Civil Engineering Reference
In-Depth Information
work-related musculoskeletal disorders of the neck, upper extremity, and low back and summarized
major findings on the various exposure parameters (NIOSH, 1997). In 2001, the National Research
Council published a comprehensive review of the evidence on work-related musculoskeletal disorders
in which they concluded that repetition, force, and vibration, as well as high job demands and job
stress, were particularly important risk factors for upper extremity disorders (Panel on Musculoskeletal
Disorders and the Workplace, 2001). They also found that modification of these factors could substan-
tially reduce the risk for these disorders.
The way work is organized and performed often determines subsequent physical
mechanical and
psychological job demands on individual workers. Work organization also encompasses the organi-
zational practices and production methods that affect job design. These include the temporal aspects
of work (e.g., work-rest schedules, work shifts, hours of work, work pacing), job content (e.g., repeti-
tiveness of tasks, use of skills, vigilance, participation in decision-making), compensation arrangements
(salary, hourly, quota, piece rate), work status (fulltime, part-time, seasonal, temporary), social inter-
actions (isolated, various levels of team work), task (single, rotating, multiple), and opportunities for
development (Kasl, 1992; Sauter and Swanson, 1996). Consideration of work organization provides
information at the group level and enables multilevel analysis. Work organizational observational
exposure assessment methods that are potentially relevant for assessing relationships with musculo-
skeletal disorders include those of Rohmert and Landau (1983), Ergonomic Workplace Analysis
(Ahonen et al., 1996), Meaning of Work (MOW International Research Team, 1987), and the Occu-
pational Stress Index (Belkic et al., 1995).
Typically, physical exposures identified in workplaces include forceful exertions (Stetson et al., 1993;
Fransson-Hall et al., 1996; Roquelaure et al., 1997), such as gripping a high force demanding hand
tool, lifting a heavy object, pushing a fully loaded cart. Non-neutral postures of hands and upper extre-
mities (Frost and Andersen, 1999; Punnett et al., 2000; Viikari-Juntura et al., 2000), such as bending the
wrist when using a hand tool and raising the hand above the head when performing a task, increase force
requirements. Highly repetitive motions of the hand, wrist, and upper arms (Veiersted and Westgaard,
1993; Blanc et al., 1996; Nordstrom et al., 1997; Punnett, 1998) are found in hand-intensive jobs such
as assembly and data entry. Some other physical demand parameters at workplaces include hand-arm
vibration, wearing gloves, and some environmental conditions such as extremely cold or hot tempera-
tures. Work organization parameters such as work methods, social content, and task pacing may also
influence the development of work-related upper extremity disorders.
Different measurement strategies may be used to meet the various needs of the exposure assessments.
For example, most cross-sectional epidemiological studies measure exposure parameters at a certain
point in time, while most prospective epidemiological studies require the quantification of the exposures
for the days, weeks, and years on the job. Thus, data collected for prospective studies should make it pos-
sible to calculate cumulative exposures. For example, a worker performs two different tasks in a workday.
Exposure from both tasks should be measured and the compound exposure for the whole day should be
calculated depending on the task distribution (time spent on the two tasks). If the worker's exposure is
changed during the course of the study (e.g., job changes), a new exposure measurement should be per-
formed, and the accumulated exposure is then calculated. If the purpose of the measurement is to assess
exposure differences among two or several conditions, measurement can be done for each of the
conditions.
When considering the measurement strategy to be used, one should also consider the three main
dimensions of physical exposure: amplitude, frequency, and duration, rather only one single dimension.
This is because the physiological significance is dependent on the combination of these exposure dimen-
sions. Therefore, exposure quantification should include the measurement of exposure amplitude (e.g.,
level of hand force, degree of a joint angle), exposure frequency (e.g., number of exertions per minute),
and exposure duration (e.g., length of time in hours). Other aspects of physical exposure may also need
to be quantified, such as duty cycle and speed.
After deciding on the measurement strategy, one should consider the selection of exposure quanti-
fication methods to be used. There are numerous exposure quantification methods available.
/
Search WWH ::
Custom Search