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New ergonomic problems in mechanized logging operations
InternationalJournal of Industrial Ergonomics, 5 (1990) 267-273 Elsevier
267
NEW ERGONOMIC PROBLEMS IN MECHANIZED LOGGING OPERATIONS Sven-Ake Axelsson and Bengt Pont6n Department of Operational Efficiency, College of Forestry, Swedish University of Agricultural Sciences, S-770 73 Garpenberg (Sweden)
ABSTRACT A Health Risk Program for forest work has been developed in order to improve health risk identification by systematic evaluation of the relationships between work and health complaints, and to create a base for decisions on different actions to reduce the health risk. This paper deals particularly with logging-machine operators and the problem of the "'overload syndrome" characterized by complaints and injuries to the neck, arms, and cervical spine. The results of health investigations of 1,174 machine operators indicate a prevailing average overload syndrome of 50 %, mainly due to one-sided, repetitive, short-cycle working movements with arms and hands. The analyses show that a whole battery of measures is needed to radically improve this serious situation. Single measures might be positive, but are not enough. To be effective, the full program of measures must be carried out and adapted individually to each machine operator. Improvements in technology/ergonomics are needed, especially regarding the sitting work posture in the cabin, i.e., design of the arms of the chair, controls, and instruments. Important individual factors are working techniques, micropauses, and physical fitness. New work organization is the most difficult part of the measures to realize in practice, but also has the highest potential for improving the situation. Examples of issues to address in this area are design and length of the working shift, job rotation, work tasks and responsibilities, team work, and motivation and payment systems.
RELEVANCE TO INDUSTRY Ergonomic improvements in forest machine design have created a new class of musculoskeletal problems. Continuing ergonomic redesign is necessary to address the problem of overload syndrome. The "'Health Risk Program" developed for forest work evaluation couM be applied in other occupational health situations.
KEYWORDS Controls, job rotation, overload syndrome, musculoskeletal disorders.
INTRODUCTION The extensive mechanization of tree harvesting has significantly improved the forest workers' safety and health. The man with the chain saw has 0169-8141/90/$03.50 © 1990 - Elsevier Science Publishers B.V.
become a machine operator, well-protected in a cabin meeting good ergonomic standards. Successful improvements have been made regarding the classical problems of industrialized work such as noise, vibration, oil, and maintenance.
268 During recent years, a new kind of occupational health problem has emerged in modem industrial work. It has been called the overload syndrome and is characterized by complaints and injuries to the neck, arms, and cervical spine. Man is not "designed" to sit down and perform repetitive work for many hours in a fixed position. Even very light, short-cycle movements of hands and arms may cause overload symptoms, and with prolonged exposure, lead to injuries. Reports from medical experts related to forestry indicate that these serious health problems now also affect today's specialized logging-machine operators. The objectives of this study were (1) to establish the prevalence of the overload syndrome among logging-machine operators in Sweden, and (2) to evaluate some preventive and remedial actions in practice.
MATERIALS AND METHODS A Health Risk Program for forest work has been developed in order to improve health risk identification by systematic evaluation of the relaINDIVIDUAL LEVEL INTERVIEW
tionship between work and health complaints, and to create a base for decisions on different actions to reduce the health risk. The program is based on cooperation between the forestry Occupational Health Service (OHS) units in Sweden and the College of Forestry at the Swedish University of Agricultural Sciences. Joint studies are carried out in which the OHS units collect data and the College processes the results and coordinates the studies. The principal structure of the program is illustrated in Fig. 1. In the screening part, the employees fill in a standardized questionnaire dealing with their work tasks, background, living conditions, state of health, and the possible connections between health problems and work. The answers are checked and completed in an interview by the OHS nurse. Measurements of hearing and blood pressure are also made. If necessary, rehabilitative measures are taken by the OHS doctor or physiotherapist. The data collected in the broad survey is used to identify and analyze health risks in forest work. So far 78 companies and management districts have participated at 24 OHS units. A total of some 6,700 forest employees (among these 3,600 ~E
GROUP LEVEL )
- by company nurse - structured by questionnaire
SCREENING
)
- questionnaire on health, work, l i v i n g conditions
i COMPANY REPORT
LEVEL
BROADSURVEY - data on ca. 6700 forest workers
IDENTIFICATION AND ANALYSES OF HEALTH RISKS
- analyses by safety committee and OHS
- broad survey - knowledge from OHS, research
FURTHER INVESTIGATIONS
FURTHER INVESTIGATIONS
TARGETSTUDIES
- by company doctor, physiotherapist,
- towards groups with many complaints
- towards groups at risk or of other
BASE FOR DECISIONS
BASE FOR DECISIONS
BASE FOR DECISIONS
- by f o r e s t worker, OHS unit and company
- by company and OHS unit
- by OHS, companies, researchers, manuf a c t u r e r s , etc.
I
Fig. l. The pfincip~ structure o f t h e H e ~ t h R i s k P r o g r a m . The total program includes h e a t h investigations of 6,700workers, carried out by the forestry OccupationalHealthService(OHS).
269 I
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THORACIC BACK LOIN/LUMBAR. BACK/LEG. " ' - - ~ OTHER 'L ' - " IMPAIRED HEARING BLOOD PRESSURE.
