WORKING WITH HORSES: AN OWAS WORK TASK ANALYSIS
Lotta Löfqvist, PhD-student
Swedish University of Agricultural Sciences, Division of Work Science
PO. Box 88, SE-23053 Alnarp, Sweden
lotta.lofqvist@ltj.slu.se
Most labour in horse stables is performed manually as it was done a century
ago. People working with horses are exposed to several risk factors for
developing musculoskeletal problems, because they often work in bended
and twisted positions, lift heavy loads, perform repetitive work with high
velocity and work in cold climates.
A previous Swedish study (2007) among female riding instructors showed a
high prevalence of musculoskeletal problems in the shoulder (60 %), low
back (56 %) and neck (52 %). Instructors indicated that the shoulder and
low back were the most strained regions when they performed work tasks.
The aim of the ongoing study was to obtain a deeper understanding of the
work tasks around horses and the physical work in performing those tasks.
The personnel in five riding schools, all together 20 subjects, was video
recorded when performing the work in the stable and preparing and
conducting riding lessons. The work was analyzed with the Ovako Working
posture Analysis System (OWAS) a system to register arm, back and leg
positions and to categorize the harmfulness of the work postures. A test run
made on seven work tasks, showed that over 30 % of the work postures in
the two work tasks, mucking out and preparing the bedding, ended up in the
Action Categories (AC) 3 and 4.
With a more in-depth knowledge about the work tasks performed at riding
schools it will be easier to plan and implement measures to prevent
musculoskeletal symptoms in this unique group of workers.
Key word: Horses, work load, work task, OWAS
Topic: Physical workload
1 Introduction
There are about 300 000 horses in Sweden and the horse industry generates about
28 000 fulltime work positions. Farming is a hazardous occupation and accidents and
work related injuries are frequent when working with animals (Pinzke and Lundqvist
2006; Thelin et al. 2004; Walker-Bone and Palmer 2002). Musculoskeletal disorders
(MSD) are also common in farm work (Holmberg et al. 2003; Pinzke 1996; Stal et al.
1996). Equestrian activities are dangerous because the participant handle large animals
capable of 40mph speeds and kicking with a force of up to one ton (Bixby-Hammett and
Brooks 1990; Ceroni et al. 2007; Fleming et al. 2001). Thus, horse riding and the work
around horses constitutes an increased risk for accidents (Bixby-Hammett and Brooks
1990; Fleming et al. 2001; Iba et al. 2001; Kriss and Kriss 1997; Lim et al. 2003).
1
Most labour in horse stables is performed manually and as it was done a century ago.
People working with horses are exposed to several risk factors for developing
musculoskeletal problems, because they work in bended and twisted positions, lift
heavy loads, perform repetitive work with high velocity and work in cold climates.
A previous Swedish study among female riding instructors showed a high prevalence of
musculoskeletal problems in the shoulder, low back and neck. Instructors indicated that
the shoulder and low back were the most strained regions when they performed work
tasks and that mucking out was considered to be the task involving the heaviest work
(Löfqvist et al. 2007). The work load on people doing horse back riding are described in
a couple of studies (Alfredson et al., 1998; Meyers, 2006; Matsuura et al., 2003; Pugh
and Bolin, 2004; Westerling, 1983; Terada et al., 2004), but the work load when
performing manual tasks in the stable or teaching riding has not been investigated.
There are several methods to analyze risk factors for developing MSD, postures,
movements and physical work load (Li and Buckle 1999; Pinzke 1997; Wells et al.
1997; Westgaard 1988; Winkel and Mathiassen 1994; Åkesson et al. 1997), and these
methods can be divided into three groups (Li and Buckle 1999; Pinzke 1997):
Observational methods that depends on the judgement of an observer, for example
OWAS (Karhu et al. 1977; McAtamney and Corlett 1993), RULA (McAtamney and
Corlett 1993) and REBA (McAtamney and Hignett 1995), Direct methods which
requires instrumentation or technical devices such as EMG and electrogoniometry
(Karpovich et al. 1960) and Self reports that relay on a subjective assessment on
physical work load, for example questionnaires (Kuorinka et al. 1987), checklists
(Keyserling et al. 1992) and rating scales.
The aim of the study is to obtain a deeper understanding of the work tasks around
horses and the physical work in performing those tasks.
With a more in-depth knowledge about the work tasks performed around horses it will
be easier to plan and implement measures to prevent musculoskeletal symptoms in this
unique group of workers.
