Kaj Bo Veiersted

Pattern of muscle activity during stereotyped work and its relation to muscle pain

SummaryStandardized and machine-paced work tasks at a packing machine were examined to evaluate interindividual variability of muscle activity patterns. Ten trained female workers, without musculo-skeletal complaints at the time of the recording, performed the work tasks while electromyographic (EMG) recordings were obtained from both upper trapezius muscles. Static muscle activity and periods of between 0.2 and 2 s duration with low muscle activity, EMG gaps, were analysed. Complaints of muscular fatigue, soreness or pain in the neck and shoulders during the last 12 months were recorded. The level of static muscle activity was 1.6 (range 0.4 to 2.5) per cent of maximal voluntary contraction and median number of EMG gaps was 4.8 (range 0.8 to 20) per minute. Workers with previous episodes of complaints (five subjects) had higher levels of static muscle activity and fewer EMG gaps than workers without such episodes (p < 0.05, Wilcoxon 2-sample test, one-tailed). Considerable interindividual variability of muscle activity patterns was found in spite of stereotyped work. No causal relations may be inferred from the correlation between the level of trapezius activity and complaints, though it indicates that individual, inexpedient muscle activity patterns may constitute an important risk factor for development of musculo-skeletal complaints.

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.

Sustained muscle tension as a risk factor for trapezius myalgia

Abstract Thirty female chocolate packers were included in a prospective study to relate trapezius muscle activity during work to the development of myalgia. Electromyographic (EMG) recordings and interviews on risk factors were performed at start of employment and every 10th week. The muscle activity was characterized by the averaged static and median level. Only data obtained before a possible development of severe symptoms of trapezius myalgia (patient) was used in the analysis. Seventeen of the subjects became patients within the first year of employment. Machine-stops occurred accidentally during work. At one task the stops induced a pause where the subjects passively waited for the machine to start. Twenty-one subjects experienced machine-stops of a sufficient duration to be evaluated for a potential “resting tension”. Future patients showed significantly higher “resting tension” compared to healthy controls.

Effect of acupuncture treatment on chronic neck and shoulder pain in sedentary female workers: a 6-month and 3-year follow-up study

&NA; The study was carried out to examine whether acupuncture treatment can reduce chronic pain in the neck and shoulders and related headache, and also to examine whether possible effects are long‐lasting. Therefore, 24 female office workers (47±9 years old, mean±SD) who had had neck and shoulder pain for 12±9 years were randomly assigned to a test group (TG) or a control group (CG). Acupuncture was applied 10 times during 3–4 weeks either at presumed anti‐pain acupoints (TG) or at placebo‐points (CG). A physician measured the pain threshold (PPT) in the neck and shoulder regions with algometry before the first treatment, and after the last one and six months after the treatments. Questionnaires on muscle pain and headache were answered at the same occasions and again 3 years after the last treatment. The intensity and frequency of pain fell more for TG than for CG (Pb≤0.04) during the treatment period. Three years after the treatments TG still reported less pain than before the treatments (Pw<0.001), contrary to what CG did (Pb<0.04). The degree of headache fell during the treatment period for both groups, but more for TG than for CG (Pb=0.02). Three years after the treatments the effect still lasted for TG (Pw<0.001) while the degree of headache for CG was back to the pre‐treatment level (Pb<0.001). PPT of some muscles rose during the treatments for TG and remained higher 6 months after the treatments (Pw<0.05), which contrasts the situation for CG. Adequate acupuncture treatment may reduce chronic pain in the neck and shoulders and related headache. The effect lasted for 3 years.

