Scapular muscle activity from selected strengthening exercises performed at low and high intensities

A balanced level of muscle strength between the different parts of the scapular muscles is important in optimizing performance and preventing injuries in athletes. Emerging evidence suggests that many athletes lack balanced strength in the scapular muscles. Evidence-based recommendations are important for proper exercise prescription. This study determines scapular muscle activity during strengthening exercises for scapular muscles performed at low and high intensities (Borg CR10 levels 3 and 8). Surface electromyography (EMG) from selected scapular muscles was recorded during 7 strengthening exercises and expressed as a percentage of the maximal EMG. Seventeen women (aged 24-55 years) without serious disorders participated. Several of the investigated exercises-press-up, prone flexion, one-arm row, and prone abduction at Borg 3 and press-up, push-up plus, and one-arm row at Borg 8-predominantly activated the lower trapezius over the upper trapezius (activation difference [Δ] 13-30%). Likewise, several of the exercises-push-up plus, shoulder press, and press-up at Borg 3 and 8-predominantly activated the serratus anterior over the upper trapezius (Δ18-45%). The middle trapezius was activated over the upper trapezius by one-arm row and prone abduction (Δ21-30%). Although shoulder press and push-up plus activated the serratus anterior over the lower trapezius (Δ22-33%), the opposite was true for prone flexion, one-arm row, and prone abduction (Δ16-54%). Only the press-up and push-up plus activated both the lower trapezius and the serratus anterior over the upper trapezius. In conclusion, several of the investigated exercises both at low and high intensities predominantly activated the serratus anterior and lower and middle trapezius, respectively, over the upper trapezius. These findings have important practical implications for exercise prescription for optimal shoulder function. For example, both workers with neck pain and athletes at risk of shoulder impingement (e.g., overhead sports) should perform push-up plus and press-ups to specifically strengthen the serratus anterior and lower trapezius.

Does work-site physical activity improve self-reported psychosocial workplace factors and job satisfaction? A randomized controlled intervention study

PURPOSE

To investigate whether a work-site strength-training program has a positive effect on self-reported psychosocial workplace factors and job satisfaction.

METHODS

We conducted a randomized controlled trial among laboratory technicians implementing neck and shoulder exercises for pain relief, with 199 participants in the training group and 228 in the control group. Influence at work, sense of community, time pressure, and job satisfaction were measured with the Copenhagen Psychosocial Questionnaire at baseline and post-intervention after 20 weeks.

RESULTS

There was no statistically significant change in any of the four variables in the training group from baseline to follow-up (all p ≥ 0.39). When we used MANOVA to test for between-group effects over time, we did not find any statistically significant result (all p > 0.14).

CONCLUSIONS

This study does not provide evidence for an effect of a work-site strength-training program on self-reported psychosocial workplace factors and job satisfaction.

Influence of frequency and duration of strength training for effective management of neck and shoulder pain: a randomised controlled trial

BACKGROUND

Specific strength training can reduce neck and shoulder pain in office workers, but the optimal combination of exercise frequency and duration remains unknown. This study investigates how one weekly hour of strength training for the neck and shoulder muscles is most effectively distributed.

METHODS

A total of 447 office workers with and without neck and/or shoulder pain were randomly allocated at the cluster-level to one of four groups; 1×60 (1WS), 3×20 (3WS) or 9×7 (9WS) min a week of supervised high-intensity strength training for 20 weeks, or to a reference group without training (REF). Primary outcome was self-reported neck and shoulder pain (scale 0-9) and secondary outcome work disability (Disability in Arms, Shoulders and Hands (DASH)).

RESULTS

The intention-to-treat analysis showed reduced neck and right shoulder pain in the training groups after 20 weeks compared with REF. Among those with pain ≥3 at baseline (n=256), all three training groups achieved significant reduction in neck pain compared with REF (p<0.01). From a baseline pain rating of 3.2 (SD 2.3) in the neck among neck cases, 1WS experienced a reduction of 1.14 (95% CI 0.17 to 2.10), 3WS 1.88 (0.90 to 2.87) and 9WS 1.35 (0.24 to 2.46) which is considered clinically significant. DASH was reduced in 1WS and 3WS only.

CONCLUSION

One hour of specific strength training effectively reduced neck and shoulder pain in office workers. Although the three contrasting training groups showed no statistical differences in neck pain reduction, only 1WS and 3WS reduced DASH. This study suggests some flexibility regarding time-wise distribution when implementing specific strength training at the workplace.

Effect of specific resistance training on forearm pain and work disability in industrial technicians: cluster randomised controlled trial

OBJECTIVES

To determine the effect of specific resistance training on forearm pain and work disability in industrial technicians.

DESIGN AND SETTING

Two-armed cluster randomised controlled trial of 20 weeks performed at two industrial production units in Copenhagen, Denmark.

PARTICIPANTS

Working-age industrial technicians both with and without pain and disability.

INTERVENTIONS

The training group (n=282) performed specific resistance training for the shoulder, neck and arm muscles three times a week. The control group (n=255) was advised to continue normal physical activity.

OUTCOME

All participants rated forearm pain intensity (Visual Analogue Scale, 0-100 mm) once a week (primary outcome) and replied to a questionnaire on work disability (Disability of the Arm Shoulder and Hand, 0-100) at baseline and follow-up (secondary outcome).

RESULTS

Questionnaires were sent to 854 workers of which 30 (n=282) and 27 (n=255) clusters were randomised to training and control, respectively. Of these, 211 and 237 participants, respectively, responded to the follow-up questionnaire. Intention-to-treat analyses including both individuals with and without pain showed that from baseline to follow-up, pain intensity and work disability decreased more in the training group than in the control group (4-5 on a scale of 0-100, p<0.01-0.001). Among those with pain >30 mm Visual Analogue Scale at baseline (n=54), the OR for complete recovery at follow-up in the training group compared with the control group was 4.6 (95% CI 1.2 to 17.9). Among those with work disability >30 at baseline (n=113), the OR for complete recovery at follow-up in the training group compared with the control group was 6.0 (95% CI 1.8 to 19.8).

CONCLUSION

Specific resistance training of the shoulder, neck and arm reduces forearm pain and work disability among industrial technicians.

TRIAL REGISTRATION NUMBER

NCT01071980.

