Occupational lifting by nursing aides and warehouse workers

Nursing aides (18 women and six men) at one traditional and one modern geriatric ward, and warehouse workers (16 men) at two different types of warehouse departments were studied during occupational work. The vertical load during manual handling was measured using strain gauges built into wooden shoes. The warehouse workers performed four times as many lifts as the nursing aides and transferred five times as great a mass per unit time. Less than 25% of the lifts were carried out with the load evenly distributed on both feet during both the upward lift and lowering. In the warehouses the lifts were short, while the nursing aides were exposed both to lifts of longer duration and to carrying, as well as a greater frequency of unexpected, sudden and high peak load. The heart rate and oxygen uptake values recorded were relatively low, and both groups utilized approximately 25% of their maximum aerobic power. According to official occupational injury statistics, both warehouse workers and nursing aides belong to risk groups with a high frequency of reported back injuries. However, more injuries are reported by nursing aides than by warehouse workers. Greater muscle strength in male workers may partly explain this difference. Qualitative differences in the design of the lifting work, with more lifts of long duration in awkward work postures, more carrying, more exertion of horizontal forces and a greater frequency of unexpected rapid lifts in the nursing aides may also contribute to the differences in risk of injury between these occupational groups. Considerable differences were found between the two hospital wards as regards lifting frequency, force, duration and the proportion of lifts with an even distribution of load on both feet during upward lift. The lifting work was approximately 50% less in the modern ward, which has easily maneuvered electric overhead hoists, spacious premises and better work organization than in the traditional ward, even though the patient handling needs were equivalent. In the warehouse department at which the wares were stored with easy access, the frequency of lifts with an even distribution of load on both feet was approximately 25%, compared to 7% in the other warehouse department. In conclusion, evaluations of occupational lifting work should include a quantitative assessment of the duration and load distribution of lifting, as well as of postures. Workstation design, technical aids and work organization have a profound effect on the lifting work load even in jobs with equal manual handling demands.     

An experimental evaluation of psychophysical criteria for repetitive lifting work

Two experiments were performed to test the reliability and validity of psychophysically determined maximum acceptable workloads for setting lifting standards. The perceived workload in a repetitive diagonal lifting task was found to be a positively accelerated function of the weight lifted and of the work pace respectively. A twofold increase in objective workload resulted in a four- to fivefold increase in perceived workload. This relation was independent of previous occupational experience of lifting work. The psychophysically assessed maximum acceptable workloads for this type of lifting task appeared to be satisfactorily reproducible when subjects had to adjust work pace or when they were left free to adjust both the weight and the work pace. However, the results raised several questions concerning the applicability of the psychophysical assessment of maximum acceptable lifting work. Slight changes in the instructions given to the subjects had a definite effect on the selection of workloads. Furthermore, the workloads selected by subjects with previous occupational experience of lifting work — i e, warehouse workers — were systematically lower than those selected by subjects without such previous experience — i e, office employees. At the same time, the warehouse workers rated perceived exertion higher than the office employees, indicating that previous occupational experience of lifting work enhanced the subjective assessment of physical effort. There were no consistent relations between the workloads found acceptable by the subjects and their physical characteristics and performance capacity.     

Need for recovery from work: evaluating short-term effects of working hours,patterns and schedules

In this paper working hours, patterns and work schedules of employees were evaluated in terms of need for recovery from work. Self-administered questionnaire data from employees of the Maastricht Cohort Study on Fatigue at Work (n = 12,095) were used. Poisson regression analyses and multivariate logistic regression analyses revealed that higher working hours a day and working hours a week generally went together with more need for recovery from work. Overtime work was particularly associated with higher need for recovery from work in both genders. Both male and female three-shift or irregular shift workers had higher odds of elevated need for recovery compared to day workers. When additionally controlling for work-related factors, need for recovery levels among shift workers substantially lowered. This study clearly showed that working hours and schedules are associated with need for recovery from work, with different associations for men and women. Especially the associations between work schedules and need for recovery from work were very interrelated with other work-related factors. Future studies could further investigate the possibility that shift work might function as a proxy of other work-related factors that explain the different levels in need for recovery from work, or that job demands are perceived higher among shift workers and may therefore lead to more need for recovery from work.     

