Biomechanical strains on the hand-wrist system during grapevine pruning

OBJECTIVES: In order to understand the high prevalence of musculoskeletal disorders of the hand among vineyard workers, we conducted a study to evaluate biomechanical strains on the hand-wrist system during grapevine pruning. METHODS: Surface electromyography (sEMG) activity of the right flexor digitorum muscle and wrist posture were analysed in six healthy vineyard workers using the same hand-powered pruning shears during grapevine pruning. RESULTS: The biomechanical strains on the hand-wrist system were high during grapevine pruning. Mean sEMG activity during pruning was high [23.5% (standard error of the mean (SEM): 0.4) in the maximal voluntary handgrip contraction (MVC)], as was the mean cutting frequency per minute (38; range=24-48). Approximately 14% of cuts were performed with the wrist in extreme flexion/extension (F/E) (>60% of the maximum range). Numerous cuts required moderate (20%-40% of the maximum range) or extreme (>50% of the maximum range) ulnar deviation (17% and 12% of cuts, respectively). Approximately 18% of cuts required both high muscular activity (sEMG >15% MVC) and extreme ulnar/radial (U/R) deviation of the wrist (>50% of the maximum range). CONCLUSION: Pruning imposes high biomechanical strains on the hand-wrist system in view of the repetitiveness of the task. The magnitude of physical exposure during pruning explains the high prevalence of hand disorders among vineyard workers. The use of ergonomic pruning shears is advised to lower force exertion and to reduce the frequency of awkward wrist postures during pruning.