Morten Wærsted

Computer work and musculoskeletal disorders of the neck and upper extremity: a systematic review.

BackgroundThis review examines the evidence for an association between computer work and neck and upper extremity disorders (except carpal tunnel syndrome).MethodsA systematic critical review of studies of computer work and musculoskeletal disorders verified by a physical examination was performed.ResultsA total of 22 studies (26 articles) fulfilled the inclusion criteria. Results show limited evidence for a causal relationship between computer work per se, computer mouse and keyboard time related to a diagnosis of wrist tendonitis, and for an association between computer mouse time and forearm disorders. Limited evidence was also found for a causal relationship between computer work per se and computer mouse time related to tension neck syndrome, but the evidence for keyboard time was insufficient. Insufficient evidence was found for an association between other musculoskeletal diagnoses of the neck and upper extremities, including shoulder tendonitis and epicondylitis, and any aspect of computer work.ConclusionsThere is limited epidemiological evidence for an association between aspects of computer work and some of the clinical diagnoses studied. None of the evidence was considered as moderate or strong and there is a need for more and better documentation.

Activity of single motor units in attention-demanding tasks: firing pattern in the human trapezius muscle

Activity of single motor units in relation to surface electromyography (EMG) was studied in 11 subjects in attention-demanding work tasks with minimal requirement of movement. In 53 verified firing periods, single motor units fired continuously from 30 s to 10 min (duration of the experiment work task) with a stable median firing rate in the range of 8–13 Hz. When the integrated surface EMG were stable, the motor units identified as a rule were continuously active with only small modulations of firing rate corresponding to low-amplitude fluctuations in surface EMG. Marked changes in the surface EMG, either sudden or gradual, were caused by recruitment or derecruitment of motor units, and not by modulations of the motor unit firing rate. Motor unit firing periods (duration 10 s-35 s) in low-level voluntary contractions (approximately 1%–5% EMGmax) performed by the same subjects showed median firing rates (7–12 Hz) similar to the observations in attention-related activation.

Human muscle activity related to non-biomechanical factors in the workplace

Abstract This paper presents current knowledge on low-level, long-lasting work-related muscle activity, focusing on the shoulder and the upper part of the trapezius muscle, and on mental, rather than biomechanical reasons for the muscle activation. The paper identifies three sources of vocational muscle activity: the biomechanical need for force production in order to perform movements or maintain postures against the force of gravity, the biomechanical need to stabilise body parts as a reference for performing movements and securing a stable visual field, and finally, muscle activity without obvious biomechanical purposes. This last category has been labelled non-biomechanical muscle activity in this review. Non-biomechanical muscle activity is related to the mental load, the emotional load and the individual characteristics of the subject, and is identified as having a low-level and a low second-to-second variability, resembling a static muscle contraction. Recent research has indicated that the size principle for motor unit recruitment order puts a strain on a limited number of low-threshold motor units which might be heavily taxed despite the overall low level of this muscle activity. However, the paper also cites a recent report showing that motor unit substitution may occur in prolonged low-level muscle activation (longer than a few minutes). Evaluations of muscle load at work usually omit the possibility of extra muscle activation due to non- biomechanical factors, and thus may often give estimates of the muscle load that are too low, or misinterpret non-biomechanical muscle activity as biomechanical muscle load.

A Prospective Study of Neck, Shoulder, and Upper Back Pain Among Technical School Students Entering Working Life

PURPOSE The aim of this prospective study was to relate the prevalence of neck, shoulder, and upper back pain to occupational and individual risk factors among a population of technical school students in their transition from school to working life. In addition, we wanted to assess the changes in pain prevalence during follow-up. METHODS A cohort consisting of 173 technical school students was followed up during a 3-year period, from their last year of school through their first years of working life. Data on self-reported neck, shoulder, and upper back pain and factors such as mechanical exposure, perceived stress, and physical activity in leisure time were collected. RESULTS A high prevalence of pain in the neck, shoulder, and upper back among the technical school students was found. There were however few students reporting severe pain. Reporting pain at baseline gave over three times higher risk of reporting it at follow-up. A high level of physical activity outside working hours gave a lower risk of reporting neck, shoulder, and upper back pain at follow-up. High and moderate levels of mechanical exposure and high stress level were not found to be risk factors for pain after entering working life. CONCLUSION Neck, shoulder, and upper back pain are common among adolescents and may persist into working life. These results may give potential for preventive efforts at a young age. There is still much uncertainty about the factors leading to musculoskeletal pain, and more research is needed on this topic.

