Journal of Occupational Rehabilitation, Vol. 6, No. 3, 1996

Effects of Occupationally-Oriented Rehabilitation on Farmers' Work Techniques, Musculoskeletal Symptoms, and Work Ability Nina Nevala-Puranen 1,2

Changes in work techniques, musculoskeletal symptoms and work ability were studied after occupationally-oriented rehabilitation courses for farmers experiencing low back or shoulder pain. Fifty-two women and 43 men participated. The OWAS analysis of work postures, biomechanical modeling of lifting techniques, and a questionnaire were used before and after the courses and after 1 year of follow-up. Bent and twisted postures or postures with the arms over the shoulders occurred more seldom after the courses and the follow-up. Changes in lifting techniques were minor. The musculoskeletal pain index decreased by 12 and 3 points for the women and men, respectively. The mean work ability index increased from 33.5 (men and women) to 36.5 (women) and 35.1 (men). This study showed that rehabilitation can produce significant, long-lasting effects on rehabilitees' work techniques, work ability, and subjective well-being. KEY WORDS: agriculture; rehabilitation; motor skill; work technique; work posture; lifting.

INTRODUC~ON

Farmers' work includes many physically heavy work phases and often a combination of high postural load, manual materials handling, and the use of muscular force (1-3). Working in a stooped posture results in higher heart rates, energy expenditure, and ratings of discomfort and fatigue (4). In addition, the ability to produce maximal forces considerably depends on the work posture used (5). According to a recent case study (3), farmers work in barns 60% of the milking time with their back bent or simultaneously bent and twisted. Manual materials handling influences the compressive forces on the vertebral disks and the activity of erector spinal muscles (6-7). Lifting can be performed from squatting, stooped, or free-style (semi-squatting, semi-kneeling) postures that IKuopio Regional Institute of Occupational Health, Kuopio, Finland.

2Correspondenceshould be directed to Nina Nevala-Puranen, Kuopio Regional Institute of Occupational Health, Box 93, FIN-70701 Kuopio, Finland. 191 I053--0487/96/0900-0191509.50/09 1996 Plenum PublishingCorporation

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have different force and energy requirements (8). The squatting posture minimizes stress on the spinal column and the back muscles, but increases energy expenditure. The stooped posture requires less energy but leads to severe load on the back. Leskinen (6) showed that compressive forces on the spine are already high during the lifting of boxes with a mass of 10-15 kg. He found that the biomechanical stress on the spine varied little with different lifting techniques and that lifting from the floor always led to high loads on the spine. Spinal loads can be effectively decreased only by avoiding manual lifts from low levels. If the lifts are necessary, the load on the spine can be minimized by keeping the mass to be lifted as low and close to the body as possible. Previous studies have demonstrated that the individual variation in work techniques is large, even among persons performing exactly the same work tasks (9). Persons who use inadequate work techniques run a higher risk of acquiring musculoskeletal disorders. Prolonged work in poor postures and heavy manual materials handling have been shown to cause or accelerate musculoskeletal disorders (10, 11, 2). Although it has been reported that back pain is attributable to high dynamic overload and bent or twisted postures, the data on which the reports were based stem from self-reports rather than from observation or objective measurements. It is possible to prevent these problems through ergonomic measures at worksites and better occupational skills (i.e., work techniques). Training in work techniques has been used in the prevention of injury recurrence (i.e., for secondary prevention), in neck and back schools and in rehabilitation (12, 13). In most cases, the effectiveness of rehabilitation has been assessed from the changes in physical performance, musculoskeletal symptoms, individual work ability, and work absenteeism (14-16). Few studies have indicated that work techniques can be changed during rehabilitation courses or interventions carried out at worksites. V'~iyrynen and K6n6nen (13) reported that loggers were able to change their work postures during occupationally-oriented medical rehabilitation courses, and their new tree-felling technique was preserved over the 4-year follow-up period. Hopsu and Louhevaara (17) also reported that it was possible to decrease cleaners' poor work postures of the back with educational training that included ergonomic job redesign. Videman et al. (18) evaluated two training programs designed to improve patient-handling skills and prospectively assessed the predictive power of skill on subsequent back pain and injuries in nursing. The specially trained group who participated in the special training program (40 hours of practical and theoretical training during 2.5 years) had better patient-handling skills than the control group (traditional form of training) when they were qualified as a nurse. Inadequate patient-handling skill was found to be one of the major risk factors for back injuries during the first year as a qualified nurse. Those rated to have bad or poor patienthandling skill had more back injuries (24%) than those having good or excellent skill (2%). Only a few studies have been published concerning the effects of rehabilitation programs on workers' work techniques even though occupationally-oriented courses have been organized for different occupational groups for many years. The aim of this study was to evaluate the effects of occupationally-oriented medical rehabili-