A randomised controlled trial among cleaners--effects on strength, balance and kinesiophobia

Background

Cleaners constitute a job group with poor health and low socioeconomic resources. Therefore, there is a great need for scientifically documented health promoting initiatives for cleaners. However, both workplace initiatives and high quality intervention studies are lacking. The aim of this study was to evaluate the effects of a 3-month workplace trial with interventions to improve physical or cognitive behavioural resources among cleaners.

Methods

A cluster randomised controlled trial was conducted among 294 female cleaners from 9 workplaces. The participants were allocated to three groups: Physical coordination training (PCT, n = 95), Cognitive behavioural theory-based training (CBTr, n = 99) and Reference group (REF, n = 100). Interventions were conducted during work hours for an average of 1 hour/week. Muscle strength was measured by maximal voluntary contractions in trunk/extension, and shoulder abduction/elevation. Postural balance was measured on a force platform. Kinesiophobia was measured with Tampa Scale for Kinesiophobia. Test and questionnaires were completed at baseline and at 3-month follow-up and analyses followed the intention-to-treat (ITT) principle with last observation carried forward in case of missing data at follow-up. Reports and analyses are given on true observations as well.

Results

ITT-analyses revealed that PCT improved strength of the trunk (p < .05) and postural balance (p < .05) compared to CBTr and REF. Based on true observations the strength and balance improvements corresponded to ~20% and ~16%, respectively. ITT-analyses showed that CBTr reduced kinesiophobia compared to PCT and REF (p < .05). Based on true observations, the improvement corresponded to a ~16% improvement.

Conclusion

This workplace-based intervention study including PCT and CBTr among cleaners improved strength and postural balance from PCT, and kinesiophobia from CBTr. The improved strength, postural balance and kinesiophobia may improve the cleaners' tolerance for high physical work demands. Future studies should investigate the potential in the combination of PCT and CBTr in a workplace intervention.

Trial registration

Current controlled trials ISRCTN96241850

Strength training increases the size of the satellite cell pool in type I and II fibres of chronically painful trapezius muscle in females

While strength training has been shown to be effective in mediating hypertrophy and reducing pain in trapezius myalgia, responses at the cellular level have not previously been studied. This study investigated the potential of strength training targeting the affected muscles (SST, n = 18) and general fitness training (GFT, n = 16) to augment the satellite cell (SC) and macrophage pools in the trapezius muscles of women diagnosed with trapezius myalgia. A group receiving general health information (REF, n = 8) served as a control. Muscle biopsies were collected from the trapezius muscles of the 42 women (age 44 ± 8 years; mean ± SD) before and after the 10 week intervention period and were analysed by immunohistochemistry for SCs, macrophages and myonuclei. The SC content of type I and II fibres was observed to increase significantly from baseline by 65% and 164%, respectively, with SST (P < 0.0001), together with a significant correlation between the baseline number of SCs and the extent of hypertrophy (r = -0.669, P = 0.005). SST also resulted in a 74% enhancement of the trapezius macrophage content (P < 0.01), accompanied by evidence for the presence of an increased number of actively dividing cells (Ki67(+)) post-SST (P < 0.001). GFT resulted in a significant 23% increase in the SC content of type II fibres, when expressed relative to myonuclear number only (P < 0.05). No changes in the number of myonuclei per fibre or myonuclear domain were detected in any group. These findings provide strong support at the cellular level for the potential of SST to induce a strong myogenic response in this population.

Implementation of neck/shoulder exercises for pain relief among industrial workers: a randomized controlled trial

BACKGROUND

Although leisure-time physical activity is important for health, adherence to regular exercise is challenging for many adults. The workplace may provide an optimal setting to reach a large proportion of the adult population needing regular physical exercise. This study evaluates the effect of implementing strength training at the workplace on non-specific neck and shoulder pain among industrial workers.

METHODS

Cluster-randomized controlled trial involving 537 adults from occupations with high prevalence of neck and shoulder pain (industrial production units). Participants were randomized to 20 weeks of high-intensity strength training for the neck and shoulders three times a week (n = 282) or a control group receiving advice to stay physically active (n = 255). The strength training program followed principles of progressive overload and periodization. The primary outcome was changes in self-reported neck and shoulder pain intensity (scale 0-9).

RESULTS

85% of the participants followed the strength training program on a weekly basis. In the training group compared with the control group, neck pain intensity decreased significantly (-0.6, 95% CI -1.0 to -0.1) and shoulder pain intensity tended to decrease (-0.2, 95% CI -0.5 to 0.1, P = 0.07). For pain-cases at baseline (pain intensity > = 3) the odds ratio - in the training group compared with the control group--for being a non-case at follow-up (pain intensity < 3) was 2.0 (95% CI 1.0 to 4.2) for the neck and 3.9 (95% CI 1.7 to 9.4) for the shoulders.

CONCLUSION

High-intensity strength training relying on principles of progressive overload can be successfully implemented at industrial workplaces, and results in significant reductions of neck and shoulder pain.

TRIAL REGISTRATION

NCT01071980.

Neck pain and postural balance among workers with high postural demands - a cross-sectional study

Background

Neck pain is related to impaired postural balance among patients and is highly prevalent among workers with high postural demands, for example, cleaners. We therefore hypothesised, that cleaners with neck pain suffer from postural dysfunction. This cross-sectional study tested if cleaners with neck pain have an impaired postural balance compared with cleaners without neck pain.

Methods

Postural balance of 194 cleaners with (n = 85) and without (N = 109) neck pain was studied using three different tests. Success or failure to maintain the standing position for 30 s in unilateral stance was recorded. Participants were asked to stand on a force platform for 30 s in the Romberg position with eyes open and closed. The centre of pressure of the sway was calculated, and separated into a slow (rambling) and fast (trembling) component. Subsequently, the 95% confidence ellipse area (CEA) was calculated. Furthermore a perturbation test was performed.

Results

More cleaners with neck pain (81%) failed the unilateral stance compared with cleaners without neck pain (61%) (p < 0.01). However, the risk of failure in unilateral stance was statistically elevated in cleaners with concurrent neck/low back pain compared to cleaners without neck/low back pain (p < 0.01), whereas pain at only neck or only low back did not increase the risk. Impaired postural balance, measured as CEA (p < 0.01), rambling (p < 0.05) and trembling (p < 0.05) was observed among cleaners with neck pain in comparison with cleaners without neck pain in the Romberg position with eyes closed, but not with eyes open.

