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settings, Andersson (1997) reported that LBDs affect an estimated 80% of the population during their
working career, and The National Center for Health Statistics (1977) has documented that LBDs are
the prime reason for activity limitation in those 45 yr of age or younger. Guo et al. (1999) estimated
that back pain accounts for 149 million lost workdays in the U.S. annually; 68% of these are associated
specifically with work-related back pain. Cats-Baril (1996) has shown that LBDs cost society up to 100
billion dollars annually. Despite the prevalence and cost of these injuries, there are relatively few accurate
methods available to predict the risk of occupationally related LBDs.
49.1.2 Tools for Analyzing Low Back Injury Risk
Awide range of tools is available to evaluate LBD risk in industrial jobs. These tools vary considerably in
their applicability, complexity, and ease of use. When choosing the appropriate analysis technique it is
important to match the capabilities of the tool to the characteristics of the job being evaluated.
Lifting equations, such as the NIOSH Work Practices Guide, and tables of acceptable load weight limits
are easy to use. They require only a few measurements of the workplace and some observations of a lifting
task to compute recommended lifting limits. However, they assume that all movements are slow and
smooth. Two- and three-dimensional static biomechanical models also are readily available and can
often be relatively easy to apply. However, these also do not take into account trunk motions and,
thus, may not accurately reflect the job's level of risk.
Recent research has suggested that motion plays a role in LBD risk. Numerous epidemiological studies
have specifically indicated that the risk of LBD increases when dynamic lifting occurs. Data from a retro-
spective study of over 4500 injuries (Bigos et al., 1986) found that there were greater reports of LBD with
dynamic tasks as compared to awkward static tasks. Magora (1973) concluded that lateral bending and
twisting were only significant risk factors when they occurred simultaneously with sudden (quick) move-
ments. Punnet et al. (1991) studied non-neutral postures in automobile assembly plants and reported
that postural stress to the back was more a function of dynamic than static tasks. All of these studies indi-
cated that the risk of LBD increases with dynamic activity, especially when the body moves asymmetri-
cally. Therefore, if a job being evaluated has a dynamic component it is important to choose an analysis
method that accounts for the additional risk that motion imparts.
Video-based motion analysis systems offer one way to study the dynamic components of a job, but
they have several drawbacks when used in an industrial setting. First, video assessments must take
place in a calibrated space of usually no more than two to three cubic meters. Cameras must be carefully
placed to obtain data for all three planes of motion, and time-consuming analysis is necessary to obtain
usable data. In industrial environments, these motion analysis systems often are not practical, as tasks
typically involve movement outside of the calibrated space and work areas often make setting up of
cameras difficult. These limitations often make video-based systems impractical for routinely evaluating
a large number of industrial jobs.
49.2 Development of the Industrial Lumbar Motion Monitor
49.2.1 Physical Description
The industrial lumbar motion monitor (iLMM) (Figure 49.1) was developed in the Biodynamics Labora-
tory at The Ohio State University's Institute for Ergonomics. Its development was in response to the need
for a practical method of assessing the dynamic component of occupationally related LBD risk in indus-
trial settings. The patented iLMM is a triaxial electrogoniometer that acts as a lightweight exoskeleton of
the lumbar spine. It is positioned on the back of an individual directly in line with the spine and is
attached using a waist belt at the pelvis and a harness worn over the shoulders. Four potentiometers
at the base of the iLMMmeasure the instantaneous position of the spine (as a unit) in three-dimensional
space relative to the pelvis. Position data from the potentiometers are recorded at 60 Hz, converted to a
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