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tation courses on farmers' work techniques, musculoskeletal symptoms, and work ability.

MATERIALS AND METHODS Subjects

The subjects were 95 farmers: 52 women with the mean age of 42.5 (SD = 6.3) years and 43 men with the age of 41.4 (SD = 6.8) years. Most (80%) of the subjects worked on dairy farms and the rest worked in different production sectors (i.e., beef cattle, grain, or pig production). The mean height and weight of the female subjects were 164 (SD = 6) cm and 74 (SD = 12) kg, respectively. The corresponding values for the men were 178 (SD = 8) cm and 82 (SD = 11) kg. According to the body mass index (BMI), 52% of the subjects were overweight (25 < BMI < 30 kg/m 2) and 20% were obese (BMI > 30 kg/m2) (19). The subjects took part in ten occupationally oriented medical rehabilitation courses in three Finnish rehabilitation centers in 1992. The selection criteria of the Social Insurance Institution included the following prerequisites: (a) if possible age at most 45 years, (b) full-time farmer at least 3 years and intention to continue as a farmer, (c) musculoskeletal symptoms causing sick leave for a maximum of 60 days during the last 2 years, (d) no other diseases that prevent rehabilitation, (e) motivation to work, and (f) voluntary participation in the course. Rehabilitation Courses

The occupationally oriented rehabilitation courses for farmers were developed and funded by the Social Insurance Institution in Finland. The main goals of the courses, lasting 3 weeks, were to increase the subjects' physical and psychological abilities and to train them to use work techniques that optimize the load on the musculoskeletal system in their daily tasks. The courses included training of ergonomically sound work techniques (first in a classroom situation and then in the actual work environment), many kinds of physical activities, and learning of the structure and physiological strain responses of the musculoskeletal system. The work techniques were taught by a physiotherapist and a teacher of agricultural ffork. Methods

The different work techniques were analyzed by the evaluation of work postures and lifting techniques. Musculoskeletal symptoms and perceived work ability were assessed with a questionnaire. The assessments were performed in the beginning and at the end of the 3-week rehabilitation courses and after 1 year of follow-up.