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Fig. 2. Results of health investigations of 6,700 forest employees at 78 companies/districts. The percentile frequencies of forest employees with health complaints during the last 12 months. Each point represents one company/district. Only units with at least 20 forest employees are presented.
cutters, 1,200 machine operators, and 600 supervisors) and 500 employees from other trades (i.e., industry, office work) have been studied (see Fig. 2). Two target studies of 300 machine operators (of forwarders, processors, and harvesters) have been completed in order to get a more detailed picture of how the technical-ergonomic improvements of new machines, job rotation, and some individual factors affect the overload syndrome.
RESULTS Health status The machine operator's work is characterized by one-sided, repetitious, short-cycle working
movements. He is sitting in a locked position many hours per day working mostly with his arms and hands. The results of health investigations of 1,174 machine operators indicate a prevailing average overload syndrome of 50%, mainly characterized by neck/shoulder complaints. The complaints are also influenced by other work factors (e.g., working technique, psycho-social situation). The prevalence slightly increases with age. (See Fig. 3.) Even for young operators (20-25 years), however, the prevalence is high, i.e., 44%. The prevalence is highest (60%) in the age group of 45-55 years, with a working time of 10-19 years as machine operators. The lowest value, 27%, refers to 35-44 year old operators, with a working time of 1-4 years. The number of operators studied, divided into
270 Machine operators w i t h c o m p l a i n t s {%)
general. More knowledge was needed to establish a base for recommendations on measures to be taken. In order to get a more detailed picture of how the technical improvements of the machines, job rotation, and some individual factors affect the neck/shoulder complaints, two target studies were carried out.
Y e a r s o f work:
100
-
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[]
-
0
0
-
I0 -- 19 years
P,
A
.
20
90
-
-
BO
1 year
~
1
4 years
5 -
9 years years
70 60 50 40
Operators of new logging machines
30
As stated in the introduction, the modern logging machines now used in Sweden have a significantly improved ergonomic standard, particularly regarding the design of the operator's workplace in the cabin. The objective of the first target study was to find out whether this favourable ergonomic development of new machines has had any positive impact on the overload syndrome among the machine operators. The study was carried out in 1983-84. A " n e w " machine was defined as one manufactured in 1978 or later. Only full-time operators working with one new machine during at least the last two years were included. This means that the operators' exposure time to work with new machines was 2 - 4 years. A total of 169 operators of both forwarders (75), processors (57), and harvesters (37) participated. Health examinations and interviews were done by 11 of the larger OHS units in the whole country. The results are summarized in Table 2. Of the 169 machine operators, 43% indicated that they had symptoms of overload injuries at the time when they changed from the old to the new machine. After 2 - 4 years of working with the new machines, the prevalence figure had increased from 43 to 58%. There were no obvious differences between operators of forwarders, processors, and
20 'tO 0
1
0
~.0
1
20
I
30 AGE CLASS
I
dO
I
I
50
60
I
70
(years)
Fig. 3. Logging machine operators (%) with neck/shoulder complaints by age and number of years at work.
groups by age and years of work as a machine operator, is shown in Table 1. Groups in brackets are not included in Fig. 3.
Relationship between health status and work environment Analyses of the broad survey show that m a n y of the processor and harvester operators particularly had overload symptoms. Most of the operators (about 90%) stated that their complaints were related to the one-sided, static work movements, the controls, and the seat. There was little difference between those operating new and old machines and between those working different time schedules. There were also small differences between those who did and those who did not do physical exercise in their spare time. However, the results from the broad survey are fairly rough and
TABLE 1 The total of 1,174 machine operators divided into groups by age and years of work as a machine operator Total
Time as machine operator (years)
Age < 24
25-34
35-44
45-54
55 +
<1 1- 4 5- 9 10-19
(13) 56 (13) (0)
22 81 142 74
(9) 50 85 224 37 405
(2) (11) 40 140 66 259
(0) (2) (5) 52 50 109
20 + Total
(o) 82
(o) 319
46 200 285 490 153 1174
271
Earlier studies F e w studies have b e e n m a d e in forestry o f the r e l a t i o n s h i p b e t w e e n j o b r o t a t i o n a n d the o v e r l o a d s y n d r o m e . Studies in o t h e r trades o f t e n stress the positive i m p a c t of v a r i a t i o n a n d p a u s e s d u r i n g work, b u t few studies have dealt with a c t u a l j o b r o t a t i o n . J o b r o t a t i o n has b e e n c o n s i d e r e d to b e s o m e t h i n g positive, for health (physical a n d p s y c h o l o g i c a l ) as well as for longt e r m p r o d u c t i v i t y . However, f o r m e r studies have also p o i n t e d o u t several c o n s t r a i n t s to j o b rotation, such as: - M a n y o l d e r forest w o r k e r s n o t w a n t i n g to learn n e w types of work, - M a c h i n e o p e r a t o r s n o t w a n t i n g to " l e n d " their m a c h i n e to others, - Practical p r o b l e m s , for i n s t a n c e in c h a n g i n g b e t w e e n m a c h i n e w o r k a n d c h a i n - s a w cutting, - U n s u i t a b l e wage forms, - E d u c a t i o n a n d t r a i n i n g of the p a r t i c i p a n t s , - Difficulties in f i n d i n g m e a n i n g f u l w o r k tasks to r o t a t e to, for i n s t a n c e d u r i n g the shift " o n the g r o u n d " in the 3 - h o u r shift (see F i g u r e 4).
