Musculoskeletal disorders among female and male air traffic controllers performing identical and demanding computer work

Operators with identical, demanding computer work (90 female and 97 male air traffic controllers) were found to have high prevalences of disorders (assessed by questionnaire and physical examination) in neck, shoulders and upper back. In spite of the identical work, the women displayed higher prevalences than the men (e.g. neck diagnoses 21% vs. 4%). Disorders in elbows, wrists and hands were less common, with similar rates in both genders. Generally, the psychosocial work environment (assessed by questionnaire) was found to be good, but with large inter-individual variation. Women experienced lower decision latitude than men, particularly regarding influence and freedom at work, but perceived higher social support. Physically, the work was characterized by relatively low angular velocities of upper arms (measured by inclinometry) and wrists (right: < 1 degrees/s during 19% of time, measuring by goniometry), dynamic muscular activities and high time fractions of rest in the trapezius and forearm extensor muscles (measuring by electromyography). There were only minor differences between the genders.     

Guidelines for wrist posture based on carpal tunnel pressure thresholds

OBJECTIVE: To develop work guidelines for wrist posture based on carpal tunnel pressure. Background: Wrist posture is considered a risk factor for distal upper extremity musculoskeletal disorders, and sustained wrist deviation from neutral at work may be associated with carpal tunnel syndrome. However, the physiologic basis for wrist posture guidelines at work is limited. METHODS: The relationship of wrist posture to carpal tunnel pressure was examined in 37 healthy participants. The participants slowly moved their wrists in extension-flexion and radioulnar deviation while wrist posture and carpal tunnel pressure were recorded. The wrist postures associated with pressures of 25 and 30 mmHg were identified for each motion and used to determine the 25th percentile wrist angles (the angles that protect 75% of the study population from reaching a pressure of 25 or 30 mmHg). RESULTS: Using 30 mmHg, the 25th percentile angles were 32.7 degrees (95% confidence interval [CI] = 27.2-38.1 degrees) for wrist extension, 48.6 degrees (37.7 -59.4 degrees) for flexion, 21.8 degrees (14.7-29.0 degrees) for radial deviation, and 14.5 degrees (9.6-19.4 degrees) for ulnar deviation. For 25 mmHg, the 25th percentile angles were 26.6 degrees and 37.7 degrees for extension and flexion, with radial and ulnar deviation being 17.8 degrees and 12.1 degrees, respectively. CONCLUSION: Further research can incorporate the independent contributions of pinch force and finger posture into this model. APPLICATION: The method presented can provide wrist posture guidelines for the design of tools and hand-intensive tasks.     

The influence of desk and display design on posture and muscle activity variability whilst performing information technology tasks

Desk design and computer display height can affect posture and muscle activation during computer use. Amplitudes of postural variables and muscle activity during computer use do not explain the results from epidemiological studies of musculoskeletal discomfort and disorders related to computer use. The purpose of this study was to assess variability of posture and muscle activity during work with two computer display heights and book/paper, in conjunction with a curved desk designed to provide forearm support and a traditional, straight desk.18 male and 18 female participants performed 10-min tasks involving keying, mousing, reading and writing in six desk/display conditions. 3D posture and surface emg were assessed for the final 2 min of each task.The curved desk resulted in greater postural and muscle activity variation, suggesting an advantage of this supportive surface over the straight desk. There was little difference in variability associated with the two display heights. However, greater variability of posture and muscle activity was evident with the book/paper condition. Non-touch typists had greater neck flexion variation.The design of information technology tasks and workstations can influence the short term variation in posture and muscle activity. Variation is influenced independently of mean postures and muscle amplitudes and therefore needs to be considered to adequately assess the risk of musculoskeletal disorders.     

