Can a metric combining arm elevation and trapezius muscle activity predict neck/shoulder pain? A prospective cohort study in construction and healthcare.

OBJECTIVE: To determine whether a composite metric of arm elevation and trapezius activity (i.e. neck/shoulder load) is more strongly associated with the 2-year course of neck and shoulder pain intensity (NSPi) among construction and healthcare workers than each exposure separately. METHODS: Dominant arm elevation and upper trapezius muscle activity were estimated in construction and healthcare employees (n = 118) at baseline, using accelerometry and normalized surface electromyography (%MVE), respectively. At baseline and every 6 months for 2 years, workers reported NSPi (score 0-3). Compositions of working time were determined for arm elevation (< 30°; 30-60°; > 60°), trapezius activity (< 0.5%; 0.5-7.0%; > 7.0%MVE), and a composite metric "neck/shoulder load" (restitution, low, medium, and high load). Associations between each of these three compositions and the 2-year course of NSPi were determined using linear mixed models. RESULTS: Associations between exposure compositions and the course of NSPi were all weak and in general uncertain. Time spent in 0.5-7.0%MVE showed the largest and most certain association with changes in NSPi during follow-up (ß = - 0.13; p = 0.037; corresponding to a -0.01 change in NPSi every 6 months). Among pain-free workers at baseline, medium (ß = - 0.23; p = 0.039) and high (ß = 0.15; p = 0.031) neck/shoulder load contributed the most to explaining changes in NSPi. CONCLUSION: The composite metric of neck/shoulder load did not show a stronger association with the course of NSPi than arm elevation or trapezius activity alone in the entire population, while some indications of a stronger association were found among those who were pain-free at baseline.

Associations of objectively measured total duration and maximum bout length of standing at work with lower-extremity pain intensity: a 2-year follow-up of construction and healthcare workers.

BACKGROUND: Musculoskeletal disorders are among the major reasons for years lived with disability. Approximately one third of the European working population report lower-extremity discomfort and many attribute these discomforts to work-related factors. Employees in the healthcare and construction sectors reports high levels of lower-extremity pain and commonly relate the pain to their profession. These workers spend a large part of their workday standing. Periods of prolonged standing is suggested to increase lower-extremity symptoms, but this cannot be concluded on, since limited evidence is available from longitudinal studies using objective measures. This study aimed to determine possible associations between objectively measured total duration and maximum bout length of static- and dynamic standing at work and lower-extremity pain intensity (LEPi) among Norwegian construction- and healthcare workers. METHODS: One-hundred and twenty-three construction and healthcare workers wore two accelerometers for up to four consecutive days, to establish standing behavior at baseline. The participants reported LEPi (Likert scale 0-9) for the preceding 4 weeks at baseline and after 6, 12, 18, and 24 months. We investigated associations between standing at work and average and change in LEPi using linear mixed models with significance level p ≤ 0.05. RESULTS: Total duration of static- and dynamic standing showed weak associations with average LEPi, for the total sample and for construction workers. Maximum bout of static- and dynamic standing was associated with average LEPi in construction workers, but not in healthcare workers. Furthermore, we found no associations between standing and change in LEPi over the 2-year follow-up in any of our analyses. CONCLUSIONS: This study indicate that objectively measured standing is associated with average LEPi over 2-years follow-up in construction workers, and that maximal bout of standing have a stronger association to LEPi than total duration. For every 10 min added to the maximal length of continuous standing during an average workday, we found approximately one unit increase in pain on a 0-9 scale. The lack of significant findings in analyses on healthcare workers suggest that the association between standing and LEPi depend on work-tasks, gender and/or other sector-specific factors.

Work above shoulder level and shoulder complaints: a systematic review.

