Influence of adherence to autonomous job rotation on musculoskeletal symptoms,occupational exposure,and work ability

Job rotation is widely used in the manufacturing industry. The aim of this study was to investigate the influence of adherence to autonomous job rotation on the prevalence of musculoskeletal symptoms, occupational exposure, and work ability. A total of 120 blue-collar workers from an automotive manufacturing company with a job rotation program as an organizational strategy were included in this study. Job rotation performance, musculoskeletal symptoms, perceived occupational and biomechanical exposure, and work ability were evaluated. For the statistical analyses, the departments were divided into high (83.7%–100%) and low (0–36.4%) job rotation adherence. Two departments showed high adherence to job rotation (n = 78 workers). Workers who had high job rotation adherence had a higher prevalence of musculoskeletal symptoms (32.1%) and higher perceived occupational exposure for the occurrence of musculoskeletal symptoms (71.4 ± 45.7 points) (P > 0.05). Work ability was considered good or excellent for both high- and low-adherence groups (P > 0.05). High adherence to job rotation had no positive influences on the musculoskeletal symptoms, occupational exposure, and work ability of workers.     

Risk assessment of cheese processing tasks using the Strain Index and OCRA Checklist

The purpose of this study was to conduct and compare two ergonomic risk assessment methods often used in occupational health research and practice: the Strain Index (SI) and Occupational Repetitive Actions (OCRA) Checklist. Seven raters used the SI and OCRA Checklist to assess task-level physical exposures to the upper extremity of workers performing 21 cheese-manufacturing tasks. Of the total task exposures assessed with both methods, nearly half (49.1%) were classified as hazardous using the OCRA Checklist while 60.2% were classified as hazardous using the SI. Although the underlying injury risk characterization constructs of the SI and OCRA Checklist differ, the results indicated that the SI and OCRA Checklist often classified job tasks into similar risk categories. The differences in risk classifications determined by the SI and OCRA Checklist for job tasks were likely related to the definition of variables measured by these assessment methods as well as the complexity of tasks evaluated. By design, the SI is specific to the distal upper extremity while the OCRA Checklist accounts for the entire upper extremity including the shoulder. When conducting risk assessments of industrial work tasks, the choice of analysis tools should be based on the purpose of the assessment and the complexity of task functions. Both the SI and OCRA Checklist yield risk assessment ratings that are similar for cheese processing tasks.     

Good vacation and job rotation systems were beneficial for the hemoglobin level of workers at high altitude,a cross-sectional study along the Qinghai Tibet railway,China

Working and travelling in high-altitude regions have been associated with a variety of adverse health effects. The aim of this study was to explore a good vacation and job rotation system to prevent workers at high altitude from chronic altitude sickness. A total of 985 healthy male workers along the Qinghai-Tibet Railway, aged from 21 to 58 years (mean age 37.7 ± 8.6 years), were included into this study. The subjects took different short–term vacations, with different ratios of rest and work days. Furthermore, job rotation in low altitude was implemented in 127 (12.9%) subjects, who were transferred to relatively low altitude areas after working in plateau areas for more than three months. The association between vacation type and low altitude job rotation with prevalence of hyperhemoglobin (hemoglobin >175 g/L) was analyzed. Results showed that the risk of hyperhemoglobin decreased significantly with the increase of ratio of rest and work days, after adjusting for other confounding variables (age, ethnicity, education, body mass index, etc.) using multivariable logistic regression analysis. Meanwhile, the prevalence of hyperhemoglobin in job rotated workers was significantly lower than that in non-rotated workers [OR = 0.56, 95% CI: 0.37 to 0.84, p < 0.05]. Besides that, BMI, labor intensity, altitude at the workplace and frequency of oxygen supplementation were also closely related to the increase of hemoglobin level. We concluded that good vacation and job rotation system were effective means to prevent hyperhemoglobin and should be promoted in immigrants at high altitude for a long time.     

