Job demands, physical fitness, work ability, and age of vehicle inspectors

The aim of this field, laboratory, and questionnaire study was to quantify and compare job demands, physical fitness, and work ability of aging (over 45 years) and young male vehicle inspectors. Dynamic and perceived job demands were moderately low, whereas static load on the neck-shoulder region was high due to bent and/or twisted head and neck postures which occurred at an average of 42% of working hours. Physical job demands were about equal for aging and young subjects. Aging subjects had lower aerobic and muscular fitness than young ones. A reduced work ability was detected in 14% of the aging inspectors. Technical and organizational measures are necessary to reduce static load and fixed repetitiveness of the job. Furthermore, individual physical training is recommended to maintain work ability of both the aging and young vehicle inspectors.     

Determination of physical stress in agricultural work

The aim of this study was to find a method or combination of methods appropriate for defining the physical stress imposed by jobs carried out in the farm environment. Besides charting research methods, various other methods were applied to three sample jobs (making a load of bales, lowering of tomatoes and mechanised loading and transportation of timber). The sample jobs were selected to represent dynamic loading, static stress and work posture stress. The methods chosen were: oxygen consumption, pulse-blood pressure measurement, electromyography, the OWAS work posture observation method, and the Borg RPE scale for recording the test person's subjective stress estimate. The experiments were conducted using four test persons in real working environments. According to this study different methods for determining the physical stress of work are needed.The stress of dynamic work can best be investigated by means of oxygen consumption or heartbeat frequency. Furthermore, with these methods it is possible to classify jobs. The static stress can be determinated by means of the stress felt by the test person and electromyographic recordings of changes in muscle tension, although these are quite person-sensitive methods. Static stress also affects heartbeat frequency and blood pressure. The OWAS method is probably the best method available when studying the work postures in agricultural work - at least when involved in whole body work requiring moving about on the part of the person doing the job.     

Assessment of back load in assemblyline work using electromyography

Abstract

When the back is loaded, the amplitude of the myoelectric signals in the lumbar region of the back has been found to correlate well to the compression force in the spine measured by means of disc pressure. The purpose of this paper is to use surface electromyography to quantify the load on the back in several working situations.

Thirteen male workers participated in a study of three strenuous workstations along the assembly line of a car factory; mounting of a side panel and a sound insulator in the front compartment, mounting of floor mats, and mounting of the left front seat. Electrodes were placed at the level T8, LI and L3 on both sides of the spine.

The average load during a work cycle is given as mean values of signal amplitude. Standard deviations are calculated to indicate the average load variations. Amplitude histograms are also presented to illustrate the loading pattern in more detail.

The results show that it is possible to record myoelectric signals at the workplace without serious disturbance. The amplitude levels were high at all three workstations. The actual way in which each task was carried out resulted in differences in activity level between the thoracic and lumbar regions of the back which could be used to identify incorrect body postures or work activities. The use of a lifting aid at one workstation was found to give a significant decrease in high amplitude levels. Analysis of myoelectric activity patterns give useful guidance about how to reduce body loading in heavy work situations and also permits quantitative evaluation of such improvements.     

Influence of material handling devices on the physical load during the end assembly of cars

The effect of using a mechanical device on physical load was analysed during the end assembly of cars. Five tasks, further sub-divided into lifting and positioning, were performed by someone experienced in working with and without the mechanical tool. A practical methodology was used: the subjective walk and talk through method, the NIOSH equation (1991), a three-dimensional goniometer (Back Tracker) and surface electromyography (EMG) of the relevant muscle groups. According to the NIOSH equation, 8 out of 10 of the tasks should only be performed by trained workers and preferably with tools. The Back Tracker revealed that the mechanical tools reduced posture angles significantly (p0.05) for installing the windows, but not for left lateroflexion during pre-assembly of windows. It was clear from the EMG analysis that using tools did not always decrease muscular activity significantly. In general, the appropriateness of each tool needs to be evaluated separately taking the subjective criteria into account.

Relevance to industry

In this study, the relevance of using a mechanical device to reduce the physical load during car assembly, is evaluated. As the tools are expensive, it is important to the industry whether they are being used and how efficient they are.     

