Perceived Discomfort and Electromyographic Activity of the Upper Trapezius While Working at a VDT Station

Ten female participants performed work at a video display terminal (VDT) station over a whole working day. Subjective local muscular fatigue was evaluated by means of the Category Ratio 10 scale. Electromyographic activity of the upper right and left trapezius was measured. A comparison was made between 5 participants who had previous complaints and 5 participants who reported no musculoskeletal problems in the shoulder-neck region. The subjective scores for the shoulder differed significantly between the two groups, being higher for the group with complaints. Both groups showed a decrease in discomfort after the lunch break. The activity of the trapezius increased significantly for both groups, in a more pronounced way for the group with disorders. Although it is found in literature that VDT work is a task with very low static loads, it seems from this study that the EMG activity increase can be an indication of muscle fatigue: More effort was required to accomplish the same VDT task at the end of the day.     

Musculoskeletal symptoms as related to ergonomic factors in Iranian hand-woven carpet industry and general guidelines for workstation design.

Carpet weaving is a high risk occupation for developing musculoskeletal disorders (MSDs). The objectives of the present study, which was carried out in the Iranian hand-woven carpet industry, were determination of the prevalence of MSD symptoms, identification of major factors associated with MSD symptoms and development of guidelines for workstation design. 1,439 randomly selected weavers participated in this study. A questionnaire was used to collect data on MSD symptoms. The results revealed that the prevalence rates for symptoms in different body regions were high as compared to the general Iranian population (for neck, back and large joints, p <.0001). The results of multivariate analyses showed that major ergonomic factors associated with musculoskeletal symptoms were loom type, working posture, daily working time and seat type. Based on the results, some general guidelines for designing weaving workstations were developed. A prototype test showed that the new workstation was acceptable for subject tests and that it improved working posture.     

肘部支撑在视频显示终端作业过程中对背部和右手表面肌电影响的Meta分析

本文主要探讨肘部支撑在视频显示终端作业过程中对背部和右手表面肌电的影响。采用Meta分析方法对以往研究资料进行筛检及汇总分析。结果发现：左右侧斜方肌的最大自主收缩百分比（MVC％）分别下降了0．83％（95％CI-1．00％--0．66％）和0．61％（95％CI-0．78％～-0．43％），对于右手食指伸指肌而言，其影响并不具有显著性。可以认为肘部支撑是一种比较简单而且有效的预防措施。     

A pre/post evaluation of fatigue,stress and vigilance amongst commercially licensed truck drivers performing a prolonged driving task

Purpose. The main purpose of this research study was to evaluate changes in fatigue, stress and vigilance amongst commercially licensed truck drivers involved in a prolonged driving task. The secondary purpose was to determine whether a new ergonomic seat could help reduce both physical and cognitive fatigue during a prolonged driving task. Two different truck seats were evaluated: an industrial standard seat and a new truck seat prototype. Methods. Twenty male truck drivers were recruited to attend two testing sessions, on two separate days, with each session randomized for seat design. During each session, participants performed two 10-min simulated driving tasks. Between simulated sessions, participants drove a long-haul truck for 90 min. Fatigue and stress were quantified using a series of questionnaires whereas vigilance was measured using a standardized computer test. Results. Seat interactions had a significant effect on fatigue patterns. Conclusion. The new ergonomic seat design holds potential in improving road safety and vehicle accidents due to fatigue-related accidents.     

Variability of Musculoskeletal Strain on Dentists: An Electromyographic and Goniometric Study

Introduction. Dentists and hygienists are strongly affected by musculoskeletal disorders (MSDs). As workstation concepts are supported by subjective arguments only, the aim of this study was to use objective measurements to compare the variability of strain in various concepts: a dental chair equipped with a cart or an over-the-patient delivery system without an assistant, and Dr Daryl Beach’s concept with an assistant. Methods. Goniometric and electromyographic recordings were made on 8 subjects, during a scaling operation. The electrical activity of their trapezius and lumbar muscles was compared, as were their cervical and lumbar ranges of motion. Results. The results showed that there was a wide variability depending on the workstation. However, the Beach concept tended to reduce physical strain on most parameters: duration of left lumbar muscle activity (2% compared to 15% of time spent in >10% maximal voluntary contraction, MVC), time spent in cervical side bending (4% compared to 30%), cervical flexion of >20° (9% compared to 40%), and left trapezius activity (9% of time spent >10% MVC compared to 28%). Conclusion. Practitioners and students should adjust their workstations to reduce the prevalence of MSDs.     

