The ergonomics of microscope work

Transcription

1 A. Méndez-Vilas and J. Díaz (Eds.) The ergonomics of microscope work J. Sillanpää 1 and M. Nyberg 1 1 Finnish Institute of Occupational Health, P.O. Box 486, FI Tampere, Finland By nature, work with microscopes demands precision and the ability to concentrate over long periods of time, and it requires the worker to maintain static work postures that strains the musculoskeletal system. Ergonomics has a special status with respect to the development and improvement of microscope work. This section presents means with which to develop and improve microscope work, and it provides an ergonomic guide for this type of work. Keywords microscope work; ergonomics; musculoskeletal system 1. Introduction By nature, work with microscopes demands precision and the ability to concentrate over long periods of time. In their work, microscopists often have to maintain static work postures that strain the musculoskeletal system. In addition to the load on the musculoskeletal system, microscope work causes eye strain, which, in turn, is related to muscular strain. Microscopists experience a significant number of musculoskeletal symptoms. In some studies, low-back pain, neck pain, and tension headaches have been reported by as high as 80% of microscopists [1, 2]. Electromyographic (EMG) examinations of microscopists have revealed that, after 4 hours of work with a microscope, muscle strain in the neck and shoulder region and in the back is 25% 65% greater than at the beginning of the work [3]. It has been shown that EMG examinations can efficiently assess the success of ergonomic actions [4, 5]. The box below presents a short description of the principles and use of EMG measurements. Brief description of the principles and use of EMG measurements Measures the electric activity of muscles Electrodes are glued to the skin covering the muscle The weak voltage (microvolts, µv) between two electrodes is measured, and the result is comparable to muscle activity The measurement is recorded, and the results are processed by a computer The results can used to assess a person s performance in relation to different conditions (work method, work equipment, furniture) In an article on microscope work in the electronic industry, Helander et al. [7] recommended, for example, more efficient product design, the replacement of microscopes by projected images, better ergonomic design of microscope workstations and microscopes, training of microscope users and work rotation, as well as the restriction of continuous work, as means with which to develop and improve microscope work. In the next section, case examples are used to illustrate how microscope work can be improved. 2. Case examples 2.1 Head support (forehead) Looking through a microscope requires keeping the head in the same exact position for long periods. This prerequisite especially strains the neck muscles, especially if the ocular angle is great. One possibility is to attach a head support to the microscope. The support helps the head to remain in the proper position and therefore lessens the strain in the neck muscles. In one workplace, an experiment was carried out with a new microscope table and a head support fastened to a microscope as a means of stabilizing the position of the head (the eyes directed towards the ocular aperture). The microscopist alternated 10 times between working at her old workstation, then at a new table without a head support and finally at the new table while using a head support (Fig. 1), working at each station for a period of 1 minute each time. Between each test period there was a 1-minute rest period. The task was planned so that the microscopist worked only with the microscope during each work period. EMG signals were recorded from muscles in the neck shoulder region and the back during the experiment. The use of the new table improved the microscopist s work posture with FORMATEX

2 Microscopy: Science, Technology, Applications and Education A. Méndez-Vilas and J. Díaz (Eds.) respect to the back, upper extremities, and the neck. The result was clearly evident from the decrease in muscle activity. In addition, the use of the head support lessened the muscle activity even more (Fig. 2). The improvement in the microscopist s work posture that was found in the test indicates that the use of the new table and the headrest would have a positive effect on the musculoskeletal symptoms of microscopists. Fig. 1 A microscope equipped with a head support µv New Table New Table with Support 15.0 Old Table Neck-Shoulder Back Fig. 2 Muscular activity (µv) in the neck shoulder region and in the back during the use of the new table, the new table and a head support attached to the microscope, and the old table FORMATEX 2010

