Influence of Small Control Levers of Grapple Loader on Muscle Strain, Productivity and Control Errors

Small-sized mini-levers were compared to conventional levers in forwarder grapple loading of timber using a forest machine simulator in clear-cutting and thinning conditions. No effect on time consumption per burden was observed, but muscle constriction in the trapezius muscle measured using EMG was lower when the mini-lever option was used. Control errors were measured by counting the contacts between the remaining trees and the machine elements. These were interpreted to result in damage to the trees. The frequency of this kind of damages was significantly smaller when using the mini-lever option