ANALYSIS OF THE EFFECTS OF WORKING POSITION ON MUSCLE FATIGUE DURING HEDGE PRUNING: A CROSS-SECTIONAL STUDY BASED ON CHINESE GARDEN WORKERS

Abstract

Occupational health is still in the developmental stage in China. There is a lack of focus on garden workers. Hedge pruning is one of garden workers’ main tasks, a common operation form in modern landscaping. Garden workers who operate the hedge trimmer generally suffer from work-related musculoskeletal disorders (WMSDs). This study aims to demonstrate which working condition causes the most muscle fatigue, evaluate work fatigue accurately, and reduce WMSDs in garden workers. One hundred and twenty garden workers were studied during six hedge pruning conditions using surface electromyography (sEMG) and a motion capture system. The sEMG of the erector spinae, trapezius, biceps brachii and brachioradialis muscle, and kinematic parameters was measured during the operation. The average standardized sEMG values of upper-limb and trunk muscles in different working conditions were analyzed using single-factor analysis of variance. In the six working conditions, the trunk inclination angle was the largest (40–50∘) in horizontal pruning of short hedges, and the load of erector spinae (39.31–39.62%) was the highest in this condition. Operators’ arms were above shoulder height in high hedge pruning, the shoulder joint angle and the elbow joint angle were generally larger, the load of trapezius (49.33–55.65%), biceps brachii (46.50–52.35%) and right brachioradialis (52.35%) was the highest in horizontal pruning of high hedges, and the load of left brachioradialis (40.91%) was the highest in vertical pruning of high hedges. Awkward working postures can lead to problems such as overwork of upper-limb and trunk muscles, representing a risk that increases occupational illness, injuries and chronic diseases among garden workers. Preventive measures are required to reduce the occurrence of excessive local muscle load, and prevent the occurrence of occupational diseases.