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.     

Validity of self-reported duration of work postures obtained by interview

The aim of the study was to validate interview data concerning the duration of four work postures (1) sitting, (2) standing/walking with hands above shoulder level, (3) standing/walking with hands between shoulder and knuckle level, and (4) standing/walking with hands below knuckle level. The self-reported time spent in each posture was tested in relation to observations and technical measurements in 20 subjects during two full working days. The linear relationships between self-reports and observations were strong for the three postures; sitting (r²=0.55), hands above shoulder level (r²=0.58) and hands below knuckle level (r²=0.69). Thus, using this interview technique, self-reports concerning time spent in (1) sitting, (2) standing/walking with hands above shoulder level and, (3) standing/walking with hands below knuckle level may be accurate enough for studying these work postures in epidemiological studies.     

Assessment of duration and frequency of work tasks by telephone interview: reproducibility and validity

Quantitative estimation of physical work load requires breakdown of jobs into smaller entities. The objective was to study the inter-rater reproducibility of the contents, frequency and duration of work tasks assessed by telephone interview. Two researchers interviewed 18 industrial workers with an interval of from 2 to 3 weeks in a balanced and blinded design. Altogether 114 tasks were identified, 68 of which were recorded by both interviewers. The tasks were classified into regularly occurring (n=34) and occasional (n= 80). The outcome was the total duration of the tasks per day computed from the data on frequency and duration. Validity of the interview was studied against prestructured diaries filled in by nine workers. The interviewers' assessments of the overall contents of the tasks were rated as ‘similar’ or ‘very similar’ for 17 of the 18 workers. Both interviewers detected all 34 regularly occurring tasks. The intraclass correlation coefficient (ICC) of the total duration between the interviewers was 0.81 for regularly occurring tasks. ICCs of the total duration between the diary and the two interviewers were 0.90 and 0.91. However, in many cases the workers could not give a numerical value for duration or frequency. A telephone interview can be used as a first step in exposure assessment in epidemiological studies on risk factors of musculoskeletal disorders. These results show that a single telephone interview can give reproducible and valid information of the frequency and duration of tasks occurring daily. For occasional tasks interview methods should be developed further.     

Assessment of duration and frequency of work tasks by telephone interview: reproducibility and validity

Quantitative estimation of physical work load requires breakdown of jobs into smaller entities. The objective was to study the inter-rater reproducibility of the contents, frequency and duration of work tasks assessed by telephone interview. Two researchers interviewed 18 industrial workers with an interval of from 2 to 3 weeks in a balanced and blinded design. Altogether 114 tasks were identified, 68 of which were recorded by both interviewers. The tasks were classified into regularly occurring (n = 34) and occasional (n = 80). The outcome was the total duration of the tasks per day computed from the data on frequency and duration. Validity of the interview was studied against prestructured diaries filled in by nine workers. The interviewers' assessments of the overall contents of the tasks were rated as 'similar' or 'very similar' for 17 of the 18 workers. Both interviewers detected all 34 regularly occurring tasks. The intraclass correlation coefficient (ICC) of the total duration between the interviewers was 0.81 for regularly occurring tasks. ICCs of the total duration between the diary and the two interviewers were 0.90 and 0.91. However, in many cases the workers could not give a numerical value for duration or frequency. A telephone interview can be used as a first step in exposure assessment in epidemiological studies on risk factors of musculoskeletal disorders. These results show that a single telephone interview can give reproducible and valid information of the frequency and duration of tasks occurring daily. For occasional tasks interview methods should be developed further.     

Relating heart rate and rate of perceived exertion in two simulated occupational tasks.