TABLE 2 The development of symptoms of overload injuries among 169 operators after 2-4 years of work with new machines (percentage figures) Group 1. Operators with previous symptoms After 2-4 years of w o r k : Recovered 2% Improved 10% No change 18% Deteriorated 13%
43%
Group 2. Operators without previous symptoms 57% After 2-4 years of work: New symptoms 17% Still without symptoms 40% Total after 2-4 years of work with the new machine: Operators with symptoms: Operators without symptoms:
58% 42%
harvesters. It m i g h t b e n o t e d f r o m the t a b l e t h a t o n l y 2% o f the o p e r a t o r s recovered a n d 10% imp r o v e d after having c h a n g e d to the new machine, while 13% d e t e r i o r a t e d in r e l a t i o n to earlier s y m p toms a n d 17% d e v e l o p e d new s y m p t o m s . T h e target s t u d y o n o p e r a t o r s of new m a c h i n e s showed, in short, that the general t e c h n i c a l - e r g o n o m i c i m p r o v e m e n t s c a r r i e d o u t in the n e w e r m a c h i n e s have n o t b e e n e n o u g h to relieve the o p e r a t o r s of their s y m p t o m s a n d to p r e v e n t the d e v e l o p m e n t of new ones.
The broad survey A d e t a i l e d analysis of the 431 p r o c e s s o r o p e r a t o r s that h a d p a r t i c i p a t e d in the b r o a d survey up to t h a t p o i n t gave a p i c t u r e of the s i t u a t i o n where o p e r a t o r s were w o r k i n g with j o b r o t a t i o n . T h e analysis showed that: - T h e r e was a t e n d e n c y for j o b r o t a t i o n to b e m o r e c o m m o n a m o n g the y o u n g e r a n d those with short m a c h i n e - o p e r a t i n g experience; - J o b r o t a t i o n was m o r e c o m m o n a m o n g t r a i n e d operators; - J o b r o t a t i o n was as c o m m o n in p a r t l y m e c h a nized as in fully m e c h a n i z e d systems; -Job r o t a t i o n was as c o m m o n a m o n g those w o r k i n g on piece rate as a m o n g those w o r k i n g o n time wage; - M o r e o f those w h o r o t a t e were p h y s i c a l l y active in their s p a r e time.
Job rotation of Iogglng-machlne operators I n o r d e r to get a p i c t u r e of h o w j o b r o t a t i o n a n d some i n d i v i d u a l factors affect the o v e r l o a d s y n d r o m e , a s e c o n d target s t u d y was m a d e in close c o l l a b o r a t i o n with 3 of the larger O H S units. T h e study was l i m i t e d to p r o c e s s o r o p e r a t o r s . J o b r o t a t i o n was d e f i n e d as the a l t e r n a t i o n b e t w e e n m a c h i n e driving a n d o t h e r types of w o r k d u r i n g the d a y (e.g., shift form), the week (e.g., r o t a t i o n b e t w e e n m a c h i n e w o r k a n d c h a i n saw cutting), a n d the season (e.g., planting, cleaning).
Operator A Operator B
06.00
09.00
,
i ~- . . . . . . !
The second target study A t o t a l o f 110 p r o c e s s o r o p e r a t o r s p a r t i c i p a t e d in the s e c o n d 12.00 -t
i
I t ....
15.00
18.00
Hours
i ~ ~
i
Fig. 4. The organization of the 3-hour shift. Two operators are assigned to one machine, and they rotate in 3-hour periods. Operator A start at 6 a.m, and operator B at 9 a.m. During the 3 hours "on the ground", the operator takes his lunch break and carries out repairs, planning, chain saw cutting, etc; - machine work, - - - - - - lunch break and work "on the ground".
272 TABLE 3 The development of symptoms of overload injuries among processor operators after changing from regular 8-hour shift to 3-hour shift (percentage figures) 3-hour shift 8-hour shift (76 operators). (25 operators) Operators with previous symptoms: Recovered 12 Improved 22 No change 21 Deteriorated 1 Operators without previous symptoms
Total after 3-4 years of work: Operators with symptoms Operators without symptoms
24 8 28 4
44
36
100%
100%
44 56
40 60
100%
100%
target study. The objective was to study the effect of job rotation (especially the 3-hour shift, as shown in Fig. 4) and some individual factors on the symptoms of overload injuries. Of the 110 machine operators in the study, 76 had worked the 3-hour shift during at least the last 2 years (on an average, 3 - 4 years), and 25 operators had worked a regular 8-hour shift. (Nine operators had various shift forms and are not included in this analysis.) The results are summarized in Table 3. The figures indicate that the effect on the overload symptoms of changing from a regular 8-hour shift to the 3-hour shift is limited and uncertain (prevalence figure of 40% and 44% respectively, after 3 - 4 years of work). These figures are influenced by the fact that more of those working an 8-hour shift (24%) had recovered than had those working a 3-hour shift (12%). In total, an equal share of the two groups had improved or recovered. On the other hand, the 3-hour shift seems to have a positive effect on earlier established symptoms. Among the 30% of the operators who had established symptoms before they started to work the 3-hour shift, 74% improved or recovered. The corresponding figure among the 22% who established symptoms when they were working the 3-hour shift was 47%. (Three operators had given incomplete answers.) The results indicate that the 3-hour shift, as a general measure, did not
radically solve the neck/shoulder problems, but it may have positive effects on some operators with established complaints. Pauses and micropauses during work are not very common. Forty-nine percent of the processor operators seldom or never released the controls, and forty percent seldom or never stepped out of their machine during the work shift. One reason that the 3-hour shift has not led to the expected decrease in complaints could be that the operators work more intensively during the 3 running hours. Operators who worked the 3-hour shift stepped out of the machine and let go of the handles significantly less often than did the operators working a regular 8-hour shift.