Estimation of spinal loads in overhead work

To explore the spinal loads occurring in overhead working postures and to assess the value of ergonomic reduction of lumbar extension, spinal strain was measured by stature change in simulated motor vehicle maintenance tasks. A field study identified the typical extent of lumbar extension incurred in this type of work. In the laboratory eight male volunteers tightened and loosened bolts both overhead and at chest-height for 30min periods; records were made of lumbar posture, ground reaction force, and perceived exertion. Stature change was measured using a refined technique which permitted estimation of net effect of the work loads. The field study revealed that motor mechanics typically spent 8% of their time working overhead with up to 10° of lumbar extension. In the laboratory study, the overhead task entailed more lumbar extension and perceived exertion than did the chest-height task; ground reaction forces did not differ substantially between tasks. Only small changes in stature were observed at the end of the work period, and there was no significant difference between the tasks (means: overhead, + 0.61 mm; chest-height, ? 0.23 mm: p = 0.31). Stature change was significantly correlated with lordosis for overhead work such that increased lordosis (compared with chest-height work) was associated with relative stature gain. No evidence was found to indicate a need for ergonomic intervention in overhead work tasks so far as spinal loading is concerned. The lack of substantial change in stature from tasks perceived to involve moderately high levels of exertion was unexpected; it would appear that some elements of dynamic work tasks may have a relative unloading effect, and that lordotic postures reduce load on the spinal discs.     

The daily work load of refuse collectors working with three different collecting methods: a field study

The daily work load of 116 Dutch (male) refuse collectors working with polythene bags, two-wheeled mini-containers and large four-wheeled containers was studied. To this end a time analysis of the tasks and activities in the real working situation was made and the postures and the physiological work load of the collector working with the three different methods was assessed. Manual materials handling and the corresponding working postures were studied by means of observations. Heart rate (HR) was continuously recorded during the working day. Furthermore, to enable the assessment of the work load during refuse collecting as a percentage of the maximal oxygen uptake ([Vdot]O₂max) every refuse collectors' relationship between HR and oxygen uptake was measured during a simulation of the tasks and activities in the laboratory. The range in total working time of the refuse collectors was large. Most time is spent on the task ‘loading’; this lasted on average about 5?h. The mean number of handled objects for the three refuse collecting methods is 1500 bags, 500 mini-containers and 120 large containers respectively. The mean amount of collected refuse per collector of bags and mini-containers is about 11000kg. For the collectors of the large containers it is 27% higher, namely about 14000kg. The mean weight of one object for the bags, mini-container and large container is 7, 22 and 110?kg respectively. The straight posture was the most common in refuse collecting by bags. The posture flexed at the trunk and bent forwards or backwards occurred often while pushing and pulling containers. However, the refuse collectors of the large containers pushed and pulled for shorter periods during a working day in comparison with collectors of the mini-containers. Criteria for energetic overload were set at a mean energy expendiiure of 30% [Vdot]O₂ max and an energy expenditure of 50% [Vdot]O₂ max or more for a maximum of 60?min per day. According to these limits the energetic work load of the collectors of bags was indicated as being too high. In order to formulate guidelines in terms of mechanical and energetic load it is necessary to measure more accurately these loads during refuse collecting activities.     