Updating reference values and predictive models of the OCRA method in the risk assessment of work-related musculoskeletal disorders of the upper limbs

A database has been established combining existing data for 23 groups of workers with different level of exposure to repetitive movements of the upper limbs. For all groups, data were available regarding an exposure index (OCcupational Repetitive Actions - OCRA index) and clinically determined UL-WMSDs outcomes (PA = Prevalence of workers affected by one or more UL-WMSDs; PC = Prevalence of single diagnosed cases of an UL-WMSDs). Using these data, new critical values of the OCRA index have been estimated for discriminating different exposure levels (green, yellow, red areas) and new forecasting models of expected PA and PC in exposed populations based on OCRA exposure indexes. The new critical values of the OCRA index were estimated by an original approach in which data for the effect variable (PA) in a reference population not exposed to the relevant risks are combined with the regression function between OCRA and PA. The best simple regression functions between OCRA exposure indexes and health outcomes variables (PA; PC) were researched to obtain forecasting models of effects starting from exposure. Discussion of the results obtained considers their intrinsic limitations, as they are based on prevalence studies, as well as providing recommendations and cautions in the use of the proposed classification system and forecasting models when the OCRA method is applied.     

Preventing upper limb work-related musculoskeletal disorders (UL-WMSDS): new approaches in job (re)design and current trends in standardization

In industrialized countries, upper limb work-related musculoskeletal disorders (UL-WMSDs) are the most common form of occupational diseases. They are generating a growing population of workers with reduced working capacity. The link between these pathologies and different aspects of work organization has been convincingly proven. Recent experiences in Europe supporting the combination of traditional work design methods used in manufacturing companies with ergonomics methods are reported briefly, with special focus on the use of the occupational repetitive action (OCRA) method for risk assessment and management of manual repetitive tasks. The combined approach strives to achieve the goal of maintaining a satisfactory level of productivity while respecting ergonomics criteria and, definitely, workers' health. New ergonomics standards provide for interaction between job and machinery designers and ergonomists in the design of work processes and workplaces. These standards generally refer only to the healthy adult working population and do not always provide criteria for protecting particular working populations, such as that represented by workers affected by UL-WMSDs. The results of preliminary studies concerning productive re-employment of workers with UL-WMSDs allow the introduction of some criteria for implementing current ergonomics standards in this connection. One aim of this paper is to summarize experiences of close cooperation between ergonomists, machinery designers and job designers to guarantee productivity and the prevention of musculoskeletal disorders. A second aim is to examine current ergonomics standards in the field of manual physical work (designed for healthy workers) and to suggest preliminary criteria for their implementation taking into account the capabilities and needs of specific sub-groups of the working population.     

Insights about mental health aspects at intralogistics workplaces – A field study

The present field study investigated mental health aspects at intralogistics workplaces, as cognitive and social demands have largely changed in this branch. Within a cross-sectional, mixed methods study design, forty-one intralogistics employees completed a survey about their working conditions and mental states. Further, nine workers participated in a systematic, qualitative group interview to obtain intralogistics specific job resources and job demands. The results were compared to known mechanisms from a long-established psychological model (the Job-Demands and Resources model, JD-R model) to evaluate if these general assumptions still apply at modern working conditions. As expected and in line with the JD-R model, regression analyzes supported that job resources predicted work engagement (p < .05) and job demands predicted burnout symptoms (p < .001) even at modern intralogistics workplaces. However, no interaction effects (Job Demands X Job Resources) were found. The qualitative interviews highlighted several job demands and job resources, which were reported as especially relevant for modern intralogistics workplaces by the participants. Based on the findings, practical recommendations were evolved for the improvement of mental health at intralogistics workplaces. Job resources, for example process transparency or respectful and esteeming leadership behavior, can be increased in order to improve work engagement. Job demands, for example task interruptions, excessive time pressure or profuse exposure to physical stress should be controlled to reduce burnout symptoms.     

