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[Proposal of a concise index for the evaluation of the exposure to repetitive movements of the upper extremity (OCRA index)].

In the light of data and speculation contained in the literature, and based on procedures illustrated in a previous research project in which the authors describe and evaluate occupational risk factors associated with work-related musculoskeletal disorders of the upper limbs (WMSDs), this article proposes a method for calculating a concise index of exposure to repetitive movements of the upper limbs. The proposal, which still has to be substantiated and validated by further studies and applications, is conceptually based on the procedure recommended by the NIOSH for calculating the Lifting Index in manual load handling activities. The concise exposure index (OCRA index) in this case is based on the relationship between the daily number of actions actually performed by the upper limbs in repetitive tasks, and the corresponding number of recommended actions. The latter are calculated on the basis of a constant (30 actions per minute) which represents the action frequency factor, and is valid-hypothetically-under so-called optimal conditions; the constant is diminished case by case (using appropriate factors) as a function of the presence and characteristics of the other risk factors (force, posture, complementary elements, recovery periods). Although still experimental, the exposure index can be used to obtain an integrated and concise assessment of the various risk factors analysed, and to classify occupational scenarios featuring significant and diversified exposure to such risk factors.

Analysis of Variance↗

Electromyographic study of overuse syndromes in sign language interpreters.

Sign language is the fourth most common language in the United States; this mode of communication involves sustained, repetitive use of the hand, wrist, and arm. Signers, therefore, are at risk of overuse disorders as carpal tunnel syndrome (CTS) and ulnar neuritis (UL). Using electrodiagnostic methods, the prevalence of hand nerve entrapments in signers was investigated. Thirty-three signers, six of whom were deaf, were compared to 21 age-matched controls (mean age = 31 and 29 years; respectively). Demographics were obtained by questionnaire. Physical examination and nerve conduction studies followed; 78 hands were examined. No significant mean differences in median motor or sensory latencies discriminated signers from controls. Although no signer's median SNAP latency was greater than 2 SDs from controls, some signers could be considered "abnormal" by other published criteria (eg, median/ulnar mid-palmer comparisons). Using these, 10 of 33 signers had mild abnormalities, five suggestive of CTS, three of UL, and two of both; of controls, two had CTS and two UL. The ratio of electrodiagnostic abnormalities did not differentiate the two groups (p > .05). Reports of hand and/or wrist pain were extremely high in interpreters (nondeaf signers) and were linked to EMG findings (p < .05). Deaf signers, even those with ED findings consistent with CTS, all reported no symptoms, possibly because their signing is less stressful or learned at an earlier age.

Carpal Tunnel Syndrome↗

Rat model of Achilles tendon disorder. A pilot study.

Three-month-old male rats were subjected 3 times weekly for 1 h to eccentric exercise of one triceps surae muscle (30 stimulations/min) under general anesthesia in order to induce Achilles tendon disorder corresponding to paratenonitis and tendinosis in man. Net muscle work during the sessions ranged between 0.67 and 4.37 mJ (mean 1.72, SD 0.77). After 9 and 13 sessions, respectively, 2 rats started to show gait alterations during the functional test which was performed 2-3 times weekly. These rats were killed after additional sessions which showed a worsening of the limp. The other trained rats and controls did not limp and were killed after 7-11 weeks. Histologic evaluation of the Achilles tendons from the exercised limb showed in the majority of the cases hypervascularization, increased number of nerve filaments and increased immunoreactivity for substance P and calcitonin gene-related peptide. The tendons from the nonstimulated limb looked normal. The distribution of collagen types I and II appeared normal in the tendon and its insertion to the calcaneus. Inflammation of the epi- and paratenon could be provoked in the rat, but tendon changes corresponding to chronic tendinosis did not develop within 11 weeks with the used training regime. The clinical relevance of this model for chronic tendon disease needs to be evaluated further.

Achilles Tendon↗

Interindividual variation of physical load in a work task.