Quantitative postural load assessment for whole body manual tasks based on perceived discomfort

Many Korean workers are exposed to repetitive manual tasks or prolonged poor working postures that are closely related to back pain or symptoms of musculoskeletal disorders. Workers engage in tasks that require not only handling of heavy materials, but also assuming prolonged or repetitive non-neutral work postures. Poor work postures that have been frequently observed in the workplaces of shipbuilding shops, manufacturing plants, automobile assembly lines and farms often require prolonged squatting, repetitive arm raising and wrist flexion and simultaneous trunk flexion and lateral bending. In most manufacturing industries, workers have to assume improper work postures repetitively, several hundreds of times per day depending on daily production rate. A series of psychophysical laboratory experiments were conducted to evaluate the postural load at various joints. A postural load assessment system was then developed based on a macro-postural classification scheme. The classification scheme was constructed based on perceived discomfort for various joint motions as well as previous research outcomes. On the basis of the perceived discomfort, postural stress levels for the postures at individual joints were also defined by a ratio scale to the standing neutral posture. Laboratory experiments simulating automobile assembly tasks were carried out to investigate the relationship between body-joint and whole-body discomfort. Results showed a linear relationship between the two types of discomfort, with the shoulder and low back postures being the dominant factor in determining the whole body postural stresses. The proposed method was implemented into a computer software program in order to automate the procedure of analysing postural load and to enhance usability and practical applicability.     

Quantitative postural load assessment for whole body manual tasks based on perceived discomfort

Many Korean workers are exposed to repetitive manual tasks or prolonged poor working postures that are closely related to back pain or symptoms of musculoskeletal disorders. Workers engage in tasks that require not only handling of heavy materials, but also assuming prolonged or repetitive non-neutral work postures. Poor work postures that have been frequently observed in the workplaces of shipbuilding shops, manufacturing plants, automobile assembly lines and farms often require prolonged squatting, repetitive arm raising and wrist flexion and simultaneous trunk flexion and lateral bending. In most manufacturing industries, workers have to assume improper work postures repetitively, several hundreds of times per day depending on daily production rate. A series of psychophysical laboratory experiments were conducted to evaluate the postural load at various joints. A postural load assessment system was then developed based on a macro-postural classification scheme. The classification scheme was constructed based on perceived discomfort for various joint motions as well as previous research outcomes. On the basis of the perceived discomfort, postural stress levels for the postures at individual joints were also defined by a ratio scale to the standing neutral posture. Laboratory experiments simulating automobile assembly tasks were carried out to investigate the relationship between body-joint and whole-body discomfort. Results showed a linear relationship between the two types of discomfort, with the shoulder and low back postures being the dominant factor in determining the whole body postural stresses. The proposed method was implemented into a computer software program in order to automate the procedure of analysing postural load and to enhance usability and practical applicability.     

Long-duration assessment of upper arm posture and motion and their association with perceived symptoms among bakery workers

Awkward shoulder postures have been suggested to be a cause of shoulder discomfort among bakery workers. This study aimed at long-duration assessment of upper arms posture and motion and their association with perceived symptoms among bakery workers. Among workers in three types of bread systems, fifty-seven bakers were randomly selected. The self-reported rates for the perceived severity and frequency of shoulder discomfort were collected through questionnaires. Working postures and movements of the shoulders during work were continuously recorded with inclinometry measurements for three hours. Percentage of time spent with the upper arm right elevated more than 60° was significantly correlated with the perceived discomfort rate in the right shoulder for all bakery workers (r = 0.48 to 0.63, p ≤ 0.05). A significant correlation was found between angular velocity with the perceived discomfort intensity for right upper arm.(r = 0.60 to 0.87, ≤0.005) of all workers in the three baking systems. Physical exposure in bakers was characterized by significantly more awkward postures and the percentage of time spent with the upper arms elevated more than 60°. The current findings can facilitate more informed decisions with respect to both engineering (e.g.ergonomic workstation and tool design) and administration (e.g. work organization) control strategies.     

Postural load and back pain of workers in the manufacturing of prefabricated concrete elements.

