during assembly. Three vehicle rotation angles were examined for each region. The standard horizontal assembly condition (0° rotation) was the reference frame. Exposure was assessed on the spine loads and posture, shoulder posture and muscle activity, neck posture and muscle activity as well as wrist posture. In all regions, rotating the vehicle reduced musculoskeletal exposure. In five of the seven regions 45° of vehicle rotation represented the position that reduced MSD exposure most. Two of the seven regions indicated 90° of vehicle rotation had the greatest impact for reducing MSD exposure. This study demonstrated that vehicle rotation shows promise for reducing exposure to risk factors for MDS during automobile assembly tasks.     

Computer-telephone interactive tasks: predictors of musculoskeletal disorders according to work analysis and workers' perception

Sixty-two workers engaged in computer-telephone interactive tasks in an active telemarketing center and a telephone call center of an international bank subsidiary in S?o Paulo. Brazil, were assessed by means of a work analysis and a self-administered questionnaire aiming to determine the statistical relationship of ergonomic, organizational and psychosocial characteristics of their jobs with the report of symptoms in neck-shoulder and hand-wrist for more than 7 consecutive days and any time away from work during the current job due to musculoskeletal disorders (MSD). According to chi-square univariate tests and multiple logistic regression models, active telemarketing operations, duration in the job and the low level of satisfaction with the physical arrangement of the workstation emerged as the factors most related to neck-shoulder and hand-wrist MSD and MSD-induced time away from work. This study emphasizes the role of psychosocial factors and duration in the job in MSD occurrence and induced absenteeism among workers engaged in computer-telephone interactive tasks.     

Biomechanical risk assessment during field loading of hydraulic stretchers into ambulances

The process of loading a stretcher into an ambulance is known to cause a high incidence of back injuries among paramedics. This study aimed to assess the forces at L5/S1 during real-life stretcher loading activities and to determine the variables that contribute significantly to these forces. Analyses involved 58 paramedics (111 shifts) and 175 stretcher loading activities. Estimates of compression and shear forces at L5/S1 were calculated using the 3DSSPP program. Seventy-one percent of loading activities exceeded the safe loading level of 3.4 kN compression force at L5/S1 (mean: 3.9 kN, min–max: 2.1–7.0 kN). About 92% of the variance can be predicted from a combination of several variables, notably hand load (mean: 0.72 kN/number of paramedics) and back sagittal flexion (mean: 32°). Recommendations to reduce the risk of back injuries are proposed with regard to stretcher and ambulance loading design as well as training in stretcher lifting for paramedics.Relevance to the industryThe results of this study suggest that ambulance stretcher manufacturers should make ergonomic design changes to reduce the physical strain on paramedics’ backs during the process of loading a stretcher into an ambulance. Other preventive measures (e.g., training) must be formulated and applied to reduce the risk of back musculoskeletal disorders during the loading of stretcher patients. For instance, training should focus on back posture, teamwork and equipment/patient positioning on stretchers.     

Biomechanical analyses of paramedics simulating frequently performed strenuous work tasks

Firefighters performing emergency rescue functions are at an elevated risk of musculoskeletal injuries. The objective of the current study was to analyze the biomechanical stresses placed on the body based on simulations of the following strenuous and frequently performed emergency rescue tasks: (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 through a landing using a stairchair, (4) carrying a victim down a set of stairs and through a landing using a backboard, and (5) carrying a victim down a straight set of stairs using a stretcher. Postural data were analyzed using the University of Michigan's Three-Dimensional Static Strength Prediction Program and the relative risk of low back disorder (LBD) was quantified using the trunk motion model published by Marras et al. (1993, spine 18, 617-628). Peak compression values and the probabilities from the Marras et al. (1993) model indicated that the most hazardous tasks performed as part of this simulation included pulling a victim from a bed to a stretcher, the initial descent of a set of stairs when using the stretcher, and lifting a victim on a backboard from the floor. Overall, the two models were well correlated in their assessment of the task components modelled (r = 0.78). These data indicate where engineering changes to equipment regularly used by emergency rescue personnel would have the greatest impact in reducing the risk of musculoskeletal injury.     

Physical demands analysis of occupational tasks in neighborhood pubs

This paper describes a case study of a neighborhood pub in British Columbia, Canada. This case study is an examination of three common pub occupations-bartending, waitressing and cooking (n = 17). The aims of this study are to determine the biomechanical loads of job tasks identified as physically demanding for the three occupations analyzed, to assess the potential risk of musculoskeletal injury in these job tasks, and to recommend injury prevention measures. Risk of musculoskeletal injury was assessed with four validated methods (RULA, NIOSH lifting equation, Shoaf pulling model, 3D Static Strength prediction program). Tasks commonly and frequently performed were observed to pose some risk to the working populations and require investigation and changes soon as indicated by the upper extremity and low-back assessment procedures used. Mean combined compression at the lumbrosacral disc in common tasks have been demonstrated to exceed the action limit described by NIOSH. Ligament strain was observed to reach as high as 18% at the lumbosacral joint.     

Biomechanical response of the musculoskeletal system to whole body vibration using a seated driver model

ObjectiveThis study aimed to assess the effects of backrest inclination and vibration frequency on muscle activity in a dynamic environment using a musculoskeletal model.MethodThe muscle activity modeling method was used to analyze a full body musculoskeletal system of a seated person with a public domain rigid body model in an adjustable car seat. This model was established using AnyBody Modeling System, based on the inverse dynamic approach. And the min/max criterion in dealing with the muscle redundancy problem. Ten healthy subjects were exposed to whole body vibration (WBV) with five frequencies (3, 4.5, 6, 7, and 8 Hz) in the vertical direction in a randomized order on three separate days. The displacement of the seat-pan and head was measured using a hybrid Polaris spectra system to obtain the seat-to-head (STH) transmissibility. Muscle oxygenation was measured using near-infrared spectroscopy. The validity of the model was tested using STH transmissibility and muscle oxygenation.ResultsIncreased vibration frequency caused high muscle activities of the abdomen and the right leg with a backrest forward inclination angle. The muscle activities of the left leg decreased at a backrest backward inclination except at inclination angles of 15° and 30°. Muscle activity of the lumbar suddenly increased at a backrest inclination angle of 5° and vibration frequency of 5 Hz. Muscle activities were higher under vibration than that without vibration.ConclusionVibration frequency significantly affected the muscle activity of the lumbar area. Likewise, the inclination degree of the backrest significantly affected the muscle activities of the right leg and the abdomen. The combination of vibration and forward inclination of the backrest can be used to maximize the muscle activity of the leg, similar to the abdomen and lumbar muscles.Relevance to the industryThe musculoskeletal model established in the present study provides a method that can be used to investigate the biomechanical response of seated drivers to WBV. This model helps protect drivers from occupational injury.     

A master-slave manipulator for excavation and construction tasks

Currently used excavators and other construction machines use hydraulic actuators as the means of providing the necessary power to their effector tooling. The tools lack the flexibility of applying varying forces on an excavated object, thus preventing the use of powered equipment for the excavation and handling of buried sensitive objects. The prototype design of a master-slave force-feedback hydraulic manipulator described here will enable equipment operators to “feel” the force applied by the tool on a handled object as well as its location in space. This new tool may be provided as an optional feature on the traditional excavators, thus contributing to a greater flexibility of these machines and to the productivity enhancement of related work tasks.