Neck/shoulder and low-back disorders in the forestry industry: relationship to work tasks and perceived psychosocial job stress

In a national cross-sectional study, the prevalence of neck/shoulder and low-back disorders and their relationship to work tasks and perceived psychosocial job stress was studied among forestry employees. The data were collected by occupational health service staff using Karasek's demand/control questionnaire for the psychosocial measures and the Standardized Nordic questionnaire for the analysis of musculoskeletal disorders. Based on data about past and present work tasks, the study population was classified into three groups: 645 manual workers, 66 machine operators and 124 administrative workers. Low-back disorders were more common among the manual workers than among the administrative workers \[odds ratio (OR) = 1.98]. For the machine operators and manual workers, an increasing level of psychological demands was significantly associated with an increased prevalence of low-back disorders. The prevalence of neck/ shoulder disorders was significantly higher among the machine operators (OR = 3.37) and manual workers (OR = 2.34) than among the administrative workers. An increasing level of psychological demands combined with a decreasing level of intellectual discretion was associated with an increased prevalence of neck/shoulder disorders. Authority over decisions was not associated with musculoskeletal disorders. In conclusion, musculoskeletal disorders were associated with both physical and psychosocial work factors. The modest strength of the associations between each individual independent variable and the outcome measure shows, however, that a substantial reduction in the prevalence of musculoskeletal disorders may be difficult to achieve. Nevertheless, the study clearly suggests that in the forestry industry attention should be paid to psychosocial work factors in future organizational changes and preventive programmes.     

Reducing the physical work load and strain of personal helpers through clothing redesign

This study assessed the effects of redesigning clients’ clothing on the physical work load and strain of personal helpers. Five women, aged 18–54 years, who helped persons with physical disabilities were measured at their worksites before and after development of the clothes worn by clients. The physical work load and strain of the helpers’ dressing/undressing of clients were determined from their hand and back movements, work time, muscular activity, heart rate (HR), percentage of heart rate range (%HRR), and rating of perceived exertion (RPE). The muscular activity of the right (p=0.05) and left (p=0.02) trapezius muscles, HR (p=0.03), and %HRR (p=0.03) of the helpers were lower when the new outerwear was used in place of traditional outerwear. Four helpers reported lower perceived exertion, and three had shorter work time with the new outerwear. This study showed that redesigning clients’ clothing can help reduce the physical work load and strain of personal helpers.     

Effect of block weight on work demands and physical workload during masonry work

The effect of block weight on work demands and physical workload was determined for masons who laid sandstone building blocks over the course of a full work day. Three groups of five sandstone block masons participated. Each group worked with a different block weight: 11 kg, 14 kg or 16 kg. Productivity and durations of tasks and activities were assessed through real time observations at the work site. Energetic workload was also assessed through monitoring the heart rate and oxygen consumption at the work site. Spinal load of the low back was estimated by calculating the cumulated elastic energy stored in the lumbar spine using durations of activities and previous data on corresponding compression forces. Block weight had no effect on productivity, duration or frequency of tasks and activities, energetic workload or cumulative spinal load. Working with any of the block weights exceeded exposure guidelines for work demands and physical workload. This implies that, regardless of block weight in the range of 11 to 16 kg, mechanical lifting equipment or devices to adjust work height should be implemented to substantially lower the risk of low back injuries.     

Effect of horizontal position of the computer keyboard on upper extremity posture and muscular load during computer work

The distance of the keyboard from the edge of a work surface has been associated with hand and arm pain; however, the variation in postural and muscular effects with the horizontal position have not been explicitly explored in previous studies. It was hypothesized that the wrist approaches more of a neutral posture as the keyboard distance from the edge of table increases. In a laboratory setting, 20 adults completed computer tasks using four workstation configurations: with the keyboard at the edge of the work surface (NEAR), 8 cm from the edge and 15 cm from the edge, the latter condition also with a pad that raised the work surface proximal to the keyboard (FWP). Electrogoniometers and an electromagnetic motion analysis system measured wrist and upper arm postures and surface electromyography measured muscle activity of two forearm and two shoulder muscles. Wrist ulnar deviation decreased by 50% (4°) as the keyboard position moved away from the user. Without a pad, wrist extension increased by 20% (4°) as the keyboard moved away but when the pad was added, wrist extension did not differ from that in the NEAR configuration. Median values of wrist extensor muscle activity decreased by 4% maximum voluntary contraction for the farthest position with a pad (FWP). The upper arm followed suit: flexion increased while abduction and internal rotation decreased as the keyboard was positioned further away from the edge of the table. In order to achieve neutral postures of the upper extremity, the keyboard position in the horizontal plane has an important role and needs to be considered within the context of workstation designs and interventions.     