The relationship between work productivity and acute responses at different levels of production standard times

Work productivity is typically associated with production standard times. Harder production standards generally result in higher work productivity. However, the tasks become more repetitive in harder production standard time and workers may be exposed to higher rates of acute responses which will lead to higher risks of contracting work-related musculoskeletal disorders (WMSDs). Hence, this paper seeks to investigate the relationship between work productivity and acute responses at different levels of production standard times. Twenty industrial workers performed repetitive tasks at three different levels of production standard time (PS), corresponding to “normal (PSN)”, “hard (PSH)” and “very hard (PSVH)”. The work productivity and muscle activity were recorded along these experimental tasks. The work productivity target was not attainable for hard and very hard production standard times. This can be attributed to the manifestations of acute responses (muscle activity, muscle fatigue, and perceived muscle fatigue), which increases as the production standard time becomes harder. There is a strong correlation between muscle activity, perceived muscle fatigue and work productivity at different levels of production standard time. The relationship among these variables is found to be significantly linear (R = 0.784, p < 0.01). The findings of this study are indeed beneficial to assess the existing work productivity of workers and serves as a reference for future work productivity planning in order to minimize the risk of contracting WMSDs.     

Examining joint loading and self-reported exertion and discomfort during ladder handling

Ladder handling by telecommunications technicians represents an indispensable part of their daily work, but may generate musculoskeletal injury risk. These workers have a high prevalence of shoulder and back injuries, motivating research to quantify postures and loading using different ladders during common handling tasks. Twenty-five participants completed carry, raise (against a wall or free standing), and simulated removal from a van roof tasks using three ladders (8.5m 2-piece wood; 8.5m 2-piece fibreglass, 9.2m 3-piece wood). Data collection included kinematics and kinetics during these ladder handling tasks, as well as perceived discomfort, perceived exertion and post-collection ladder and task preferences. Significant effects depended on task and ladder. Dominant arm (the arm completing the primary action) elevation was higher while extending the ladder (114.7 ± 3.4°) than the carry task (53.5 ± 3.5°) (p < 0.05). Joint moments in the dominant shoulder and trunk were highest for the 2-piece wood ladder (59.0 ± 2.2 Nm and 254.8 ± 8.8 Nm) averaged across all tasks. Joint forces were increased when using the 2-piece wood ladder compared to the 3-piece wood ladder (p < 0.05), while the greatest discomfort in the shoulders occurred using the 2-piece wood ladder in the carry task. Many tasks approached or exceeded strength capability of a 50th percentile male's predicted strength. While no ladder universally mitigated physical demands while lowering perceptual difficulty, construction differences yielded trends toward preferring the 2-piece fibreglass or 3-piece wood ladders over the 2-piece wood ladder. This work has direct relevance to workplaces with ladder handling and provides recommendations for ladder selection and strength requirements across tasks.     

Comparing the biomechanical and perceived exertion imposed on workers when using manual mechanical and powered cargo management systems during ladder loading and unloading tasks

This study aimed to compare the effects of two different cargo management systems (one powered system, i.e., the RazerLift®, and one Traditional system) on the biomechanical and perceived exertion experienced by workers when performing routine ladder loading and unloading tasks. Seven experienced workers performed ladder loading and unloading tasks. Compared to when the Traditional system was being used, the cumulative static low-back compression force was reduced by 57.9% (p < 0.05) and 39.3% (p < 0.05) when the RazerLift® was being used to perform ladder loading and unloading tasks, respectively. Overall, the cumulative shoulder flexor moments were reduced by 34.8% (p < 0.05) and 41.3% (p < 0.05) when the RazerLift® was being used to perform ladder loading and unloading tasks, respectively. Overall, the perceived exertion score was reduced by 250.1% (p < 0.05) when the RazerLift® was being used compared to the Traditional system. In conclusion, our study demonstrated that the RazerLift® reduces the biomechanical and psychophysical exposure associated with the development of musculoskeletal disorders while performing ladder loading and unloading tasks.     