Musculoskeletal disorders among female and male air traffic controllers performing identical and demanding computer work

Operators with identical, demanding computer work (90 female and 97 male air traffic controllers) were found to have high prevalences of disorders (assessed by questionnaire and physical examination) in neck, shoulders and upper back. In spite of the identical work, the women displayed higher prevalences than the men (e.g. neck diagnoses 21% vs. 4%). Disorders in elbows, wrists and hands were less common, with similar rates in both genders. Generally, the psychosocial work environment (assessed by questionnaire) was found to be good, but with large inter-individual variation. Women experienced lower decision latitude than men, particularly regarding influence and freedom at work, but perceived higher social support. Physically, the work was characterized by relatively low angular velocities of upper arms (measured by inclinometry) and wrists (right: <1°/s during 19% of time, measuring by goniometry), dynamic muscular activities and high time fractions of rest in the trapezius and forearm extensor muscles (measuring by electromyography). There were only minor differences between the genders.     

The effects of shoulder posture on neck and shoulder musculoskeletal loading and discomfort during smartphone usage

While using their smartphone, users tend to adopt awkward neck and shoulder postures for an extended duration. Such postures impose the risk of MSDs on those body parts. Numerous studies have been undertaken to examine neck posture; however, few studies have investigated shoulder postures. This study examined various shoulder postures during smartphone use and their effect on neck and shoulder kinematics, muscle loading, and neck/shoulder discomfort. Thirty-two asymptomatic young adult smartphone users randomly performed texting tasks for 3 min at four different shoulder flexion angles (15°, 30°, 45°, and 60°), while maintained a neck posture in the neutral position (0° neck flexion angle). Measures were taken of neck and shoulder muscle activity of the cervical erector spinae (CES), anterior deltoid (AD), upper trapezius (UT) and lower trapezius (LT), and kinematic data (angle, distance and gravitational moment). Results showed AD and LT muscle activity significantly increased when the shoulder flexion angle increased with an opposite effect on CES and UT. A recommended shoulder posture was identified as 30° flexion, as this yielded the best compromise between activation levels of the four muscles studied. This angle also induced the lowest neck/shoulder discomfort score. The findings suggest smartphone users hold their device at approximately 30° shoulder flexion angle with their neck in a neutral posture to reduce the risk of shoulder and neck musculoskeletal disorders when smartphone texting.Relevance to industrySmartphone use in the manufacturing and service industries is an integral part of work and useful means of communication tool. Awkward postures during extensive smartphone use impose an increased risk of both neck and shoulder musculoskeletal disorders. Shoulder flexion angles need consideration when making recommendations about safe work postures during smartphone use.     

The investigation of work-related musculoskeletal disorders among female workers in a hazelnut factory: Prevalence,working posture,work-related and psychosocial factors

BackgroundWork-related musculoskeletal disorders (WMSDs) are the most common occupational health problems in the industrialized world. The identification of WMSDs specific to occupation is essential to plan and implement preventative programs. This study investigated the prevalence of WMSDs and determined the factors related to the severity of the most common disorders among female workers in a hazelnut factory.MethodsA total of 114 female workers were examined in this cross-sectional study using the Nordic Musculoskeletal Questionnaire, the Dutch Musculoskeletal Questionnaire, and an author-developed questionnaire (for socio-demographic characteristics and psychosocial factors). Working posture, craniovertebral angle, thoracic kyphosis angle (TKA), and lumbar lordosis angle were evaluated based on a photogrammetry method using the ImageJ program.ResultsThe prevalence of WMSDs in at least one body part during the last 12 months was 92.1%. The highest prevalence of WMSDs was in the lower back (61.4%), neck (57.9%), shoulder (53.6%), and upper back (45.6%). The least affected part was the elbow. Lower back, shoulder, and neck disorders were the most common causes of activity limitation. The severity of lower back pain was associated with stress in the workplace and work-related factors. The neck pain severity was related to craniovertebral angle and work-related factors. The shoulder pain severity increased with TKA and employment duration. TKA was related to upper back pain severity.ConclusionsWMSDs are common among female workers in a hazelnut factory. Reorganizing of working posture, work-related factors, and stress at work may be beneficial to decrease the prevalence of WMSDs and pain severity.Relevance to Industry; The female workers in the hazelnut factory are vulnerable to the work-related musculoskeletal disorders, particularly in the spinal region. The employers should endeavor to improve the health of the workers by the adjustment of the working posture and environmental factors.     

