ABSTRACT
Occupational low back pain represents an enormous cost to society both financially and in terms of
morbidity. Several occupational factors have been explored as to their contribution to low back dis-
orders (LBDs). Frequently, combinations of lifting, bending, twisting, and general material handling
tasks are described as the precursors of back injuries (Frymoyer et al., 1983; Damkot et al., 1984;
Kelsey et al., 1984; Klein et al., 1984; Bigos et al., 1986; Punnett et al., 1991; Marras et al., 1993; Anders-
son, 1997; Kraus et al., 1997). Kumar (1990) showed that the cumulative loading experience of an indi-
vidual is a predictor of low back pain. Andersson (1997) pointed out that low back pain represents the
leading cause of activity limitation in individuals under 45 yr of age. This should not be surprising
since this is the age group that more often have jobs with substantial manual material handling
demands.