PRACTICAL IMPLICATIONS For measures to reduce the prevailing health risks in practice, it is feasible to group the various actions into the following three categories: - Technical - Individual - Organizational The work situation and work factors change over time. The effect on the individual complaint can be illustrated as in Figure 5. A certain work produces specific risks for the development of "Health r i s k "
at work
Individual .............................................. Organizational
Individual "limit"
Individual
Organizational Technical
Technical
....................................................
(1)
(2)
Time
Fig. 5. The multiple effect on the health risks of different individual, organizational, and technical work factors, of points in time. The individual limit is the limit above which a complaint may be developed. (1); In this case the risk of neck/shoulder complaints is evident for the operator, case (2): The work organization has been changed for the operator, e.g., by job rotation between machine work and other work tasks (decreasing the time of exposure for the high tensions in the neck/shoulder muscles). There is no risk of complaints at present.
273 complaints. The health risks from various factors are added to each other. Each individual has a limit above which he will develop a complaint. This limit depends on the physical and psychological status of the individual, as well as on his body's resistibility to stress. The limit can also change: for instance, a severe cold or problems at home might lower the limit; physical training might raise the limit. The actual development of a complaint or illness also depends on the time worked above the limit. Working high above the limit may result in a complaint after only a short period of time (e.g., a cutter taking down a hanging tree and using his ultimate strength in an awkward position might get an acute back pain). Working just at the limit might result in a complaint only after a very long period of time (e.g., a skidder operator working with small tensions in the muscles might take up to 20 years to develop a complaint). Since the factors are added to each other, a factor with a high risk to the employee can be compensated for by a low risk from another factor, as shown in Figure 5. The intention of Figure 5 is to serve as a pedagogic model. This model is now being used to facilitate and motivate the implementation of measures in Swedish forestry. New projects have recently been started at several forest companies. The results of the Health Risk Program reported in this paper indicate an alarmingly high prevailing average overload syndrome figure of 50% among the forest workers. The results and experiences so far also indicate that a whole battery of measures is needed to radically improve this serious situation, including new technology and new forms of work organization, as well as motivation of the machine operator to influence his own situation. Single measures might be positive, but are not enough. To be effective, the full program of measures must be carried out, and it must be adapted individually to each machine operator. Rehabilitative measures should be taken as soon as possible after the complaint first appears. Improvements in t e c h n o l o g y / e r g o n o m i c s are needed. This is especially true regarding the sitting work posture in the cabin, i.e., design of the arms of the chair, controls, and instruments. Reduction of whole-body vibrations is also important.
Important individual factors are working techniques, micropauses, and physical fitness. Support from a physiotherapist is essential. It might even be necessary to introduce physical training during the work shift. A new work organization is the most difficult part of the proposed battery of measures to realize in practice, but is also the part that probably has the highest potential for improving the situation. Examples of issues to address are design and length of the working shift, job rotation, work tasks and responsibilities, team work, and motivation and payment systems. This is a real challenge to undertake, both for the researchers and the companies. The experience thus far indicates that the difficulties are great and the long-term effects uncertain. One particular difficulty is with developing new methods for evaluating the effect of measures undertaken. The effects of several factors should be evaluated, not only on health aspects, but also productivity, quality of the work, organization, economy, and others. Evaluations from a health risk point of view are complicated in this case, for overload complaints and injuries often take a long time to develop. The fact is that the positive effects of various measures are often short-term and might weaken and disappear with time. Thus far, we have learned from the current attempts and trials at different forest companies that, in order to get the full effect of the program of suggested measures, it is necessary to start by increasing the motivation and by improving the cooperation of all parties involved. This means not only the researchers and the manufacturers of logging machines, as in the past, but also the forest company, management, supervisors in the field, and the logging-machine operators themselves.
References This paper is based mainly on results from the current Health Risk Program at the Swedish College of Forestry, Garpenberg. Details of the program and comprehensivelist of references are given in: Pontgn, B., 1988. Health Risks in Forest Work--A Program for Action. Report No. 177, Department of Operational Efficiency, College of Forestry, S-770 73 Garpenberg, Sweden.