OBJECTIVES: This study analyzed the variation in physical work load among subjects performing an identical work task. METHODS: Electromyographs from the trapezius and infraspinatus muscles and wrist movements were recorded bilaterally from 49 women during a highly repetitive industrial work task. An interview and a physical examination were used to define 12 potential explanatory factors, namely, age, anthropometric measures, muscle strength, work stress, and musculoskeletal disorders. RESULTS: For the electromyographs, the means of the 10th percentiles were 2.2% and 2.8% of the maximal voluntary electrical activity (%MVE) for the trapezius and infraspinatus muscles, respectively. However, the interindividual variations were very large [coefficients of variation (CV) 0.75 and 0.62, respectively]. Most of the variance could not be explained; only height, strength, and coactivation of the 2 muscles contributed significantly (R2(adj)0.20-0.52). The variation was still large, though smaller (CV < or =0.63), for values normalized to relative voluntary electrical activity (RVE). For the wrist movements, the median velocity was 29 degrees per second, and the interindividual variations were small (CV < or =0.24). Six factors contributed to the explained variance (R2(adj)0.12-0.55). CONCLUSIONS: The interindividual variation is small for wrist movements when the same work tasks are performed. In contrast, the electromyographic variation is large, even though less after RVE normalization, which reduces the influence of strength, than when MVE is used. Because of these variations, several electromyographs are needed to characterize the exposure of a specific work task in terms of muscular load, and individual electromyographs are preferable when the worker' s risk of myalgia is being studied.

Adult↗

A comparison of symptomatic and asymptomatic office workers performing monotonous keyboard work--1: neck and shoulder muscle recruitment patterns.

Work-related neck and upper limb disorders (WRNULD) are common problems among office workers who use computers intensively and maintain prolonged static postures. These disorders have often been attributed to result from sustained muscle activity in the neck-shoulder musculature. The present study examined whether symptomatic subjects exhibited the same muscle activity patterns as asymptomatic controls when they performed a prolonged computer task under the same conditions. Surface electromyography (EMG) of four major neck-shoulder muscles were compared between a Case Group (n=23) and a Control Group (n=20) of female office workers. The Case Group had higher activity in the right upper trapezius (UT) while the Control Group had more symmetrical muscle activity between left and right UT. The Case subjects could also be differentiated into "High Discomfort" and "Low Discomfort" sub-groups based on their discomfort scores. The High Discomfort Group had significantly higher right UT activity compared to the Low Discomfort and Control Groups. Results suggested that symptomatic individuals had altered muscle recruitment patterns that persisted throughout the sustained occupational task, while discomfort increased with time-at-task. These findings indicate that altered muscle recruitment patterns observed in the symptomatic subjects preceded the onset of task discomfort, and this finding may have important implications for the etiology of WRNULD.

Adult↗

Effects of ergonomic intervention in work with video display units.

OBJECTIVES: This study evaluated the effect of an intensive ergonomic approach and education on workstation changes and musculoskeletal disorders among workers who used a video display unit (VDU). METHODS: A randomized controlled design was used. The subjects (N=124) were allocated into three groups (intensive ergonomics, ergonomic education, reference) using stratified random sampling. The evaluation involved questionnaires, a diary of discomfort, measurements of workload, and an ergonomic rating of the workstations. The assessments were made 2 weeks before the intervention and after 2 and 10 months of follow-up. RESULTS: The intensive and training groups showed less musculoskeletal discomfort than the reference group after 2 months of follow-up. Positive effects on discomfort were seen primarily for the shoulder, neck, and upper back areas. No significant differences were found for the strain levels or prevalence of pain. After the intervention the ergonomic level was distinctly higher in the intensive ergonomic group than in the education or reference group. CONCLUSIONS: Both the intensive ergonomics approach and education in ergonomics help reduce discomfort in VDU work. In attempts to improve the physical ergonomics of VDU workstations, the best result will be achieved with cooperative planning in which both workers and practitioners are actively involved.

Adult↗

Ache, pain, and discomfort: the reward for working with many cows and sows?