Conclusions

Postural balance is impaired among cleaners with neck pain and the current study suggests a particular role of the slow component of postural sway. Furthermore, the unilateral stance test is a simple test to illustrate functional impairment among cleaners with concurrent neck and low back pain.

Trial registration

ISRCTN96241850

Scapular dyskinesis in trapezius myalgia and intraexaminer reproducibility of clinical tests

The aims were to test the intraexaminer reproducibility and report the presence of specific clinical variables of scapular dyskinesis in cases with trapezius myalgia and healthy controls, along with general health and work ability. A total of 38 cases and 23 controls were tested for scapular dyskinesis, general health, and work ability, and 19 cases and 14 controls participated in the reproducibility study. Intraexaminer reproducibility was good to excellent for 6 of 10 clinical variables (Intraclass Correlation Coefficient [ICC] 0.76-0.91; kappa 0.84-1.00), and fair to good for four variables (ICC 0.42-0.74), test for muscular weakness having the lowest ICC (0.42). Cases showed significantly larger medial border misalignment, larger lower horizontal distance of the inferior scapular angle and larger passive shoulder internal rotation, by 110% (1.02 cm), 15% (1.38 cm), and 8% (5.5°), respectively. Cases with the highest degree of scapular dyskinesis showed reduced work ability and general health. The present specific clinical variables on scapular dyskinesis showed satisfactory intraexaminer reproducibility. An increased standardization must be implemented to increase reproducibility of tests for muscular weakness, and the interexaminer reproducibility must be tested for all variables. Finally, scapular dyskinesis in cases with trapezius myalgia must be followed longitudinally for clinical importance.

Biofeedback effectiveness to reduce upper limb muscle activity during computer work is muscle specific and time pressure dependent

Continuous electromyographic (EMG) activity level is considered a risk factor in developing muscle disorders. EMG biofeedback is known to be useful in reducing EMG activity in working muscles during computer work. The purpose was to test the following hypotheses: (1) unilateral biofeedback from trapezius (TRA) can reduce bilateral TRA activity but not extensor digitorum communis (EDC) activity; (2) biofeedback from EDC can reduce activity in EDC but not in TRA; (3) biofeedback is more effective in no time constraint than in the time constraint working condition. Eleven healthy women performed computer work during two different working conditions (time constraint/no time constraint) while receiving biofeedback. Biofeedback was given from right TRA or EDC through two modes (visual/auditory) by the use of EMG or mechanomyography as biofeedback source. During control sessions (no biofeedback), EMG activity was (mean ± SD): 2.4 ± 1.1, 2.5 ± 2.1, and 9.1 ± 3.1%max-EMGrms for right and left TRA and EDC, respectively. During biofeedback from TRA, activity was reduced in right TRA (1.7 ± 1.6%max-EMGrms) and left TRA (1.2 ± 2.0%max-EMGrms) compared to control. During biofeedback from EDC, activity in EDC was reduced (8.3 ± 3.3%max-EMGrms) compared with control. During time constraint, activity was reduced in right TRA (1.9 ± 1.3%max-EMGrms), left TRA (1.5 ± 1.5%max-EMGrms), and EDC (8.4 ± 3.2%max-EMGrms), during biofeedback compared to control.

CONCLUSION

biofeedback reduced muscle activity in TRA by ∼ 30-50% and in EDC by ∼ 10% when given from the homologous or bilateral muscle but not from the remote muscle, and was significant in the time constraint condition; while feedback source and presentation mode showed only minor differences in the effect on reducing homologous muscle activity. This implies that biofeedback should be given from the most affected muscle in the occupational setting for targeting relief and prevention of muscle pain most effectively.

Changed activation, oxygenation, and pain response of chronically painful muscles to repetitive work after training interventions: a randomized controlled trial

The aim of this randomized controlled trial was to assess changes in myalgic trapezius activation, muscle oxygenation, and pain intensity during repetitive and stressful work tasks in response to 10 weeks of training. In total, 39 women with a clinical diagnosis of trapezius myalgia were randomly assigned to: (1) general fitness training performed as leg-bicycling (GFT); (2) specific strength training of the neck/shoulder muscles (SST) or (3) reference intervention without physical exercise. Electromyographic activity (EMG), tissue oxygenation (near infrared spectroscopy), and pain intensity were measured in trapezius during pegboard and stress tasks before and after the intervention period. During the pegboard task, GFT improved trapezius oxygenation from a relative decrease of −0.83 ± 1.48 μM to an increase of 0.05 ± 1.32 μM, and decreased pain development by 43%, but did not affect resting levels of pain. SST lowered the relative EMG amplitude by 36%, and decreased pain during resting and working conditions by 52 and 38%, respectively, without affecting trapezius oxygenation. In conclusion, GFT performed as leg-bicycling decreased pain development during repetitive work tasks, possibly due to improved oxygenation of the painful muscles. SST lowered the overall level of pain both during rest and work, possibly due to a lowered relative exposure as evidenced by a lowered relative EMG. The results demonstrate differential adaptive mechanisms of contrasting physical exercise interventions on chronic muscle pain at rest and during repetitive work tasks.

The health paradox of occupational and leisure-time physical activity

BACKGROUND

Occupational and leisure-time physical activity are considered to provide similar health benefits. The authors tested this hypothesis.

METHODS

A representative sample of Danish employees (n=7144, 52% females) reported levels of occupational and leisure-time physical activity in 2005. Long-term sickness absence (LTSA) spells of ≥3 consecutive weeks were retrieved from a social-transfer payment register from 2005 to 2007.

RESULTS

341 men and 620 females experienced a spell of LTSA during the period. Cox analyses adjusted for age, gender, smoking, alcohol, body mass index, chronic disease, social support from immediate superior, emotional demands, social class and occupational or leisure-time physical activity showed a decreased risk for LTSA among workers with moderate (HR 0.85, CI 0.72 to 1.01) and high (HR 0.77, CI 0.62 to 0.95) leisure-time physical activity in reference to those with low leisure-time physical activity. In contrast, an increased risk for LTSA was shown among workers with moderate (HR 1.59, CI 1.35 to 1.88) and high (HR 1.84, CI 1.55 to 2.18) occupational physical activity referencing those with low occupational physical activity.