OBJECTIVE: To investigate the association and the exposure-response relationship between work above shoulder height and shoulder pain or disorders. METHODS: A systematic search was performed in Medline, Embase, and Health and Safety Science Abstracts. Included were articles with prospective cohort, case-control, cross-sectional, or intervention study designs. Quality assessment was based on an evaluation scheme adjusted to study design and normalized to 100%. The cut-off for sufficient quality to include articles was above 40% and cut-off for high-quality articles was above 50% of maximal score. The level of strength of evidence for an association between exposure and effect was assessed according to the GRADE guidelines. RESULTS: Thirty-four articles were included. Articles that document large effects (higher risk estimates; OR ≥ 2) have higher quality score, include analyses of severe arm elevation, more often use clinical outcome, and report an exposure-response relationship compared to studies reporting lower risk estimates. The studies that reported large effects were all significant. An exposure-response relationship was found in many high-quality studies when relating exposure intensity of arm elevation (level of arm elevation, amplitude) as well as duration of arm elevation, especially > 90°. CONCLUSION: We conclude on a limited evidence for an association between arm elevation at work and shoulder disorders. Severe arm elevation with elbows above shoulder level (i.e., > 90°) shows a moderate evidence for an association with shoulder disorders.

Associations of objectively measured forward bending at work with low-back pain intensity: a 2-year follow-up of construction and healthcare workers.

OBJECTIVES: This study aimed to determine possible associations between objectively measured forward bending at work (FBW) and low-back pain intensity (LBPi) among Norwegian construction and healthcare workers. METHODS: One-hundred and twenty-five workers wore two accelerometers for 3-4 consecutive days, during work and leisure to establish duration of ≥30° and ≥60° forward bending. The participating workers reported LBPi (0-3) at the time of objective measurements and after 6, 12, 18 and 24 months. We investigated associations using linear mixed models with significance level p≤0.05 and presented results per 100 min. RESULTS: The duration of ≥30° and ≥60° FBW was not associated with average LBPi during follow-up, neither for the total sample nor stratified on work sector. Furthermore, analyses on all workers and on construction workers only found no significant association between ≥30° or ≥60° FBW and change in LBPi over the 2-year follow-up. For healthcare workers we found a consistent significant association between the duration of ≥30° FBW at baseline and the change in LBPi during follow-up, but this was not found for ≥60° FBW. CONCLUSIONS: This study suggests that objectively measured duration of FBW in minutes is not associated with average levels of, or change in LBPi in construction workers over a 2-year period. In healthcare workers, exposure to ≥30° FBW was associated with change in LBPi, while we did not find this for ≥60° FBW. Results may indicate that the associations between FWB and LBP vary depending on type of work tasks, gender or sector-specific factors.

Physical capacity, occupational physical demands, and relative physical strain of older employees in construction and healthcare.

PURPOSE: To assess age-related differences in physical capacity, occupational physical demands, and relative physical strain at a group level, and the balance between capacity and demands at an individual level, for construction and healthcare workers. METHODS: Shoulder strength, back strength, and aerobic capacity were assessed among construction (n = 62) and healthcare workers (n = 64). During a full working day, accelerometers estimated upper-arm elevation, trunk flexion, and occupational physical activity as indicators of occupational physical demands. Simultaneously, normalised surface electromyography (%sEMGmax) of the upper trapezius and erector spinae muscles, and normalised electrocardiography (percentage heart rate reserve (%HRR)) estimated relative physical strain. Differences between younger (≤ 44 years) and older (≥ 45 years) workers, as well as the moderating effect of age on the associations between capacity and demands, were analysed per sector. RESULTS: Compared to younger workers, older workers had similar strength and lower aerobic capacity; older construction workers had similar demands while older healthcare workers had higher demands. Compared to younger workers, older employees had unfavourable muscle activity patterns; %HRR had a tendency to be lower for older construction workers and higher for older healthcare workers. Among construction workers, age moderated the associations between shoulder strength and arm elevation (p = 0.021), and between aerobic capacity and occupational physical activity (p = 0.040). Age did not moderate these associations among healthcare workers. CONCLUSIONS: In both sectors, the level of occupational physical demands and the higher relative physical strain in older employees require addressing to promote sustainable work participation among an aging population.

Association between V̇O2max, handgrip strength, and musculoskeletal pain among construction and health care workers.