The main purpose of the study was to investigate the prevalence of perceived symptoms of musculoskeletal disorders (MSD) among workers on large-scale dairy and pig farms in Sweden (herd size more than 300 cows and 450 sows) and to identify potential risk factors in the development of MSD. A study based on questionnaires was carried out among 42 workers on 10 large dairy farms and among 37 workers on 10 large pig farms in Southern Sweden during the autumn of 2002. Most importantly, the study showed that 86% of the dairy workers and 78% of the pig workers reported some kind of MSD during a period of 12 months prior to the study. The most frequently reported MSD among both the dairy and the pig workers were in the "upper extremities" (52% and 62%, respectively) especially in the shoulders and in "the back" (60% and 57%, respectively) especially in the lower back. Furthermore, being of short stature, doing repetitive work, working in awkward positions and being exposed to dust were significant risk factors in having MSD among the workers in this study. Thus, working with many cows and sows on large-scale farms in Sweden can be considered as a high risk job with regard to MSD.

Adult↗

[Guitarist's cramp: management with sensory re-education].

INTRODUCTION: Dystonia is defined as a sustained co-contraction of agonistic and antagonistic muscles that can cause twisting, twitching and abnormal postures. Occupational dystonias are included in a special group of pathologies that are secondary to a repeated effort related to the professional activity carried out by the sufferer, as can occur in guitarists, violinists and trumpet players, for example. Its pathophysiology includes descriptions of disorders affecting the peripheral and central nervous systems. Studies conducted in monkeys have shown that, through sensory stimulation, repeated movements can give rise to central anomalies in the somatosensory cortex, with growth of the receptive fields that are stimulated and deformation of the separations between those fields. CASE REPORT: We describe the case of a professional guitarist with a seven-year history of symptoms. A neurological examination revealed a co-contraction in the right hand that triggered the extension of the index and little fingers, which made it difficult for him to play his instrument. The patient was submitted to sensory re-education therapy with the use of a splint and a two-month routine of exercises. The response was evaluated using a subjective scale of the patient's symptoms and measurements of the maximum angles of flexion and extension of the affected fingers. Both methods reduced the patient's discomfort and allowed him to exhibit greater skill when playing the guitar. CONCLUSIONS: Occupational dystonias produced by repeated stimulation present alterations in the sensory region of the cortex, with the involvement of motor performance that improves with sensory re-education therapy.

Adult↗

Clinical disorders and pressure-pain threshold of the forearm and hand among automobile assembly line workers.

The prevalence of forearm and hand disorders was examined by questionnaire and clinical examination in 199 automobile assembly line workers and in 186 controls. The pressure-pain threshold, hand grip force and hand anthropometry were also studied. There was an increased prevalence of de Quervain's disease for male automobile assembly line workers, and of carpal tunnel syndrome in female workers. The prevalence of symptoms in the forearm and hand during the last 7 days were twice as high among automobile assembly line workers than controls for both men and women. The occurrence of symptoms in the last 7 days was associated with de Quervain's disease, carpal tunnel syndrome and sick-leave due to forearm or hand problems, and it also influenced activities of daily living. Hand grip strength and anthropometrics were not associated with findings in the clinical examination or the occurrence of symptoms in the last 7 days. Low pressure-pain threshold was not associated with findings in the clinical examination, except for reported occurrence of symptoms in the last 7 days for women. Pressure-pain threshold as an indicator of tissue damage is discussed.

Adolescent↗

Load pattern and pressure pain threshold in the upper trapezius muscle and psychosocial factors in medical secretaries with and without shoulder/neck disorders.

