Exoskeletons are wearable devices designed to mechanically assist workers in the workplace.
By Zhenhua Zhu, Ph.D., P.Eng, and Mariya Sorensen
The construction industry is labor-intensive even with the continuous development and advent of new tools and machines in the market. Millions of people are hired and associated with different trades (e.g., laborer, carpenter, plumber, and electrician). They are heavily involved in the vast majority of skilled manual handling work. Almost 90% of their jobs require manual handling of materials for approximately one-half of their time.  The long-time, repetitive, and physically demanding manual handling work exposes them to a great risk of work-related musculoskeletal disorders (WMSDs), a group of painful disorders of muscles, tendons, and nerves caused or aggravated by work.
At present, the industry has not recognized the price, stability, and versatility of active full-body exoskeletons, while arm- and back-support passive exoskeletons, such as Hilti-EXO 01, Ekso EVO, HeroWear Apex, and Ottobock SuitX, have entered the marketing stage and received wide attention. Their effectiveness has been tested in a number of controlled laboratory studies. The results have illustrated that the use of these exoskeletons could help test participants reduce their muscle activity levels, perceived exertion, and metabolic costs, although the magnitude of these beneficial effects depend on specific task conditions and individual differences. For example, more neutral work postures and reduced spinal muscle loading were noted when lifting with low-back exoskeletons.  Deltoid muscle strain was also decreased for overhead tasks while using shoulder-assist exoskeletons. 
Despite the promising effects noted from the laboratory-based studies, it is still essential and critical to collect field-based evidence to support the safe and efficient use of exoskeletons by construction workers before any decision is made to deploy exoskeletons in practice. So far, the quantitative assessment of exoskeletons’ efficacy as an intervention to control the risks of WMSDs in construction fields is limited. Most assessment works were built upon qualitative or subjective measures through interviews and surveys. To address this limitation, the Digital and Robotics Construction Research Group at the University of Wisconsin–Madison has been working with the Milwaukee-based team in the M.A. Mortenson Company. Several pilot tests (photos on the previous page) were conducted to compare the joint motions, heart rates, task completion time, and opinions of professional construction workers when they perform routine tasks with and without exoskeletons. The quantitative comparison results help researchers and construction practitioners advance an understanding of the actual effectiveness, practicality, safety, and user acceptance of exoskeletons in construction fields. Also, they provide insightful thoughts on optimizing the match among exoskeletons, workers, and tasks to maximize exoskeletons’ beneficial effects and minimize their potential undesirable outcomes or risks. This ongoing work is financially supported by the National Science Foundation.
If the accumulated field-based evidence supports the efficacy of exoskeletons, it will facilitate and promote the use and integration of exoskeletons in construction operations. Then, the following benefits or broad impacts are expected:
Improving the safety of construction workers and creating a better safety culture.
Workers are critical assets contributing to the success of construction projects. The use of exoskeletons will improve their safety by reducing the chance of fatigue and muscle strain and the risk of wear and tear injuries at work. This, in return, will benefit the construction industry and society with huge cost savings.
Alleviating the shortage of skilled construction workforce.
The use of exoskeletons will provide additional assistance for post-surgery construction workers and help them with recovery and discomfort. It facilitates retaining the current workforce by extending their career life spans. Also, it can expand the skilled workforce by attracting candidates (e.g., women) into construction trades who may otherwise not consider such jobs due to their physically demanding nature.
Enhancing construction labor productivity.
The work performance gains achieved by exoskeleton-enabled work may help increase construction productivity and reduce project cost overruns and schedule delays. The construction industry accounts for a significant portion of the economy and it is still booming. However, its productivity has only grown by 1% over the past two decades, compared with the 2.8% growth of global productivity.  44% of construction firms reported that projects have taken longer than originally anticipated, and 43% reported that costs have been higher.  With the passing of the $1 trillion Infrastructure Bill in 2021, it has become imperative that we address the need for growing the construction workforce and improving construction productivity.
Zhenhua Zhu, Ph.D., P.Eng. is Assistant Professor at the UW-Madison Dept. of Civil and Environmental Engineering. Mariya Sorenson is Senior Integrated Construction Manager with M.A. Mortenson Company, Waukesha.
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