267
NEW ERGONOMIC PROBLEMS IN MECHANIZED LOGGING OPERATIONS Sven-Ake Axelsson and Bengt Pont6n Department of Operational Efficiency, College of Forestry, Swedish University of Agricultural Sciences, S-770 73 Garpenberg (Sweden)
ABSTRACT A Health Risk Program for forest work has been developed in order to improve health risk identification by systematic evaluation of the relationships between work and health complaints, and to create a base for decisions on different actions to reduce the health risk. This paper deals particularly with logging-machine operators and the problem of the "'overload syndrome" characterized by complaints and injuries to the neck, arms, and cervical spine. The results of health investigations of 1,174 machine operators indicate a prevailing average overload syndrome of 50 %, mainly due to one-sided, repetitive, short-cycle working movements with arms and hands. The analyses show that a whole battery of measures is needed to radically improve this serious situation. Single measures might be positive, but are not enough. To be effective, the full program of measures must be carried out and adapted individually to each machine operator. Improvements in technology/ergonomics are needed, especially regarding the sitting work posture in the cabin, i.e., design of the arms of the chair, controls, and instruments. Important individual factors are working techniques, micropauses, and physical fitness. New work organization is the most difficult part of the measures to realize in practice, but also has the highest potential for improving the situation. Examples of issues to address in this area are design and length of the working shift, job rotation, work tasks and responsibilities, team work, and motivation and payment systems.
RELEVANCE TO INDUSTRY Ergonomic improvements in forest machine design have created a new class of musculoskeletal problems. Continuing ergonomic redesign is necessary to address the problem of overload syndrome. The "'Health Risk Program" developed for forest work evaluation couM be applied in other occupational health situations.
KEYWORDS Controls, job rotation, overload syndrome, musculoskeletal disorders.
INTRODUCTION The extensive mechanization of tree harvesting has significantly improved the forest workers' safety and health. The man with the chain saw has 0169-8141/90/$03.50 © 1990 - Elsevier Science Publishers B.V.
become a machine operator, well-protected in a cabin meeting good ergonomic standards. Successful improvements have been made regarding the classical problems of industrialized work such as noise, vibration, oil, and maintenance.
268 During recent years, a new kind of occupational health problem has emerged in modem industrial work. It has been called the overload syndrome and is characterized by complaints and injuries to the neck, arms, and cervical spine. Man is not "designed" to sit down and perform repetitive work for many hours in a fixed position. Even very light, short-cycle movements of hands and arms may cause overload symptoms, and with prolonged exposure, lead to injuries. Reports from medical experts related to forestry indicate that these serious health problems now also affect today's specialized logging-machine operators. The objectives of this study were (1) to establish the prevalence of the overload syndrome among logging-machine operators in Sweden, and (2) to evaluate some preventive and remedial actions in practice.
MATERIALS AND METHODS A Health Risk Program for forest work has been developed in order to improve health risk identification by systematic evaluation of the relaINDIVIDUAL LEVEL INTERVIEW
tionship between work and health complaints, and to create a base for decisions on different actions to reduce the health risk. The program is based on cooperation between the forestry Occupational Health Service (OHS) units in Sweden and the College of Forestry at the Swedish University of Agricultural Sciences. Joint studies are carried out in which the OHS units collect data and the College processes the results and coordinates the studies. The principal structure of the program is illustrated in Fig. 1. In the screening part, the employees fill in a standardized questionnaire dealing with their work tasks, background, living conditions, state of health, and the possible connections between health problems and work. The answers are checked and completed in an interview by the OHS nurse. Measurements of hearing and blood pressure are also made. If necessary, rehabilitative measures are taken by the OHS doctor or physiotherapist. The data collected in the broad survey is used to identify and analyze health risks in forest work. So far 78 companies and management districts have participated at 24 OHS units. A total of some 6,700 forest employees (among these 3,600 ~E
GROUP LEVEL )
- by company nurse - structured by questionnaire
SCREENING
)
- questionnaire on health, work, l i v i n g conditions
i COMPANY REPORT
LEVEL
BROADSURVEY - data on ca. 6700 forest workers
IDENTIFICATION AND ANALYSES OF HEALTH RISKS
- analyses by safety committee and OHS
- broad survey - knowledge from OHS, research
FURTHER INVESTIGATIONS
FURTHER INVESTIGATIONS
TARGETSTUDIES
- by company doctor, physiotherapist,
- towards groups with many complaints
- towards groups at risk or of other
BASE FOR DECISIONS
BASE FOR DECISIONS
BASE FOR DECISIONS
- by f o r e s t worker, OHS unit and company
- by company and OHS unit
- by OHS, companies, researchers, manuf a c t u r e r s , etc.
I
Fig. l. The pfincip~ structure o f t h e H e ~ t h R i s k P r o g r a m . The total program includes h e a t h investigations of 6,700workers, carried out by the forestry OccupationalHealthService(OHS).
269 I
I
50
|
I
I
100:
I
L
;
EYESI NOSE' THROAT' COUGHS' HEADACHE' DIZZINESS' TEMPER INSOMNIA] WEIGHT INCREASE] STOMACH
[
l
Average
.-.
. . . . . . .
......
~
STOM~ ,CHu ,RD N IK E N IS E IA LE R G Y E Z cE M S A Y .S T E M O T H E R H ~ E A R T .~ _ ' T : .
"..
WHITE FINGERS • • I ..... SHOULDER ....... I UPPERA R M ~ ..... ELBOW.IZ~Z.___/ .... F O R E A R M ~ "" HANDI ~ ' - - - - ' ' " FINGERl - - T - - " " HIP[ . . . . ~ - - " " THIGH ~"~--- ' KNEEL" • - ~' --FORELEG FOOT BACK NECK/APJ4 " [ ......
