Shoulder-Assist Exoskeleton Effects on Balance and Muscle Activity During a Block-laying Task on a Simulated Mast Climber

Masonry work, a sub-specialty of the construction industry, consists of brick and block-laying. Masonry workers often perform these tasks daily using an elevated work platform (e.g., mast climbers). Mast climbers are elevating equipment used to replace traditional scaffolds. They have been available in the United States since the 1980s. Mast climbers are capable of handling much greater loads of workers and materials than traditional scaffolding. They also make reaching greater heights much easier, thereby improving efficiency on construction projects. However, working on an unstable work platform at elevation can increase the risks of slips, trips and falls, including falls to a lower level. From 1990 to 2017, there were a total of 35 recorded fatalities associated with the use of mast climbers. Of the 35 fatalities, 13 were masonry workers (OSHA report). Additionally, working on a mast climber can also create awkward working postures due to the confined nature of the workspace. Masonry work can be physically demanding. Concrete block can weigh between 9-27 kg. The rate of overexertion among masonry workers was 33.4 per 10,000 FTEs compared to the average rate of 21.5 per 10,000 FTEs in all industries (BLS data). Shoulder-assist exoskeletons present an attractive possibility to reduce MSD risks in masonry workers if the exoskeletons do not cause adverse effects to the workers’ stability and balance. In this study, we evaluated effects of three models of passive shoulder-assist exoskeletons on balance and shoulder muscle activity during a masonry task on a simulated mast climbing work platform. The balance-related parameters and shoulder muscle activities were compared when using or not using the exoskeletons. We want to evaluate the hypotheses that the exoskeletons (1) reduce shoulder muscle activity and (2) decrease the stability of the workers.