The effect of work-related sustained trapezius muscle activity on the development of neck and shoulder pain among young adults

OBJECTIVE This study aimed to evaluate if sustained trapezius muscle activity predicts neck and shoulder pain over a 2.5-year period. METHODS Forty young adults (15 hairdressers, 14 electricians, 5 students and 6 with various work) were followed during their first years of working life. Self-reported neck and shoulder pain during the last four weeks was assessed seven times over the observational period. Upper-trapezius muscle activity was measured during a full working day by bilateral surface electromyography (EMG) at baseline (winter 2006/7). Sustained trapezius muscle activity was defined as continuous muscle activity with amplitude >0.5% EMGmax lasting >4 minutes. The relative time of sustained muscle activity during the working day was calculated and further classified into low (0-29%), moderate (30-49%) and high (50-100%) level groups. RESULTS Generalized estimating equations (GEE), adjusted for time, gender, mechanical workload, control-over-work intensity, physical activity, tobacco use, and prior neck and shoulder pain, showed that participants with a high level of sustained muscle activity had a rate of neck and shoulder pain three times higher than the low level group during a 2.5-year period. The association was strongest at the same time and shortly after the EMG measurement, indicating a time-lag of ≤6 months. CONCLUSION The results support the hypothesis that sustained trapezius muscle activity is associated with neck and shoulder pain. This association was strongest analyzing cross-sectional and short-term effects.

The impact of psychosocial and organizational working conditions on the mental health of female cleaning personnel in Norway

BackgroundThis study examined the association between psychosocial and organizational work conditions and mental health among women employed in the cleaning profession in Norway.MethodsSelf-report questionnaires were mailed to 661 cleaning staff personnel from seven cleaning organizations in seven different cities across Norway. The response rate was 64%, of which 374 (88%) respondents were women. The questionnaires assessed socio-demographic information and employment history, work organization, and psychosocial working conditions. The Hopkins Symptoms Checklist (HSCL-25) was included to assess mental health.ResultsOn average, respondents were 43 years old and reported 10.8 years of experience working in the cleaning industry. The proportion of women scoring a HSCL-25 equal to or above 1.75 was 17.5%, which was higher than the average prevalence of mental health problems among working Norwegian women (8.4%). A factor analysis of the questions specific to the psychosocial work environment identified the following four underlying dimensions: leadership, co-workers, time pressure/control, and information/knowledge. Two of these, poor satisfaction with leadership (OR = 3.6) and poor satisfaction with co-workers (OR = 2.3), were significantly related to mental health. In addition, having contact with colleagues less than once a day (OR = 2.4) and not being ethnically Norwegian (OR = 3.0) increased the risk for mental health problems.ConclusionMental health problems are frequent among female cleaning professionals in Norway. Our results indicate that quality of leadership, collaboration with co-workers, and ethnicity were significantly associated with mental health.

Muscle pain, physical activity, self-efficacy and relaxation ability in adolescents

The main aim was to examine the prevalence of neck, shoulder and upper back pain, and evaluate possible associations between such symptoms and physical activity, self-efficacy and relaxation ability in a sample of adolescents. The data come from a cross-sectional field study on 416 Norwegian second-year electrician, hairdresser, art/design and media students from 13 technical schools, 265 females and 151 males. The mean age was 17.5 years. Data was acquired from a questionnaire and clinical examination. More female than male students (28% vs. 15%) reported high pain complaint levels. Females were engaged in less physical activity and obtained lower self-efficacy scores, but demonstrated better relaxation ability than male students. In bivariate analyses, high self-efficacy scores were significantly associated with high levels of physical activity and poor relaxation ability among males. No significant associations were found in multivariate analyses between physical activity, self-efficacy or relaxation ability and pain symptoms in either males or females. Among males, a tendency of increasing pain odds ratios with increasing physical activity level was seen. Follow-up research on this cohort is needed to explore further differences between males and females, and identify factors associated with neck, shoulder or upper back pain among these adolescents.