In a population of male workers in a concrete manufacturing plant (n = 114), the occurrence of back pain was studied in relation to a control group of maintenance engineers (n = 52). The prevalence of back pain in the 12 months preceding the investigation was 59% among the concrete workers, and 31% among the controls. After excluding persons with existing back pain before starting work in the present factory, a comparison between concrete workers and maintenance engineers showed an aged-adjusted odds ratio for back pain of 2.80 (1.31-6.01). Postural load of workers in both plants were measured using the Ovako Working posture Analysis System. During 4009 observations working postures concerning the back, lower limbs, and lifting activities were recorded. The average time spent working with a bent and/or twisted position of the back was found to contribute to the prevalence of back pain. The results of this study also suggest that exposure to whole-body vibration, due to operating vibrotables, is a second risk factor for back pain.     

Concordance between VDU-users' ratings of comfort and perceived exertion with experts' observations of workplace layout and working postures

The aim of the present study was to evaluate the concordance (agreement) between VDU-users' ratings of comfort and ergonomists' observations of workplace layout, and the concordance between VDU-users' ratings of perceived exertion and ergonomists' observations of working postures during VDU-work. The study population consisted of 853 symptom free subjects. Data on perceived comfort in different dimensions and data regarding perceived exertion in different body locations were collected by means of a questionnaire. Data concerning workplace layout and working postures were collected with an observation protocol, by an ergonomist. Concordance between ratings of comfort and observations of workplace layout was reasonably good for the chair and the keyboard (0.60, 0.58) and good regarding the screen and the input device (0.72, 0.61). Concordance between ratings of perceived exertion and observations of working postures indicated good agreement (0.63-0.77) for all measured body locations (neck, shoulder, wrist and trunk). In conclusion ratings of comfort and perceived exertion could be used as cost-efficient and user-friendly methods for practitioners to identify high exposure to poor workplace layout and poor working postures.     

Work postures and strain of workers in nordic forest work: A selective review

In this paper, ergonomic characteristics of forest work and particularly the strain related to work postures are reviewed. Both in manual and mechanized forest work, working postures play an important role, separately and combined with other strain factors. The combined effect mmay be worse than those of single factors. Examples of such combinations include bad work postures in conjunction with heavy lifting while cutting or during maintenance of machines and whole-body vibration and repetitive steering work while operating machines. The situation becomes even more complicated when the whole work environment is taken into consideration. Work postures often contribute to strains that have far-reaching effects, but have no immediate impact on the worker's behaviour or injury rates. Even in highly mechanized forest work, problems still exist despite extensive development of cabs. Some new technical and design solutions have recently been introduced.     

Evaluation of two floor-mopping work methods by measurement of load

The workload for two different methods of floor mopping in 11 healthy female cleaners was evaluated by rating the perceived exertion, by recording the ECG and EMG and by video analysis of postures and movements. There was less perceived exertion and local muscle loading during work when the 'push' method was used than with the 'figure-of-eight' method. The 'push' method nevertheless still implied a level of static loading that may be harmful during long term work. The methods did not differ regarding measured heart rate and oxygen consumption. However, for two cleaners the 'figure-of-eight' method and for three cleaners the 'push' method implied a work load corresponding to more than 40% of their normal oxygen uptake. Large individual variations in work postures and movements were found for both methods.     

Postural load and back pain of workers in the manufacturing of prefabricated concrete elements

In a population of male workers in a concrete manufacturing plant (n= 114), the occurrence of back pain was studied in relation to a control group of maintenance engineers (n=52). The prevalence of back pain in the 12 months preceding the investigation was 59% among the concrete workers, and 31% among the controls. After excluding persons with existing back pain before starting work in the present factory, a comparison between concrete workers and maintenance engineers showed an age-adjusted odds ratio for back pain of 2·80 (1·31?6·01). Postural load of workers in both plants were measured using the Ovako Working posture Analysis System. During 4009 observations working postures concerning the back, lower limbs, and lifting activities were recorded. The average time spent working with a bent and/or twisted position of the back was found to contribute to the prevalence of back pain. The results of this study also suggest that exposure to whole-body vibration, due to operating vibrotables, is a second risk factor for back pain.     

