PHYSICAL WORKLOAD AS A RISK FACTOR FOR SYMPTOMS IN
THE NECK AND UPPER LIMBS: EXPOSURE ASSESSMENT AND ERGONOMIC INTERVENTION*
dissertation presented on Friday 12th September 2003
at the the Faculty of Medicine of the University of Kuopio, Finland,
by permission of the Faculty of Medicine of the University of Kuopio,
Finnish Institute of Occupational Health, Helsinki, Finland.
Department of Physiology, University of Kuopio, Kuopio
Department of Physiology, Finnish Institute of Occupational Health, Finland
Journal of Sports Science and Medicine (2004) 3, Suppl.5,
1 - 46
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review is based on the following orginal publications, which will be referred
to in the text as Studies 1-4:
Korhonen, T., Ketola, R., Toivonen, R., Luukkonen, R., Häkkänen, M. and
Viikari-Juntura, E. (2003) Work-related and individual predictors for
incident neck pain among office employees working with video display unit
work. Occupational and Environmental Medicine 60, 1-8.
Ketola, R., Toivonen, R., Häkkänen, M., Luukkonen, R., Takala, E-P. and
Viikari-Juntura, E. (2002) Effect of ergonomic intervention in work with
video display units. Scandinavian Journal of Work, Environment &
Health 28, 18-24.
Ketola, R., Toivonen, R., Luukkonen, R., Takala, E-P. and Viikari-Juntura,
E. (2003) Expert assessment of ergonomics at video display unit (VDU)
workstation: repeatability, validity and responsiveness to changes Internetional
Archives of Occupational and Environmental Health. Submitted.
Ketola, R., Toivonen, R. and Viikari-Juntura, E. (2001) Interobserver
repeatability and validity of an observation method to assess physical
loads imposed on the upper extremities. Ergonomics 44, 119-131.
aims of this study were to investigate work related and individual
factors as predictors of insident neck pain among video display
unit (VDU) workers, to assess the effects of an ergonomic intervention
and education on musculoskeletal symptoms, and to study the repeatability
and validity of an expert assessment method of VDU workstation ergonomics.
A method to assess the risk factors for upper limb disorders was
developed, and its validity and repeatability were studied.
The annual incidence of neck pain was 34.4%. A poor physical work
environment and placement of the keyboard were work-related factors
increasing the risk of neck pain. Among the individual factors,
female sex was a strong predictor.
The randomized intervention study included questionnaire survey,
a diary of discomfort, and ergonomic rating of the workstations.
The subjects (n=124) were allocated into three groups. The intensive
and the education groups had less musculoskeletal discomfort than
the control group at the 2-month follow-up. After the intervention,
the level of ergonomics was distinctly higher in the intensive ergonomic
group than in the education or control group.
Two experts in ergonomics analyzed and rated the ergonomics of workstations
before and after intervention. The validity of the assessment method
was rated against the technical measurements, assessment of tidiness
and space, and work chair ergonomics. The intraclass correlation
coefficient between ratings of the two experts was 0.74. Changes
in the location of the input devises and the screen, as well as
the values of tidiness and space and work chair ergonomics showed
a significant association with the ratings of both experts.
The method to assess the loads imposed on the upper limbs was validated
against the expert observations from the video, continuous recordings
of myoelectric activity of forearm muscles, and wrist posture, measured
with goniometers. Inter-observer repeatability and validity were
good or moderate.
Both intensive ergonomics approach and education in ergonomics have
effects in reducing discomfort in VDU work. In attemps to improve
the ergonomics of VDU workstation, the best result will be achieved
with cooperative palaning in which both workers and pratitioners
are actively invoved. The assessment methods for VDU work ergonomics
and upper limb load studied here can be utilized in a repeatable
WORDS: Human engineering, computer terminals, neck pain, upper
extremity, workload, risk factors, risk assessment, randomized controlled
trials, observation, video recording.