ERGONOMICS NEWS AND INFORMATION

The relation between working posture in overhead work and the complaints of farmers cultivating pears and apples were investigated by comparing pear work with apple work. The same 20 male and 28 female orchard workers were questioned about complaints associated with thinning out pears and bagging them, and bagging apples. The angle of forward flexion in the shoulder and neck extension was also measured in each job. The prevalence of tiredness, stiffness and pain in the neck, shoulders and arms was significantly higher in thinning out pears and bagging them than in bagging apples. Dizziness and tinnitus among female workers was more frequent in thinning pears. The posture of raising arms and bending the head backwards was higher in thinning and bagging pears. These results suggest that the working postures of elevated arms and backward head bending can cause symptoms in the neck, shoulders and arms. In some cases, they may also lead to symptoms of vertebral artery insufficiency.     

Effect of visual display height on modelled upper and lower cervical gravitational moment,muscle capacity and relative strain

Head and neck posture is an important factor in neck pain related to computer use; however, the evidence for an optimal posture is unconvincing. This study measured the 3-D postures of 36 young adults during use of three different display heights. Cervical extensor muscle strain was estimated using modelled gravitational load moments and muscle capacities. The influence of more or less upper vs. lower cervical movement was also explored across a broad range of potential postures. Overall cervical extensor muscle capacity diminished away from a neutral posture whilst gravity moment increased with flexion. Overall cervical extensor muscle strain increased with head flexion but remained stable into head extension. Individual differences in the amount of upper and lower cervical movement had an important effect on strain, particularly for some muscles. Computer display height guidelines are an important component of ergonomics practice, yet the relative strain on neck extensor muscles as a function of display height has not been examined. The current findings provide more detailed biomechanical evidence that ergonomists can incorporate with usability and other evidence to determine appropriate display height recommendations.     

Effect of a desk attachment board on posture and muscle activity in women during computer work

Working at a computer is part of a large number of jobs and has been associated with upper extremity musculoskeletal disorders and back pain. The study evaluated the effects of a board attachment on upper extremity and back. The findings are mixed in that the board may have a positive effect in preventing back pain, but may be detrimental to upper extremities. Effect of a desk attachment board on upper extremity and trunk posture, and muscle activity was assessed in women video display terminal users. Participants completed a standard 20-min computer task under two conditions: 1) using a standard desk; 2) using a desk attachment board designed to support the forearms. Bilateral electromyography of the trapezius, multifidus and longissimus muscles and the right anterior deltoid and forearm extensor muscles was recorded. 3-D trunk and upper extremity posture was monitored. Participants were tested before and after 2 weeks of familiarisation with the board in their workplace. Perceived tension and discomfort were recorded before and after use of the board. Use of the board tended to increase muscle activity in the right trapezius and forearm extensor and to decrease muscle activity in the back. Perceived tension in the low back decreased slightly with the board. The board may be useful in reducing tension in the low back during computer work, but may adversely affect the upper extremities.     

Effect of a desk attachment board on posture and muscle activity in women during computer work

Working at a computer is part of a large number of jobs and has been associated with upper extremity musculoskeletal disorders and back pain. The study evaluated the effects of a board attachment on upper extremity and back. The findings are mixed in that the board may have a positive effect in preventing back pain, but may be detrimental to upper extremities. Effect of a desk attachment board on upper extremity and trunk posture, and muscle activity was assessed in women video display terminal users. Participants completed a standard 20-min computer task under two conditions: 1) using a standard desk; 2) using a desk attachment board designed to support the forearms. Bilateral electromyography of the trapezius, multifidus and longissimus muscles and the right anterior deltoid and forearm extensor muscles was recorded. 3-D trunk and upper extremity posture was monitored. Participants were tested before and after 2 weeks of familiarisation with the board in their workplace. Perceived tension and discomfort were recorded before and after use of the board. Use of the board tended to increase muscle activity in the right trapezius and forearm extensor and to decrease muscle activity in the back. Perceived tension in the low back decreased slightly with the board. The board may be useful in reducing tension in the low back during computer work, but may adversely affect the upper extremities.     