A postural workload evaluation system based on a macro‐postural classification

Many Korean workers are exposed to repetitive or prolonged poor working postures, which are closely related with pains or symptoms of musculoskeletal disorders. Poor working postures in Korea were reviewed and an observational method to assess the postural load was developed. A computer‐based postural workload evaluation system based on a macro‐postural classification scheme was developed. The macro‐postural classification is based on the perceived discomforts for various joint motions. On the basis of the perceived discomfort, postural stress levels for the postures at each joint were also defined in a ratio scale to the standing neutral posture. A neural network approach was used to predict the whole‐body postural stresses from the body joint motions. A computer‐based postural stress evaluation system was designed to automate the procedure for analyzing postures and enhance the usability and practical applicability. © 2002 Wiley Periodicals, Inc.     

Observations of working postures in garages using the Ovako Working posture Analysing System (OWAS) and consequent workload reduction recommendations

The working postures of mechanics (n = 84) in 42 garages were observed using the Ovako Working posture Analysis System (OWAS). During observation, both working postures and work activities were recorded. A computer program was developed for the data analyses. Using this program it is possible to calculate the working posture load for each work activity and the contribution of a specific activity to the total working posture load. This is a substantial extension of the original OWAS method. Five out of 19 observed postures of the body members were classified as Action Category 2, which suggests they were slightly harmful to the musculoskeletal system and likely to cause discomfort. Of the so-called typical working postures, 31.9% was classified in Action Category 2, suggesting that during a substantial part of the working day typical working postures occur which are at least slightly harmful to the musculoskeletal system. Moreover, those work activities principally causing the workload to fall in OWAS' higher Action Categories were identified. For each of these three work activities an alternative work method was observed. The data show that in all three work activities the use of a vehicle lift reduces the number of poor working postures thereby reducing the load on the musculoskeletal system.     

An OWAS-based analysis of nurses' working postures

Abstract

The working postures of Dutch nurses (n = 18) in an orthopaedic ward and a urology ward were observed using-the Ovako Working posture Analysis System (OWAS). During observation, both working postures and activities were recorded. A specially developed computer program was used for data analysis. By means of this program, it was possible to calculate the working posture load for each activity and the contribution of a specific activity to the total working posture load. This study shows that some activities of the nurses in both wards were performed with poor working postures. In the orthopaedic (resp. urology) ward two (resp. one) out of 19 observed postures of parts of the body were classified as Action Category 2. Moreover, 20% (resp. 16%) of the so-called typical working postures was classified in Action Category 2. This suggests, that in both wards working postures that are slightly harmful to the musculoskeletal system, occur during a substantial part of the working day. Differences between both wards with respect to working posture load and time expenditure were determined. Activities causing the workload to fall into OWAS higher Action Categories were identified. The data show that poor working postures in the nursing profession not only occur during patient handling activities but also during tasks like ‘administration’. Focusing on patient-handling (i.e., lifting patients) in order to determine the load on the musculoskeletal system would therefore lead to an underestimation of the total working posture load of nurses     

Test-retest reliability and concurrent validity of a web-based questionnaire measuring workstation and individual correlates of work postures during computer work