CONCLUSION

The hypothesis was rejected. In a dose-response manner, occupational physical activity increased the risk for LTSA, while leisure-time physical activity decreased the risk for LTSA. The findings indicate opposing effects of occupational and leisure-time physical activity on global health.

Protocol for shoulder function training reducing musculoskeletal pain in shoulder and neck: a randomized controlled trial

BACKGROUND

Neck and shoulder complaints are common among employees in sedentary occupations characterized by intensive computer use. Such musculoskeletal pain - which is often associated with restricted range of motion and loss of muscle strength - is one of the most common conditions treated by physical therapists. The exact mechanism of neck pain is rarely revealed by clinical examination and the treatment has varied from passive rest to active treatments. Active treatments have often been divided into either training of the painful area or the surrounding musculature avoiding direct training of the painful area. Our study investigates the effect of the latter approach.

METHODS/DESIGN

A randomized controlled trial of 10 weeks duration is currently being conducted. Employed office workers with severe neck-shoulder pain are randomized to 3 × 20 min shoulder function training with training supervision or to a reference group receiving advice to stay physically active. Shoulder function training primarily focuses on the serratus anterior and lower trapezius muscle with only minimal activation the upper trapezius.An announcement was sent to the administrative section of the university including jobs characterized by intensive computer work. The first 100 positive replies entered the study. Among these inclusion criteria were pain intensity in the neck/shoulder of at least 3 on a 0-9 scale. Exclusion criteria were cardiovascular disease, trauma, hypertension, or serious chronic disease. Before and after the intervention period the participants replied to a questionnaire about musculoskeletal disorders and work disability, and underwent a standardized clinical examination of the neck and shoulder girdle. Further, on a weekly basis the participants log pain intensity of the neck and shoulder during the previous week.The primary outcome measure is pain in the neck and shoulders at week 10 based on the weekly pain registration and results from the clinical examination. Secondary outcomes are strength and work disability.

TRIAL REGISTRATION

ClinicalTrials (NCT): NCT01205542.

Distribution of myogenic progenitor cells and myonuclei is altered in women with vs. those without chronically painful trapezius muscle

It is hypothesized that repeated recruitment of low-threshold motor units is an underlying cause of chronic pain in trapezius myalgia. This study investigated the distribution of satellite cells (SCs), myonuclei, and macrophages in muscle biopsies from the trapezius muscle of 42 women performing repetitive manual work, diagnosed with trapezius myalgia (MYA; 44 ± 8 yr; mean ± SD) and 20 matched healthy controls (CON; 45 ± 9 yr). Our hypothesis was that muscle of MYA, in particular type I fibers, would demonstrate higher numbers of SCs, myonuclei, and macrophages compared with CON. SCs were identified on muscle cross sections by combined immunohistochemical staining for Pax7, type I myosin, and laminin, allowing the number of SCs associated with type I and II fibers to be determined. We observed a pattern of SC distribution in MYA previously only reported for individuals above 70 yr of age. Compared with CON, MYA demonstrated 19% more SCs per fiber associated with type I fibers (MYA 0.098 ± 0.039 vs. CON 0.079 ± 0.031; P < 0.05) and 40% fewer SCs associated with type II fibers (MYA 0.047 ± 0.017 vs. CON 0.066 ± 0.035; P < 0.05). The finding of similar numbers of macrophages between the two groups was not in line with our hypothesis and suggests that the elevated SC content of MYA was not due to heightened inflammatory cell contents, but rather to provide new myonuclei. The findings of greater numbers of SCs in type I fibers of muscle subjected to repeated low-intensity work support our hypothesis and provide new insight into stimuli capable of regulating SC content.

Protocol for work place adjusted intelligent physical exercise reducing musculoskeletal pain in shoulder and neck (VIMS): a cluster randomized controlled trial

BACKGROUND

Neck and shoulder complaints are common among employees in sedentary occupations characterized by intensive computer use. Specific strength training is a promising type of physical exercise for relieving neck and shoulder pain in office workers. However, the optimal combination of frequency and exercise duration, as well as the importance of exercise supervision, is unknown. The VIMS study investigates in a cluster randomized controlled design the effectiveness of different time wise combinations of specific strength training with identical accumulated volume, and the relevance of training supervision for safe and effective training.

METHODS/DESIGN

A cluster randomized controlled trial of 20 weeks duration where employed office workers are randomized to 1 x 60 min, 3 x 20 min, 9 x 7 min per week of specific strength training with training supervision, to 3 x 20 min per week of specific strength training with a minimal amount of training supervision, or to a reference group without training. A questionnaire will be sent to 2000 employees in jobs characterized by intensive computer work. Employees with cardiovascular disease, trauma, hypertension, or serious chronic disease will be excluded. The main outcome measure is pain in the neck and shoulders at week 20.

TRIAL REGISTRATION

The trial is registered at ClinicalTrials.gov, number NCT01027390.

Worksite interventions for preventing physical deterioration among employees in job-groups with high physical work demands: background, design and conceptual model of FINALE

BACKGROUND

A mismatch between individual physical capacities and physical work demands enhance the risk for musculoskeletal disorders, poor work ability and sickness absence, termed physical deterioration. However, effective intervention strategies for preventing physical deterioration in job groups with high physical demands remains to be established. This paper describes the background, design and conceptual model of the FINALE programme, a framework for health promoting interventions at 4 Danish job groups (i.e. cleaners, health-care workers, construction workers and industrial workers) characterized by high physical work demands, musculoskeletal disorders, poor work ability and sickness absence.

METHODS/DESIGN

A novel approach of the FINALE programme is that the interventions, i.e. 3 randomized controlled trials (RCT) and 1 exploratory case-control study are tailored to the physical work demands, physical capacities and health profile of workers in each job-group. The RCT among cleaners, characterized by repetitive work tasks and musculoskeletal disorders, aims at making the cleaners less susceptible to musculoskeletal disorders by physical coordination training or cognitive behavioral theory based training (CBTr). Because health-care workers are reported to have high prevalence of overweight and heavy lifts, the aim of the RCT is long-term weight-loss by combined physical exercise training, CBTr and diet. Construction work, characterized by heavy lifting, pushing and pulling, the RCT aims at improving physical capacity and promoting musculoskeletal and cardiovascular health. At the industrial work-place characterized by repetitive work tasks, the intervention aims at reducing physical exertion and musculoskeletal disorders by combined physical exercise training, CBTr and participatory ergonomics. The overall aim of the FINALE programme is to improve the safety margin between individual resources (i.e. physical capacities, and cognitive and behavioral skills) and physical work demands, and thereby reduce the physical deterioration in a long term perspective by interventions tailored for each respective job-group.