3 A. Méndez-Vilas and J. Díaz (Eds.) 2.2 Good sitting posture, chair adjustments and variation in posture Sitting for long periods in the same position tires the back and shoulders. Maintaining the same posture requires static muscle work that weakens blood circulation, muscle oxygenation, and muscle function. A poor sitting posture can cause muscles to ache. It is important to sit with good support and at the same time be as relaxed as possible in the sitting position used. It is also important to take breaks regularly to stretch one s legs by walking around. In other words, when one works sitting one should take one s breaks standing. Chairs that permit versatile adjustment make it possible for the worker to find a work posture that is both good and healthy Good sitting posture Criteria for a good sitting posture follow: The sitting height should allow the feet to be firmly on the floor. The back support should be slanted backwards (about ), the back position being almost relaxed, so that the muscle activity and the pressure on the intervertebral discs are decreased. With respect to the lower back, the posture of the spine should be nearly the same as in a standing position. Supporting the arms on the arm supports of the chair or on the table lessens the activity of the back muscles and decreases the pressure on the vertebra. A sitting surface that is slanted downward (5 30 ), helps the worker to maintain the natural curvature of the back. In work with a microscope, using a posture that is slightly slanted backwards helps reduce back strain. A backwardleaning posture is possible if a high-backed chair with a neck support is used (Fig. 3) and the inclination of the microscope can be adjusted (or the ocular angle of the microscope is adjustable). Microscope work could also be done standing (Fig. 4). As an alternative, work in a standing position efficiently interrupts the detrimental effects of sitting work. Standing work could possibly be used as an alternative for short microscope tasks if the microscope base is adaptable, the table is adjustable, and the working height is adjusted properly. It should be possible to adjust the height of the table sufficiently ( mm). A straight symmetric position is the best work posture. When standing, the microscopist has a stable position, when the centre of gravity of his or her body is above the area outlined by the feet. In this manner, the line of the centre of gravity travels down to the centre point of the supporting area, and maintaining one s balance is easy. Fig. 3 Using a microscope while sitting. Fig. 4 Using a microscope while standing. FORMATEX

4 A. Méndez-Vilas and J. Díaz (Eds.) 2.3 Support of the upper extremities Work with a microscope often requires forward or side abduction movements of the upper extremities in order for the adjustment knobs to be used. If the location of the knobs or their usability cannot be improved, it is important that the need to hold up the arms be reduced. Such a reduction can be made with the help of side extensions added to the adjustable table and adding a support for the arms to the table. The supports are, to a great extent, dependent on the microscope, but also on the person in question. This need for individuality places demands on the material used, which should be easily shaped, cheap, and durable. A worktable developed at a workplace was compared with a table in use earlier [5]. The height of the prototype table and its side extensions was adjustable. In addition, the angle of the microscope base could be adjusted, and the front edge of the table had an indentation in the area of the stomach. The 10 microscopists who participated in the study were given an opportunity to practice using the table before the beginning of the experiment. The participants also familiarized themselves with the task, were provided with individual instruction, and given time to become trained. A standardized task was repeated 10 times. The repetitions were randomised so that the task was carried out at both tables 5 times. During each repetition the muscle activity was recorded for each muscle. The duration of the standardized test averaged about 1 minute 15 seconds. Each repetition was followed by a 3-minute recovery break, during which the persons moved to the other table if needed and at the same time tried to relax the muscles of their upper extremities and neck shoulder region. The performed task was comprised of one of the general phases of microscope work. Work at the prototype table caused less strain in the neck shoulder region and shoulder muscles, and the work posture was better than when the participants worked at their own tables (Fig. 5). Fig. 5 Work at the ergonomically designed microscope table lessened the muscle activity in both the right and left neck shoulder regions and shoulder joints by 9 36% in comparison with work at the earlier used table FORMATEX 2010