Inter-rater reliability of an inertial measurement unit sensor-based posture-matching method: A pilot study

Posture quantification is important for analyzing trunk and upper extremity loading and estimating the risk of work-related musculoskeletal disorders. This study introduced an inertial measurement unit sensor-based posture-matching (ISPM) method. The ISPM method is the concept that involves observers wearing sensors and simulating postures in photos or videos obtained at job sites to assess the postural risks for the trunk and upper extremity. We tested the inter-rater reliability of the method in 4 novice observers. For the trunk, shoulder/elbow, and wrist joint angle category, weighted kappa scores were 0.89, 0.52, and 0.26, respectively. The results of the ISPM method indicated moderate or high inter-rater reliability for trunk flexion, shoulder flexion/extension, shoulder abduction/adduction, and elbow flexion. The ISPM method was more reliable than conventional observation-based posture assessment tools used for trunk posture analyses. However, the assessment of upper extremity angles indicated that the reliability of ISPM was lower than that of conventional observation-based posture assessment tools. This was a proof-of-concept study conducted using a few samples. Therefore, further testing is necessary to support the findings.Relevance to industryThe ISPM method requires a minimal level of training. It uses conventional video recording and imposes almost no interruptions to the workers’ performance. The ISPM method showed moderate inter-rater reliability for the trunk, shoulder flexion/extension, shoulder abduction/adduction, and elbow flexion during the joint angle analysis.     

Continuous assessment of back and upper arm postures by long-term inclinometry in carpet weavers

Awkward back and shoulder postures have been suggested to be a cause of back and shoulder discomfort in carpet weavers. This study aimed at continuous assessment of the upper arm and back postures and estimation of biomechanical load subtasks using inclinometers during 4 h.Median of trunk flexion angle in weavers was 18° and 13° during knotting and compacting subtasks, respectively. The weavers worked with arms elevated greater than 45° for %4.5 of the work time. The average cumulative compression load for males and females were estimated at 22 MN-S and 13 MN-S, respectively.In addition to poor workstation design, constrained posture of the trunk and low elevation and velocity for both arms may be the main risk factors for developing fatigue and disorders in the back and shoulder regions among carpet weavers. Therefore, any ergonomic interventions should be focused on reducing trunk flexion and the constrained postures of weavers.     

Classroom posture and self-reported back and neck pain in schoolchildren

The study reported here aims to identify the extent of back pain experienced by 11-14 year old schoolchildren, and establish the intensity, duration and frequency of exposure to physical risk factors present in schools. This paper considers the sitting postures of schoolchildren in the classroom. The sitting postures of 66 children were recorded in normal lessons using the Portable Ergonomic Observation Method (PEO). The study found significant associations between flexed postures and low back pain. Static postures and neck and upper back pain were also associated. This study has implications for schools, designers and people in the field of work related musculoskeletal disorders. Further research is required to examine the association between sitting posture and pain reported at different spinal locations.     

Impact of physical exposure on neck and upper limb disorders in female workers

Physical workload [muscular load of the trapezius and infraspinatus muscles using electromyography (EMG), wrist positions and movements by electrogoniometers] and neck and upper limb disorders (from, for example, a physical examination) were studied in women with repetitive industrial work (n = 95) and referents (n = 74). The repetitive work displayed higher ratings for wrist movements, but not for EMG. The prevalences of neck, shoulder and wrist/hand disorders were elevated for women with repetitive work [age-adjusted prevalence odds ratios (PORs) 2.0-7.5]. For the left hand, high frequency of wrist movements (mean power frequency 0.53 Hz) was associated with a high prevalence of disorders (56%), as compared to low (0.28 Hz and 26%; POR 3.5). We found no consistent and significant effect of muscular load, on either neck or shoulder disorders. However, selection and other bias may have diminished our possibility to observe such effects. Psychosocial work environment factors were not confounding the results. Measurements of wrist movements may be used for identification of high-risk work tasks.     

