Effect of Time Elapsed since Last Pruner Maintenance on Upper-Extremity Biomechanics during Manual Flower Cutting

Objective: Manual flower cutting imposes large biomechanical demands on workers’ upper extremities. Solutions are required to reduce these demands. This study investigated the effect of time elapsed since the last pruner maintenance on the biomechanical demands of the upper extremities during flower-cutting operations. Methods: Sixteen experienced workers were recruited. All workers performed flower cutting 1, 15, and 30 days after standard pruner maintenance, including cleaning, adjustment, and sharpening. The outcomes included kinematics of the wrist, elbow, and forearm; muscular activity of the extensor carpi radialis, extensor carpi ulnaris, flexor carpi radialis, flexor carpi ulnaris, biceps and medium deltoids of the dominant arm; and self-reported effort. Results: On average across muscles, a 15-day delay (from 1 to 15 and from 15 to 30 days) in the execution of pruner maintenance increased over 8% the median recorded muscular activity as measured by the percentage of the maximum voluntary contraction of the root mean square signal. An increase in time since last pruner maintenance resulted in an increase in the 90th percentile pronation–supination posture (larger excursion toward pronation); the median and the 90th percentile velocity of the wrist and elbow; and the 90th percentile acceleration in the pronation–supination direction. There was an increase in perceived effort as measured by a Borg scale as time since last maintenance increased from 1 to 15 days. Conclusion: Increasing the frequency of pruner maintenance procedures can effectively reduce workers’ mechanical exposures during manual flower-cutting operations. Companies should implement daily maintenance programs considering their implementation capacity and expected benefits.