Heavy load carrying and musculoskeletal health: An exploratory study of biomechanical risk factors among sand miners in Pokhara,Kaski District,Nepal

BackgroundTrends in urbanization contribute to the growing global demand for raw construction materials. The health effects of load carrying among occupational groups that mine and carry sand and stone used for construction of roads and buildings remains poorly understood.MethodsWe conducted an exploratory cross-sectional study among a convenience sample of sand miners working at an excavation site on the Seti River in Pokhara, Nepal. Load carrying weight, duration, and frequency were used to categorize miners as having “low” or “high” load-carrying exposures. Musculoskeletal disorders (MSDs) were identified using self-reported symptoms of moderate to severe musculoskeletal pain, as well as physical examinations.ResultsThe average loads carried by female and male sand miners weighed 66 kg and 87 kg, respectively. Among all participants (N = 42), 45% reported moderate to severe musculoskeletal pain in at least one body region and 16 (38%) had MSDs identified using specified case criteria. The prevalence of MSDs was lower among miners carrying, on average, heavier loads compared to those carrying lighter loads (OR = 0.18; 95% CI: 0.04, 0.7), possibly indicative of the healthy worker survival effect. Miners carrying loads for longer durations had higher odds of MSDs compared with those carrying for shorter durations.ConclusionThis study has provided data on the extraordinary loads carried by sand miners in Nepal and preliminary evidence of health impacts associated with these loads. However, larger epidemiologic studies are needed to justify action to protect the health and safety of these unrecognized and understudied groups.     

Efficacy of adjusting working height and mechanizing of transport on physical work demands and local discomfort in construction work

The efficacy of ergonomics measures to reduce physical work demands in a real working situation is often assumed, but seldom studied. In this study, the effect of adjusting working height and mechanization of transport on physical work demands and local discomfort of bricklayers' work was evaluated during a field experiment in the construction industry. In a within-subjects controlled experiment, 10 bricklayers and 10 bricklayers' assistants worked in two different conditions. Working height of bricks and mortar, and transport of materials were manipulated. The physical work demands were assessed through real time observations at the work site. Local discomfort of the lower back and of the shoulder region was measured by means of a visual analogue scale. Working with a scaffolding console to adjust the working height of the storage of materials resulted in a significant reduction of the frequency and duration of trunk flexion (?>?60°) by 79% and 52% respectively, compared with bricks set out on the ground floor. Mechanization of transport of materials resulted in a significant reduction of the frequency and duration of trunk flexion (?>?60°) by 94% and 92% respectively, compared with the condition of manual handling. The frequency of handling objects (?>?4?kg) reduced significantly by 86%. Local discomfort of the lower back was significantly less in the ergonomic conditions, while no significant difference was found for local discomfort of the shoulder between both conditions in bricklayers' assistants.     

Comparison of concepts in easy-to-use methods for MSD risk assessment

This article presents a comparative analysis of easy-to-use methods for assessing musculoskeletal load and the risk for developing musculoskeletal disorders. In all such methods, assessment of load consists in defining input data, the procedure and the system of assessment. This article shows what assessment steps the methods have in common; it also shows how those methods differ in each step. In addition, the methods are grouped according to their characteristic features. The conclusion is that the concepts of assessing risk in different methods can be used to develop solutions leading to a comprehensive method appropriate for all work tasks and all parts of the body. However, studies are necessary to verify the accepted premises and to introduce some standardization that would make consolidation possible.     