The purpose of this study was to examine the relationship between ratings of perceived exertion (RPE) and activity intensity, as determined by heart rate. Fifteen participants completed a standardized treadmill protocol in order to establish a heart rate--RPE calibration profile. These participants then completed two simulated occupational tasks--box carrying and sweeping. During the simulated tasks, heart rates and RPE values were recorded every minute from the third to tenth minute and then averaged over that period. There was a moderate, but statistically significant, correlation between monitored heart rate and heart rate predicted from RPE scores for both the box carrying (r = 0.70) and sweeping (r = 0.73) simulations. Direct prediction of task heart rate from RPE reported during the task was not as strongly correlated for the box carry (r = 0.11), as it was for the sweeping activity (r = 0.68). Results from this study suggested that heart rate monitoring alone does not account for enough of the variability resulting from both local and central mediation of RPE.     

Quantifying exposure in occupational manual tasks with cumulative trauma disorder potential.

A method of describing the musculoskeletal loads in the hand and wrist during manual tasks is presented. A profile of twelve factors is used to quantify the exposure of applicable soft tissues to modes of loading suggested as being related to a number of chronic, work-related musculoskeletal disorders such as chronic muscle strain, tenosynovitis, and carpal tunnel syndrome. These factors include estimates of tendon loads and movement, frictional work done on the tendon sheaths, and muscle activation determined using electromyography. The response of these measures to changes of force, repetition, and posture was studied using eight conditions of a simulated task utilizing a pistol grip tool. Measures of tendon frictional work and dynamic electromyographic activity best paralleled the injury outcomes of an epidemiological study using similar task definitions (Silverstein et al. 1986). This field-usable system is being used currently to investigate the relationship between occupational exposure and musculoskeletal disorders.     

Computer-assisted predictive mathematical relationship among electroshock voltage and duration and occurrence of convulsion in mice

A microcomputer program in BASIC for predicting percentage of occurrence of electroshock-induced convulsion in mice was designed. A formula published by the author to express the mathematical relationship among the drug dose, the time, and the biological response was used in this program. Analysis of the actual, and the computer-assisted predicted percentages of occurrence of convulsion has shown that the program is fairly accurate in expressing convulsion response of mice as a function of the voltage and the duration.     

Developing a verbal protocol method for collecting and analysing reports of workers' thoughts during manual handling tasks

Concurrent and retrospective verbal protocol methods were used to collect thoughts from 18 participants during a manual handling task involving the repeated transfer of loads between locations at two tables. The effectiveness of qualitative and quantitative methods of analysing the reported information was tested in the study. A simple taxonomy was developed to investigate the content of the reports (including reports on postures and loads) and determine how the participants approached the task (whether they made plans, described actions or evaluated their completion of the task). References to posture were obtained in the verbal protocol reports, indicating that the participants had some awareness of their postures during parts of the task. There were similarities in the content of the concurrent and retrospective reports, but there were differences in the amount of detail between the methods and differences in the way the reports were constructed. There could be some scope for developing the quantitative analysis of the frequencies of references to classes of information, though this can only be recommended for concurrent reports on tasks of short duration. The analyses of qualitative data gave a deeper insight into the reports, such as identifying factors that can be important when planning to handle a load, or illustrating how participants can change their focus of attention periodically throughout the task. The relative strengths of the concurrent and retrospective methods are described, along with ideas for improving the quality of information collected in future studies. A number of potential problems with the interpretation of the reported information are explained.     

Comparative assessment of 3D joint marker sets for the biomechanical analysis of occupational tasks

This study involves the comparative assessment of three joint marker sets to estimate joint centres. One set consists of wide elastic bands for marking the joint centres of the ankle, knee, elbow, and wrist joints (band method), a second set uses two spherical markers on either side of the joint (ball method), and a third set defines the location of a local coordinate system from spherical markers placed near the joint (coordinate method). The three marker sets were compared relative to each other. The ball method and the coordinate method were the most similar (average differences ranged from 6 to 16 mm), which is due in part to the common markers in these sets. The band method and the coordinate method were generally the least similar (average differences ranged from 15 to 31 mm). However, the results support the assumption that the marker set consisting of elastic bands can be used as an alternative to other commonly used sets. It may even be better for certain applications because of the relatively small number of missing points. Since the bands encircle the joint they are less likely to be hidden from the view of the cameras than the two marker sets that use balls to mark the joints. Most movements filmed for ergonomic analysis are complex and the incidence of missing points with traditional marker sets is high. Therefore, the band method is a very practical alternative when studying complex occupational tasks.