A field comparison of neck and shoulder postures in symptomatic and asymptomatic office workers

Poor neck and shoulder postures have been suggested to be a cause of neck and shoulder pain in computer workers. The present study aimed to evaluate and compare the head, neck and shoulder postures of office workers with and without symptoms in these regions, in their actual work environments. The two all female subject groups reported significantly different discomfort scores across five trials repeated in a single working day. The results of repeated video capture and two-dimensional motion analysis showed that there were trends for increased head tilt and neck flexion postures in the symptomatic subjects (n = 8), compared to the asymptomatic subjects (n = 8). Symptomatic subjects also tended to have more protracted acromions compared with asymptomatic subjects and showed greater movement excursions in the head segment and the acromion. All subjects demonstrated an approximately 10% increase in forward head posture from their relaxed sitting postures when working with the computer display, but there were no significant changes in posture as a result of time-at-work.     

Work posture,working conditions and musculoskeletal outcomes in agricultural workers

This study evaluated the working postures, working conditions and musculoskeletal outcomes among different agricultural workers in Iran. Data were collected using questionnaires and direct observations of posture (using the Rapid Upper Limb Assessment [RULA] method) from 377 farmers including 150 rice farmers, 122 vegetable growers, and 105 greenhouse workers. The overall prevalence of musculoskeletal symptoms, particularly in the low back (75.1%), knees (62.1%), upper back (61.55%), and neck (59.9%) was very high, and 72.6% of farmers experienced more than three locations of pain/discomfort. The mean RULA grand score of 6.7 highlighted that most farmers needed immediate investigation and changes in their working postures. Being female (neck pain), occupation (rice farmers – low back pain), number of years worked as an agricultural worker (neck and knee pain), prolonged daily working hours (upper back pain), job satisfaction (neck and low back pain), fast working (upper back pain), and working postures (neck, upper back, low back and knee pain) were independently associated with the presence of musculoskeletal symptoms. These findings emphasise the need for multiple component interventions to improve the working conditions of this population.     

Children's posture and muscle activity at different computer display heights and during paper information technology use

OBJECTIVE: The 3-D posture and muscle activity in the neck and upper limb were assessed in children using high-, mid-, and book-level displays, which correspond to working conditions frequently observed when children interact with computers or books and paper. BACKGROUND: The 3-D posture and muscle activity of children reading and inputting data with computers and paper had not been previously assessed. METHODS: Twenty-four children aged 10 to 12 years and of normal height performed an interactive task involving reading from a book and writing on paper or reading from a computer display and inputting data using a mouse and keyboard. RESULTS: Head and neck flexion increased as the visual target was lowered. The high display resulted in mainly upper cervical relative extension, and the book display resulted in both upper and lower cervical flexion. The book condition resulted in greater cervical erector spinae and upper trapezius activity than did the mid and high conditions. CONCLUSION: The data suggest that a mid-level display may be more appropriate for children than a high display (e.g., when the display is placed on top of the central processing unit). The mid display also results in a more upright and symmetrical posture and lower mean muscle activity than does working with books and paper flat on the desk. APPLICATION: This study provides short-term laboratory study evidence for the formulation of guidelines for workstation design and adjustment for children. Use of computers by children is increasing, yet ergonomic guidelines lag behind those for adults.     

Muscular Activity in Relation to Support of the Upper Extremity in Work With a Computer Mouse