OBJECT: A current hypothesis for the genesis of muscular complaints in the shoulder/neck region postulates that short periods with a completely relaxed muscle are essential to avoid complaints. Another hypothesis is that these disorders are related to psychosocial conditions at work. In order to test these hypotheses, 23 medical secretaries were investigated. METHODS: The load pattern during work in the upper trapezius muscle bilaterally was assessed with electromyographic (EMG) technique and exposure variation analysis (EVA). In addition, pressure pain threshold (PPT) was measured on the trapezius muscle bilaterally and on the sternum. Psychosocial conditions at work were assessed with a questionnaire. RESULTS: The medical secretaries with complaints had significantly fewer episodes with totally or close to totally relaxed muscle compared with the healthy group. The group with complaints tended to have a more monotonous load pattern at low levels (approx. 1%-5% maximum voluntary contraction) while the healthy group had more frequent pauses but also somewhat more frequent short load peaks. The group with complaints showed lower PPT readings compared with the healthy group. However, the whole group had considerably lower PPTs than is usually reported in the literature. Of the 12 questions in the psychosocial questionnaire only one regarding work task satisfaction showed a significant difference between the two groups. CONCLUSION: Support is found for hypothesis that secretaries without complaints have more frequent episodes with totally relaxed muscle. A significant difference is found regarding work task satisfaction.

Adult↗

Measurement properties of a self-report index of ergonomic exposures for use in an office work environment.

Office work-related upper extremity symptoms and disorders have been associated with static work posture, repetition, and inadequate recovery in the anatomic structures of the neck and upper extremities. Despite these associations, relatively little research has been conducted on the development of practical measures of these ergonomic exposures. The present study examines the measurement properties of an upper-extremity-specific self-report index of ergonomic exposures. Ninety-two symptomatic office workers completed a Web-based questionnaire measuring demographic variables, ergonomic exposures, pain, job stress, and functional limitations. Comparisons of internal consistency, construct validity, and discriminative and predictive abilities were made between the self-report index and an observational exposure assessment checklist. Results indicated that the self-report index had acceptable measurement properties. Furthermore, higher levels of self-reported ergonomic exposures were associated with upper extremity pain, symptom severity, and functional limitations. In contrast, higher levels of observed exposure were related only to lower levels of general physical function. The self-report measure has potential for use in occupational health surveillance programs for office work environments and as an outcome measure of ergonomic exposure in intervention trials. These results also suggest the need for using multiple methods when assessing ergonomic exposures.

Adult↗

Anthropometric dimensions and overuse injury among Australian keyboard operators.

This study was instigated to examine the relationship between overuse injury and anthropometric dimensions of Australian keyboard operators to investigate the possibility that a poor anthropometric fit of the workstation may result in greater incidence of such disorders. There were no differences between the anthropometric dimensions of sufferers and nonsufferers of overuse injury among the male keyboard operators. Among men in this study, stature and several other anthropometric dimensions as a proportion of stature were similar to those of North American and European populations for which equipment used in Australia is designed. In contrast, among women, significant differences were evident between sufferers and nonsufferers. The sufferers had greater hip widths and seat breadths, and a greater proportion were overweight (body mass greater than 26). There was also a tendency for shorter limb segment lengths among the sufferers. The women as a group, and the sufferers in particular, had several anthropometric dimensions that, as a proportion of stature, were outside the range of reference populations for design of Australian office workstations. The subject numbers in the present study are relatively small; however, they suggest that a proportion of the female population may not be accommodated by equipment currently in use. The increased proportion of sufferers who are overweight may suggest a relationship between overuse injury and lack of exercise, since the latter is well known to cause increased weight. A longitudinal study is needed to confirm this observation.

Adult↗

The effects of periodontal instrument handle design on hand muscle load and pinch force.

BACKGROUND: In comparison with people in other occupations, dentists and dental hygienists are at increased risk of developing work-related musculoskeletal disorders, including carpal tunnel syndrome. An important risk factor in dental practice is forceful pinching, which occurs during dental scaling. Ergonomically designed dental instruments may help reduce the prevalence of MSDs among dental practitioners. METHODS: In the authors' study, 24 dentists and dental hygienists used 10 custom-designed dental scaling instruments with different handle diameters and weights to perform a simulated scaling task. The authors recorded the muscle activity of two extensors and two flexors in the forearm with electromyography, while thumb pinch force was measured by pressure sensors. RESULTS: Handle designs of periodontal instruments had significant (P < .05) effects on hand muscle load and pinch force during a manual scaling task. The instrument with a large diameter (10 millimeters) and a light weight (15 grams) required the least amount of muscle load and pinch force. There was a limit to the effect of handle diameter, with diameters larger than 10 mm having no additional benefit; however, the study did not identify a limit to the effect of reducing the weight of the instrument, and therefore instruments lighter than 15 g may require even less pinch force. CLINICAL IMPLICATIONS: The results from this study can guide dentists and dental hygienists in selection of dental scaling instruments.