Relevance to industry

Manual materials handling is a source of industrial injury. Video systems and cinematography are widely used tools to analyze occupational tasks. The use of adequate markers on the subject is essential to have reliable and accurate results for task evaluation.     

Assessment of an EMG-based method for continuous estimates of low back compression during asymmetrical occupational tasks

Variables, such as peak and accumulated moments and spine compression forces, have been shown to be risk factors for occupational low back pain. Estimates of these forces during prolonged, dynamic, asymmetric tasks using biomechanical models is complex and time-consuming. A simple technique for continuous measurement of these variables over a prolonged period is needed to measure the distribution of spinal loading during both sagittal plane lifts and complex asymmetrical jobs. The aim of this study was to determine whether a linear normalization of erector spinae EMG to spine compression force, called compression normalized EMG (CNEMG), could be used to estimate spinal loading for simulations of asymmetrical occupational tasks. The estimates of spine compression force obtained using the normalized EMG are presented in the form of an amplitude probability distribution function and are compared with estimates of a three-dimensional biomechanical model. The per cent time a worker spends above particular levels of spinal loading of interest, such as the NIOSH action limit for compression, are displayed. Five males performed simulated occupational tasks. The exposure time at a specific level of spine compression force for a combination of three tasks, estimated by CNEMG, was, on average, within 6.5% of the time calculated by the biomechanical model. However, if the task combination was dominated by an axial twisting moment, then the difference was, on average, 13.4%. The difference in magnitude of spine compression at a specific probability was, on average, 14.9% and when axial trunk twist dominated, 30.7%. It is concluded that CNEMG can estimate probability at a specific level of spine compression force when the task combination is characterized by a predominant extensor moment in the sagittal plane. Estimates of spine compression at a specific probability, and estimates obtained during task combinations dominated by an axial twisting moment, are poor.     

Assessment of an EMG-based method for continuous estimates of low back compression during asymmetrical occupational tasks.

Variables, such as peak and accumulated moments and spine compression forces, have been shown to be risk factors for occupational low back pain. Estimates of these forces during prolonged, dynamic, asymmetric tasks using biomechanical models is complex and time-consuming. A simple technique for continuous measurement of these variables over a prolonged period is needed to measure the distribution of spinal loading during both sagittal plane lifts and complex asymmetrical jobs. The aim of this study was to determine whether a linear normalization of erector spinae EMG to spine compression force, called compression normalized EMG (CNEMG), could be used to estimate spinal loading for simulations of asymmetrical occupational tasks. The estimates of spine compression force obtained using the normalized EMG are presented in the form of an amplitude probability distribution function and are compared with estimates of a three-dimensional biomechanical model. The per cent time a worker spends above particular levels of spinal loading of interest, such as the NIOSH action limit for compression, are displayed. Five males performed simulated occupational tasks. The exposure time at a specific level of spine compression force for a combination of three tasks, estimated by CNEMG, was, on average, within 6.5% of the time calculated by the biomechanical model. However, if the task combination was dominated by an axial twisting moment, then the difference was, on average, 13.4%. The difference in magnitude of spine compression at a specific probability was, on average, 14.9% and when axial trunk twist dominated, 30.7%. It is concluded that CNEMG can estimate probability at a specific level of spine compression force when the task combination is characterized by a predominant extensor moment in the sagittal plane. Estimates of spine compression at a specific probability, and estimates obtained during task combinations dominated by an axial twisting moment, are poor.     

