اثر مداخله ارگونومیک بر احساس ناراحتی در کاربران کامپیوتر مبتلا به سندرم کشش گردن

To investigate the long-term effects of ergonomic intervention on neck and shoulder discomfort among computer users who have symptoms of tension neck syndrome, using simple materials and protocols, 80 Thai volunteers with symptoms of tension neck syndrome were identified through administration of a questionnaire to 470 computer users. Two pre-tests were conducted to determine subjects’ level of discomfort before the planned intervention commenced. Half of the subjects’ work stations were immediately adjusted according to ergonomic recommendations for individual anthropometry. The other half received the intervention 3 months later. Discomfort evaluations (head, neck, shoulders, arms, and back) were conducted eight times within 6 months for both groups. The same patterns of decrease in the levels of discomfort of all body parts were present in both groups. Substantial variation in the level of discomfort over time for each body part in each subject was noted after the intervention. However, the mean level of discomfort ratings before and after receiving intervention were significantly different. It was concluded that ergonomic intervention can help reduce the discomfort level of subjects with tension neck syndrome. In addition, the study supports the use of simple materials which can be used by individuals to adjust their own workstations according to ergonomic recommendations.

It has been proposed that the most important negative consequence of computers is the relationship between musculoskeletal disorders (MSDs) and their usage (McIntosh, 1994; Ong, 1994). The presence of MSD has been confirmed by Bergqvist et al. (1995) and Knave et al. (1985). They found that there was a connection between working with VDTs and the incidence of various MSDs. Among the MSDs in computer users, tension neck syndrome (TNS) is commonly found (Kroemer, 1992). Prevention programs structured around ergonomically based recommendations have been introduced to help reduce the negative consequences of computer use and have been reported to be successful by some authors. Aarås (1994a) introduced ergonomic intervention in a group of assembly workers and VDT users and found a reduction in the static load of trapezius muscle and decreases of pain intensity in various areas. Interestingly, the survey reports for 1992–1995 from the Bureau of Labour Statistics (BLS) of the US Department of Labour indicated that repetitive strain injuries declined from 11.8 cases per 10 000 workers in 1992 to 10.1 cases in 1995 (Bernard, 1997). This decline may partially be the result of efforts to publicise the success of intensive efforts to decrease the number of disorders through prevention and treatment programs, and may provide motivation for researchers to continue to investigate ways to help reduce or prevent disorders. However, recommendations for ergonomic prevention which have appeared in the literature have not been consistent in the way they are described and may be hard for novice users to understand causing confusion. Such confusion may occur because the reported recommendations are often specific to a single work task and a particular individual. For example, recommendations for the monitor position for computer-aided design users is much higher (middle of the monitor is at eye level; Wall et al., 1992) than those for general computer users, such as data enters and word processors. These have been debated between moderate monitor height (the top of monitor being around eye level or the centre of monitor being at 15° downward of from the eye level; Grandjean, 1988; Standards Australia, 1990) and lower monitor height (the top of screen being at 15° downward from eye level; Ankrum and Nemeth, 1995). Furthermore, most studies have concentrated on the effects of particular features of the workstation such as seat height and inclination (Bridger, 1988; Mandal, 1981), seat and desk height and inclination (Bendix, 1984), monitor height (Burgess-Limerick et al., 1999; Turville et al., 1998), and keyboard use (Fernström et al., 1994). Most recommendations have been based upon the finding of experimental studies (Burgess-Limerick et al., 1999; Lie and Fostervold, 1995) or from preferences of subjects using their own set-up (Grandjean et al., 1984). It could be argued that one recommendation used in isolation may not be totally effective when interactions between the body part and workstation are needed. Therefore, recommendations for workstation set-up should include every aspect of the workstation. In the commercial world, most workplaces already have computers and workstations installed, and financial constraints mitigate against wholesale replacement of old equipment and the installation of new workstations. Furthermore, in most developing countries, replacement of computers and use of ergonomically adjustable workstations is not feasible because of the costs involved. Moreover, employees in such working environments may not be protected by ‘duty of care’ and occupational health and safety laws. Therefore, it is necessary to assist employers to use ergonomic principles, which do not require expensive alternatives and can ensure an increase in profitability and a decrease in symptoms of work-related disorders among their workers. Instructions for such intervention must be clear and readily understandable to ensure successful application. 