BACKGROUND: Construction and health care workers have a high prevalence of musculoskeletal disorders, and they are assumed to have physically demanding jobs. Profession- and gender-specific associations between individual capacity and musculoskeletal pain have not been sufficiently investigated. The main aim of this study was to examine the association between individual capacity (maximal oxygen uptake (V̇O2max) and handgrip strength) and musculoskeletal pain among construction and health care workers. METHODS: This cross-sectional study examined 137 construction and health care workers (58 women and 79 men) with a mean age of 41.8 years (standard deviation 12). Aerobic capacity was indirectly assessed by the Åstrand cycle test, and strength was assessed by a handgrip test. Musculoskeletal pain was described by total pain, divided into neck, shoulder, and low back pain, during the last 12 months, and it was dichotomized in below or above 30 days. Logistic regression was used to analyse the associations between V̇O2max, strength, and musculoskeletal pain in the total study sample and separately for construction and health care workers. Analyses were adjusted for age, gender, body mass index (BMI), and selected mechanical and psychosocial factors. RESULTS: Every second participant (51.8%) reported pain in either neck, shoulders or low back for more than 30 days during the last 12 months. Among the health care workers, a small but significant association was found between a high V̇O2max, high handgrip strength, and a low level of musculoskeletal pain. No association was found for the construction workers. CONCLUSIONS: An association between V̇O2max, handgrip strength, and musculoskeletal pain was found for health care workers but not for construction workers. These results indicate that activities promoting individual capacity may reduce musculoskeletal pain for health care workers.

Multisite musculoskeletal pain among young technical school students entering working life.

BACKGROUND: There is a need to investigate the occurrence of multisite pain in young adults and to determine potential factors contributing to the early course of multisite musculoskeletal pain. The aim of this prospective study was to assess the occurrence and change of prevalence in the number of pain sites. We also wanted to identify work-related and individual risk factors associated with the number of musculoskeletal pain sites. METHODS: We monitored musculoskeletal pain from 4 body regions, individual and work-related factors on 21 occasions over a 6.5 year period. The cohort consisted of 420 technical school students entering working life. Data were analyzed by generalized estimating equations (GEE). RESULTS: Pain from more than one body site was prevalent in this cohort of young adults (69 % at baseline), and the number of body sites in pain was found quite stable over the 6.5 year follow-up period. Women had higher number of pain sites compared with men and gender specific risk factors were identified. Increased mechanical workload and quantitative demands and low socioeconomic status were associated with increased number of musculoskeletal pain sites among women, while tobacco use was found as a risk factor among young men. Increased perceived muscle tension was the only factor significantly associated with increased number of pain sites in both genders. CONCLUSION: The current study supports earlier findings and show that pain from multiple body sites are frequent also among young workers. The identification of gender specific risk factors in our study is important and may facilitate practical prevention and future research.

Are elderly construction workers sufficiently fit for heavy manual labour?

This study analysed the work ability of elderly construction workers. Forty male construction workers, 20 young (age < 33 yrs) and 20 senior (age>44 yrs) workers, were tested regarding aerobic power (VO2max) and muscle strength. The aerobic demand of a number of tasks in construction work was measured and compared with the workers' aerobic power. VO2max was higher for the young, and they performed better on most muscle strength tests. The measurements showed that about half of the senior workers had to use more than 30% of their maximum oxygen uptake on some tasks. In conclusion, because elderly construction workers decline in physical fitness, they are more exposed to overload when performing heavy manual work than are their younger peers. Increasing their individual fitness or adjusting their workload may be important for staying in the workforce for such workers. PRACTITIONER SUMMARY: Construction workers must occasionally perform strenuous work tasks that may endanger their safety. This was more often the case for elderly workers investigated here. Elderly workers should therefore be particularly observant of their physical fitness, and should possibly train during leisure time to improve their fitness.

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

BACKGROUND: Musculoskeletal 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 DESIGN: This 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. DISCUSSION: The 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.

Frequency of breaks, amount of muscular rest, and sustained muscle activity related to neck pain in a pooled dataset.