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The work postures of 46 subjects in two rehabilitation centers were video recorded in three daily work tasks (milking, silage handling, and cow brushing or floor cleaning) for 12 minutes per subject. These work tasks were selected because they were the most common daily tasks of those taught in all three rehabilitation centers. Before the video recordings the subjects were asked to use the work tools and work techniques used in their habitual work situation. The work postures were analyzed with the OWAS (Ovako Working posture Analysing System) method (20, 21). The OWAS method identifies four work postures for the back, three for the arms, and six plus walking for the legs. It also estimates the weight of the load handled or the amount of force used. The method classifies single combinations of these factors according to their harmfulness to the musculoskeletal system. The degree of harmfulness of a single posture or posture combination is ranked into four action categories that indicate the urgency to change the posture with ergonomic measures. The action categories are 1 = normal posture--no need for corrective measures, 2 = may have a harmful effect--corrective measures in the near future, 3 = harmful effect--corrective measures as soon as possible, 4 = very harmful effect--corrective measures immediately. The OWAS observations were made by a researcher from still videotape frames every 10 seconds. The data were stored in a microcomputer using the OWAS collection program (OWASCO), and the total number of observations was 3312 for each measurement. The results were analyzed using a computerized analyzing program (OWASAN). The lifting technique of each subject was video recorded from a lateral position as the subjects lifted a feed sack (30 kg for the men and 20 kg for the women) from the floor to a height of 45 cm and back to the floor in a simulated classroom situation. The subjects were asked to use their habitual lifting technique. The initial point of the lift was photographed from still video frames and the biomechanical data were manually determined from the photographs. The computerized 2D Static Strength Prediction Program (2D SSPP version 4.2e) was used to analyze the individual changes in postural load during the lifting (7). The angles for five body links (elbow, shoulder, back, knee, and ankle) were measured with respect to the horizontal level. Lines were drawn on the photograph for each of the body links, and the angles were measured with a protractor. The biomechanical data, height, and weight of the subject, weight of the load, and the number of hands lifting were stored in the microcomputer. The outcome variable was the L5/S1 disk compression. All 95 subjects were asked to rate their musculoskeletal symptoms for nine body parts on lines (100 mm) developed on the basis of the standardized Nordic questionnaire (22). The subjects marked the amount of pain they experienced at that instant. The index was the mean (0-100) of the nine body segments (neck, shoulders, elbows, wrists/hands, upper back, low back, hips, knees, and ankles/feet). The subjects were asked to estimate their work ability with the aid of the work ability index (23). The index included subjective estimations in light of diseases, job demands, and psychological resources, and also included information about illnesses and work absenteeism. The items and the classification of the work ability index are presented in Table I.

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Table I. Work Ability Index

I II III IV V VI VII

Item a

Scaleb

Current work ability compared with the lifetime best Work ability in relation to the demands of the work Number of diagnosed diseases Estimated work impairment due to diseases Sick leave during the past year Own prognosis of work ability after 2 years Mental resources (enjoying daily tasks, activity and life

0-10 2-10 1-7 1-6 1-5 1, 4, 7 1--4

spirit, optimistic about the future) aCategories of the Work Ability Index: poor = 7-27; below average = 28-36; above average = 37--43;

ood = A.4 49. he range of the scale for each item is the following: (I) 0 = very poor, 10 = very good; (II) 2 = very poor, 10 = very good; (III) 1 -- 5 or more diseases, 7 = no diseases; (IV) 1 = fully impaired, 6 = no impairment; (V) 1 = 100 days or more, 5 = 0 days; (VI) 1 = hardly able to work, 4 = not sure, 7 = relatively certain, and (VII) 1 = very poor, 4 = very good. Means and standard deviations were used for the descriptive evaluation of the data. The changes in work postures were tested with the multivariable variance analysis (before vs. after 1 year) and with Students t-test for paired observations for the lifting techniques, pain lines, and work ability index. The statistical analyses were done by the SAS Statistical Package.

RESULTS The proportion of poor back postures in daily work tasks was smaller (p < 0.001) after the rehabilitation courses and also after 1 year than before the courses (Fig. 1). In the beginning of the courses, the subjects worked with a bent and rotated/twisted back for 28% of the studied time, and after 1 year the same proportion was 6%. Postures with one or both arms over shoulder level (Fig. 2) covered 34% of the studied time in the beginning of the courses and 13% in the 1-year follow-up (p < 0.001). Sitting postures increased from 2% to 8% of the studied time. Before the rehabilitation courses, 14% of the subjects used a chair during milking and in the 1-year follow-up the corresponding proportion was 54%. Standing with both legs straight decreased from 55% to 44%, and kneeling postures increased from 1% to 6% of the work time when compared with the postures used before the courses and after 1 year. In the beginning of the rehabilitation, 48% of the work postures during milking belonged to action categories 3 and 4, and after 1 year the same proportion was 20%. The most typical postures according to the OWAS classification before and after the rehabilitation and after 1 year are presented in Fig. 3. The L5/S1 disk compression force was unchanged among the women and greater after 1 year than in the beginning of the rehabilitation among the men (Table II). The musculoskeletal pain index was 34 for the women and 21 for the men in the beginning of the rehabilitation. The values after 1 year were 22 (p < 0.001) and 18, respectively. The changes were greatest for the neck, lower back, and hip symptoms among the women (p < 0.001) and for lower back symptoms