1.1. Tension neck syndrome Tension neck syndrome (TNS) is one type of occupational cervicobrachial syndrome, a term used to refer to those disorders of the neck and shoulder which are (or can be) related to occupational factors. Thus, TNS can be categorised as one of a group of ‘work-related’ neck and shoulder disorders. There are some closely related terminologies which may be used in similar studies, for example, repetitive strain injuries (RSI), cumulative trauma disorder (CTD), and cervicobrachial disorder (Winkel and Westgaard, 1992). These terms are broad and sometimes may be conflicting. TNS can be differentiated from the other terms in that it is used in cases of non-articular and non-neurological pain in the neck and shoulder areas. Some papers refer to TNS as tension myalgia fibrositis, fibromyositis, or myofascial syndrome (Waris, 1980). Hagberg and Wegman (1987) identified the symptoms of TNS as constant muscle fatigue or stiffness in the neck and shoulder areas along with subjective neck pain or headache. Palpation along the shoulder and neck muscles may identify at least two tender spots or trigger points. Waris (1980) defined tension myalgia as a complex of pain, tenderness, hardened bands or nodularities, and stiffness of muscle which is physically palpable. Waris (1980) reviewed the incidence of TNS from several studies which used pain and discomfort measures as criteria to define TNS. The author reported that cervicobrachial myalgia has been found to occur previously more often among workers who had mental and physical stress. The percentage of people who are office workers and have pain and discomfort around the neck and shoulder area has been reported to be between 4% and 42%. Hagberg and Wegman (1987) reported the prevalence to be 25%, mostly in women, with the ratio of females to males at 5.9 : 1. The odds ratio is greater than 1 for those who are engaged in data entry and incidence of TNS appears to be increasing (Bergqvist et al., 1995; Hagberg and Wegman, 1987). Bergqvist et al. (1995) recently reported an incidence of over 20% for MSD and 60% for discomfort in the neck–shoulder region among computer users. The pathomechanics of this disorder is uncertain. Waris (1980) has proposed that one possibility is the accumulation of end products from muscle metabolism resulting in sustained muscle contraction and low blood flow leading to insufficient oxygen supply. The concept of pain sensitisation can be also used to explain both physical and psychosocial factors. The deep pain system, which can be described as related to scleratome distribution when occurring in the cervicothoracic region, may be sensitive to any functional changes through the spinal cord and central nervous system. Lack of movement as a result of the pain may lead to loss of pain inhibitor substance in the peripheral pain pathways (Hazleman, 1994). Armstrong et al. (1993) proposed an alternative model of work-related disorders which includes internal and external factors. The internal factors include ‘dose’ which is the way the body reacts to external exposure (work environment and job requirements). The ‘dose’ can result in the body responding either physiologically or psychologically. Body responses can lead to the ‘dose’ acting again through the body as ‘capacity’ (the ability of an individual to resist various influencing factors). According to this model, any changes in the exposure would result in changes to the ‘dose’ and ‘response’ according to ‘capacity’. Therefore, changing exposure is one way to manage TNS and may avoid medical treatment being required.

This study has introduced a means of using inexpensive interventions for the workplace and a clear and readily understandable method for using ergonomic suggestions to alter individual workstations. This study has proved that using this simple method can help reduce discomfort in all of the areas assessed. Therefore, it is recommended that all computer users, with or without symptoms of TNS or other musculoskeletal disorders, should use ergonomic recommendations to structure their workplace to gain the benefits of discomfort reduction. For those without access to modern workstations, simple materials for workstation modification and a computer program which calculates recommendation are available and can be used to assist individuals adjust their own workstations with minimum training.