DISCUSSION

The FINALE programme has the potential to provide evidence-based knowledge of significant importance for public health policy and health promotion strategies for employees at high risk for physical deterioration.

TRIAL REGISTRATIONS

ISRCTN96241850, NCT01015716 and NCT01007669.

Systematic evaluation of observational methods assessing biomechanical exposures at work

OBJECTIVES

This systematic review aimed to identify published observational methods assessing biomechanical exposures in occupational settings and evaluate them with reference to the needs of different users.

METHODS

We searched scientific databases and the internet for material from 1965 to September 2008. Methods were included if they were primarily based on the systematic observation of work, the observation target was the human body, and the method was clearly described in the literature. A systematic evaluation procedure was developed to assess concurrent and predictive validity, repeatability, and aspects related to utility. At least two evaluators independently carried out this evaluation.

RESULTS

We identified 30 eligible observational methods. Of these, 19 had been compared with some other method(s), varying from expert evaluation to data obtained from video recordings or through the use of technical instruments. Generally, the observations showed moderate to good agreement with the corresponding assessments made from video recordings; agreement was the best for large-scale body postures and work actions. Postures of wrist and hand as well as trunk rotation seemed to be more difficult to observe correctly. Intra- and inter-observer repeatability were reported for 7 and 17 methods, respectively, and were judged mostly to be good or moderate.

CONCLUSIONS

With training, observers can reach consistent results on clearly visible body postures and work activities. Many observational tools exist, but none evaluated in this study appeared to be generally superior. When selecting a method, users should define their needs and assess how results will influence decision-making.

Muscle oxygenation and glycolysis in females with trapezius myalgia during stress and repetitive work using microdialysis and NIRS

The aim of this investigation was to study female workers active in the labour market for differences between those with trapezius myalgia (MYA) and without (CON) during repetitive pegboard (PEG) and stress (STR) tasks regarding (1) relative muscle load, (2) trapezius muscle blood flow, (3) metabolite accumulation, (4) oxygenation, and (5) pain development. Among 812 female employees (age 30-60 years) at 7 companies with high prevalence of neck/shoulder complaints, clinical examination identified 43 MYA and 19 CON. At rest, during PEG, and STR the trapezius muscle was measured using (1) EMG and MMG, (2) microdialysis, and (3) NIRS. Further, subjective pain ratings were scored (VAS). EMGrms in %MVE (Maximal Voluntary EMG-activity), was significantly higher among MYA than CON during PEG (11.74 +/- 9.09 vs. 7.42 +/- 5.56%MVE) and STR (5.47 +/- 5.00 vs. 3.28 +/- 1.94%MVE). MANOVA showed a group and time effect regarding data from the microdialysis: for MYA versus CON group differences demonstrated lower muscle blood flow and higher lactate and pyruvate concentrations. Potassium and glucose only showed time effects. NIRS showed similar initial decreases in oxygenation with PEG in both groups, but only in CON a significant increase back to baseline during PEG. VAS score at rest was highest among MYA and increased during PEG, but not for CON. The results showed significant differences between CON and MYA regarding muscle metabolism at rest and with PEG and STR. Higher relative muscle load during PEG and STR, insufficient muscle blood flow and oxygenation may account for the higher lactate, pyruvate and pain responses among MYA versus CON.

Effect of contrasting physical exercise interventions on rapid force capacity of chronically painful muscles

Rapid force capacity of chronically painful muscles is inhibited markedly more than maximal force capacity and is therefore relevant to assess in rehabilitation settings. Our objective was to investigate the effect of two contrasting types of physical exercise on rapid force capacity, as well as neural and muscular adaptations in women with chronic neck muscle pain. A group of employed women ( n = 42) with a clinical diagnosis of trapezius myalgia participated in a 10-wk randomized controlled trial; specific strength training of the neck/shoulder muscles, general fitness training performed as leg-bicycling; or a reference intervention without physical activity. Maximal voluntary shoulder abductions were performed at static angles of 35° and 115° with simultaneous recording of electromyography (EMG) in the trapezius and deltoid. Maximal muscle strength and activation (peak torque and peak EMG) as well as rapid muscle strength and activation [rate of torque development (RTD) and rate of EMG rise] were subsequently determined. Trapezius muscle fiber characteristics were determined with ATPase histochemistry. Significant changes were observed only in the specific strength training group. Whereas peak torque increased 18–29% ( P < 0.01), RTD increased 61–115% ( P < 0.001). Peak EMG and rate of EMG rise increased correspondingly ( P < 0.05–0.001), and trapezius type II muscle fibers hypertrophied 20% ( P < 0.001). In conclusion, rapid force capacity of chronically painful muscles is highly responsive to rehabilitation with specific strength training. The underlying mechanisms were related to both pain reduction and general neuromuscular adaptations to strength training. Potentially, the present method can be a useful clinical screening tool of muscle function in rehabilitation settings.

Effect of physical training on function of chronically painful muscles: a randomized controlled trial

Pain and tenderness of the upper trapezius muscle is frequent in several occupational groups. The objective of this study is to investigate the effect of three contrasting interventions on muscle function and pain in women with trapezius myalgia. A group of employed women ( n = 42) with a clinical diagnosis of trapezius myalgia participated in a 10-wk randomized controlled intervention: specific strength training of the neck/shoulder muscles, general fitness training performed as leg bicycling, or a reference intervention without physical activity. Torque and electromyography (EMG) were recorded during maximal shoulder abductions in an isokinetic dynamometer at −60, 60, 0, and 180°/s. Furthermore, a submaximal reference contraction with only the load of the arms was performed. Significant changes were observed only in the specific strength training group. Pain decreased by 42–49% ( P < 0.01–0.05). Whereas the EMG activity of the unaffected deltoid remained unchanged during the maximal contractions, an increase in EMG amplitude (42–86%; P < 0.001–0.05) and median power frequency (19%; P < 0.001) were observed for the painful trapezius muscle. Correspondingly, torque increased by 18–53% ( P < 0.001–0.05). EMG during the reference contraction decreased significantly for both the trapezius and deltoid muscles ( P < 0.01). In conclusion, specific strength training relieves pain and increases maximal activity specifically of the painful trapezius muscle, leading to increased shoulder abduction strength in women with trapezius myalgia. Furthermore, decreased relative workload may indirectly augment pain reduction.