Adult↗

Interobserver repeatability and validity of an observation method to assess physical loads imposed on the upper extremities.

Interobserver repeatability and validity were assessed for a new semiquantitative, time-based observation method for the estimation of physical loads imposed on the upper extremities. Six risk factors of upper extremity disorders were included in the method: repetitive use of hand, use of hand force, pinch grip, non-neutral wrist posture, elevation of upper arm, local mechanical pressure. Two occupational health nurses were trained to use the method. They observed 127 work cycles at a food-processing plant and a paper mill. The method was validated against expert observations from the video, continuous recordings of myoelectric activity (EMG) of forearm muscles, and wrist posture measured with goniometers. Interobserver repeatability was good or moderate for repetitive use of hand, hand force, pinch grip (range kappa = 0.58-0.71 on the right; 0.60-0.61 on the left side). Interobserver repeatability was moderate or poor for non-neutral wrist posture, elevation of the upper arm and local mechanical pressure. Validity ranged from moderate to good for repetitive use of hand, use of hand force, pinch grip and non-neutral wrist posture when expert observation was used as reference standard. When observations were validated against force estimations (EMG) and wrist goniometer data, validity was poor. In the absence of generally accepted reference values, arbitrarily chosen limits were used for the proportional duration of some physical load factors. Studies should be carried out to assess the limits that best differentiate between safe and hazardous jobs.

Adult↗

Reliability assessment of a coding scheme for the physical risk factors of work-related musculoskeletal disorders.

OBJECTIVES: This study assessed the reliability of a novel coding scheme for physical risk factors for musculoskeletal disorders reported to an occupational surveillance scheme. METHODS: Since 1997 new cases of musculoskeletal disease have been reported as part of a surveillance scheme by over 300 consultant rheumatologists in the United Kingdom; the rheumatologists also gave a short description of the tasks and activities they considered to be causal. With the use of a summary of the activities described, a coding scheme was developed comprising 16 categories of task codes and another 16 categories of movement codes. Four reviewers coded the work activities independently for 576 cases. The fourth rater coded the cases twice. With the use of a single summary kappa statistic and the matrix of kappa coefficients, both interrater reliability and intrarater reliability were assessed. RESULTS: The overall interrater agreement on the task codes was good (kappa = 0.73), with the best agreement for keyboard work (kappa = 0.96) and the worst for assembly work (kappa = 0.40, kappa = 0.37). The interrater agreement on movement codes was also good (kappa = 0.79), with the best agreement for kneeling (kappa = 0.94) and the worst for materials handling (kappa = 0.10). The intrarater agreement was somewhat better than the interrater agreement with both codes. CONCLUSIONS: The results suggest that the coding scheme was, on the whole, reliable for classifying the physical risk factors reported as causal.

Cumulative Trauma Disorders↗

What is known about temperature and complaints in the upper extremity? A systematic review in the VDU work environment.

UNLABELLED: Upper extremity musculoskeletal complaints and disorders are frequently reported among visual display units (VDU) workers. These complaints include cold forearms, hands or fingers. OBJECTIVE: The aim of this systematic review was to gain an insight into the relationship between objective and subjective temperature decrease and musculoskeletal disorders (MSDs) in the upper extremity in a VDU work environment by (internal or external) cooling of the arm and hand. Two questions were formulated: (1) Is a VDU work environment (temperature between 15 and 25 degrees C) associated with temperature decrease of the arm, hand or fingers in healthy subjects? (2) Is there a difference in arm, hand and finger temperature between patients with upper extremity MSDs and healthy subjects in a VDU work environment? METHODS: Through a systematic literature search in six databases between 1989 and October 2005, 327 articles were retrieved and 17 included. RESULTS: Forearm, hand and finger temperature significantly decreases when the ambient temperature (between 15 and 25 degrees C) decreases. The skin temperature in the hand that uses a computer mouse is lower than the other hand in the same ambient temperature. At baseline, no objective temperature differences are found between patient groups and controls, whereas in patients with cold hand complaints, lower skin temperatures are found compared to controls. The association between temperature (changes) in the forearm, hand or fingers during VDU work, and MSDs in the upper extremity is not clear. CONCLUSION: There is no consistent evidence available for the association between upper extremity MSDs and temperature changes in forearm, hand or fingers in an office work environment.

