Biomechanical evaluation of postures assumed when harvesting from bush crops
The objectives of this research were to explore the changes in the low back biomechanical responses during a harvesting task as a function of different harvesting techniques/postures and to explore the effects of an ergonomic intervention designed to reduce the low back stress during this work activity. Nine participants performed a series of simulated harvesting activities in a laboratory setting using four different harvesting techniques: full kneeling posture, squatting posture, stooping posture and kneeling on a knee support device (the intervention). As they performed these tasks the activity of muscles of the torso and thighs was captured using electromyography and trunk kinematics were captured using the lumbar motion monitor and a magnetic field-based motion tracking system. The results showed that (1) three postures – knee support, squatting, and stooping – required high flexion of low back (more than 60°) and (2) squatting and stooping postures showed significantly higher passive tissue moment compared with two kneeling postures. The results also indicate that the beneficial aspects of the knee support intervention appear to be outweighed by reduced productivity and the high degree of trunk flexion and that the current strategy used by these workers of alternating between the various harvesting postures may be the best strategy available.