Responses of algesic and metabolic substances to 8 h of repetitive manual work in myalgic human trapezius muscle

The trapezius muscle often develops pain as the result of repetitive and stressful work tasks although it is unclear to what extent this pain is due to alterations in muscle concentrations of algesic/nociceptive substances. Twenty women with chronic neck- and shoulder pain (TM) whose work required highly repetitive work tasks and 20 pain-free female colleagues (CON) were studied during and after a full 8-hour workday. We collected microdialysates from their dominant/most painful trapezius muscle; concentrations of serotonin, glutamate, lactate, pyruvate, potassium, bradykinin, and cytokines and blood flow were determined. In addition, we measured surface electromyogram, task exposure level, pain intensity, perceived mental stress, and urine-cortisol. In connection to the clinical neck and shoulder examination, we determined pressure pain thresholds (PPTs) over the trapezius and tibialis muscles. TM had higher concentrations of glutamate (71+/-42 vs. 36+/-15 micromol l(-1)) and pyruvate (187+/-89 vs. 125+/-63 micromol l(-1)) than CON. Interstitial serotonin was higher in TM (before work: 10.6+/-10.8 vs. 2.2+/-1.2 nM; after work: 9.2+/-8.3 vs. 1.5+/-2.9 nM). The trapezius blood flow during the working day was higher in TM than in CON. TM had lower PPT and higher pain intensity throughout the working day. No differences in EMG, task exposure level, mental stress, or urine-cortisol in the groups were found. These findings support the idea that peripheral nociceptive processes are activated in occupationally active subjects, who are diagnosed with trapezius myalgia. In contrast, no sign of low blood flow or increased stress or muscle activity markers were found in TM.

One-year randomized controlled trial with different physical-activity programs to reduce musculoskeletal symptoms in the neck and shoulders among office workers

OBJECTIVES

This study evaluates the effect of two different worksite physical-activity interventions on neck-shoulder symptoms, together with perceived work ability and sick leave among office workers.

METHODS

An examiner-blinded randomized controlled trial was conducted with 549 office workers allocated to one of three intervention groups: one with specific resistance training (SRT) of the neck-shoulder region (N=180), one with all-round physical exercise (APE) (N=187), and one which acted as a reference group, which was informed about general health-promoting activities but did not include a physical activity program (N=182). Questionnaires were filled out at baseline and after 1 year of training.

RESULTS

The duration and intensity of neck and shoulder symptoms was lower after the specified worksite physical-activity interventions than in the reference group. On an intervention group level, SRT was not more effective than APE in reducing the duration and intensity of neck and shoulder symptoms. However, those asymptomatic at baseline had a significant lower prevalence of neck-shoulder symptoms at follow-up when allocated to the SRT group than placed in the APE group or reference group. At baseline the work ability index (WAI) was close to 90% of the maximum score, and the mean sick leave was 5 days per year, both being unaffected by the interventions.

CONCLUSIONS

Different physical-activity interventions were successful in reducing neck-shoulder symptoms, and SRT was superior to APE in the primary prevention of such symptoms. The initially relatively high WAI was the most probable reason for no further increase in WAI. Likewise the mean sick leave the year before the intervention was very low, and it was probably not possible to reduce it further.

Increased proportion of megafibers in chronically painful muscles

Trapezius myalgia - chronic pain from the upper trapezius muscle - is frequent in female employees in monotonous stressful jobs, potentially due to chronic overload of type I muscle fibers. In this study, we investigated the intra-individual distribution of trapezius muscle fiber size, and hypothesized that females with myalgia compared with matched healthy controls have a higher percentage of grossly hypertrophied type I fibers with poor capillarization. Forty-two female office workers with trapezius myalgia (MYA) and 20 healthy matched controls (CON) participated in the study. Standard histochemical methods were used to determine fiber size, fiber type, and capillarization. Type I megafiber were defined as at least twice the size of the median type I fiber size of each individual. The main finding was that MYA had a significantly higher proportion of type I megafibers than CON, in spite of no significant difference in overall type I fiber size. In MYA and CON type I megafibers were located in 46% and 11% of the females, respectively. Capillarization of the overall type I fiber pool was not different between CON and MYA, but was significantly lower in type I megafibers of both groups. The percentage of megafibers was positively related to age and weekly working hours, indicating an effect of long-term exposure. In conclusion, this study shows that trapezius myalgia is associated with a significantly higher percentage of grossly hypertrophied type I muscle fibers with poor capillarization - type I megafibers.

Selective activation of neuromuscular compartments within the human trapezius muscle

Task-dependent differences in relative activity between "functional" subdivisions within human muscles are well documented. Contrary, independent voluntary control of anatomical subdivisions, termed neuromuscular compartments is not observed in human muscles. Therefore, the main aim of this study was to investigate whether subdivisions within the human trapezius can be independently activated by voluntary command using biofeedback guidance. Bipolar electromyographical electrodes were situated on four subdivisions of the trapezius muscle. The threshold for "active" and "rest" for each subdivision was set to >12% and <1.5% of the maximal electromyographical amplitude recorded during a maximal voluntary contraction. After 1h with biofeedback from each of the four trapezius subdivisions, 11 of 15 subjects learned selective activation of at least one of the four anatomical subdivisions of the trapezius muscle. All subjects managed to voluntarily activate the lower subdivisions independently from the upper subdivisions. Half of the subjects succeeded to voluntarily activate both upper subdivisions independently from the two lower subdivisions. These findings show that anatomical subdivisions of the human trapezius muscle can be independently activated by voluntary command, indicating neuromuscular compartmentalization of the trapezius muscle. The independent activation of the upper and lower subdivisions of the trapezius is in accordance with the selective innervation by the fine cranial and main branch of the accessory nerve to the upper and lower subdivisions. These findings provide new insight into motor control characteristics, learning possibilities, and function of the clinically relevant human trapezius muscle.

