Longer lifting hooks for forestry workers: An evaluation of ergonomic effects

Abstract

This study analysed the load-reducing effects of using lifting hooks that were 0.09 m longer than those conventionally employed by forestry workers. A method for recording and analysing repetitive lifting movements is also presented. Nine experienced workers performed a standardized sagittal symmetric repetitive lifting task, with the Long and the Standard types of hook. To simulate the aerobic stress during motor-manual cutting, a 17-kg log was lifted 15 lifts·min −1. Heart rate, oxygen consumption, sagittal body movements, vertical force plate measurements, and vertical movement of the log lifted, were recorded continuously. Sagittal load moments and forces in hip and L5-S1 segment were calculated. The subjects also rated their overall, low-back and thigh exertions. The use of the Long hook resulted in a 12% reduction in O 2 consumption. Mean and peak load moments in hip and L5-S1 were reduced by 14% and 9% respectively. The loads were rated significantly lower with all three assessments. The movement analyses showed a significant difference in movement pattern between the two types of hook, and that the kinematic variables were related to each other and to the VO 2 measurements in a consistent way.