Myoelectric manifestation of muscle fatigue in repetitive work detected by means of miniaturized sEMG sensors

Upper limb work-related musculoskeletal disorders have a 12-month prevalence ranging from 12 to 41% worldwide and can be partly caused by handling low loads at high frequency. The association between the myoelectric manifestation of elbow flexor muscle fatigue and occupational physical demand has never been investigated. It was hypothesized that an elbow flexor muscle fatigue index could be a valid risk indicator in handling low loads at high frequency. This study aims to measure the myoelectric manifestation of muscle fatigue of the three elbow flexor muscles during the execution of the work tasks in different risk conditions. Fifteen right-handed healthy adults were screened using a movement analysis laboratory consisting of optoelectronic, dynamometer and surface electromyographic systems. The main result indicates that the fatigue index calculated from the brachioradialis is sensitive to the interaction among risk classes, session and gender, and above all it is sensitive to the risk classes.     

Effects of customized foot orthoses on manufacturing workers in the metal industry

This 8-week study evaluates the effects of customized foot orthoses on work-related musculoskeletal disorders (WMSDs) of metal industry workers. These WMSDs were evaluated applying the Nordic musculoskeletal questionnaire (NMQ) at three different times (start, 4th week and 8th week) and additional questions were also formulated to obtain information about adaptation, fatigue, comfort and possible improvements. According to the NMQ results, statistical significance was found in the improvements after 4?weeks (p?<?0.05 in two areas, p?<?0.01 in three areas, p?<?0.001 in two areas and no significance in the other two) and after 8?weeks (p?<?0.01 in three areas, p?<?0.001 in four areas and no significance in the other two). The additional questions indicated fatigue reduction (both in general and in lower extremity), comfort level increase (after the adaptation period) and good acceptance, according to workers’ answers, suggesting customized orthoses can be effective in reducing and preventing WMSDs in several body regions.     

Associations Between Worker Characteristics,Workplace Factors,and Work-Related Musculoskeletal Disorders: A Cross-Sectional Study of Male Construction Workers in Nigeria

Objective. This study assessed the association between worker characteristics, workplace factors, and work-related musculoskeletal disorders (WMSDs) in Nigeria’s construction industry. Methods. A cross-sectional site-by-site survey was conducted in 5 existing construction companies in Uyo, Nigeria. The subjects (n = 1200 males), aged 18-55 years, filled in the semistructured Nordic musculoskeletal questionnaire and the job content questionnaire on demographics, work and lifestyle characteristics, and workplace risk factors for WMSDs. Results. The overall prevalence of WMSDs was 39.25%. Differences in age, race, weight, body mass index (BMI), education status, and employment status were significantly associated with the prevalence of WMSDs. Prevalence according to trade was as follows: ironworkers highest at 49% and administrative staff lowest at 31%. Ironworkers (55.7%), administrative staff (53.3%), and security staff (38.7%) scored higher on physical, psychosocial, and individual risk factors, respectively. Workplace factors with increased odds for WMSDs were psychological demands and mental workload, age, BMI, low work experience, low education status, awkward movement of head and arms, working against force or vibration, fast work pace, and race. Conclusion. The recorded high prevalence was multifactorial in etiology; hence, multi-intervention strategies are required.     

Influence of type of MVC test on electromyography measures of biceps brachii and triceps brachii

Objective. This study aimed to investigate the amplitude and frequency measures of the electromyography (EMG) signal in agonistic and antagonistic muscles (biceps brachii, triceps brachii). Methods. Fifteen males (22.9?±?2.1 years old) took three isometric maximum voluntary contraction (MVC) tests. Two tests were typical MVC tests for biceps brachii and triceps brachii. The third was a test often used to obtain MVC for forearm muscles (arm and forearm hanging down). The EMG signal was recorded during three isometric MVC muscle contractions and during a relaxation test. Results. There were no differences in amplitude between relaxation and MVC antagonist in static contraction, with higher values for frequency measures in relaxation. When biceps brachii and triceps brachii act as antagonists in an MVC test, frequency measures present lower values than when the muscles act as agonists. Biceps brachii shows much lower amplitude than during an agonist MVC contraction with similar spectral measures. Triceps brachii presents much higher values of spectral measures than during an agonist MVC test. Conclusion. The type of exerted force, i.e., if a muscle acted as an agonist, antagonist or stabilizer, affects the relationship between the time and frequency domain measures.     