The occurrence of musculoskeletal alterations in worker populations not exposed to repetitive tasks of the upper limbs

A total of 749 workers (males: 139 aged between 15 and 35 years, and 171 aged > 35 years; females: 176 aged between 15 and 35 years, and 263 aged >35 years) performing tasks not at risk for work-related musculoskeletal disorders of the upper limbs (WMSDs) underwent a clinical examination using a standardized method. The ‘anamnestic cases’ were defined on the basis of pain or paraesthesia present for at least 1 week during the previous 12 months, or appearing at least once a month, and not subsequent to acute trauma. The anamnestic cases among the males amounted to 4.4% (age 15–35 years) and 12.3% (age> 35 years); among the females, 4.6% (age 15–35 years) and 14.2% (age> 35 years). Of the 1498 limbs examined, the prevalent diseases reported were: suspect narrow chest syndrome: 0.3% among the males > 35 years, 0.6% among the females aged 15 35 years, 1% among the females > 35 years; scapulo-humeral periarthritis: 0.3% among the males aged > 35 years, 0.3% among the females aged 15–35 years, 1.3% among the females aged > 35 years; lateral epicondylitis: 0.3% among the males aged > 35 years, 0.2% among the females aged > 35 years; trapeziometacarpal arthrosis: 0.8% among the females aged > 35 years; wrist-hand tendinitis: 0.9% among the males aged > 35 years, 0.9% among the females aged 15–35 years; carpal tunnel syndrome: 2.5% among the females aged > 35 years. No disorders were detected outside the age ranges indicated. Several workers reported more than one disorder. The number of workers with at least one WMSD was: males 0% in the 15–35 years age range, 3.5% in the > 35 years age range; females 2.3% in the 15–35 years age range, 7.2% in the > 35 years age range; 3.9% of the total sample population. The prevalences were on average quite low, particularly among the older workers, hence the authors recommend that even minimal prevalences detected in particular work environments should not be underestimated.     

The accuracy of conventional 2D video for quantifying upper limb kinematics in repetitive motion occupational tasks

Marker-less 2D video tracking was studied as a practical means to measure upper limb kinematics for ergonomics evaluations. Hand activity level (HAL) can be estimated from speed and duty cycle. Accuracy was measured using a cross-correlation template-matching algorithm for tracking a region of interest on the upper extremities. Ten participants performed a paced load transfer task while varying HAL (2, 4, and 5) and load (2.2 N, 8.9 N and 17.8 N). Speed and acceleration measured from 2D video were compared against ground truth measurements using 3D infrared motion capture. The median absolute difference between 2D video and 3D motion capture was 86.5 mm/s for speed, and 591 mm/s² for acceleration, and less than 93 mm/s for speed and 656 mm/s² for acceleration when camera pan and tilt were within ± 30 degrees. Single-camera 2D video had sufficient accuracy ( < 100 mm/s) for evaluating HAL.

Practitioner Summary: This study demonstrated that 2D video tracking had sufficient accuracy to measure HAL for ascertaining the American Conference of Government Industrial Hygienists Threshold Limit Value^® for repetitive motion when the camera is located within ± 30 degrees off the plane of motion when compared against 3D motion capture for a simulated repetitive motion task.     

Experience effects on the accuracy of self-assessed user competence

Self-managed learning is the normal way that users learn to work with software within organizations. To be effective, self-managed, learning requires individuals to self-assess their IT knowledge; accurate self-assessment helps them optimize the capabilities they possess and be aware of those they do not. This study demonstrated that, in general, individuals did not accurately self-assess their knowledge of the software they used. However, we also found that the accuracy of self-assessment increased with greater experience in, and better understanding of, IT domains.Organizations need to recognize the self-assessment problem to facilitate effective software learning and to gain the most from their software investments.     

Using a smart textile system for classifying occupational manual material handling tasks: evidence from lab-based simulations

Physical monitoring systems represent potentially powerful assessment devices to detect and describe occupational physical activities. A promising technology for such use is smart textile systems (STSs). Our goal in this exploratory study was to assess the feasibility and accuracy of using two STSs to classify several manual material handling (MMH) tasks. Specifically, commercially-available ‘smart’ socks and a custom ‘smart’ shirt were used individually and in combination. Eleven participants simulated nine separate MMH tasks while wearing the STSs, and task classification accuracy was quantified subsequently using several common models. The shirt and socks, both individually and in combination, could classify the simulated tasks with greater than 97% accuracy. Thus, using STSs appears to have potential utility for discriminating occupational physical tasks in the work environment.