The objective of this study was to compare the effects of using a forearm or wrist support on muscular load in the forearm and neck-shoulder region during work with a computer mouse. Fourteen 35- to 50-year-old healthy women who worked with a video display unit for at least 4 hr a day in an office and who also used a computer mouse for at least 2 hr a day participated in this experimental study. In the laboratory, computer mouse use with the forearm supported was compared with computer mouse use with the wrist supported. The participants edited a text table by moving symbols from one square to another in a fixed order. Each trial was a set of 64 movements. The trials were repeated 10 times in random order, 5 trials with each method of support. The dependent variable was electromyographic activity measured from muscles in the preferred lower arm and in the neck-shoulder region. Normalization to the individual mean of each participant was found to be more effective in reducing the interindividual variation than normalization to the maximal electrical activity (MEMG) obtained during isometric maximal voluntary contraction using the variation coefficient. The amplitudes normalized to the individual mean of each participant were used to evaluate the statistical significance of the difference between the methods of support. To interpret the magnitude and the practical meaning of the statistically significant differences, the corresponding mean percentages of the MEMG were used. The results of the study indicate that changing the position and support of the upper extremity affects muscular activity in the forearm and neck-shoulder region. The load on the trapezius muscle is significantly lower when the forearm is supported, and therefore such support may offer one means of preventing common disorders in the neck-shoulder region in office work. The load on the infraspinatus muscle and on forearm flexor muscles was, on the contrary, higher when the forearm was supported. The result may indicate the difficulty that workers have in adopting new hand and upper arm movements when using a computer mouse.     

Effect of load mass on posture, heart rate and subjective responses of recreational female hikers to prolonged load carriage

Load carriage has been associated with a risk of upper and lower limb musculoskeletal disorders with women suffering significantly higher injury rates than their male counterparts. Despite this injury risk, there are limited evidence-based guidelines for recreational hikers, particularly female recreational hikers, regarding safe backpack loads. The purpose of the present study was to determine how variations in load mass affected the heart rate, posture and subjective responses of women during prolonged walking to provide evidence for a load mass limit for female recreational hikers. Heart rate (HR), posture and ratings of perceived exertion (RPE) and discomfort were collected for 15 female experienced recreational hikers (22.3 ± 3.9 years) while they hiked for 8 km at a self-selected pace under four different load conditions (0%, 20%, 30% and 40% of body weight (BW)). Although HR was not significantly affected by load mass or walking distance, increasing load mass and distance significantly affected posture, RPE and discomfort of the upper body. Carrying a 20% BW load induced significant changes in trunk posture, RPE and reported shoulder discomfort compared to the unloaded condition. The 20% BW load also resulted in a mean RPE rating of ‘fairly light’, which increased to ‘hard’ when carrying a 40% BW load. As load carriage distance increased participants reported significantly increased shoulder, neck and upper back discomfort. Based on the changes to posture, self-reported exertion and discomfort when carrying loads of 20%, 30% and 40% BW over 8 km, it was concluded that a backpack load limit of 30% BW should be recommended for female recreational hikers during prolonged walking.     

Trunk posture: reliability, accuracy, and risk estimates for low back pain from a video based assessment method

It has been recently reported that both dynamic movement characteristics, as well as the duration of postures adopted during work, are important in the development of low back pain (LBP). This paper presents a video-based posture assessment method capable of measuring trunk angles and angular velocities in industrial workplaces. The inter-observer reliability, system accuracy, and the relationship of the measured exposures to the reporting of low back pain are reported. The video analysis workstation consisted of a desktop computer equipped with digital video capture and playback technology, a VCR, and a computer game type joystick. The operator could then use a joystick to track trunk flexion and lateral bending during computer-controlled video playback. The joystick buttons were used for binary input of twisting. The inter-observer reliability for peak flexion and percentage of time spent in posture category variables were excellent (ICC>0.8). Lower reliability levels were observed for peak and average velocity and movement related variables. The video analysis system time series data showed very high correlation to the criterion optoelectronic imaging system (r=0.92). Root mean square errors averaged 5.8° for the amplitude probability distribution function data. Trunk flexion variables including peak level, peak velocity, average velocity indicators, and percent time in flexion category indicators all showed significant differences between cases and controls in the epidemiological study. A model consisting of the measures peak trunk flexion, percent time in lateral bend and average lateral bending velocity emerged after multivariable analysis for relationship to low back pain.

Relevance to industry

Risk of injury for the low back is multifactorial. The trunk position and movement velocity are emerging as important parameters. This analysis confirms the importance of these factors and demonstrates the utility of a video-based method to measure them in industrial settings.