Evaluation of scapular kinematics during milking

Increase in milk production over the past twenty years have forced dairy milkers to work long hours, which predisposes them to musculoskeletal symptoms (MSS), particularly at the shoulder and neck region. These MSS are attributed to repetitive lifting and attaching the cluster to the udder. It is critical to understand the biomechanics of the attachment task in order to prevent development of MSS in milkers. Therefore, the primary purpose of the study was to describe the effects of udder height on trunk, shoulder, scapular kinematics and muscle activity. The secondary purpose of the study was to compare the trunk, shoulder, scapular kinematics and muscle activity during an attachment task in setting that simulate two parlor styles (herringbone and parallel parlor). Data collection took place in a laboratory. A total of twenty participants performed five trials of attachment task under four conditions: udder placed 15cm above shoulder height (HIGH), at shoulder height (NORM), 15cm below shoulder height (LOW), and shoulder height with wide opening for arms (WIDE). Video-based motion capture system and EMG was used to capture data. The trunk, shoulder, and scapula kinematics and muscle activation levels during the attachment task were compared among the four conditions using 1-way repeated measures analysis of variance. The results indicated that the HIGH condition resulted in the lowest trunk flexion angle, and erector spinae and neck extensor muscle activity. The LOW condition resulted in greatest trunk flexion angle, elbow extension angle, and erector spinae and neck extensor muscle activation level. The WIDE condition resulted in less shoulder horizontal adduction angle, anterior deltoid muscle activation level, and greater elbow flexion and anterior tilt. Our observation suggests that cluster attachment 15cm above the shoulder may reduce strain on the trunk/neck area. When comparing milking in herringbone to parallel parlor styles, herringbone resulted in lower activation of anterior deltoid muscle, which could potentially result in decreased arm fatigue.