For approximately three decades, researchers have utilized psychophysics to
develop guidelines (weights, forces and frequencies) for manual materials
handling tasks. Early work by Stover Snook and his colleagues provided the
foundations of the experimental methodologies that would be used by other r
esearchers as well as design data that would be used by practitioners. Curr
ently, there are extensive psychophysical data for designing a variety of m
aterials handling tasks. The current state of psychophysical data will be e
xamined, and the psychophysical approach will be compared to the biomechani
cal and physiological approaches to setting limits for materials handling t
asks. The advantages and disadvantages of the psychophysical approach will
be discussed, as will the research needs required to address the current li
mitations of the psychophysical approach.