Electromyographic analysis of relevant muscle groups during completion of computer tasks using different computer mouse positions

Background. We analyzed muscular activity for different computer mouse positions during the completion of a timed computer task and determined whether the different mouse positions could affect muscular activity, productivity and perceived fatigue. Methods. The subjects were nine healthy young men. Two mouse positions were studied: the distal position (DP), with the forearm rested on the desk; the proximal position (PP), with only the wrist rested on the desk. The subjects performed a 16-min task in each position. Surface electromyography data were recorded for the upper back and shoulder muscles. Work productivity and muscular activity were measured for each mouse position. A visual analog scale was used to assess subjective fatigue. Results. Muscular activity was higher in muscle (m.) deltoideus (posterior) for the DP, while it was significantly higher in m. inferior infraspinatus for the PP. The visual analog scale score was significantly higher and work productivity was lower in the PP. Conclusions. We found that using a mouse in the DP rather than the PP leads to less activity of the external rotators, less perceived fatigue and more productivity. This suggests that the DP is preferable to the PP for computer work involving a mouse.     

A dental stool with chest support reduces lower back muscle activation

Activation of back musculature during work tasks leads to fatigue and potential injury. This is especially prevalent in dentists who perform much of their work from a seated position. We examined the use of an ergonomic dental stool with mid-sternum chest support for reducing lower back muscle activation. Electromyography of lower back extensors was assessed from 30 dental students for 20?s during three conditions in random order: (a) sitting upright at 90° of hip flexion on a standard stool, (b) leaning forward at 80° of hip flexion on a standard stool, and (c) leaning forward at 80° of hip flexion while sitting on an ergonomic stool. Muscular activity of the back extensors was reduced when using the ergonomic stool compared to the standard stool, by 33–50% (p?相似文献   

Upper limb load as a function of repetitive task parameters: part 1--a model of upper limb load.

The aim of the study was to develop a theoretical indicator of upper limb musculoskeletal load based on repetitive task parameters. As such the dimensionless parameter, Integrated Cycle Load (ICL) was accepted. It expresses upper limb load which occurs during 1 cycle. The indicator is based on a model of a repetitive task, which consists of a model of the upper limb, a model of basic types of upper limb forces and a model of parameters of a repetitive task such as length of the cycle, length of periods of the cycle and external force exerted during each of the periods of the cycle. Calculations of the ICL parameter were performed for 12 different variants of external load characterised by different values of repetitive task parameters. A comparison of ICL, which expresses external load with a physiological indicator of upper limb load, is presented in Part 2 of the paper.     

Overhead drilling: Comparing three bases for aligning a drilling jig to vertical

Problem

Drilling overhead into concrete or metal ceilings is a strenuous task done by construction workers to hang ductwork, piping, and electrical equipment. The task is associated with upper body pain and musculoskeletal disorders. Previously, we described a field usability evaluation of a foot lever and inverted drill press intervention devices that were compared to the usual method for overhead drilling. Both interventions were rated as inferior to the usual method based on poor setup time and mobility.

Method

Three new interventions, which differed on the design used for aligning the drilling column to vertical, were compared to the usual method for overhead drilling by commercial construction workers (n = 16).

Results

The usual method was associated with the highest levels of regional body fatigue and the poorest usability ratings when compared to the three interventions.

Conclusion

Overall, the 'Collar Base' intervention design received the best usability ratings.

Impact on Industry

Intervention designs developed for overhead drilling may reduce shoulder fatigue and prevent subsequent musculoskeletal disorders. These designs may also be useful for other overhead work such as lifting and supporting materials (e.g., piping, ducts) that are installed near the ceiling. Workplace health and safety interventions may require multiple rounds of field-testing prior to achieving acceptable usability ratings by the end users.     

Saddle seat reduces musculoskeletal discomfort in microsurgery surgeons

Background. Microsurgery is a surgical procedure requiring a high degree of precision and is commonly facilitated through the use of an intraoperative microscope. When operating the microscope system, the long-term posture leads to musculoskeletal disorders in surgeons, and seats are commonly employed to diminish these problems. The present study was conducted to evaluate musculoskeletal discomfort during work with a saddle seat in comparison with conventional seats for microscopic work. Methods. Two types of seats, a saddle and a conventional one, were evaluated for 73 microsurgical surgeons in terms of musculoskeletal discomfort. Corlett and Bishop's body part discomfort scale was used to assess musculoskeletal discomfort before and after working with the seats. Results. The highest amount of discomfort that microsurgical surgeons acquire in the workplace was focused on their neck, shoulders, arms and back. During work with a saddle seat, a significant reduction was found for discomfort values in the neck, shoulder, arm, back, elbow and forearm, as well as the whole body (p?<?0.05). Conclusion. This study showed that the use of saddle seats provides a more appropriate physical posture at work, and can decrease musculoskeletal discomfort in different parts of the body of microsurgical surgeons.     