::~---.
NECK.~ : ;
THORACIC BACK LOIN/LUMBAR. BACK/LEG. " ' - - ~ OTHER 'L ' - " IMPAIRED HEARING BLOOD PRESSURE.
;
.
.
.
.
.
.
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........
.
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........
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I
100~
Fig. 2. Results of health investigations of 6,700 forest employees at 78 companies/districts. The percentile frequencies of forest employees with health complaints during the last 12 months. Each point represents one company/district. Only units with at least 20 forest employees are presented.
cutters, 1,200 machine operators, and 600 supervisors) and 500 employees from other trades (i.e., industry, office work) have been studied (see Fig. 2). Two target studies of 300 machine operators (of forwarders, processors, and harvesters) have been completed in order to get a more detailed picture of how the technical-ergonomic improvements of new machines, job rotation, and some individual factors affect the overload syndrome.
RESULTS Health status The machine operator's work is characterized by one-sided, repetitious, short-cycle working
movements. He is sitting in a locked position many hours per day working mostly with his arms and hands. The results of health investigations of 1,174 machine operators indicate a prevailing average overload syndrome of 50%, mainly characterized by neck/shoulder complaints. The complaints are also influenced by other work factors (e.g., working technique, psycho-social situation). The prevalence slightly increases with age. (See Fig. 3.) Even for young operators (20-25 years), however, the prevalence is high, i.e., 44%. The prevalence is highest (60%) in the age group of 45-55 years, with a working time of 10-19 years as machine operators. The lowest value, 27%, refers to 35-44 year old operators, with a working time of 1-4 years. The number of operators studied, divided into
270 Machine operators w i t h c o m p l a i n t s {%)
general. More knowledge was needed to establish a base for recommendations on measures to be taken. In order to get a more detailed picture of how the technical improvements of the machines, job rotation, and some individual factors affect the neck/shoulder complaints, two target studies were carried out.
Y e a r s o f work:
100
-
[]
[]
-
0
0
-
I0 -- 19 years
P,
A
.
20
90
-
-
BO
1 year
~
1
4 years
5 -
9 years years
70 60 50 40
Operators of new logging machines
30
As stated in the introduction, the modern logging machines now used in Sweden have a significantly improved ergonomic standard, particularly regarding the design of the operator's workplace in the cabin. The objective of the first target study was to find out whether this favourable ergonomic development of new machines has had any positive impact on the overload syndrome among the machine operators. The study was carried out in 1983-84. A " n e w " machine was defined as one manufactured in 1978 or later. Only full-time operators working with one new machine during at least the last two years were included. This means that the operators' exposure time to work with new machines was 2 - 4 years. A total of 169 operators of both forwarders (75), processors (57), and harvesters (37) participated. Health examinations and interviews were done by 11 of the larger OHS units in the whole country. The results are summarized in Table 2. Of the 169 machine operators, 43% indicated that they had symptoms of overload injuries at the time when they changed from the old to the new machine. After 2 - 4 years of working with the new machines, the prevalence figure had increased from 43 to 58%. There were no obvious differences between operators of forwarders, processors, and
20 'tO 0
1
0
~.0
1
20
I
30 AGE CLASS
I
dO
I
I
50
60
I
70
(years)
Fig. 3. Logging machine operators (%) with neck/shoulder complaints by age and number of years at work.
groups by age and years of work as a machine operator, is shown in Table 1. Groups in brackets are not included in Fig. 3.
Relationship between health status and work environment Analyses of the broad survey show that m a n y of the processor and harvester operators particularly had overload symptoms. Most of the operators (about 90%) stated that their complaints were related to the one-sided, static work movements, the controls, and the seat. There was little difference between those operating new and old machines and between those working different time schedules. There were also small differences between those who did and those who did not do physical exercise in their spare time. However, the results from the broad survey are fairly rough and
TABLE 1 The total of 1,174 machine operators divided into groups by age and years of work as a machine operator Total
Time as machine operator (years)
Age < 24
25-34
35-44
45-54
55 +
<1 1- 4 5- 9 10-19
(13) 56 (13) (0)
22 81 142 74
(9) 50 85 224 37 405
(2) (11) 40 140 66 259
(0) (2) (5) 52 50 109
20 + Total
(o) 82
(o) 319
46 200 285 490 153 1174
271
Earlier studies F e w studies have b e e n m a d e in forestry o f the r e l a t i o n s h i p b e t w e e n j o b r o t a t i o n a n d the o v e r l o a d s y n d r o m e . Studies in o t h e r trades o f t e n stress the positive i m p a c t of v a r i a t i o n a n d p a u s e s d u r i n g work, b u t few studies have dealt with a c t u a l j o b r o t a t i o n . J o b r o t a t i o n has b e e n c o n s i d e r e d to b e s o m e t h i n g positive, for health (physical a n d p s y c h o l o g i c a l ) as well as for longt e r m p r o d u c t i v i t y . However, f o r m e r studies have also p o i n t e d o u t several c o n s t r a i n t s to j o b rotation, such as: - M a n y o l d e r forest w o r k e r s n o t w a n t i n g to learn n e w types of work, - M a c h i n e o p e r a t o r s n o t w a n t i n g to " l e n d " their m a c h i n e to others, - Practical p r o b l e m s , for i n s t a n c e in c h a n g i n g b e t w e e n m a c h i n e w o r k a n d c h a i n - s a w cutting, - U n s u i t a b l e wage forms, - E d u c a t i o n a n d t r a i n i n g of the p a r t i c i p a n t s , - Difficulties in f i n d i n g m e a n i n g f u l w o r k tasks to r o t a t e to, for i n s t a n c e d u r i n g the shift " o n the g r o u n d " in the 3 - h o u r shift (see F i g u r e 4).