2 Materials and methods
2.1 Preparation of the study
To investigate the work load and identify activities involving poor working postures
concerning different work tasks performed among employees at riding schools, a study
was done on five riding schools in the south of Sweden. 35 letters were sent in May
2007 to riding schools, all members of the Swedish Equestrian Federation
(www2.ridsport.se). The letters were sent within a radius of 70 kilometres from Alnarp,
with an offer to participate in a study concerning the work load in connection to work
tasks on riding schools. Five riding schools answered that they would like to participate
in the study. The study was conducted between October 2007 and February 2008. Video
recording was made with a Panasonic NV-GS5 video camera using 60 minutes DVC
digital tapes.
2.2 Study group
The personnel in five riding schools, riding instructors and stable attendants, was video
recorded when performing the work in the stable and preparing and conducting riding
lessons.
All the workers were asked questions concerning age, work hours, length, weight, right
or left handed etc. Altogether 20 workers participated in the study.
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2.3 Study methods
The work tasks were analyzed with the Ovako Working posture Analysis System
(OWAS) which is a system to register arm, back and leg positions and to categorize the
harmfulness of the work tasks (Table 1). OWAS is a method for observing work
postures and conducted by watching a work task being performed and taking notes in
decided intervals, the observer will stop the film for example every third second and
make a note of the posture. The back, arm and leg positions are registered and the
weight of the load is accounted for. The method is used to show harmful work positions
and work tasks. 84 different combinations are possible. Based on the different posture
combinations four different action categories are established and used to classify the
harmfulness in the different work tasks (Engels et al. 1994; Karhu et al. 1977).
The different Action Categories (AC):
AC 1: Normal posture, no action required.
AC 2: The stress load of the posture is slightly harmful. Action to change the posture
should be taken in the near future.
AC 3: The stress load of the posture is distinctly harmful. Action to change the posture
should be taken as soon as possible.
AC 4: The stress load of the posture is extremely harmful. Action to change the posture
should be taken immediately.
AC 3 and AC 4 will in this paper be regarded as the two hazardous A C, were actions
are necessary, and therefore these AC will be considered together.
Table1. Schematic view of the OWAS analyzing system
Body
OWAS
Description of the posture
score
Back
1
2
3.
4
Straight
Bent
Twisted
Both bent and twisted
Legs
1
2
3.
4.
5
6.
7
Sitting
Straight standing
Standing on one straight leg
Standing with two bended knees
Standing with one bended knee
Kneeling
Walking
Arms
1
2
3
Both arms below shoulder level
One arm above shoulder level
Both arms over/ or on the level of
the shoulder
Loads
1
2
3
Weight < 10 kg
10< weight <20 kg
Weight > 20 kg
2.4
Statistic analysis
3
The statistical analysis SPSS program 14.0 for Windows was used for all statistical
analysis. Means and standard deviations were used to describe the background factors,
such as weight, height, age.
3 Preliminary Results
3.1 Background factors
In total, 20 subjects participated in the study, 75% (n=15) were women and 25% (n=5)
were men. The age of the participants ranged from 21 to 64 years. The mean age was
37.7 years. The participants worked 32.9 hours per week in average. In average the
subjects had worked in the occupation for 8.8 years, range 0-26 years (Table 1).
Table 1. Background factors of the subjects (N=20), number (n), percent (%), mean, median, standard deviation (sd) and range.
Individual factors
n
Age (Year)
19
Gender
Male
Female
20
5
15
No. of hours working per week
%
mean
median
sd
range
37.7
39.0
13.96
21-64
20
32.9
40.0
10.55
5-40
No. of years in the occupation
18
8.8
5.5
8.24
0-26
Left handed
Right handed
2
17
Body weight (kg)
19
70.3
67.5
11.62
55-100
Body height (cm)
19
173.3
173.0
8.96
160-192
Body Mass Index (kg/m2)
19
23.4
22.8
3.19
19.6-32.3
25.0
75.0
10.5
89.5
a
3.2 OWAS
An OWAS test run was made on four subjects performing three minutes of each work
task performed in the stable.
More than 30 % of the work postures in the work tasks mucking out and preparation of
bedding were categorized to AC 3 and AC 4. Also sweeping and feeding with hay had
almost 30 % in AC3 and AC4 (Figure 1) 28 % and 25.4 %, respectively.
4
(%)
100
90
80
70
60
50
AC4
40
AC3
30
AC2
AC1
20
10
0
Mucking out
Bedding
preparation
Disposal of
manure to
haystack
Sweeping
Feeding
Feeding with Work tasks
hay
Figure 1. Work tasks performed in the stable by four subjects
4 Discussion
The test run of the collected data showed that there were work tasks performed in the
stable which included work postures in the action categories AC3 and AC4, were
actions should be taken. The test run was made with four subjects and when the whole
material has been analysed the results should be more conclusive. The test run showed
that mucking out was a work task with AC 3 and AC 4 for over 30 %. This work task
was considered to be the task with the highest strain in a study made in 2007 (Löfqvist
et al. 2007). The present study confirmed that mucking out contained some work
postures that could be considered hazardous in a work perspective.
