Prediction of maximum acceptable weight of lift in the horizontal and vertical planes using simulated job dynamic strengths

Abstract

An investigation was undertaken to determine the feasibility of predicting maximum weights of lift that are acceptable to individuals by measuring the individuals' simulated job dynamic strengths. Since almost all manual materials handling jobs are dynamic in nature, it was hypothesized that correlations between maximum weights acceptable for lifting and the dynamic strengths measured under similar conditions would be high compared to isometric strengths. If so, then a relatively simple procedure can be developed to estimate what people are willing to lift safely. With the use of a specially designed and constructed three-dimensional dynamic strength simulator, 19 males and 6 females lifted loads in two vertical and two horizontal planes. Their dynamic strengths also were measured under identical conditions. The correlations between simulated job dynamic strengths and acceptable weights of lift were much higher (0.52 to 0.67) compared to correlations between isometric strengths and acceptable weights of lift (0.29 to 0.38). This also confirmed earlier findings that dynamic strengths are more suitable predictors of the maximum weights people are willing to handle. Simple equations are presented between simulated job dynamic strengths and maximum acceptable weights of lift in the horizontal and vertical planes. These equations demonstrate that dynamic strength can be used reliably when matching jobs with individuals.