TABLE 2 The development of symptoms of overload injuries among 169 operators after 2-4 years of work with new machines (percentage figures) Group 1. Operators with previous symptoms After 2-4 years of w o r k : Recovered 2% Improved 10% No change 18% Deteriorated 13%
43%
Group 2. Operators without previous symptoms 57% After 2-4 years of work: New symptoms 17% Still without symptoms 40% Total after 2-4 years of work with the new machine: Operators with symptoms: Operators without symptoms:
58% 42%
harvesters. It m i g h t b e n o t e d f r o m the t a b l e t h a t o n l y 2% o f the o p e r a t o r s recovered a n d 10% imp r o v e d after having c h a n g e d to the new machine, while 13% d e t e r i o r a t e d in r e l a t i o n to earlier s y m p toms a n d 17% d e v e l o p e d new s y m p t o m s . T h e target s t u d y o n o p e r a t o r s of new m a c h i n e s showed, in short, that the general t e c h n i c a l - e r g o n o m i c i m p r o v e m e n t s c a r r i e d o u t in the n e w e r m a c h i n e s have n o t b e e n e n o u g h to relieve the o p e r a t o r s of their s y m p t o m s a n d to p r e v e n t the d e v e l o p m e n t of new ones.
The broad survey A d e t a i l e d analysis of the 431 p r o c e s s o r o p e r a t o r s that h a d p a r t i c i p a t e d in the b r o a d survey up to t h a t p o i n t gave a p i c t u r e of the s i t u a t i o n where o p e r a t o r s were w o r k i n g with j o b r o t a t i o n . T h e analysis showed that: - T h e r e was a t e n d e n c y for j o b r o t a t i o n to b e m o r e c o m m o n a m o n g the y o u n g e r a n d those with short m a c h i n e - o p e r a t i n g experience; - J o b r o t a t i o n was m o r e c o m m o n a m o n g t r a i n e d operators; - J o b r o t a t i o n was as c o m m o n in p a r t l y m e c h a nized as in fully m e c h a n i z e d systems; -Job r o t a t i o n was as c o m m o n a m o n g those w o r k i n g on piece rate as a m o n g those w o r k i n g o n time wage; - M o r e o f those w h o r o t a t e were p h y s i c a l l y active in their s p a r e time.
Job rotation of Iogglng-machlne operators I n o r d e r to get a p i c t u r e of h o w j o b r o t a t i o n a n d some i n d i v i d u a l factors affect the o v e r l o a d s y n d r o m e , a s e c o n d target s t u d y was m a d e in close c o l l a b o r a t i o n with 3 of the larger O H S units. T h e study was l i m i t e d to p r o c e s s o r o p e r a t o r s . J o b r o t a t i o n was d e f i n e d as the a l t e r n a t i o n b e t w e e n m a c h i n e driving a n d o t h e r types of w o r k d u r i n g the d a y (e.g., shift form), the week (e.g., r o t a t i o n b e t w e e n m a c h i n e w o r k a n d c h a i n saw cutting), a n d the season (e.g., planting, cleaning).
Operator A Operator B
06.00
09.00
,
i ~- . . . . . . !
The second target study A t o t a l o f 110 p r o c e s s o r o p e r a t o r s p a r t i c i p a t e d in the s e c o n d 12.00 -t
i
I t ....
15.00
18.00
Hours
i ~ ~
i
Fig. 4. The organization of the 3-hour shift. Two operators are assigned to one machine, and they rotate in 3-hour periods. Operator A start at 6 a.m, and operator B at 9 a.m. During the 3 hours "on the ground", the operator takes his lunch break and carries out repairs, planning, chain saw cutting, etc; - machine work, - - - - - - lunch break and work "on the ground".