Investigation of work-related musculoskeletal disorders among male kitchen workers in South India

Objective. This study aims to quantify the prevalence of work-related musculoskeletal disorders (MSDs) and risks among male kitchen workers in the catering industry. Method. Data were collected with the help of the Nordic musculoskeletal questionnaire and by direct observations. Results. In total, 114 male kitchen workers from various hostels of a college in South India were considered for this study. The average age and mean years of employment of the workers are 26.4 (SD 7.7) and 7.8 respectively. The statistical analysis carried out reveals that 67.5% of male kitchen workers reported MSDs during the past 12 months. The highest prevalence rate has been found in the lower back (65.8%) and shoulder region (62.3%). Among different categories of kitchen work analyzed, it is evident that chief cooks suffer more from MSDs (79.2%) than assistant cooks (74.3%) and kitchen aides (30.0%). Workers in the older group, i.e., ≥41 years, and workers with 6–10 years of experience suffer with higher risk of MSDs, i.e., 93.9% and 87.5%, respectively. Conclusion. The male kitchen workers who participated in this research were found to possess both MSDs and ergonomic hazards.     

Musculoskeletal Symptoms In Workers

Self-report measures of musculoskeletal discomfort are a widely used and generally accepted risk factor for musculoskeletal disorders in epidemiologic research. The aim of this study was to investigate the prevalence of musculoskeletal symptoms in packing workers. A cross-sectional study of 75 workers was carried out using a modified Nordic questionnaire. Prevalence was determined with the percentage of positive responses to questions on musculoskeletal symptoms. Odds ratios and 95% confidence intervals were the measures of association between prevalent musculoskeletal symptoms and demographic factors; they were determined with logistic regression. Most musculoskeletal symptoms in workers were from the low back (44.0%), shoulders (33.3%) and neck (32.0%). Years worked were strongly significantly associated with musculoskeletal symptoms and pain in the neck, shoulders and wrists/hands, P< .001-.050. Hazards related to repetitive movements and discomfort postures could be reduced with stretching exercises, rotation schedules and through new engineering solutions.     

Symptoms and musculoskeletal diseases in hospital nurses and in a group of university employees: a cross-sectional study

Background. Most studies have shown that nurses have a higher risk of developing musculoskeletal symptoms compared with other occupational groups. Aim. A cross-sectional study was performed to gain more insight into the prevalence rates of musculoskeletal disorders (MSDs) in nurses. Methods. The presence of musculoskeletal symptoms was revealed by personal interviews in a sample of 177 hospital nurses and in a reference group of 185 university employees. Musculoskeletal diseases were based on radiological examinations in all subjects. Results. Lower back pain (61% vs 42.2%) was the most frequently reported symptom, followed by neck pain (48.6% vs 38.4%) and shoulder pain (36.7% vs 25.9%), with a significantly higher prevalence in nurses. Women had about a 2-fold risk of upper limb region and neck pain compared with men. The most common abnormal findings on radiological examinations were disc herniations (n?=?40). Conclusions. Nurses showed a significantly higher risk of MSDs. Prevalence rates in nurses increased significantly with age. Musculoskeletal symptoms were also common in university employees. This suggests the need for effective intervention strategies involving workers’ active participation, in order to improve the process and organization of work and promote a positive psychosocial work environment.     

Combined Effects of Physical Demands and Shift Working on Low Back Disorders Among Nursing Personnel

The aim of this study was to investigate the synergistic effects of physical demands and shift working on low back disorders (LBDs) among nursing personnel. The study used 2 questionnaires: a self-administered questionnaire composed of parts of Nordic musculoskeletal questionnaire to assess LBDs and job content questionnaire to assess physical demands. The participants were divided into 4 groups: from group 1 (low physical demands day workers) to group 4 (high physical demands shift workers). In regression analysis, high physical demands were associated with the prevalence of LBDs independently (OR 4.4, 95% CI [2.40, 8.00] and p < .05), but there was no association between shift working and LBDs (p > .05). Odds ratio in high physical demands shift workers was 9.33 compared to the reference group (p < .001). Calculated synergistic index was 7.37. Simultaneous impacts of shift working and high physical demands may increase the prevalence of LBDs among nursing personnel.