A COMPARISON OF RISK ASSESSMENT OF SINGLE AND COMBINATION MANUAL HANDLING TASKS .2. DISCOMFORT, RATING OF PERCEIVED EXERTION AND HEART-RATEMEASURES

Although many manual handling activities involve combinations of pull, lift, carry, lower and push, there are few reports of investigation o f how to assess the risk in these combination tasks. Two strategies ha ve been suggested in the literature for estimating the risk in a combi nation task based on the measures of the separate components of that t ask. The aim of the study was to compare the risks assessed in single manual handling tasks with those in combination tasks. Ratings of disc omfort, exertion and heart rate were collected from nine male and nine female students. performing combination and single tasks. Combination tasks consisted of sequences of pull, lift, carry, lower and push tas ks. Combination tasks were performed at 1.min(-1) and 3.min(-1) whilst single tasks (lift, lower, push, pull and carry) were performed at 3. min(-1) and 6.min(-1). The rating of exertion and heart rate for each combination task was compared to the exertion rating and heart rare of the single tasks which comprised the combination task using repeated measures anaylsis of variance with specified contrasts. Similar compar isons for the discomfort data were performed using Friedman and Wilcox on tests. In at least one of the twelve comparisons performed for each dependent variable, the combination task value was significantly diff erent to each single task value. The differences occurred regardless o f whether the most critical single task value or an average of all sin gle task values was used. It was concluded that the risk in combinatio n manual tasks can not be accurately assessed by using estimates from discomfort, exertion ratings and heart rate measures of single tasks.