Effect of two contrasting types of physical exercise on chronic neck muscle pain

OBJECTIVE

The prevalence of neck muscle pain has steadily increased and especially pain from the descending part of the trapezius muscle has been associated with monotonous work tasks such as computer work. Physical exercise is generally recommended as treatment, but it is unclear which type of training is most effective. Our objective was to determine the effectiveness of specific strength training of the painful muscle versus general fitness training without direct involvement of the painful muscle (leg bicycling) on work-related neck muscle pain.

METHODS

We conducted a randomized controlled trial and recruited subjects from 7 workplaces characterized by monotonous jobs (e.g., computer-intensive work). Forty-eight employed women with chronic neck muscle pain (defined as a clinical diagnosis of trapezius myalgia) were randomly assigned to 10 weeks of specific strength training locally for the affected muscle, general fitness training performed as leg bicycling with relaxed shoulders, or a reference intervention without physical activity. The main outcome measure was an acute and prolonged change in intensity of neck muscle pain (100-mm visual analog scale [VAS]).

RESULTS

A decrease of 35 mm (approximately 79%; P<0.001) in the worst VAS pain score over a 10-week period was seen with specific strength training, whereas an acute and transient decrease in pain (5 mm; P<0.05) was found with general fitness training.

CONCLUSION

Specific strength training had high clinical relevance and led to marked prolonged relief in neck muscle pain. General fitness training showed only a small yet statistically significant acute pain reduction.

Voluntary activation of trapezius measured with twitch interpolation

This study investigated the feasibility of measuring voluntary activation of the trapezius muscle with twitch interpolation. Subjects (n=8) lifted the right shoulder or both shoulders against fixed force transducers. Stimulation of the accessory nerve in the neck was used to evoke maximal twitches in right trapezius. The twitch-like increments in force (superimposed twitches) evoked during different strength voluntary contractions were linearly related to voluntary force (r=-0.82 to -0.99). Hence, voluntary activation could be quantified by twitch interpolation with this stimulus. Comparison of unilateral and bilateral MVCs showed that maximal voluntary force was greater in unilateral than bilateral efforts (92.7+/-2.9% and 82.3+/-5.8% MVC, respectively) but voluntary activation was similar (88.6+/-9.6% and 91.7+/-5.2%). Trapezius is commonly affected in work-related musculoskeletal disorders. Measurement of voluntary activation will be a useful technique to demonstrate whether the reduced maximal voluntary force reported in such disorders is due to muscular or neural factors.

Trapezius muscle rest time during standardised computer work – A comparison of female computer users with and without self-reported neck/shoulder complaints

Work related musculoskeletal disorders (WMSDs) in the shoulder/neck area are a common and increasing problem among European computer workers, especially women. Long-term low-level workloads with low degree of muscle rest are a potential risk factor for developing WMSDs. The purpose of the present study of female computer users (age 45-65 years) in Denmark and Sweden was to investigate if subjects with self-reported neck/shoulder complaints (cases, N=35) show less trapezius muscle relative rest time (RRT) than controls (N=44) when performing standardised short-term computer work tasks in controlled laboratory conditions. Surface electromyography (EMG) signals were recorded bilaterally from the upper trapezius muscles during a type, edit, precision and colour word stress task. Besides RRT, 10th percentile RMS values were calculated. On the average, 15 of the cases and 18 of the controls showed analysable EMG files per task. For the colour word stress task, the results showed lower RRT values and higher 10th percentile RMS amplitude levels among cases compared to controls. No such signs could be found for the other tasks performed. The present results indicate an increased motor response to a psychological stressor among subjects with self-reported neck/shoulder complaints.

Diagnostic distribution of non-traumatic upper limb disorders: vibrotactile sense in the evaluation of structured examination for optimal diagnostic criteria

BACKGROUND

Upper limb disorders (ULDs) are common, and so are the difficulties in specific diagnoses of these disorders. Prior studies have shed light on the nerves in the diagnostic approach beside disorders related to muscles, tendons and joints (MCDs).

OBJECTIVE

The study aimed to compare the distribution of upper limb disorders, and the vibration perception threshold (VPT) in different diagnostic groups according to 1) A-criteria: the SALTSA consensus criteria, including MCDs and four peripheral neuropathies, and 2) B-criteria: including MCDs and 10 different neuropathy diagnoses--re-defined in an attempt to refine diagnostic criteria of peripheral neuropathy in respect of different MCDs; and further to discuss the impact of the presented criteria.

METHODS

161 patients--recruited from 21 general practitioners--were examined by the same examiner according to the two sets of diagnostic criteria. VPT measurements were conducted in all patients.

RESULTS

Three patients did not fulfill the criteria of any ULD diagnosis. A/B criteria were fulfilled for 181/183 upper limbs, respectively, out of which 29.3%/163.3% were neuropathy diagnoses alone, 23.8%/10.9% MCD alone, and 46.9%/25.7% were categorized as neuropathy in combination with MCD diagnoses. The overall agreement on presence of neuropathy was high (75%), but on focal level there was a large discrepancy. According to the A-criteria, patients with symptoms located at wrist and shoulder were primarily defined with wrist diagnoses, and only few had concomitant shoulder diagnoses. In contrast, the B-criteria primarily defined neuropathy located at the shoulder, often concomitantly with neuropathy of the radial and the median nerve at the elbow, but seldom at the wrist level. In MCDs defined by both sets of criteria--Rotator cuff syndrome and medial/lateral epicondylitis--the A-criteria defined more MCDs than the B-criteria, the B diagnoses typically constituted only a part of the A diagnoses and additionally defined neuropathy. The B-criteria showed more significant VPT findings than the A-criteria concerning the discrimination between limbs with and contralateral limbs without diagnoses as well as between diagnostic groups with and without neuropathy.

CONCLUSIONS

The VPT findings suggest the B-criteria to be superior to A-criteria for differentiating between patients with and without neuropathy. This study shows that neuropathy is extensive in ULDs when specific diagnostic criteria are used. Additionally it suggests the importance of a critical revision of the current diagnostic criteria of upper limb neuropathy, and the differential diagnoses concerning the MCDs. Management and prevention is highly dependent on correct diagnoses.