Practitioner summary: A smart textile system could classify diverse MMH tasks with high accuracy. This technology may help in developing future ergonomic exposure assessment systems, with the goal of preventing occupational injuries.     

Computer usage and the validity of self-assessed computer competence among first-year business students

This study evaluates the reliability of self-assessment as a measure of computer competence. This evaluation is carried out in response to recent research which has employed self-reported ratings as the sole indicator of students’ computer competence. To evaluate the reliability of self-assessed computer competence, the scores achieved by students in self-assessed computer competence tests are compared with scores achieved in objective tests. The results reveal a statistically significantly over-estimation of computer competence among the students surveyed. Furthermore, reported pre-university computer experience in terms of home and school use and formal IT education does not affect this result. The findings call into question the validity of using self-assessment as a measure of computer competence. More generally, the study also provides an up-to-date picture of self-reported computer usage and IT experience among pre-university students from New Zealand and South-east Asia and contrasts these findings with those from previous research.     

Validity of the Acti4 software using ActiGraph GT3X+accelerometer for recording of arm and upper body inclination in simulated work tasks

The validity of inclinometer measurements by ActiGraph GT3X+ (AG) accelerometer, when analysed with the Acti4 customised software, was examined by comparison of inclinometer measurements with a reference system (TrakStar) in a protocol with standardised arm movements and simulated working tasks. The sensors were placed at the upper arm (distal to the deltoid insertion) and at the spine (level of T1-T2) on eight participants. Root mean square errors (RMSEs) values of inclination between the two systems were low for the slow- and medium-speed standardised arm movements and in simulated working tasks. Fast arm movements caused the inclination estimated by the AG to deviate from the reference measurements (RMSE values up to ～10°). Furthermore, it was found that AG positioned at the upper arm provided inclination data without bias compared to the reference system. These findings indicate that the AG provides valid estimates of arm and upper body inclination in working participants.     

Optimizing the stretch of independent tasks on a cluster: From sequential tasks to moldable tasks

This paper addresses the problem of scheduling non-preemptive moldable tasks to minimize the stretch of the tasks in an online non-clairvoyant setting. To the best of the authors’ knowledge, this problem has never been studied before. To tackle this problem, first the sequential subproblem is studied through the lens of the approximation theory. An algorithm, called DASEDF, is proposed and, through simulations, it is shown to outperform the first-come, first-served scheme. Furthermore, it is observed that machine availability is the key to getting good stretch values. Then, the moldable task scheduling problem is considered, and, by leveraging the results from the sequential case, another algorithm, DBOS, is proposed to optimize the stretch while scheduling moldable tasks. This work is motivated by a task scheduling problem in the context of parallel short sequence mapping which has important applications in biology and genetics. The proposed DBOS algorithm is evaluated both on synthetic data sets that represent short sequence mapping requests and on data sets generated using log files of real production clusters. The results show that the DBOS algorithm significantly outperforms the two state-of-the-art task scheduling algorithms on stretch optimization.     

Aging and performance of home tasks

Household behaviors must be understood in terms of a hierarchy of behavioral competence within which complexity determines the location of behaviors that can be evaluated in terms of basic health and social-normative criteria. Older people's household behaviors as well as higher-order behaviors are schematized in terms of physical and instrumental activities of daily living (ADL). Data on impairment rates for ADLs and time budget studies are cited to emphasize the importance of the home environment. Other behaviors that represent needs for autonomy, support, and proactivity are discussed, as are research needs, both for development of measures of microbehaviors and for the study of behaviors designed to achieve alternative routes to an instrumental goal whose preferred means of attainment has been disturbed by physical impairment.