BACKGROUND: Neck pain remains a persistent challenge in modern society and is frequently encountered across a wide range of occupations, particularly those involving repetitive and monotonous tasks. It might be expected that patterns of trapezius muscle activity at work, characterized by few breaks and prolonged periods of sustained muscle activity, are linked to neck pain. However, previous cross-sectional studies have generally failed to establish a definitive association. While some longitudinal studies have suggested that extended periods of heightened muscle activity could be a risk factor for neck pain, these findings often relied on limited participant numbers or specific professional groups. This study aimed to investigate the relationship between trapezius muscle activity and neck pain by pooling data from seven Scandinavian research institutes encompassing a diverse range of occupational backgrounds. METHODS: Electromyographic (EMG) data for the upper trapezius muscle, collected during working hours, were coupled with questionnaire responses pertaining to neck pain, individual characteristics, and potential confounding variables for a total of 731 subjects. Additionally, longitudinal data from 258 subjects were available. The various EMG datasets were consolidated into a standardized format, and efforts were made to harmonize inquiries about neck pain. Regression analyses, adjusting for sex and height, were conducted to explore the associations between muscle activity variables and neck pain. An exposure index was devised to quantify the cumulative neck load experienced during working hours and to differentiate between various occupational categories. RESULTS: The cross-sectional data displayed a distinct pattern characterized by positive associations for brief periods of sustained muscle activity (SUMA) and negative associations for prolonged SUMA-periods and neck pain. The longitudinal data exhibited a contrasting trend, although it was not as pronounced as the cross-sectional findings. When employing the exposure index, notable differences in cumulative muscle load emerged among occupational groups, and positive associations with longitudinal neck pain were identified. DISCUSSION: The results suggest that individuals with neck pain experience higher cumulative workloads and extended periods of muscle activity over the long term. In the short term, they appear to compensate by taking frequent short breaks, resulting in a lower cumulative workload. Regardless of their occupation, it is crucial to distribute work breaks throughout the workday to ensure that the cumulative load remains manageable.

Low-voltage electrical accidents, immediate reactions and acute health care associated with self-reported general health 4 years later.

BACKGROUND AND AIMS: Electricians frequently experience low-voltage electrical accidents. Some such accidents involve long-term negative health consequences. Early identification of victims at risk for long-term injury may improve acute medical treatment and long-term follow-up. This study aimed to determine acute exposure, health effects and treatment associated with general health ≥ 2 years after low-voltage electrical accidents. METHODS: In a cross-sectional study, 89 male electricians who had experienced an electrical accident between 1994 and 2001 participated in a 2003 follow-up health examination. They were identified from a registry of low-voltage electrical accidents and included in the study. Based on exposure descriptions in the original accident reports, they were stratified into the following three groups: a current arc accident group (N = 34, mean age 38.8 years [standard deviation, SD = 12.2, range = 21-59]) and two groups with the passage of current through the body, either fixed to the current source ("no-let-go" group; N = 35, mean age 34.0 years [SD = 10.5, range = 21-57]) or not ("let-go" group; N = 20, mean age = 38.7 years [SD = 10.3, range = 21-63]). They retrospectively described acute reactions and assessed their current general health at the health examination. Multivariate linear regression, ordinal logistic regression and Fisher's exact test were used to compare acute reactions with health at follow-up in each exposure group. RESULTS: The multivariate analysis indicated that after accidents with the passage of current through the body, severe acute headache (ß = - 0.56, p = 0.013), years since the accident (ß = - 0.16, p = 0.017) and the accident being perceived as frightening (ß = - 0.48, p = 0.040) were negatively associated with general health ≥ 2 years later (R2 = 0.25, p = 0.002). If the exposure included a no-let-go experience, then acute severe body numbness (ß = - 0.53, p = 0.029) was also negatively associated with general health (R2 = 0.38, p = 0.002). Without such experience, only acute confusion (ß = - 0.90, p = 0.029) was negatively associated with the health at follow-up (R2 = 0.24, p = 0.029). In univariate analyses, after the passage of current through the body, acute dizziness (p = 0.029), apathy (p = 0.028), confusion (p = 0.007) and irregular heartbeat (p ≤ 0.05) were associated with poor long-term general health. The no-let-go group, more often than the let-go group, reported panic (p = 0.001), fear of death (p = 0.029), confusion (p = 0.014), exhaustion (p = 0.009), bodily numbness (p = 0.013) and immediate unconsciousness (p = 0.019). Acute symptoms beyond the first day after a current arc accident were associated with poor long-term general health (p = 0.015). DISCUSSION AND CONCLUSIONS: The acute reactions negatively associated with general health ≥ 2 years after low-voltage electrical accidents should alert the clinician in the acute phase after an electrical accident to the risk of developing negative long-term health effects. Future studies should specify long-term health beyond the concept of general health.