Novel thoraco-lumbo-sacral corset design increases Biering-Sorensen back endurance and alters knee and ankle angles during a box lifting task

Research investigating lumbosacral corset designs and their effects are limited and conflicting. The objective was to compare thoraco-lumbo-sacral support corsets (polyester/nylon: TLSSC-poly and neoprene: TLSSC-neo) with a traditional model (TRAD) and Control. Twenty male, university-aged, healthy, recreationally active, participants performed Biering-Sorensen back endurance (BS) test and box lifting tasks (BL:30 repetitions using 20% body mass). Lower and upper erector spinae and hamstrings electromyography (EMG); trunk-hip, knee, and ankle kinematics as well as endurance time were monitored. With BL, the TLSSC-poly (121.4°±17.9) exhibited 1.9% (p = 0.01), 2.7% (p = 0.003), and 3.7% (p = 0.0003) greater knee flexion than TRAD (119.1°±17.5), TLSSC-neo (116.8°±17.4) and Control (120.1°±17.6) respectively. The TLSSC-poly (101.9°± 8.9) demonstrated significant 3.5% (p = 0.005), 2.2% (p = 0.002) and 1.4% (p = 0.01) greater dorsiflexion than TRAD (103.4°±8.7), TLSSC-neo (104.2°±9.8) and Control (105.7°±7.2) respectively. With BS, TLSSC-poly (137.4-s±31.2, 9.7%, p = 0.018) and TLSSC-neo (133.8-s±32.3, 9.2%, p = 0.006) exhibited significantly longer durations than Control (124.8-s±29.8). Relevance to industry: The TLSSC increased BS endurance and TLSSC-poly increased BL knee and ankle angles, possibly providing benefits for workers, with repeated actions over a full work day.     

The night float paradigm to decrease sleep deprivation: good solution or a new problem?

In the late 1980s physician residency training programs developed the night float rotation, characterized by a sequence of 5 - 15 days of night work without any daytime duties, thereby involving an abrupt reversal of the wake-sleep schedule. We examined the effect of the night float rotation on sleep, mood and performance of pediatric residents. Residents completed sleep diaries daily, and tests of mood (Profile of Mood States) and attention (Conner's Continuous Performance Test) three times a week during the two-week night float rotation, and during equivalent blocks of time of their daytime rotations. Results show that, despite having ample opportunity to sleep during the day, while on night float rotation residents slept less than during the nights of their normal daytime rotations, 6.3 h ± 2.5 h and 7.2 h ± 1.7 h, respectively, p < 0.0001. Also, during night float compared to daytime rotations residents had increased fatigue-inertia scores, 8.7 ± 4.1 and 4.8 ± 2.4, respectively, p < 0.0001, and decreased vigor-activity scores 10.7 ± 5.4 and 14.8 ± 5.3, respectively, p = 0.02. The scores for attention were not significantly different between night float and daytime rotations. The correlation coefficients of fatigue with measures of attention were not statistically significant for daytime rotations. However, for night float fatigue correlated with omission errors, r = 0.51, p = 0.001 and with attentiveness r = ?0.36, p = 0.03. Training programs that adopt the night float rotation must be aware of potential deleterious effects of the night float rotation as they may lead to serious consequences on residents' performance and patients' safety.     

Task rotation effects on upper extremity and back muscle activity

Job rotation is an intuitive approach to distributing work to minimize muscular fatigue. The purpose of the current study was to evaluate rotation between lifting and gripping on muscle activity and effort. Ten male participants performed all 4 combinations of two 15 min tasks in 30 min trials split between separate days to prevent fatigue. The tasks of lifting a 12 kg box and gripping at 20% of maximum were performed 6 times per minute (5 s work: 5 s rest). Muscle activity (percentiles, gaps) and perceived effort were significantly affected by the task combinations. The forearm and upper erector spinae muscles did not benefit as greatly from rotating between lifting and gripping tasks as the lower erector spinae, deltoid or trapezius. In addition to gross task differences, overlaps in muscle activity between “low back” and “upper extremity” tasks must be considered when creating effective job rotation schemes.     