Eye blink frequency during different computer tasks quantified by electrooculography

The purpose of the study was to evaluate electrooculography (EOG) as an automatic method to measure the human eye blink frequency (BF) during passive and interactive computer tasks performed at two screen heights. Ten healthy subjects (5 males and 5 females) participated in the study in a 23 degrees C temperature and 30-35% relative humidity controlled simulated office environment. Each test subject completed a 2 x 10 min active task of computer work and a 3 x 10 min passive task of watching a film on a video display unit (VDU). Both tasks included two viewing angles: standard (the monitors' upper edge was in the same height as the subjects' eyes) and low (lowered by 25 degrees). EOG signals were recorded with two Ag/AgCl surface electrodes positioned above and below the right eye, and a reference electrode was placed behind the ear. The experiments were video filmed, and eye blinks were counted manually from the video recordings and compared to the EOG measurements. The method showed a high validity to detect blinks during computer work: 95.4% of the blinks were retrieved by the EOG method and very few artefacts from eye movements were erroneously classified as eye blinks (2.4%). By use of the EOG method, the computer task was found to significantly decrease the BF by 69% compared to the passive task (P < 0.001), and a small decrease (12-14%) was found by lowering the viewing angle by 25 degrees.

Effects of electromyographic and mechanomyographic biofeedback on upper trapezius muscle activity during standardized computer work

The purpose of this laboratory study was to investigate the effects of surface electromyography (EMG)- and mechanomyography (MMG)-based audio and visual biofeedback during computer work. Standardized computer work was performed for 3 min with/without time constraint and biofeedback in a randomized order. Biofeedback was given on the basis of an individual preset threshold value for the right trapezius EMG and MMG signal and a time factor (repetition of events above the threshold). The duration of muscle activity above the preset threshold, the right trapezius EMG and MMG root mean square (RMS) values as well as the work performance in terms of number of completed graph/mouse clicks/errors, the rating of perceived exertion (RPE) and the usefulness of the biofeedback were assessed. The duration of muscle activity above the threshold was significantly lower with MMG compared with EMG as source of biofeedback (p < 0.05). Biofeedback led to a significant decrease in the right trapezius EMG RMS, lower RPE and decreased number of errors and mouse clicks, but also decreased number of completed graphs (p < 0.05). Audio and visual biofeedbacks were as effective. MMG-based biofeedback is a potential reliable alternative to EMG in ergonomics. A lowering of the trapezius muscle activity may contribute to diminish the risk of work related musculoskeletal disorders development.

[Prevention of and action on low back pain]

Prevention of low back pain involves action from both the healthcare system and the occupational system. These systems are essentially diverse and optimum solution of the problem relies on collaboration. The focus of this paper is on the occupational system, where summarised documentation--in spite of scientific uncertainty--in general supports the occupational health actions taken in Denmark. Furthermore, the paper points towards increased physically active lifestyle as a preventive action.

Relationship between efficiency and pedal rate in cycling: significance of internal power and muscle fiber type composition

Cycling was performed to test the following two hypotheses: (1) muscular efficiency is unrelated to pedal rate (61, 88, and 115 r.p.m.) for a group of subjects with a wide range of slow twitch (ST) fibers in spite of decreasing whole-body efficiency and (2) muscular efficiency correlates positively with % ST muscle fibers, and this correlation is more pronounced at low pedal rates than at high pedal rates. Whole-body gross efficiency decreased from 20-22% at 61 r.p.m. to 15-18% at 115 r.p.m. Mean muscular efficiency for all subjects (n=16) was approximately 26%, with delta efficiency being constant and muscular efficiency (taking internal power into account) slightly increasing with pedal rate. Muscular efficiency correlated positively (R(2)=0.25) with % ST fibers (21-97% ST in m. vastus lateralis) at 115 r.p.m. while not at 61 and 88 r.p.m. In conclusion, the decrease in whole-body gross efficiency with increasing pedal rate was not explained by a decrease in muscular efficiency, and supported increase in internal power to account for the increase in metabolic power with increasing pedal rate. Furthermore, differences between individuals in muscle fiber type composition affected muscular efficiency, which correlated positively with % ST muscle fibers during fast pedalling.

Vibrotactile sense in patients with different upper limb disorders compared with a control group

BACKGROUND

Upper limb disorders (ULDs) are common, and so are the difficulties with regard to their specific diagnoses. According to diagnostic consensus criteria, specific diagnoses include neuropathy and muscular- and connective-tissue disorders (MCDs). There is a need for valid objective diagnostic tools to reveal underlying mechanisms for specific diagnoses.

OBJECTIVE

To investigate the possible differences in vibration perception threshold (VPT) and tolerance to suprathreshold stimulation (STS) between controls and specific diagnostic ULD patient groups with uni- and bilateral neuropathy and/or MCD.

METHODS

In 161 ULD patients and 40 controls, the VPT of the median, ulnar, and radial nerves innervating the hand was examined by vibrometry using the "method of limits". The tolerance to STS of the anterior forearm was tested in 128 of the patients and all controls.

RESULTS

The ULD patients in all diagnostic groups had significantly higher VPT (P<0.05) in all the nerves in limbs, with and without diagnoses compared with controls. Only patient groups defined with neuropathy demonstrated significantly higher VPT in the limb with diagnoses compared with the contralateral limb without diagnoses. The highest VPTs were found in the patient group with unilateral neuropathy and MCD, and for the radial nerve, VPT was significantly higher than that for patients with unilateral MCD alone. These findings were confirmed by almost similar findings in STS responses.

CONCLUSIONS

The ULD patients generally demonstrated increased VPT compared with controls, indicating a neurogenous component independent of specific ULD diagnosis. Contralateral significant findings in limbs without diagnoses compared with controls indicate central neurogenous affection and/or the possibility of certain exposures elevating VPT before a positive status of a limb diagnosis is attained. Significantly higher VPT values in limbs with neuropathy diagnoses compared with limbs without and not in MCD alone, may indicate peripheral sensibilization or nerve affection only in the group with a specific diagnosis of neuropathy. These findings underline the importance of specific diagnoses among ULD patients.