Maximum Acceptable Weight of Lift as a Function of Material Density, Center of Gravity Location, Hand Preference, and Frequency

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Abstract
The effects of material density, center of gravity location, hand preference, and frequency on maximum acceptable weight of lift were determined experimentally in a laboratory study. Using the psychophysical methodology, 10 male college students performed lifting tasks involving three different materials, three frequencies, and three load center of gravity locations in the direction of the preferred or nonpreferred hand. Data analysis showed that maximum acceptable weight of lift is significantly reduced when the load center of gravity is offset in the direction of either the preferred or the nonpreferred hand. Lifting is relatively less stressful if the center of gravity offset is in the direction of the preferred hand as opposed to the nonpreferred hand. Significantly more weight is lifted when higher-density materials are used. Comparison with the data collected on industrial subjects showed similar, but significantly different, frequency trends. Isometric shoulder strength appears to be the limiting factor in predicting maximum acceptable weight of lift.