Effects of Measured versus Proposed Horizontal Distance on the NIOSH Action Limit and Maximum Permissible Limit for Manual Materials Handling

The objective of this research was to compare action limits and maximum permissible limits based on measured horizontal distances with those based on the rule of thumb proposed in the NIOSH Guide. Thirteen male subjects were required to lift three different boxes (25, 38 and 51 cm wide), at four different frequencies (0.2, 3, 6 and 9 lifts min−1), and at two heights (floor level to bench height (0.8 m) and bench height to 1.5 m). Each lift was performed for one hour and horizontal distances for all thirteen subjects were measured at the origin of lift. Action limits and maximum permissible limits were computed for all lifting tasks using the measured and the proposed horizontal distances. The actual measured horizontal distances were much greater than those based on half the box width plus 15 cm. The action and the maximum permissible limits based on measured horizontal distances were significantly lower than those based on H = W/2 + 15 cm. For the floor to 0.8 m lifts, the AL and MPL based on measured horizontal distances were 74% (range = 67% to 80%) of those based on H = 15 + W/2. The corresponding ratio for the 0.8 m to 1.5 m lifts was 62% (range = 56% to 66%).