Effect of ergonomic Armrest® forearm support on wrist posture related to carpal tunnel pressure during computer mouse work

ObjectiveWe validated the effect of moveable arm support (Armrest®) on wrist posture during three standardized tasks.BackgroundThe use of the computer mouse has been increasing over the years and it has been identified as one of the occupational activities related to carpal tunnel syndrome (CTS). The main mechanism for CTS is carpal tunnel pressure (CTP) that could be estimated from the wrist posture.MethodUsing an electronic goniometer, we assessed wrist extension/flexion and ulnar-radial flexion in 15 participants (age: 34.8 [8.7] years) and calculated the time the wrist posture was outside the threshold values previously related to CTP. Specifically, we estimated time when wrist posture yielded >25 mmHg of CTP: wrist extension >32.7°; wrist flexion < −48.6°; wrist ulnar flexion >14.5°; and wrist radial flexion < −21.8°.ResultsAverage wrist extension/flexion tends to be 13.4° lower (p = 0.063), while radial-ulnar flexion was 13.2° lower (p = 0.025) when Armrest® forearm support was used in comparison to fixed forearm support. Furthermore, the time spent outside the threshold wrist extension was 25.8% (p = 0.018) lower and ulnar flexion was 37.2% (p = 0.017) lower when using Armrest® compared to a fixed forearm support. Results were independent from tasks.ConclusionArmrest® diminished the time spent outside the threshold values related to 25 mmHg of CTP indicative of CTS.ApplicationA moveable arm support is a simple and effective way to increase occupational health during computer mouse work.     

Examining kinematics and muscle activity of the upper extremity while performing cleaning tasks: A pre-post shift evaluation

Custodians engage in strenuous manual labour throughout their workday. Uncertainty exists on whether kinematics or muscle activation changes as workers progress through their shift. The purpose of this study was to examine muscle activation and upper extremity kinematics during typical custodial tasks performed at the start and end of the work shift. Electromyography (EMG) of 8 torso and upper extremity muscles and motion capture of the corresponding region were collected for 10 custodial participants while they completed garbage removal, dry mopping, and vacuuming tasks at the start and end of a work shift. The start of shift assessment demonstrated larger anterior deltoid, posterior deltoid and extensor digitorum activation by up to 12.6 %maximal voluntary contraction (%MVC) (p < 0.001–0.023). Task affected mean and peak EMG in all muscles except flexor digitorum (p < 0.001–0.0293), and the greatest activation was found during vacuuming (peak <55%MVC in anterior and middle deltoid) and the heaviest garbage removal task (84% MVC peak in upper trapezius). Mopping created the lowest amounts of activation for almost all muscles. Joint range of motion (p < 0.001–0.031) in the shoulder was highest in vacuuming, while trunk flexion was largest in garbage removal tasks. This work replicated common custodial tasks in a laboratory, using actual custodial workers at times relevant to their typical work shifts. The information presented is useful for ergonomists, work tasks designers and custodial administration staff to develop guidelines for injury prevention.     

In-field instrumented ergonomic risk assessment: Inertial measurement units versus Kinect V2

Musculoskeletal disorders are a major category of nonfatal work-related diseases in the industry. Therefore, various risk factor assessment methods, such as Rapid Upper Limb Assessment (RULA), were proposed for preventing musculoskeletal disorders in industrial environments. Nevertheless, RULA measurements based on workers' self-report or external rater observation are subjective and suffer from low repeatability. Thus, the objective of this paper is to investigate the accuracy and reliability of (1) a wearable technology (using inertial measurement units) and (2) a marker-less optical technology (using Kinect V2) for RULA risk assessment tool against motion-capture cameras (reference) for different manual material handling tasks. The obtained RULA scores were compared against the reference system using the proportion agreement index (Po) and Cohen's Kappa coefficient (κ). The wearable technology showed a “substantial” agreement (κ > 0.6) with the motion-capture cameras. The marker-less technology showed inconsistency in the agreement with the motion-capture cameras ranging from “fair” (κ < 0.4) to “moderate” (κ > 0.4) agreements, caused by both self-occlusion and object occlusion. Therefore, wearable technology showed to be more suitable than marker-less optical technology for in-field ergonomic risk assessment.     

