One approach to the design or evaluation of manual materials handling (MMH)
tasks is through the use of various criteria measures that have been devel
oped. For evaluation purposes, the observed value of a criterion measure is
calculated from task and workplace parameters, and compared to a specific
criterion to assess the level of "acceptability" or "safety" associated wit
h the task. This process is usually completed at the task level. Most crite
ria are for single MMH tasks; however, the majority of jobs involving MMH a
re composed of multiple tasks. One of the biggest challenges to exposure as
sessments of multiple tasks using criteria is the aggregation of the exposu
re from the individual tasks to a single metric. This paper examines issues
relevant to the aggregation of criterion values from multiple MMH tasks. A
ssessment strategies for evaluating multiple-task MMH jobs are also discuss
ed. The conclusions are: (1) basic and applied research is needed to enhanc
e methodologies for analyzing multiple-component MMH tasks, (2) research is
needed to assess the role of MMH criteria in the prevention of low-back di
sorders when MMH exposures are complex, (3) field methodologies for applyin
g MMH criteria to complex exposures need to be operationally defined to ens
ure consistent use by practitioners, and (4) MMH criteria should be viewed
as design and task analysis tools (i.e., compliance assessment), and not as
risk assessment tools.