Computer Terminals↗

[Hand-arm vibration syndrome in foundry workers].

INTRODUCTION: The hand-arm vibration syndrome of the foundry workers using chipping hammers and grinders were analysed in Hungary last in 1950th-s years. Therefore it seemed necessary to consider the present situation of the disease. AIM: To study of the signs of the hand-arm vibration syndrome of the foundry workers using chipping hammers and grinders. METHOD: Retrospective analysis of the clinical findings of 154 foundry workers using chipping hammers and grinders. The examination included the vascular, neurological and musculoskeletal systems of the upper extremities in 95 patients. RESULTS: The first symptoms referring to hand-arm vibration syndrome appeared on the average after seven years exposure. The signs of the 95 patients were as follows: vascular disorders: 75 cases (78.9%), peripheral neurologic lesion: 62 cases (65.3%), osteoarticular damage: 35 patients (36.8%). The Raynaud's phenomenon developed more commonly on the left than the right hand. The rate of the improvement of the Raynaud's phenomenon on the average 6.5 years after the cessation of the exposure on the basis of the result of the cold provocation test was 32.8%. Lesion of the peripheral nerves of the upper limbs, mostly of distal type was experienced in 41, whereas tunnel syndromes of the upper extremities in 21 cases. The most common amongst the latter (18 cases) was the thoracic outlet syndrome. Osteoporosis of the carpal bones was detected in 36 patients (37.9%), but osteoarthrosis of the joints of the upper limbs in 12 cases (12.6%). There was no aseptic necrosis of the bones. Fatigue fracture of the spinous process of the cervical VII vertebra occurred in one single case. CONCLUSIONS: Using chipping hammers and grinders in foundry is one of the most dangerous hand-arm vibration exposure in Hungary. The most frequent signs are the vascular and neurological lesions. Due to relatively rare occurrence of osteoarticular damages X-ray examinations are not necessary during periodical medical follow up. The most effective possibility of the prevention is the diminishing of the daily exposure time.

Adult↗

Prevalence and determinants of lateral and medial epicondylitis: a population study.

Epicondylitis is a common disorder of the arm, yet the role of individual- and work-related factors has not been addressed in a population study. The aims of this study were to estimate the prevalence of lateral and medial epicondylitis and to investigate their risk factors. The target population of this study comprised a representative sample of people aged 30-64 years residing in Finland during 2000-2001. Of the 5,871 subjects, 4,783 (81.5%) were included in this study. The prevalence of definite lateral epicondylitis was 1.3%, and that of medial epicondylitis was 0.4%. The prevalence did not differ between men and women and was highest in subjects aged 45-54 years. Current smoking (adjusted odds ratio (OR) = 3.4, 95% confidence interval (CI): 1.4, 8.3) and former smoking (OR = 3.0, 95% CI: 1.3, 6.6) were associated with definite lateral epicondylitis. An interaction (p = 0.002) was found between repetitive movements of the arms and forceful activities for the risk of possible or definite lateral epicondylitis (for both repetitive and forceful activities vs. no such activity: OR = 5.6, 95% CI: 1.9, 16.5). Smoking, obesity, repetitive movements, and forceful activities independently of each other showed significant associations with medial epicondylitis. Epicondylitis is relatively common among working-age individuals in the general population. Physical load factors, smoking, and obesity are strong determinants of epicondylitis.

Adult↗