Multifactor association of job,individual and psychosocial factors in prevalence of distal upper extremity disorders and quantification of job physical exposure

The objective of this study was to develop a multifactor model of job, individual and psychosocial factors in prevalence of distal upper extremity musculoskeletal disorders (DUE MSDs); and quantify job physical exposure to establish safe exposure limits. The study sample comprised of 525 workers who were part of a large prospective cohort study and represented a broad array of industrial practices and a wide range of job physical exposure. Only baseline data was considered for the analysis in the study. Workers underwent laptop administered questionnaires, structured interviews, two standardized physical examinations and nerve conduction studies to ascertain demographic, medical history, psychosocial factors and current DUE MSDs. All workers' jobs were individually measured for job physical exposure factors and videotaped. Binomial logistic regression was used to develop and test the multifactor association and quantification of job physical exposure for safe exposure limits. Results indicated that work-related DUE MSDs are multifactor in nature and are significantly affected by specific factors of (1) job physical exposure - percentage duration of exertion (PDOE), workers' subjective ratings of perceived effort or intensity of exertion (IOE) (using Borg CR-10), hand activity level measured by the American conference of Governmental Industrial Hygienists (ACGIH) threshold limit value for hand activity level (TLV for HAL), and presence of 2-point pinch grasps; (2) individual factors - female gender, diabetes, higher body mass index (BMI), and past and current smokers; (3) psychosocial factors - neither likely/unlikely or very unlikely to take up the current job again, divorced/separated, and presence of family problems. Quantification of job physical exposure indicated that prevalence of work-related DUE MSDs significantly increases with efforts per minute (Eff/min) >8 (OR = 1.69, p = 0.006) and woker's perceived effort based on Borg rating for IOE at the end of the shift >3 (OR = 2.46, p < 0.001). Further studies should be conducted to validate these safe exposure limit criteria.     

Posture and lifting exposures for daycare workers

Daycare employees, specifically caregivers, are a distinct population that may experience increased risk of injury due to the high exposure to bent postures, lifting conditions and high stress associated with their work. The objectives of the study were to collect up to date data on daycare workers and to compare the data between groups working with children of different ages (Infant, Toddler and Preschool). The study consisted of two distinct phases: Phase 1 – Questionnaire distribution, Phase 2 – Observation and analysis involving three dimensional postural monitoring and video recording as well as an analysis of the low back forces and moments in lifting. Phase 1: Consisted of the distribution of questionnaires to all employees in each of the participating daycares (n = 73). Of the 73 questionnaires distributed 32 responses were obtained (44%). Of the 32 employees who completed the questionnaires, 19 caregivers volunteered to participate in Phase 2 of the study. An additional 5 caregivers participated in phase 2 of the study, but did not complete any questionnaires. The questionnaires indicated 81% of the workers have experienced low back pain. Phase 2: Observational data were collected on site in five local daycares, throughout the first half of each subject's shift (∼3.5 h). Caregivers from each of the three classroom age groups were recruited for participation in the direct observation (Infant: n = 7, Toddler: n = 7, Preschool: n = 8). Posture analysis revealed that on average, workers adopted trunk flexion angles greater than 55°, for 10% of the collection time, and greater than 70°, for 5% of the collection time. These postures correspond to both moderate and severe flexed postures respectively. The lifting analysis (completed using the data recorded in phase 2) revealed that workers lifted with frequencies of 0.25 lifts/minute, lifted a total weight of 501 kg (over 3.3 h) and experienced average compression and shear forces of 3323 N and 371 N, respectively. A between-group comparison showed that when compared to the Preschool group, the Infant (p = 0.008) and Toddler (p = 0.001) groups demonstrated higher relative flexed postures and lifting frequencies, and the Toddler group (p = 0.023) demonstrated higher total weight lifted. Results suggested that these employees experience an elevated risk of low back injury caused by their occupational tasks and thus, further research is required to determine appropriate worker accommodations and safe work practices to help mediate these risks for all daycare caregivers.Relevance to industryIt is thought that the results from this study could lead to the development of safe working and job sharing guidelines for daycare workers.     

