A Novel Biomechanical Analysis of Horticultural Digging

Abstract

Musculoskeletal injuries are commonly reported in workers employed in labor-intensive agricultural-type tasks. A novel method of determining joint angles, joint torques, and contact forces, using three-dimensional motion capture and musculoskeletal modeling, was applied to the movements of a sample of workers, engaged in the horticultural task of digging, to determine if objective biomechanical data could be correlated with a subjective visual assessment to predict risk of injury. The joint angle time histories of horticulturists were calculated from the motion capture data, and this was used to articulate a musculoskeletal model of the subjects. The joint torques were calculated using inverse dynamics methods from which the individual muscle loads were established using a cost function minimization approach. Finally, the joint contact forces were calculated including the muscle forces. The motion capture data of digging trials were observed by a team of horticulturists and physiotherapists who categorized each of the observed trials according to form, efficiency, and risk of injury. Trials demonstrating techniques which were more likely to yield injuries were identified as “examples of bad technique”; those judged to be less likely to yield injuries were categorized as “examples of good technique.” It was found that the joint torques and contact forces and their variability were lower in the trial which was identified as good technique, and consistently higher in the examples of bad technique. The results of the study suggest that measurement of joint angles, joint torques, joint contact forces, and forces in the muscles could serve as a valuable tool to develop training programs for horticultural workers engaged in certain high intensity tasks, such as digging, to effectively improve efficiency and reduce incidence of injury. It may also be possible to modify horticulture-related equipment to minimize the internal loads within the body to reduce the risk to health and, therefore, extend active participation in horticulture.