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Fig. 1. Postures of the back (% of the studied time) according to the OWAS method before and after the rehabilitation courses and in the 1-year follow-up.

Fig. 2. Postures of the arms (% of the studied time) according to the OWAS method (arms under shoulder level, one arm over shoulder level, both arms over shoulder level) before and after the rehabilitation courses and in the 1-year follow-up. a m o n g the men (p < 0.01). The work ability index improved both a m o n g the w o m e n (p < 0.01) and the m e n (p < 0.05) during the year (Fig. 4).

DISCUSSION Work techniques influence the biomechanical and cardiorespiratory load of work. In this study, the work techniques were analyzed from the used work postures and lifting techniques, but it could also be analyzed with the use of muscle activity,

Effects of Occupationally-Oriented Rehabilitation Pre-rehabilitation (n=46) 2121 (2)

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197

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1121 (1) 18%

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1121 (i) 10%

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7% Fig. 3. The five most typical work posture combinations according to the OWAS method before the course, after the course and in the 1-year follow-up. The figure of posture combination, the OWAS code of the combination, the action category and their proportion (%) of the studied time are given in the figure.

Table II. The Static Back Compression Force (N) During Sack Lifting (Women 20 kg, Men 30 kg) Before and After Rehabilitation and at the 1-Year Follow-up Before Mean SD

Women (n = 15) After 1 year Mean SD Mean SD

Before pa Mean SD

Men (n = 10) After 1 year Mean SD Mean SD

pa

From floor level 3202 (440) 3202 (445) 3047 (480) ns 4452 (654) 4630 (591) 4813 (770) * From 45 cm level 2841 (359) 2752 (430) 2825 (599) ns 3480 (970) 3580 (987) 4245 (1398) * aThe change between measurements before the course and after 1 year. *p < .05.

movement speed, acceleration, joint angles, heart rate, oxygen consumption, or perceived exertion (3, 24). Changes in motor function, work tools, and the work environment affect work techniques, which can be considered an integral part of occupational skill. The OWAS method was suitable for analyzing the postures used in agricultural work because the work included mainly whole-body movements. Previously Pinzke (25) has also reported that observation from video recordings is useful in analyses of postural load in agriculture. These methods can also be used for evaluating the

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Im r~

Before 1 yeor follow-up

]

40 30 20 ~0 0 Women (n=47)

Men (n=41)

Fig. 4. The work ability index of the women and men before the rehabilitation and in the 1 year follow-up. *p < .05. **p < .01.

effectiveness of rehabilitation (26). The computerized system seemed to be more accurate and repeatable than the traditional visual evaluation of work techniques. The video recordings were made during the rehabilitation courses and not in the subjects' own barns in habitual work situations. Therefore, the extent to which they used the new work techniques daily at home is not certain. At the beginning of the course and in the follow-up, the subjects were asked to work with their normal daily work techniques. The new techniques had obviously been actively used during the year because the subjects used them in the follow-up very naturally and in the same manner as at the end of the course. It would have been very difficult for the subjects to use the techniques for the video recordings if they had not worked so at home. The two-dimensional Static Strength Prediction Program seemed to be applicable in the analysis of slow movements in the sagittal plane, but the method does not take into account movement speed and acceleration. The method was heavy and time-consuming because the posture data were obtained using manual measurements from the photographs.The data of only 25 subjects were suitable for analysis since the photographs were taken straight from the side and the subjects lifted without back rotation in all three measurements. A synchronized video-EMG method would be more suitable for analyzing the changes in lifting due to rehabilitation. Other work-physiological methods might also be usable in analyses of the effectiveness of occupationally-oriented rehabilitation. Changing personal work techniques requires much training, motivation, and probably also other factors, for example motor skills (17, 13, 27). This study showed that farmers could change their daily work techniques during this kind of very active work-oriented rehabilitation, and the changes were still seen after 1 year. Bent and twisted back postures and postures with the arms over the shoulder level especially decreased. Adopting the use of a milking chair or a semi-kneeling posture effec-