5 References
Bixby-Hammett DM, Brooks WH: Common injuries in horseback riding. A review.
Sports Med 1990,9, 36-47.
Ceroni D, De Rosa V, De Coulon G, Kaelin A: The importance of proper shoe gear and
safety stirrups in the prevention of equestrian foot injuries. J Foot Ankle Surg 2007,46,
32-9.
Engels JA, Landeweerd JA, Kant Y: An OWAS-based analysis of nurses' working
postures. Ergonomics 1994,37, 909-919.
Fleming PR, Crompton JL, Simpson DA: Neuro-ophthalmological sequelae of horserelated accidents. Clin Experiment Ophthalmol 2001,29, 208-12.
Holmberg S, Thelin A, Stiernstrom E, Svardsudd K: The impact of physical work
exposure on musculoskeletal symptoms among farmers and rural non-farmers. Ann
Agric Environ Med 2003,10, 179-84.
Iba K, Wada T, Kawaguchi S, Fujisaki T, Yamashita T, Ishii S: Horse-related injuries in
a thoroughbred stabling area in Japan. Arch Orthop Trauma Surg 2001,121, 501-4.
5
Karhu O, Kansi P, Kuorinka I: Correcting working postures in industry: A practical
method for analysis. Applied Ergonomics 1977,8, 199-201.
Karpovich PV, Herden EL, Asa MM: Electrogoniometric study of joints. United States
Armed Forces Medical Journal 1960,11, 424-450.
Keyserling WM, Brouwer M, Silverstein BA: A checklist for evaluating ergonomic risk
factors resulting from awkward postures of the legs, trunk and neck. International
Journal of Industrial Ergonomics 1992,9, 283-291.
Kriss TC, Kriss VM: Euine-related neurosurgical trauma: A prospective series of 30
patients. The journal of trauma, injury, infection and critical care 1997,43, 97-99.
Kuorinka I, Jonsson B, Kilbom Å, Vinterberg H, Biering-Sörensen F, Andersson G,
Jørgensen K: Standardised Nordic questionnaires for the analysis of musculoskeletal
symptoms. Applied Ergonomics 1987,18, 233-237.
Li G, Buckle P: Current techniques for assessing physical exposure to work-related
musculoskeletal risks, with emphasis on posture-based methods. Ergonomics 1999,42,
674-695.
Lim J, Puttaswamy V, Gizzi M, Christie L, Croker W, Crowe P: Pattern of equestrian
injuries presenting to a Sydney teaching hospital. ANZ J Surg 2003,73, 567-71.
Löfqvist L, Pinzke S, Stål M, Lundqvist P: Riding instructors, their musculoskeletal
health and working conditions. in manuscript 2007.
McAtamney L, Corlett EN: RULA: a survey method for the investigation of workrelated upper limb disorders. Applied Ergonomics 1993,24, 91-99.
(ed.) 1995. Ergonomics Society of Australia, Adelaide, Australia.
Pinzke S. 1996. Musculoskeletal Disorders and Methods for Studying Working Postures
in Agriculture Report 107. Department of Agricultural Biosystems and Technology,
Swedish University of Agricultural Sciences, Lund.
Pinzke S: Observational Methods for Analyzing Working Postures in Agriculture.
Journal of Agricultural Safety and Health 1997,3, 169-194.
Pinzke S, Lundqvist P: Occupational accidents in Swedish farming and forestry in 2004.
in manuscript 2006.
Stal M, Moritz U, Gustafsson B, Johnsson B: Milking is a high-risk job for young
females. Scand J Rehabil Med 1996,28, 95-104.
Thelin A, Vingard E, Holmberg S: Osteoarthritis of the hip joint and farm work. Am J
Ind Med 2004,45, 202-9.
Walker-Bone K, Palmer KT: Musculoskeletal disorders in farmers and farm workers.
Occup Med (Lond) 2002,52, 441-50.
Wells R, Norman R, Neumann P, Andrews D, Frank J, Shannon H, Kerr M: Assessment
of physical work load in epidemiologic studies: common measurement metrics for
exposure assessment. Ergonomics 1997,40, 51-61.
Westgaard RH: Measurement and evaluation of postural load in occupational work
situations. European Journal of Applied Physiology 1988,57, 291-304.
Winkel J, Mathiassen SE: Assessment of physical work load in epidemiologic studies:
concepts, issues and operational considerations. Ergonomics 1994,37, 979-988.
Åkesson I, Hansson G-Å, Balogh I, Moritz U, Skerfving S: Quantifying work load in
neck, shoulders and wrists in female dentists. Int Arch Occup Environ Health 1997,69,
461-474.
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