Work with prolonged arm elevation as a risk factor for shoulder pain: A longitudinal study among young adults

This prospective study aimed at examining if work with prolonged arm elevation predicts shoulder pain among 41 young adults in their first years of working life. Fifteen hairdressers, 15 electricians, 5 students and 6 with various work were followed over a 2.5-year period (2006/7-2009). Arm elevation was measured with inclinometers during a full working day at baseline. Shoulder pain was reported at baseline and twice in the follow-up period. Data were analyzed by generalized estimating equations (GEE-analysis), stratified by gender and adjusted for time, mechanical workload, work demand, physical activity, tobacco use and prior shoulder pain. Work with prolonged arm elevation with angles >60° and >90° were associated with shoulder pain among women. Even though the shoulder pain levels are low the study suggests work with arms elevated as an early work-related risk factor among women, and indicates the importance of early prevention strategies.

Musculoskeletal health and work ability in physically demanding occupations: study protocol for a prospective field study on construction and health care workers

BackgroundMusculoskeletal disorders have a profound impact on individual health, sickness absence and early retirement, particularly in physically demanding occupations. Demographics are changing in the developed countries, towards increasing proportions of senior workers. These senior workers may have particular difficulties coping with physically demanding occupations while maintaining good health.Previous studies investigating the relationship between physical work demands and musculoskeletal disorders are mainly based on self-reported exposures and lack a prospective design. The aim of this paper is to describe the background and methods and discuss challenges for a field study examining physical demands in construction and health care work and their prospective associations with musculoskeletal disorders, work ability and sickness absence.Methods and designThis protocol describes a prospective cohort study on 1200 construction and health care workers. Participants will answer a baseline questionnaire concerning musculoskeletal complaints, general health, psychosocial and organizational factors at work, work demands, work ability and physical activity during leisure. A shorter questionnaire will be answered every 6th months for a total of two years, together with continuous sickness absence monitoring during this period. Analysis will prospectively consider associations between self-reported physical demands and musculoskeletal disorders, work ability and sickness absence. To obtain objective data on physical exposures, technical measurements will be collected from two subgroups of N = 300 (Group A) and N = 160 (Group B) during work and leisure. Both group A and B will be given a physical health examination, be tested for physical capacity and physical activity will be measured for four days. Additionally, muscle activity, ground reaction force, body positions and physical activity will be examined during one workday for Group B. Analysis of associations between objectively measured exposure data and the outcomes described above will be done separately for these subpopulations.DiscussionThe field study will at baseline produce objectively measured data on physical demands in the construction and health care occupations. In combination with clinical measurements and questionnaire data during follow-up, this will provide a solid foundation to prospectively investigate relationships between physical demands at work and development of musculoskeletal disorders, work ability and sickness absence.

Long periods with uninterrupted muscle activity related to neck and shoulder pain.

The aim was to analyze the relationship between periods with uninterrupted neck muscle activity for ≥ 4 min and neck and shoulder pain. The trapezius muscle activity was recorded bilaterally on 40 young workers and students during a full shift. Neck and shoulder pain, mechanical work load and decision control were reported at the same time as the muscle activity recording and 6 months later. A dose-response relationship was found between uninterrupted muscle activity and neck and shoulder pain, with a ten-fold higher risk for the group with more than half, compared to less than a third, of the shift with uninterrupted muscle activity. Self-reported mechanical work load showed a small but protective effect related to pain. Gender and decision control did not emerge as important risk factors in this model. In conclusion, this study indicates that work or other exposures that contains long periods with uninterrupted neck muscle activity of 4 min duration or longer should be minimized to reduce risk of neck and shoulder pain.