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199

tively diminishes squatting postures that hinder the circulation in lower limbs during milking (1). During the lifting of sacks, relatively high peak force values were observed. The average magnitude of the static peak compression exceeded the N I O S H criterion of 3400 N for lumbar disk compression among the men, who lifted 30 kg (28). Therefore, it seems that sacks of 30 kg cannot be lifted "ergonomically," as Leskinen (6) has shown. During rehabilitation, it would be useful to analyze the work processes that include lifting and try to find ergonomic measures to minimize the manual handling of heavy loads. Changes in the work environment (i.e., work levels, mechanical aids), load characteristics (lighter sacks), or the work method would be the most effective measures to decrease the back load. A decrease in musculoskeletal pain and an increase in work ability can indicate lighter work loads or better subjective well-being. However, it is important to note that another goal of the rehabilitation program was to develop the subjects physical and psychological abilities. This intervention study showed that it is possible to produce significant, long-lasting effects on rehabilitees' work techniques and work ability, and also improve subjective well-being.

ACKNOWLEDGMENTS The author wishes to thank Professor Veikko Louhevaara for his valuable comments during the preparation of this manuscript, Pentti Mgkel/i, M.Sc., for his help in the statistical analysis, and Georgianna Oja, ELS, for her advice when correcting the language. The author thanks the staffs of the Siilinj~irvi Rehabilitation Centre, the Kaprakka-Rehabilitation and Research Institute and the Herttua Rehabilitation Centre for their cooperation in this study. This study was funded by the Social Insurance Institution in Finland.

REFERENCES 1. 2. 3. 4. 5. 6. 7. 8. 9.

NemethG, Arborelius UP, Svensson OK, Nisell R. The load on the low back and hips and muscular activity during machine milking. Int l Ind Ergon 1990; 5: 115-123. Penttinen J. Back pain and sciatica in Finnish farmers. Helsinki: Social Insurance Institution, 1987 (publications of the Social Insurance Institution ML:71). Nevala-Puranen N, Taattola K, Ven~il~iinenJM. Rail system decreases physical strain in milking. Int I I n d Ergon 1993; 12: 311-316. Morrissey SJ. Influences of task posture on physiological task responses. Int l Ind Ergon 1987; I: 209-217. MitalA. Effect of body posture and common hand tools on peak torque exertion capabilities.Appl Ergon 1986; 17: 87-96. Leskinen T. Evaluation o f the load on the spine based on a dynamic biomechanical model, eleetromyographic activity of back muscles, and changes in stature. Tampere: Tampere University of Technology, 1993 (publications 112). ChaffinDB, Andersson G. Occupational biomechanics. New York: John Wiley & Sons, 1984. AyoubMM, Mital A. Manual materials handling. London: Taylor & Francis, 1989. Kilbom/~, Persson J, Jonsson B. Disorders of the cervicobrachialregion among female workers in the electronics industry. Int I I n d Ergon I986; 1: 37-47.