An Exploratory Study on the Physical Activity Health Paradox-Musculoskeletal Pain and Cardiovascular Load during Work and Leisure in Construction and Healthcare Workers.

Using a novel approach, this exploratory study investigated whether the physical activity (PA) paradox extends to cardiovascular load and musculoskeletal pain. At baseline, 1-2 days of 24 h heart rate was assessed in 72 workers from construction and healthcare. Workers then reported pain intensity in 9 body regions (scale 0-3) every 6 months for two years. The 2 year average of musculoskeletal pain (sum of 9 pain scores; scale 0-27) was regressed on time spent during work and leisure above three thresholds of percentage heart rate reserve (%HRR), i.e., ≥20 %HRR, ≥30 %HRR, and ≥40 %HRR, using a novel ilr structure in compositional data analysis. Analyses were stratified for several important variables. Workers spending more time in physical activity at work had higher pain, while workers with more time in physical activity during leisure had less pain (i.e., the PA paradox), but none of the associations were statistically significant. Higher aerobic capacity and lower body mass index lowered the pain score among those with higher physical activity at work. This exploratory study suggests that the PA paradox may apply to musculoskeletal pain and future studies with larger sample sizes and additional exposure analyses are needed to explain why this occurs.

Do intensity of pain alone or combined with pain duration best reflect clinical signs in the neck, shoulder and upper limb?

OBJECTIVES: It is important to validate self-reported musculoskeletal pain used in epidemiological studies for evaluation of pain outcome measures. The main objective of this paper was to assess the association between self-reported neck/shoulder/upper limb pain and clinical signs of disorders in the region, especially by comparing a measure that only used pain intensity with a measure that combined pain intensity and pain duration. METHODS: Four hundred and twenty technical school students of both genders were included with a median age of 17 years (16-28). The students stated the pain in four intensity grades and the pain duration in four period lengths within the preceding four weeks period. A pain severity index was calculated by multiplying the pain intensity (0-3) and the duration (1-4). A clinical examination was performed within a week after completing the form. The associations were evaluated by agreement, correlation and symmetric strength of association (contingency). RESULTS: The study found low correlation and low positive agreement for neck/shoulder and upper limb pain related to clinical signs of disorders in the region. However, the relationship showed high negative agreement and high contingency. The negative agreement increased for the neck/shoulder region with higher cut-off points for dichotomization, but not for the upper limb region. The index combining reports of pain intensity with pain duration, do not improve agreement, correlation or contingency with clinical signs compared to use of pain intensity alone. CONCLUSIONS: This study showed an association between self-reported neck/shoulder/upper limb pain intensity and clinical signs of musculoskeletal disorders of the region. An index combining pain intensity and duration (Pain Severity Index) did not increase this association. From the results we suggest using pain intensity reports alone and if dichotomizing is wanted, choosing a cut-off point at high pain levels, especially for neck and shoulder pain.

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

BACKGROUND: This review examines the evidence for an association between computer work and neck and upper extremity disorders (except carpal tunnel syndrome). METHODS: A systematic critical review of studies of computer work and musculoskeletal disorders verified by a physical examination was performed. RESULTS: A 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. CONCLUSIONS: There 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.

[Health and function after occupational injury]. / Helse og funksjon etter yrkesskade.

BACKGROUND: Available statistics provide relatively reliable information on the number of occupational injuries, their causes and mechanisms, but less is known about long-term health impact. MATERIAL AND METHODS: A group of workers, who had been referred to a specialist for medico-legal assessment after seeking compensation because of occupational injury, were asked to complete a questionnaire approximately three years (median) after the injury. Perceived health and function was assessed through the Short Form Questionnaire (SF-36) and a 100 mm visual analogue scale for physical and psychological health. The injuries were scored according to the Abbreviated Injury Scale (AIS). Information on outcome of the insurance claims was obtained from the Norwegian Labour and Welfare Administration (NAV). RESULTS: Of 314 distributed questionnaires, 191 (62 %) were returned. 83 % of the respondents had injuries with an AIS score < 2; mostly sprains, strains and contusions. Compared to Norwegian population norms, the claimants reported substantially reduced health and functioning; this was especially pronounced among those with soft-tissue injuries, age at injury < 45 years, and < 12 years of education. 33 % of the respondents worked full time, while 55 % were recipients of insurance benefits. 30 % had been granted workers' compensation by NAV. INTERPRETATION: The reported health deterioration in this selected injury group seems to be at odds with a biologically based disease model. Medico-legal considerations should take into account that prognosis after occupational injury may be influenced by factors other than the actual injury.