272 TABLE 3 The development of symptoms of overload injuries among processor operators after changing from regular 8-hour shift to 3-hour shift (percentage figures) 3-hour shift 8-hour shift (76 operators). (25 operators) Operators with previous symptoms: Recovered 12 Improved 22 No change 21 Deteriorated 1 Operators without previous symptoms
Total after 3-4 years of work: Operators with symptoms Operators without symptoms
24 8 28 4
44
36
100%
100%
44 56
40 60
100%
100%
target study. The objective was to study the effect of job rotation (especially the 3-hour shift, as shown in Fig. 4) and some individual factors on the symptoms of overload injuries. Of the 110 machine operators in the study, 76 had worked the 3-hour shift during at least the last 2 years (on an average, 3 - 4 years), and 25 operators had worked a regular 8-hour shift. (Nine operators had various shift forms and are not included in this analysis.) The results are summarized in Table 3. The figures indicate that the effect on the overload symptoms of changing from a regular 8-hour shift to the 3-hour shift is limited and uncertain (prevalence figure of 40% and 44% respectively, after 3 - 4 years of work). These figures are influenced by the fact that more of those working an 8-hour shift (24%) had recovered than had those working a 3-hour shift (12%). In total, an equal share of the two groups had improved or recovered. On the other hand, the 3-hour shift seems to have a positive effect on earlier established symptoms. Among the 30% of the operators who had established symptoms before they started to work the 3-hour shift, 74% improved or recovered. The corresponding figure among the 22% who established symptoms when they were working the 3-hour shift was 47%. (Three operators had given incomplete answers.) The results indicate that the 3-hour shift, as a general measure, did not
radically solve the neck/shoulder problems, but it may have positive effects on some operators with established complaints. Pauses and micropauses during work are not very common. Forty-nine percent of the processor operators seldom or never released the controls, and forty percent seldom or never stepped out of their machine during the work shift. One reason that the 3-hour shift has not led to the expected decrease in complaints could be that the operators work more intensively during the 3 running hours. Operators who worked the 3-hour shift stepped out of the machine and let go of the handles significantly less often than did the operators working a regular 8-hour shift.
PRACTICAL IMPLICATIONS For measures to reduce the prevailing health risks in practice, it is feasible to group the various actions into the following three categories: - Technical - Individual - Organizational The work situation and work factors change over time. The effect on the individual complaint can be illustrated as in Figure 5. A certain work produces specific risks for the development of "Health r i s k "
at work
Individual .............................................. Organizational
Individual "limit"
Individual
Organizational Technical
Technical
....................................................
(1)
(2)
Time
Fig. 5. The multiple effect on the health risks of different individual, organizational, and technical work factors, of points in time. The individual limit is the limit above which a complaint may be developed. (1); In this case the risk of neck/shoulder complaints is evident for the operator, case (2): The work organization has been changed for the operator, e.g., by job rotation between machine work and other work tasks (decreasing the time of exposure for the high tensions in the neck/shoulder muscles). There is no risk of complaints at present.
273 complaints. The health risks from various factors are added to each other. Each individual has a limit above which he will develop a complaint. This limit depends on the physical and psychological status of the individual, as well as on his body's resistibility to stress. The limit can also change: for instance, a severe cold or problems at home might lower the limit; physical training might raise the limit. The actual development of a complaint or illness also depends on the time worked above the limit. Working high above the limit may result in a complaint after only a short period of time (e.g., a cutter taking down a hanging tree and using his ultimate strength in an awkward position might get an acute back pain). Working just at the limit might result in a complaint only after a very long period of time (e.g., a skidder operator working with small tensions in the muscles might take up to 20 years to develop a complaint). Since the factors are added to each other, a factor with a high risk to the employee can be compensated for by a low risk from another factor, as shown in Figure 5. The intention of Figure 5 is to serve as a pedagogic model. This model is now being used to facilitate and motivate the implementation of measures in Swedish forestry. New projects have recently been started at several forest companies. The results of the Health Risk Program reported in this paper indicate an alarmingly high prevailing average overload syndrome figure of 50% among the forest workers. The results and experiences so far also indicate that a whole battery of measures is needed to radically improve this serious situation, including new technology and new forms of work organization, as well as motivation of the machine operator to influence his own situation. Single measures might be positive, but are not enough. To be effective, the full program of measures must be carried out, and it must be adapted individually to each machine operator. Rehabilitative measures should be taken as soon as possible after the complaint first appears. Improvements in t e c h n o l o g y / e r g o n o m i c s are needed. This is especially true regarding the sitting work posture in the cabin, i.e., design of the arms of the chair, controls, and instruments. Reduction of whole-body vibrations is also important.
Important individual factors are working techniques, micropauses, and physical fitness. Support from a physiotherapist is essential. It might even be necessary to introduce physical training during the work shift. A new work organization is the most difficult part of the proposed battery of measures to realize in practice, but is also the part that probably has the highest potential for improving the situation. Examples of issues to address are design and length of the working shift, job rotation, work tasks and responsibilities, team work, and motivation and payment systems. This is a real challenge to undertake, both for the researchers and the companies. The experience thus far indicates that the difficulties are great and the long-term effects uncertain. One particular difficulty is with developing new methods for evaluating the effect of measures undertaken. The effects of several factors should be evaluated, not only on health aspects, but also productivity, quality of the work, organization, economy, and others. Evaluations from a health risk point of view are complicated in this case, for overload complaints and injuries often take a long time to develop. The fact is that the positive effects of various measures are often short-term and might weaken and disappear with time. Thus far, we have learned from the current attempts and trials at different forest companies that, in order to get the full effect of the program of suggested measures, it is necessary to start by increasing the motivation and by improving the cooperation of all parties involved. This means not only the researchers and the manufacturers of logging machines, as in the past, but also the forest company, management, supervisors in the field, and the logging-machine operators themselves.
References This paper is based mainly on results from the current Health Risk Program at the Swedish College of Forestry, Garpenberg. Details of the program and comprehensivelist of references are given in: Pontgn, B., 1988. Health Risks in Forest Work--A Program for Action. Report No. 177, Department of Operational Efficiency, College of Forestry, S-770 73 Garpenberg, Sweden.