Download or read book Ergonomic and Time Cost of One-handed Lifting Tasks as a Function of Shelf Height, Item Weight and Walking Distance written by Chunyi Sun and published by . This book was released on 2019 with total page 66 pages. Available in PDF, EPUB and Kindle. Book excerpt: One-handed lifting tasks are frequently performed in warehouse operations. Often these are small piece-pick order selection jobs that are performed by female hourly employees. These jobs require the picking of single items from open boxes of items, for example, individual bottles of shampoo that are sent to retail stores to replenish stock that has been sold. Often these individual items are picked from boxes located on multi-level flow racks. The objective of this study was to quantify the time cost and ergonomic cost of one-handed lifting tasks as a function of shelf height, item weight, and walking distance. Seventeen participants lifted items of two different weights (0.45 and 0.90 kg) from seven shelf heights ( 10.8, 37.1, 63.5, 89.9, 116.2, 142.6, 168.9 cm) and either walked one step prior to picking up the item (lifting task 1) or lifted the item without needing to take a step (lifting task 2). The dependent variables were the 90th percentile electromyographic (EMG) signals of the right anterior deltoid, right lateral deltoid, left and right erector spinae; the peak value of spine twist, spine flexion, spine lateral flexion, right shoulder flexion and right shoulder abduction; and time required for walking and lifting. Results indicated that shelf height had a significant effect on all postural and EMG variables and that there is a trade-off between the back and shoulder muscle activity across the varying shelf heights. Picking from shelf heights at 142.6 and 168.9 cm resulted in greater shoulder abduction and flexion and higher shoulder muscle activity. Picking from shelf heights at 10.8, 37.1 and 63.5cm increased torso flexion, twisting, and back muscle activity. Item weight significantly affected EMG activity in both shoulder muscles and one of the back muscles. In terms of lifting task, shoulder muscle activities increased in the second lifting task (task 2) which did not require a step. All postural measurements except spine flexion were significantly affected by whether or not a step was required. The significant shelf height and item weight interaction effect showed increased muscle activities with the higher weight only for lifting from the higher shelf heights (from 116.2 to 168.9cm). In addition, the effect of shelf height and lifting task combined showed a significant effect on all postural and EMG data. In general, the EMG activity of shoulder muscles were lower in the lift where a step was required. Finally, both walk and lifting time were significantly affected by shelf height. The lowest walk and lifting time cost occurred at the middle shelf heights from 89.9 cm to 142.6cm. Lifting time also increased with the heavier item weight.