Shoulder muscle activity in off-axis pushing and pulling tasks

Workspace design can often dictate the muscular efforts required to perform work, impacting injury risk. Within many environments, industrial workers often use sub-maximal forces in offset directions in to accomplish job tasks. The purpose of this research was to develop methods to estimate shoulder muscle activation during seated, static, sub-maximal exertions in off-axis (non-cardinal) directions. Surface EMG signals were recorded from 14 upper extremity muscles in 20 right-handed university aged, right-handed males (age: 22 ± 3 years, weight: 77.5 ± 11.1 kg, height 179.0 ± 7.0 cm) participated in this study. Each participant performed 60 submaximal exertions (40N) directed at 4 off-axis phase angles of 45° (45°, 135°, 225°, and 315°) in 3 planes (frontal, sagittal, and transverse) in 5 hand locations within a right handed reach envelope. The influence of hand location and force direction on muscle activity was evaluated with a forced-entry stepwise regression model. The ability of previously published on-axis prediction equations to predict muscle activity during these off-axis exertions was also evaluated. Within each muscle, activity levels were affected by both hand location and three-dimensional force direction and activation levels ranged from <1 to 37 %MVE. For each force direction there were 75 predictive equations selected and used, and the specific equation that best predicted activation depended on the muscle, exertion direction and hand location evaluated. This work assists ergonomic workplace design to minimize muscle demands during commonly performed off-axis exertions. These estimated demands can be employed to improve workplace design to reduce workplace injuries and enhance worker productivity.     

Fatigue assessment among onshore oil rig shift workers in Thailand

This study aimed to assess fatigue among onshore oil rig shift workers in a petroleum company working in swing shifts. The work schedule consisted of 12 h of night shifts for one week followed by 12 h of day shifts for one week. Fatigue was assessed using both subjective and objective measurements which were visual analogue fatigue scale (VAFS) and simple reaction time (SRT) test, respectively. A total of 38 male onshore oil rig shift workers participated in this study. Fatigue assessment was conducted at the start and at the end of workdays on nights 1, 4 and 7, and days 1, 4 and 7. The results showed that there were significant differences of VAFS and SRT at the end of workdays, compared with at the start of workdays (p < 0.001). The fatigue level assessed by both SRT and VAFS was highest on the rotating day (p < 0.001). In conclusion, swing shifts might affect fatigue levels in shift workers. The fatigue level increased over the two-week work period. Further studies on fatigue assessment and management among onshore oil rig shift workers are still needed.     

Biomechanical analysis of upper trapezius,erector spinae and brachioradialis fatigue in repetitive manual packaging tasks: Evidence from Chinese express industry workers

This study aims to assess the effects of repetitive motion-induced fatigue during manual packaging on kinematics and muscle activity of the arm, back and shoulder. Eighteen participants performed a 60-min manual packaging task. Electromyography median frequency of RUT, RES, LES and RB decreased by 13.2% (p < 0.05), 12.8% (p < 0.05), 11.3% (p < 0.05) and 21% (p < 0.001), respectively over time. The head flexion and the right upper arm flexion angles significantly (p < 0.001) differed among different packaging sizes, and similar results were observed for left upper arm flexion and rotation. The trunk and pelvis angles significantly (p < 0.05) differed over time under three kinds of packaging. The results showed there was an increase in the rating of perceived exertion from 8.56 to 16.94 (p<0.01) during the task. The outcomes of this study indicate repetitive movements in the manual packaging task resulted in elevated prevalence of muscle discomfort in packaging workers, especially the right brachioradialis. Interventions such as specific work: rest ratios, workplace redesign should be explored to relieve muscle fatigue and discomfort.Relevance to industryFor workers performing repetitive manual packaging tasks, biomechanical analysis of different muscles groups can help in developing appropriate ergonomic interventions.