Force direction and physical load in dynamic pushing and pulling

In pushing and pulling wheeled carts, the direction of force exertion may, beside the force magnitude, considerably affect musculoskeletal loading. This paper describes how force direction changes as handle height and force level change, and the effects this has on the loads on the shoulder and low back. Eight subjects pushed against or pulled on a stationary bar or movable cart at various handle heights and horizontal force levels while walking on a treadmill. The forces at the hands in the vertical and horizontal direction were measured by a forcetransducer. The forces, body movements and anthropometric data were used to calculate the net joint torques in the sagittal plane in the shoulder and the lumbosacral joint. The magnitudes and directions of forces did not differ between the cart and the bar pushing and pulling. Force direction was affected by the horizontal force level and handle height. As handle height and horizontal force level increased, the pushing force direction changed from 45° (SD 3.3°) downward to near horizontal, while the pulling force direction changed from pulling upward by 14° (SD 15.3°) to near horizontal. As a result, it was found that across conditions the changes in force exertion were frequently reflected in changes in shoulder torque and low back torque although of a much smaller magnitude. Therefore, an accurate evaluation of musculoskeletal loads in pushing and pulling requires, besides a knowledge of the force magnitude, knowledge of the direction of force exertion with respect to the body.     

Technical Note: Method for objective assessment of physical work load at the workplace

This paper presents a method for objective assessment of physical work load at the workplace. The method is based on the DynaPort ADL Monitor. Using accelerometry, this monitor enables the assessment of gross motor activity as it occurs during the activities of daily living (ADL). A case study is conducted to explore the usefulness of the monitor in support of occupational research. The focus is on the cause and reduction of mechanical low back pain (LBP). A patient suffering from mechanical LBP participated in the study. He worked as messenger in contrast with his usual occupation. The patient was examined in both occupations using the monitor. The ADL profiles indicated that the messenger job was more likely to cause LBP than the other occupation of a mechanic.     

Relationship between trapezius load and the incidence of musculoskeletal illness in the neck and shoulder

A relationship between m. trapezius load measured by electromyography (EMG) and the incidence of musculoskeletal illness in the neck and shoulder regions, was investigated both for assembly workers and VDT operators. For assembly workers, the static trapezius load (probability 0.1 of the amplitude probability distribution function, APDF) was significantly reduced from 4.3% MVC (Maximum Voluntary Contraction) to 1.4% MVC as a group median value after an ergonomic adaptation of their work places. Musculoskeletal sickleave was significantly reduced from 22.9 days to 1.8 days as a medium duration per-man-labour year for the same group.

Three groups of VDT operators were examined in terms of trapezius load and pain intensity and duration before and after an ergonomic intervention. All groups reported significant less intensity or duration of pain either in the neck or in the shoulder regions after the intervention. The trapezius load was reduced for all groups post vs. prior intervention. This reduction was measured in terms of a decrease in the static level of APDF and an increase in the number of periods per minute and total duration of muscle activity below 1% MVC. The results from this study indicate that the trapezius load may be a predictor for development of musculoskeletal illness in the neck and shoulder regions.     

Life-time occupational exposure to heavy work and individual physical capacity

The aim of the present study was to retrospectively analyze the effect of occupational physical activity on maximal isometric hand grip strength and maximal oxygen consumption among males and females between 19 and 64 years of age in different occupations. A life-time occupational physical activity index was formed from questions in a questionnaire. The maximal isometric hand grip strength was measured with a dynamometer and maximal oxygen consumption was estimated from a submaximal bicycle ergometer test. The results showed a negative correlation between physical activity and estimated maximal oxygen consumption among males but no other statistically significant associations between life-time physical activity and the present physical capacity was found. The present results suggest that a high level of occupational physical activity does not maintain individual physical capacity.     

Self-administered questionnaire and direct observation by checklist: comparing two methods for physical exposure surveillance in a highly repetitive tasks plant

Background

We evaluated the agreement between a questionnaire and an observational checklist for exposure assessment in the setting of an upper-limb work-related musculoskeletal disorders (UWMSD) surveillance program in a population with a high level of physical exposures.

Methods

A surveillance program was implemented in a large shoe factory. Physical exposures were assessed in 1996 by a self-administered questionnaire and by the direct observation of work tasks assessed using a checklist filled out by trained assessors. Items were summed into a “questionnaire” score and an “observational” score. These scores were compared by Pearson's correlation. The association between exposure assessment by each method and UWMSD incidence between 1996 and 1997, defined by a standardized examination, was also studied.

Results

Correlation between the “questionnaire” score and the “observational” score was low among the 196 workers (77%) who received both evaluations (rho=0.06, p>0.05). Only exposure assessed by the questionnaire method was significantly associated with high incidence of UWMSD between 1996 and 1997, with good sensitivity (97%) and poor specificity (27%).

