Effect of knife sharpness on upper limb biomechanical stresses—a laboratory study

The aim of this laboratory study was to observe the effect of deteriorating knife sharpness on upper limb biomechanical stresses. Ten professional deboners were asked to perform the same carving task with both very sharp and very dull knives (i.e. under very good and very bad sharpness conditions). The knife sharpness characteristic was quantified using a cutting force measuring system. Surface electromyograms (EMGs) were recorded for the flexor digitorum superficialis, extensor digitorum communis (EDC), biceps brachii (BB), triceps brachii (TB), anterior part of the deltoid and upper part of the trapezius muscles. Wrist and elbow flexion–extension and wrist abduction–adduction angles were also recorded.The results for the considered task showed that better blade sharpness leads to significantly lower EMGs for the flexor digitorum superficialis, BB, TB, anterior deltoid (AD), upper trapezius muscles and, to lower wrist radial deviation. No significant difference was observed for the EDC muscle or for wrist and elbow flexion–extension angles in relation to knife blade sharpness. The electromyographic activity of the EDC muscle remained very high, even when knife sharpness was excellent.This study highlights the importance of training operators in knife honing/sharpening to ensure they have knives that cut easily. However, high activity of the EDC muscle demands further investigation in the field. Should this level of stress be confirmed, other prevention actions (knife design, organization-based through shift rotation or inclusion of micro-breaks, etc.) should be considered to reduce the risk of certain MSDs appearing, such as lateral epicondylitis.Relevance to industryThis paper describes how the use of a badly sharpened knife can increase upper limb biomechanical stresses. Knife-sharpening training programs should be considered, along with other prevention actions, to reduce the biomechanical stresses sustained by meat industry workers.