علایم مداخله ارگونومیک بر گردن، شانه و بازو کارکنان روزنامه در کار با واحدهای نمایش بصری
|کد مقاله||سال انتشار||تعداد صفحات مقاله انگلیسی||ترجمه فارسی|
|6927||2003||10 صفحه PDF||سفارش دهید|
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Publisher : Elsevier - Science Direct (الزویر - ساینس دایرکت)
Journal : International Journal of Industrial Ergonomics, Volume 31, Issue 1, January 2003, Pages 1–10
Shoulder and arm symptoms are typical in work with visual display units (VDUs) among newspaper employees. The aim of this study was to compare the effects of two different intervention models for VDU work (E=redesign measures for the environment only, ET=redesign measures for both the environment and work techniques) on neck, shoulder and arm symptoms among newspaper employees. Twenty newspaper employees participated in the study. Work posture, monitor viewing, muscular activity, and musculoskeletal pain were measured before and after the 7-month intervention. Difference was statistically significant between the groups for the change in shoulder flexion (p=0.0134) and the muscular activity of right trapezius (p=0.04109) and right extensor carpi radialis (p=0.0379) in the pre- and postintervention measurements. The reduction of pain symptoms in the neck (p=0.0073), shoulders (p=0.0071) and elbows (p=0.0490) was greater in the ET group than in the E group. This study showed that repeated neck, shoulder and arm symptoms can be more efficiently reduced among newspaper employees if ergonomic measures to improve the work environment are combined with changes in work techniques than if the redesign measures focus only on the work environment. Relevance to industry The results of this study can be used to develop work ergonomics for VDU workers.
Several recent studies have found a relationship between musculoskeletal disorders and the use of a video display unit (VDU) (e.g., Bernard et al., 1994; Carter and Banister, 1994; Faucett and Rempel, 1994; Amell and Kumar, 1999; Derjani Bayeh and Smith, 1999). In general, findings indicate that poor ergonomic conditions are associated with VDU users’ complaints about visual discomfort and musculoskeletal pain symptoms (Sauter et al., 1991; Bergqvist et al., 1992) Wrist and back injuries and visual strain have also been found to be the main contributors to workdays lost due to VDU-related injuries (Abib and Dutta, 1998). In addition, according to the cross-sectional study of Bernard et al. (1994), newspaper workers more frequently report neck (26%), hand or wrist (22%), shoulder (17%), and elbow (10%) symptoms than any other symptoms. Work-related musculoskeletal disorders in the neck–shoulder area and upper limbs seem to be affected by work-related, individual, and social factors (Armstrong et al., 1993; Bongers et al., 1993; Nelson and Silverstein, 1998). Bernard et al. (1994) showed that increased work load due to time pressure and a high number of hours of computer use were related to the occurrence of work-related musculoskeletal disorders, particularly for those in the hand and wrist area, among newspaper employees. However, studies often use different case definitions and the results therefore lack comparability like Beaton et al. (2000) showed in a study among newspaper workers. Faucett and Rempel (1994) also reported that upper limb disorders increased among VDU workers as the daily use of a VDU increased and decision latitude decreased. According to Carter and Banister (1994) musculoskeletal discomfort in association with VDU work is attributable to static muscle load and repetitive work. Continuous keyboard work, deviated wrist positions, seating posture and individual wrist size are reported to be related to carpal tunnel syndrome (Matias and Salvendy, 1998). According to Bergqvist et al. (1995) and Karlqvist et al (1996) and Karlqvist et al (1998) upper limb symptoms are connected to the use of forearms in an unsupported position, the placement of the keyboard, long periods of work with a mouse, and a non-optical location of the mouse on the table. Insufficient table space has also been shown to be related to neck–shoulder discomfort (Sauter et al., 1991). Some intervention studies suggest that development of ergonomics decrease musculoskeletal pain symptoms in VDU work. Aarås et al. (1998) reported a controlled ergonomic intervention study in which the lighting system, workstations and optometric examinations were redesigned for VDU operators. In the follow-up, 2 years after the intervention, static trapezius load and shoulder pain were reduced only in the study groups. Nelson and Silverstein (1998) identified a range of factors associated with an observed reduction of musculoskeletal pain when office workers were moved to a new building. They found that the reduction in upper-limb symptoms was associated with improved satisfaction with the physical workstation, whereas the reduction in neck, shoulder and back discomfort was associated with improved chair comfort, fewer housekeeping responsibilities, and female gender. Derjani Bayeh and Smith (1999) reported a longitudinal intervention field study, that included three levels of ergonomic interventions, each adding incrementally to the previous one. Reductions in self-reported musculoskeletal discomfort were found for all three levels of incremental ergonomic interventions, but the improvement in health was statistically significant for intervention group A (workstation layout changes, VDT workstation accessories, a steelcase chair) and group B (workstation layout changes, VDT workstation accessories) but not in group C (workstation layout changes). According to Lee et al. (1992) various physical exercise programs have been introduced for VDU operators, but the effectiveness of the programs is questionable. Hinman et al. (1997) reported a controlled intervention study in which a computerized exercise program (exercise 15 min per session, twice a day during 8 weeks) did not affect perceived physical or psychological stress of asymptomatic VDT users. The aim of our study was to compare the effects of 2 different intervention models (E=redesign measures for the environment only, ET=redesign measures for both the environment and work techniques) on the neck, shoulder and arm symptoms of newspaper employees.