IMPROVED WORK ABILITY AND RETURN TO WORK FOLLOWING VOCATIONAL MULTIDISCIPLINARY REHABILITATION OF SUBJECTS ON LONG-TERM SICK LEAVE

OBJECTIVE To evaluate a vocational multidisciplinary rehabilitation programme for patients on long-term sick leave with respect to their work ability and return to work. METHODS A multidisciplinary rehabilitation programme was administered to an intervention group of 183 patients on long-term sick leave (mean 12.2 months). Effects of the treatment were compared with a control group (n = 96) recruited from the national sickness insurance record of patients on sick leave of 6-12 months duration (mean 11.5 months). Perceived work ability, return to work, background factors and psychosocial aspects of work were assessed on the basis of questionnaires at baseline and after 4 months. RESULTS Perceived work ability of the intervention group improved significantly after 4 months compared with the control group (p < 0.01). In the intervention group, 80% had returned to work compared with 66% in the control group (p = 0.06). Return to work after 4 months was predicted by good work ability at baseline, improved work motivation, improved work ability at follow-up and increased rumours of change in the workplace (R2 26.1-38.6%, p < 0.05). CONCLUSION This multidisciplinary rehabilitation programme significantly improved perceived work ability compared with treatment as usual.

Effect of intensive acupuncture on pain-related social and psychological variables for women with chronic neck and shoulder pain – an RCT with six month and three year follow up

Objectives This study examines whether intensive acupuncture treatment can improve several social and psychological variables for women with chronic pain in the neck and shoulders, and whether possible effects are long-lasting. The effects on pain have been reported elsewhere. Methods Twenty-four female office workers (47±9 years old, mean ± SD) who had had neck and shoulder pain for 12±9 years, were randomly assigned to a test group or a control group. Acupuncture was applied 10 times during three to four weeks either at presumed acupuncture points for pain (test group) or at sham points (control group). In addition, acupressure was given to patients between treatments, at either real or sham points. Questionnaires for social and psychological variables were completed before each treatment, just after the course, and six months and three years later. Results The pain-related activity impairment at work was significantly less in the test group than the controls by the end of treatment (P<0.04). Also there were significant differences between the groups for quality of sleep, anxiety, depression and satisfaction with life (P<0.05). At six months and three years follow ups the acupuncture group showed further improvements in most variables and was again significantly different from the control group. Conclusion Intensive acupuncture treatment may improve activity at work and several relevant social and psychological variables for women with chronic pain in the neck and shoulders. The effect may last for at least three years.

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.

Reliability of myoelectric trapezius muscle activity in repetitive light work

The aim of this study was to evaluate the reliability of selected electromyographic (EMG) parameters describing the muscle activity in repetitive light work. EMG from the trapezius muscle of twelve female workers were recorded during a 20-min work session, morning and afternoon; Monday, Wednesday, Friday and the following Monday. The estimated reliability coefficient was 0.59 for static muscle activity and 0.85 for short interruptions in muscle activity (EMG gaps) during work. The reliability coefficient was 0.94 for the EMG signals average median frequency of test contractions associated with the work session. The median frequency declined significantly during the work session. No time trend was found during the day or the week for these parameters. Consequently, it is possible to get representative measurements of the mentioned EMG parameters during repetitive light work by a recording taken at any time of the day or week.

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.

Association between numbers of long periods with sustained low-level trapezius muscle activity and neck pain

The purpose of this prospective cohort study was to evaluate relationships between sustained low-level muscle activity (SULMA) in the neck and pain after 1 year among machine operators of forest harvesters (n = 19), forwarders (n = 20) and forest researchers (n = 20). Surface electromyography of the right upper trapezius muscle was measured during one working day. Continuous muscle activity (SULMA periods) were analysed in predetermined time intervals. Neck pain was assessed by the Borgs category-ratio scale and the Standardized Nordic Questionnaire (dichotomised into pain duration ≤30 or >30 d). Harvesters reported significantly more pain than researchers. A higher number of long SULMA periods >8 min duration increased the risk of neck pain >30 d during the successive year (odds ratio 3.0, 95% CI 1.2–7.8). Perceived personal economy above average was associated with less pain, while other potential confounders or intermediate variables were not significant. Low-level trapezius muscle activity in periods longer than 8 min may constitute a risk for neck pain.