Conclusion

In this surveillance program, self-reported physical exposures assessed by questionnaire and by direct observation did not evaluate same dimensions of high physical exposures. In this sample, exposures assessed by questionnaire identified workers at high risk of incident UWMSD more precisely than exposures identified by direct observation.     

The work load of warehouse workers in three different working systems

An investigation was conducted in five companies in the distribution branch. These companies were divided into three different working systems, i.e., highly mechanized (HM), moderately mechanized (MM), and slightly mechanized (SM). The three systems differed in logistics and kind of appliances used. The purpose of this study was to compare the three working systems with different degrees of mechanization concerning the time spent on tasks, activities during the working day, postures that occurred, physiological work load, perceived exertion and recovery from work. To investigate the different tasks, activities and working postures, 50 warehouse workers, originating from the three working systems, were observed by means of a direct observation method, called: ‘TRAC’. To investigate the physiological work load the heart rate was recorded continuously during the working day and related to the individually determined relation between heart rate and oxygen uptake. This relation was constructed with the results of a cycle ergometer test done in the laboratory. During lunch and at the end of the working day the warehouse workers filled in a questionnaire concerning their perceived exertion and recovery from work.

In the slightly mechanized system more time was spent with the trunk flexed more than 75° as compared with the other two systems. This posture was very common during lifting of objects, and lifting was done more often in this system than in the other systems. In the MM system the warehouse workers had the highest estimated oxygen uptake and reported the highest perceived exertion at the end of the working day. The workers in the HM system had a shorter working day and had less problems with recovery from work than the workers of the other two systems. Poor working postures like rotation and lateroflexion were commonly found in the HM working system. An important explanation was the difference in time spent driving an electric car. This activity was done mostly in the HM system. In conclusion, the HM system was considered most favourable when it concerned work load and recovery from work. The appliances used in the HM system, and especially the electric car, need to be designed according to ergonomic guidelines to avoid poor working postures.     

Evaluation of a participatory ergonomic intervention process in kitchen work

We evaluated a participatory ergonomic intervention process applied in 59 municipal kitchens. In groups of three to five kitchens, the workers participated in eight workshops, and generated and evaluated solutions to optimize musculoskeletal load in their work. An ergonomist initiated and supported the process. By the end, 402 changes were implemented. Evaluative data were collected using research diaries, questionnaires, and focus group interviews. The intervention model proved feasible and the participatory approach was mostly experienced as motivating. The workers’ knowledge and awareness of ergonomics increased, which improved their ability to tackle ergonomic problems by themselves. The changes in ergonomics were perceived to decrease physical load and improve musculoskeletal health. As hindering factors for implementation, lack of time and motivation, and insufficient financial resources were mentioned. In addition, the workers expressed a wish for more support from the management, technical staff, and ergonomists.     

Physical and mental strain at work: Relationships with onset and persistent of multi-site pain in a four-year follow up

This study evaluates the association of physical and mental strain with the onset and persistence of multi-site musculoskeletal pain among younger and older employees in four-year follow-up. A questionnaire survey was conducted twice in a food processing company, in 2005 and 2009, with responses from 734 employees (445 younger and 289 older; 65% female). Information on musculoskeletal pain during the preceding week and perceived mental and physical strain was obtained through a structured questionnaire. The association of onset and persistent of multi-site pain with mental and physical strain was estimated with log binomial regression analysis and stratified by age group. Risk ratios (RR) with their 95% confidence intervals (CIs) are reported for the estimates. More than 56% of the employees reported multi-site pain at baseline. Among those who reported multi-site pain at baseline 70% reported persistent multi-site pain and one-third reported new onset of multi-site pain at follow-up. Mental strain at baseline strongly predicted persistence of multi-site pain among both younger and older employees (RR from for younger employees = 1.68, 95% CI = 1.01–2.83 and RR for older employees = 2.25, 95% CI 0 1.27–3.98) but the association with physical strain was not statistically significant. Mental strain predicted the risk of persistence of multi-site pain among both younger and older employees in four-year follow-up but not onset of multi-site pain.Relevance to the industryThe results of this study suggest that monitoring working conditions of all age workers can reduce physical and mental strain, thereby reducing the incidence of multi-site musculoskeletal pain and promoting workers' health.