Self-reported versus expert-assessed work-relatedness of pain in the neck, shoulder, and arm.

OBJECTIVES: The aim of this study was to compare self-reported work-relatedness of neck-shoulder and arm pain with experts' assessments based on specific criteria. METHODS: A sample of 217 employed participants in the Oslo Health Study 2000-2001, aged 30, 40, and 45 years, who reported neck-shoulder or arm pain in the past month, underwent a health examination. A criteria document for evaluating the work-relatedness of upper-extremity musculoskeletal disorders was used to -establish clinical diagnoses and assess the work-relatedness of pain with respect to the subject's present job. We measured agreement between the participants and experts on whether pain was related to work as observed agreement, positive and negative specific agreement, and kappa. RESULTS: A major proportion of the cases were assessed as work-related, somewhat more frequently by self-report than when assessed by experts (80% versus 65% for neck-shoulder pain, and 78% versus 72% for arm pain, respectively). However, there was considerable disagreement as to which cases were work-related. The experts disagreed more frequently in cases that were reported as non-work-related (particularly for neck-shoulder pain and cases reported by men). Positive specific agreement was fairly high (76-85% in the total population), while negative specific agreement was lower (37-51%). Kappa values were also low (0.16-0.34). CONCLUSIONS: Compared with expert assessment, self-reporting did not seem to particularly exaggerate work-relatedness. Nevertheless, there was considerable disagreement, especially on cases assessed as non-work--related. However, agreement will depend on the case definitions and the criteria for work-relatedness used both by the participants and the experts.

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 Borg's category-ratio scale and the Standardized Nordic Questionnaire (dichotomised into pain duration 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.

An automatic pre-processing method to detect and reject signal artifacts from full-shift field-work sEMG recordings of bilateral trapezius activity.

Bipolar surface EMG (sEMG) signals of the trapezius muscles bilaterally were recorded continuously with a frequency of 800 Hz during full-shift field-work by a four-channel portable data logger. After recordings of 60 forest machine operators in Finland, Norway and Sweden, we discovered erroneous data. In short of any available procedure to handle these data, a method was developed to automatically discard erroneous data in the raw data reading files (Discarding Erroneous EPOchs (DESEPO) method. The DESEPO method automatically identifies, discards and adjusts the use of signal disturbances in order to achieve the best possible data use. An epoch is a 0.1 s period of raw sEMG signals and makes the basis for the RMS calculations. If erroneous signals constitute more than 30% of the epoch signals, this classifies for discharge of the present epoch. Non-valid epochs have been discarded, as well as all the subsequent epochs. The valid data for further analyses using the automatic detection resulted in an increase of acceptable data from an average of 2.15-6.5 h per day. The combination of long-term full-shift recordings and automatic data reduction procedures made it possible to use large amount of data otherwise discarded for further analyses.

Effect of an intervention addressing working technique on the biomechanical load of the neck and shoulders among hairdressers.

The purpose of this study was to describe, and analyse the effect of an intervention on, the biomechanical workload in the neck and shoulder region of female hairdressers. Arm elevation was measured by inclinometers and muscular load of m. trapezius by electromyography. The intervention comprised working technique recommendations, e.g. to work with less elevated arms and more relaxed muscles. The subjects were randomised between two different intensity levels of the intervention, one with written information only and the other with additional personal follow-up. The effect of the intervention was evaluated after 1-2 months. The hairdressers worked with their arms elevated 60 degrees or more for approximately 13% of the total working time and 16% during the specific hairdressing tasks. The intervention group including personal follow-up instructions had a reduction in workload from 4.0% to 2.5% of hairdressing time with highly elevated right upper arm, i.e. above 90 degrees . No effect was detected on muscular load or neck and shoulder symptoms after the intervention.