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10. Burdorf A. Exposure assessment of risk factors for disorders of the back in occupational epidemiology. Scand J Work Environ Health 1992; 18: 1-9. 11. Winkel J, Westgaard R. Occupational and individual risk factors for shoulder-neck complaints: Part II--The scientific basis (literature review) for the guide. Int J lnd Ergon 1992; 10: 85-104. 12. Versloot JM, Rozeman A, van Son AM, van Akkerveeken PF. The cost-effectiveness of a back school program in industry: A longitudinal controlled field study. Spine 1992; 17" 22-27. 13. V/iyrynen S, K6n6nen U. Short- and long-term effects of a training program on work postures in rehabilitees: A pilot study of loggers suffering from back troubles, lnt J Ind Ergon 1991; 7: 103-109. 14. H~irk~ip~i~iK, JLrvikoski A, Mellin G, Hurri H. A controlled study on the outcome of inpatient and outpatient treatment of low back pain: Part I. Pain, disability, compliance, and reported treatment benefits three months after treatment. Scand J Rehab Med 1989; 21: 81-89. 15. H/irk~ip~i~iK, Mellin G, Jiirvikoski A, Hurri H. A controlled study on the outcome of inpatient and outpatient treatment of low back pain: Part III. Long-term follow-up of pain, disability, and compliance. Scand J Rehab Med 1990; 22: 181-188. 16. Leino P, Kivek/is J, H/inninen K. Effects of work-oriented fitness courses in lumberjacks with low back pain. J Occup Rehab 1994; 4: 67-76. 17. Hopsu L, Louhevaara V. The influence of educational training and ergonomic job redesign intervention on the cleaners' work: A follow-up study. In: Queinnec Y, DanieUou F, eds. Design for everyone: Proceedings of the 11th Congress of the International Ergonomics Association. Paris: International Ergonomics Association, 1991, pp. 534-536. 18. Videman T, Rauhala H, Asp S, Lindstr6m K, Cedercreutz G, K~imppi M, Tola S, Troup JDG. Patient-handling skill, back injuries, and back pain: An intervention study in nursing. Spine 1989; 14: 148-156. 19. Millar WJ, Stephens T. The prevalence of overweight and obesity in Britain, Canada, and United States. Am J Public Health 1987; 77: 38-41. 20. Louhevaara V, Suurn/ikki T. OWAS: A method for the evaluation of postural load during work. Helsinki: Institute of Occupational Health and Centre for Occupational Safety, 1992 (training publication 11). 21. Mattila M, Karwowski W, Vilkki M. Analysis of working postures in hammering tasks on building construction sites using the comI~uterized OWAS method. Appl Ergon 1993; 24: 405-412. 22. Kuorinka I, Jonsson B, Kilbom A, Vinterberg H, Biering-S6rensen F, Andersson G, J6rgensen K. Standardized Nordic questionnaires for the analysis of musculoskeletal symptoms. Appl Ergon 1987; 18: 233-237. 23. Tuomi K, Ilmarinen J, Eskelinen L, J/irvinen E, Toikkanen J, Klockars, M. Prevalence and incidence rates of diseases and work ability in different work categories of municipal occupations. Scand J Work, Environ Health 1991; 17: 67-74. 24. Lusa S, Louhevaara V, Smolander J, Kinnunen K, Korhonen O, Soukainen J. Biomechanical evaluation of heavy tool-handling in two age groups of firemen. Ergonomics 1991; 34: 1429-1432. 25. Pinzke S. A computerized system for analyzing working postures in agriculture. Int J Ind Ergon 1994; 13: 307-315. 26. Carr E. Observational methods in rehabilitation research. Clin Rehab 1991; 5: 89-94. 27. Singer R. Motor learning and human performance. New York: MacMillan, 1980. 28. Waters TR, Putz-Anderson V, Garg A, Lawrence JF. Revised NIOSH equation for the design and evaluation of manual lifting tasks. Ergonomics 1993; 36: 749-776.

Effects of occupationally-oriented rehabilitation on farmers' work techniques, musculoskeletal symptoms, and work ability.

Changes in work techniques, musculoskeletal symptoms and work ability were studied after occupationally-oriented rehabilitation courses for farmers ex...
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