نتیجه گیری انگلیسی
4.1. Methodological considerations The personnel management and the occupational health care unit of the newspapers were the initiators of this study. They were responsible for the dissemination of information, which may have increased the motivation and commitment of the subjects. The subjects were divided into 2 groups so that those who worked in different local newspapers comprised the group E and those who worked in the main newspaper formed the group ET. It would have been possible also to randomize the subjects, but then it would have been possible for the contents of the intervention to be mixed within the same workplace. The several non-significant findings in this study can simply be due to low power. However, a lack of a control group makes it difficult to interpret the results. The effects of the 2 intervention models were compared. In practice, it is usual to develop only the ergonomics of the work environment without providing the workers with advice on changes in work techniques (Aarås et al., 1998). The intervention contents were based on several recent studies on VDU work (Sauter et al., 1991; Lee et al., 1992; Aarås et al., 1998; Bauer and Wittig, 1998; Fernandez and Poonawala, 1998; Karlqvist, 1998; Smith et al., 1998; Turville et al., 1998). The aim of the environmental redesign measures was to provide the workers with support for both forearms on the table, since such support has been shown to reduce muscular load. The concave symmetrical table made it possible to use the mouse with both hands. The height of the screen was decreased to obtain a 15° viewing angle, which has been recommended by Turville et al. (1998). The subjects used standard flat keyboards because the study of Smith et al. (1998) showed no differences in musculoskeletal symptoms when split, adjustable or normal flat keyboards were used. The exercise program was planned on the basis of the review article of Lee et al. (1992). The following criteria were used to choose the exercises: they should be performable while the subject was seated at the workstation, only a break of 2 min should be required, the movements should not be conspicuous, the exercises should be simple and easy to learn, the written instructions should be easily understood, and the exercises should be safe. However, it must be remembered that exercises including hyperextension of the wrist are contraindicated for persons with arthritic conditions of the hands and wrists. In the intervention study the pre- and postintervention measurements required valid and reliable methods. It would have been better to use electric goniometers, which have been shown to be valid for use in VDU work (Smutz et al., 1994), because the measurements with the manual goniometer included several possibilities for error. Care was taken to ensure that the subjects worked normally during the measurements of monitor viewing and work posture and each subject said herself what was her most typical work posture. This use of normal work methods was of great importance to ensure that the measurements were correct and also corresponded to the “everyday” situation. The synchronized video-EMG method was used to provide a possibility for feedback on work techniques and for evaluating the effects of the ergonomic redesign measures. The method made it possible to analyze the EMG of different muscles during the use of the mouse and the work on the whole. Three specific muscle groups were chosen because neck muscles contract according to the posture of head, trapezius muscles participate in almost any arm movement, and the extensor carpi radialis contracts during the use of the mouse and during typing. The mean EMG activity at work was compared with the MVC, although the calibration included several possibilities for error (Mirka, 1991). However, the lead positions were selected carefully according to the report of Zipp (1982), in an attempt to increase the repeatability of the EMG results. The questionnaire included questions about mental strain and work pace. It was important to inquire the perceived mental strain and work pace in both measurements because a high perceived work load and time pressure have been shown to be related to musculoskeletal symptoms (Bongers et al., 1993). 4.2. The results The significant difference between the groups in the reduction of musculoskeletal symptoms showed that environmental measures combined with changes in work techniques were more effective than the use of environmental measures only. The environmental intervention (group E) produced no significant decrease in the neck, shoulder or elbow symptoms. The results in group E disagree with those of the study by Aarås et al. (1998) on the effects of environmental measures on neck and shoulder pain, but they agree with the results concerning the change in pain symptoms in the forearms. The significant difference between the groups in the change in shoulder flexion was due to greater shoulder flexion in the ET group in the preintervention measurements. The muscular activity of the right trapezius muscle decreased statistically significantly more in the E group than in the ET group. The difference may have been due to the difference in the preintervention measurements, during which more subjects in group E than in group ET had unsupported forearms. However, these differences between the groups in preintervention were not statistically significant. In the ET group some subjects had used the arm supports of their chairs to support their arms during their VDU work (Lintula et al., 2001). There was a significant difference between the groups in the change in muscle activity of the right extensor carpi radialis which increased in the group E. Perhaps the subjects were not accustomed to support their forearms on the table during the mouse and keyboard work. The results indicate that environmental measures without adequate ergonomic counselling do not lead to the positive outcomes in musculoskeletal pain symptoms. During the intervention in our study, it was recognized that workers need a lot of advice and support to change their daily work techniques and to utilize ergonomic changes made in the work environment. Repeated neck, shoulder and arm symptoms among newspaper employees could be more efficiently reduced by ergonomic measures that focus both on the VDU work environment and VDU work techniques than redesign measures focusing only on the work environment. We used a multiple component intervention that prevents knowing which component was effective or not effective. However, the results of this study can be taken into account when work ergonomics is planned for VDU workers as a part of occupational health care or rehabilitation processes. In the future, randomized controlled studies are needed to evaluate the effectiveness of different types of ergonomic measures like also Derjani Bayeh and Smith (1999) has recommended.