INTRODUCTION: "Ergonomic" questionnaires are widely used in epidemiological field studies to study the association between workstation characteristics, work posture and musculoskeletal disorders among office workers. Findings have been inconsistent regarding the putative adverse effect of work postures. Underestimation of the true association might be present in studies due to misclassification of subjects to risk (i.e. exposed to non-neutral working postures) and no-risk categories (i.e. not exposed to non-neutral working postures) based on questionnaire responses. The objective of this study was to estimate the amount of misclassification resulting from the use of questionnaires. METHODS: Test-retest reliability and concurrent validity of a newly developed questionnaire was assessed. This questionnaire collects data on workstation characteristics and on individual characteristics during computer work (i.e. work postures, movements and habits). Pictures were added where possible to provide visual guidance. The study population consisted of 84 office workers of a research department. They filled out the questionnaire on the Internet twice, with an in-between period of 2 weeks. For a subgroup of workers (n=38), additional on-site observations and multiple manual goniometer measurements were performed. RESULTS: Percentage agreement ranged between 71% and 100% for the test-retest analysis, between 31% and 100% for the comparison between questionnaire and on-site observation, and between 26% and 71% for the comparison between questionnaire and manual goniometer measurements. For 9 out of 12 tested items, the percentage agreement between questionnaire and manual goniometer measurements was below 50%. CONCLUSIONS: The questionnaire collects reliable data on workstation characteristics and some individual characteristics during computer work (i.e. work movements and habits), but does not seem to be useful to collect data on work postures during computer work in epidemiological field studies among office workers.     

The impact of working technique on physical loads - an exposure profile among newspaper editors

The aim of this study was to investigate the possible associations between working technique, sex, symptoms and level of physical load in VDU-work. A study group of 32 employees in the editing department of a daily newspaper answered a questionnaire, about physical working conditions and symptoms from the neck and the upper extremities. Muscular load, wrist positions and computer mouse forces were measured. Working technique was assessed from an observation protocol for computer work. In addition ratings of perceived exertion and overall comfort were collected. The results showed that subjects classified as having a good working technique worked with less muscular load in the forearm (extensor carpi ulnaris p=0.03) and in the trapezius muscle on the mouse operating side (p=0.02) compared to subjects classified as having a poor working technique. Moreover there were no differences in gap frequency (number of episodes when muscle activity is below 2.5% of a reference contraction) or muscular rest (total duration of gaps) between the two working technique groups. Women in this study used more force (mean force p=0.006, peak force p=0.02) expressed as % MVC than the men when operating the computer mouse. No major differences were shown in muscular load, wrist postures, perceived exertion or perceived comfort between men and women or between cases and symptom free subjects. In conclusion a good working technique was associated with reduced muscular load in the forearm muscles and in the trapezius muscle on the mouse operating side. Moreover women used more force (mean force and peak force) than men when operating the click button (left button) of the computer mouse.     

An evaluation of the effect of a training program on worker lifting postures

Though worker training is often chosen as a means to reduce the risk of low back pain if involved in lifting activities, the effect on a worker's lifting posture is rarely reported. This paper describes a video analysis method of recording lifting postures and the results of one evaluation of a training program specifically designed to modify lifting postures. It is concluded that a four-hour training program had beneficial but minor effects on the lifting techniques used by healthy workers in a warehouse when handling relatively light to moderate loads (i.e., 85% of loads lifted were below 30 pounds).     

Effect of the number of two-wheeled containers at a gathering point on the energetic workload and work efficiency in refuse collecting

The effect of the number of two-wheeled containers at a gathering point on the energetic workload and the work efficiency in refuse collecting was studied in order to design an optimal gathering point for two-wheeled containers. Three sizes of gathering points were investigated, i.e. with 2, 16 and 32 two-wheeled containers at a gathering point. The collecting of two-wheeled containers was simulated in a test circuit. The energetic workload was quantified by the parameters oxygen uptake (l min⁻¹), heart rate (beats min⁻¹) and perceived exertion. The work efficiency was quantified as the time it took to collect 32 two-wheeled containers per time period. The maximum acceptable amount of two-wheeled containers collected during an 8-h working day was estimated using the energetic criterion of a maximum oxygen uptake of 30% VO_2max. The size of the gathering point had no effect on the oxygen uptake, heart rate or perceived exertion. However, the number of two-wheeled containers per collecting period (work efficiency) and the maximum acceptable amount during an 8-h working day were higher in the conditions with 16 and 32 two-wheeled containers at a gathering point compared to the condition with the 2 two-wheeled containers at a gathering point.