5 A. Méndez-Vilas and J. Díaz (Eds.) 2.3.1Characteristics of a good microscope table The results of the experiment with the microscope table indicate that a good table should have the following characteristics: firmness adjustable height sufficient space on both sides of the microscope free foot room designed so that the front edge makes sitting near the microscope easy and so that there is space to support the upper extremities possibility to slant the microscope. 3. Ergonomic guidelines for microscope work With regard to the load on the musculoskeletal system, the ergonomics of the workstation are very significant. The following set of ergonomic guidelines has been devised on the basis of several projects involving microscope work. In order to benefit from ergonomic principles, not only the furniture and equipment should be given special consideration, but also their use and adjustability. The contents of the following table form an ergonomic guide to help a worker find a posture with a suitable degree of strain. Table 1 An ergonomic guide for microscope work. Ergonomic guide for microscope work 1. Adjust the sitting height: Place both feet completely and firmly on the floor or on the footrest and adjust the height of the chair so that there is some space between the legs and the seat of the chair. 2. Adjust the back support of the chair: First adjust the height of the back of the chair so that it supports the curvature of the lower back; then adjust the position of the back in the forward backward direction so that the depth of the seat is suitable for the length of your upper legs and so that your back is against the back of the chair during your work with the microscope. 3. Choose the proper distance from the table: Sit at a distance from the table (benefiting from the possible stomach indention in the front edge of the table) that makes it possible to avoid a forward slanting work posture (back) and you can support your upper extremities on the table. 4. Adjust the height of the microscope table or the microscope: Adjust the microscope to a height at which you can look through the ocular aperture with your head as straight upward as possible but using a relaxed position and supporting your back on the back of your chair. 5. Adjust the height of the side extensions of the table: Adjust the height of the side extensions of the table to a height that, when the focus control and preparation transfer mechanism are used, the upper extremity in use can be supported on the surface and the shoulders relax. If the table does not have adjustable side extensions, use arm supports. In microscope work the wheels of the chair should either be locked or otherwise difficult to move. If you have a chair with a high back and a neck support try using a backward slanting work posture. In this manner, you can benefit from the stomach indention in front edge of the table and from the fine adjustment of the table, the height of the microscope and the ocular angle. The sitting distance depends on whether or not you use a forward slanting posture or a backward slanting posture. Try and listen to what your body tells you. With respect to the position of your head and relaxed vision, the adjustment of the ocular angle is important. A good result can be achieved using the adjustments of the microscope or, if none are available, by slanting the microscope. Support of the upper extremities in microscope work is important. The best support is obtained if your elbow and wrist supports have been specifically measured and designed to fit you. Try a temporary solution and then have your own supports made. FORMATEX

6 A. Méndez-Vilas and J. Díaz (Eds.) 4. Conclusions and the direction of developments A holistic approach should be taken in the development of microscope work. Activities to develop and improve microscope work should not only be directed towards the ergonomics of the workstations and the methods used, but also towards the microscopes. Nor should the training and work guidance of microscopists be forgotten. The examples presented earlier in this section show that even such established work can still be improved with the use of traditional ergonomic methods. Technological developments have produced a new perspective of the development of microscope work. High-resolution computer screens (Figs. 6 & 7) have made it possible to examine microscope pictures without the eyes and neck muscles being strained by the use of an eyepiece. As microscope work is, for the most part, transferred to so-called digital microscopes and the nature of the work begins to remind us of traditional computer work in offices, ergonomics must still be taken into consideration. Even in the future a good, supported sitting position, sufficient support of the upper extremities, and an optimal visual distance should be taken into consideration, as should the ocular angle between the viewer and the computer screen. Fig. 6 Picture from Fig. 7 Picture from advancedmicroscope.com. References [1] Haines H, McAtamney, L. Applying ergonomics to improve microscopy work. USA Microsc Anal. 1993;1: [2] Kalavar SS, Hunting KL. Musculoskeletal symptoms among cytotechnologists. Lab Med. 1996;27: [3] Lee KS, Waikar AM, Aghazadeh F, Tandon S. An electromyographic investigation of neck angles for microscopists. In: Proceedings of the Human Factors Society 30th Annual Meeting, Dayton, Ohio, September 29 October 3, Vol 1: [4] Kofler M, Kreczy A, Gschwendtner A. "Occupational backache" surface electromyography demonstrates the advantage of an ergonomic versus a standard microscope workstation. Eur J Appl Physiol. 2002;86(6): [5] Sillanpää J, Nyberg M, Laippala P. A new table for work with a microscope -a solution to ergonomic problems. Appl Ergon. 2003;34: [6] Basmajan JV, Luca CJ. Muscles Alive. Their Functions Revealed by Electromyography. Baltimore, Md: Williams & Wilkins; [7] Helander M, Grossmith E, Prabhu P. Planning and implementation of microscope work. Appl. Ergon. 1991;22 (1): FORMATEX 2010