Exploration of Back Exoskeleton’s Effectiveness on Transportation Maintenance Workers during Lifting Activities

Abstract

Safety statistics from Indiana Department of Labor showed that the transportation and warehousing industry has the second highest number of reported occupational fatalities (26) in 2020. One major cause of occupational fatalities is ergonomic issues including excessive force, repetitive motion, and awkward posture. These ergonomic issues have already been extensively studied and corresponding solutions were developed for the building construction activities. However, transportation activities are different from building construction activities in duration, intensity, and frequency. In addition, there lacks studies exploring whether the proposed solutions to ergonomic issues of building construction could also solve the ergonomic issues of transportation activities. To this end, field experiments were conducted with 29 transportation maintenance workers between August 9th 2023 and September 23rd 2023 at a transportation maintenance unit of Indiana Department of Transportation (INDOT). Lifting bags of dry concrete mix was identified as the activity of top concern, according to (1) the perception of which activity most likely to cause an injury to back or shoulder, (2) the frequency of performing the activity, and (3) the number of historical sprain injuries caused by the activity. Therefore, the participants were asked to lift 12 bags of three different weight of dry concrete mix with and without a back exoskeleton. Specifically, three different weights of bags include: 80-pound bags (weight of bags that INDOT maintenance workers mostly use), 50-pound bags (weight of bags that INDOT maintenance workers sometimes use and which is recommended by Recommended Weight Limit equation under the ideal condition), and 31.5-pound bags (recommended weight of bags based on applying values from real lifting practice of INDOT maintenance workers into the Recommended Weight Limit equation). The participants need to lift bags from a pallet to a truck with liftgate, have a five-minute short break, offload those bags from the truck with liftgate to the ground, and then have a 20-minute long break. Skin conductance and heart rate, as the key indicators of physical fatigue, were measured during the lifting activity. In addition, perceived level of muscle exertion was also collected by using a Borg 6-20 scale during two experiment breaks of each trial for indicating level of fatigue risk level from low to very high. After performing a paired t-test of collected data, it shows that the back exoskeleton does not significantly help workers reduce physical fatigue risks while transportation maintenance workers lift 31.5-pound bags. However, the back exoskeleton can significantly lower the physical fatigue risks when transportation maintenance workers lift 50-pound bags and 80-pound bags. This study not only fills the gap of exploring the effectiveness of back exoskeleton implementation in transportation maintenance activities, but also provides evidence and practical recommendations for transportation workers, managers, and organizations that a back exoskeleton could reduce the level of fatigue risk when lifting materials with weight of 50 pounds and above.