Mason with motion capture sensors

Lift Teams Share the Load

A bricklayer can lift the equivalent of more than five Ford F-350 trucks in a week. A new technique gives bricklayers and contractors a chance to reduce back injuries and extend careers.

No two ways about it: Masonry is hard work and stressful on the body. Masonry workers have the highest rate of back injuries causing days away from work among all of the construction trades. The rate is more than one and a half times higher than the average rate for all construction workers.

What's causing these musculoskeletal disorders (MSDs)? Overexertion while lift ing appears to lead the way as the number one cause. A bricklayer handling an average of 200 concrete masonry unit (CMU) blocks per day, weighing 38 pounds each, will lift the weight of more than five Ford F-350 pick-up trucks each week, or two and a half fully loaded Boeing 747-100s, each year. However, lift ing CMUs is not the only culprit. Workers also must bend to reach the block, then lift and twist from the waist to place the block. Just thinking about it can make you feel a twinge in your lower back.

Researchers have been working to find a way to combat these problems so that bricklayers can better tolerate the physical demands of their job and contractors can retain the knowledge of seasoned journey-level workers to mentor younger workers. Drs. Dan Anton and Ryan Mizner of the Department of Physical Therapy at Eastern Washington University and Dr. Jennifer Hess of the University of Oregon Labor Education and Research Center conducted a multi-year study to evaluate diff erent ergonomic solutions for making masonry work safer. Their research was funded by CPWR—The Center for Construction Research and Training.

The researchers' first step was to determine which ergonomic solutions were currently being used in the field. The team surveyed bricklayer and masonry contractors throughout the United States about the controls used in their area. Additionally, the research team conducted more than 80 work site audits in the Midwest, Southwest, and West Coast to find out which controls were being used. The various controls were categorized by diff erent masonry materials, equipment, and job tasks, such as use of lightweight block and Hblock; mortar mixers, grout delivery systems, and mechanical scaff olding; supply stack height; material handling methods; and rebar placement.

Based on the survey results, Anton, Hess, and Mizner selected areas of study, such as evaluating use of alternative masonry products to help reduce MSD injuries among these high-risk workers. The team also focused on the effectiveness of a two-mason lift team for laying heavier CMU. Although use of lift teams is oft en written into union contracts, the investigators found they are not commonly used in the field. No study to date had examined whether this control actually reduced injury risk.

Video Games Meet Research

Anton and Mizner worked with apprenticeship coordinators and trainers from the International Masonry Institute in Seattle, Wash., and recruited several apprentice bricklayers to participate in the study. Each bricklayer built a wall six courses (rows) high and six blocks wide, once individually and once in teams. They used 12- inch CMU weighing about 50 pounds to construct each wall.


Masons wore "motion capture sensors" similar to ones used in the video gaming and movie industries. The zombie-like creatures in the recent Harry Potter movie were created using motion capture technology.

While building the walls, bricklayers wore motion capture sensors similar to ones used in the video gaming and movie industries. For instance, the zombie-like creatures in the recent Harry Potter movie were created using motion capture. In the study, motion capture was used to measure the position of the back and arms of each bricklayer while building a wall, which helped to determine stressful positions. Anton and colleagues also measured how hard the apprentices' muscles were working using a process called electromyography. Electromyography sensors were placed on the lower back, upper back, and forearms to record the stress to the muscles in those areas during building.

Researchers found that using a lift team has the potential to reduce back injuries among bricklayers. Not only does a lift team reduce low back muscle force, but also bricklayers do not have to bend forward as much as when lift ing alone. While building the entire wall, bricklayers in lift teams spent less time enduring high levels of back and shoulder muscle exertion than did those working alone, which could reduce incidence of the all-too-common overexertion injury. The downside of using lift teams is that it increases shoulder stress on the non-trowel side at the higher courses.

"Although the results were not all positive, there is enough evidence to show that lift teams may still be an effective way to reduce back injuries in the masonry profession, especially when lift ing around waist level," said Anton. "However, lift teams are not recommended at the higher courses." He notes the lift team should be coupled with adjustable work platforms to get maximum health benefits of the technique. "We know that lift ing large CMUs overhead puts extraordinary stress on shoulders," Anton says. "Masons should use an adjustable work platform that keeps the work of buttering and placing the block at waist height."

Learning the Technique

The lift team technique is fairly simple yet takes a little practice to master. Each bricklayer on a lift team plays a diff erent role. One is in charge of finishing the wall, while the other prepares the next block by putting mortar on it. When ready, the bricklayers lift the block from the supply stack and set it on the wall together. Eff ective lift teams create a rhythm while working that requires getting "in sync" to avoid waiting on each other. It is likely that lift teams reduce worker fatigue over the course of the day, though field studies would be necessary to evaluate this.

"When on construction sites, I have frequently heard bricklayers and contractors say that lift teams are more productive because a mason working alone gets more fatigued by lift ing and placing these large CMUs during the work week," said Hess. "We know that workers who push themselves when they are tired are more likely to make mistakes or injure themselves from overexertion."

Dr. Laura Welch, who is medical director for CPWR and oversees the work of CPWR's ergonomics/MSD researchers, believes further study is warranted. She sees the next investigation taking place on a job site, such as a "big box store" where bricklayers are building walls using large CMUs, to test the theory that workers will be more productive over time when using the team lift ing technique.

"Still, you can't ignore the findings that bricklayers have less stress on their backs when using the two-mason lift technique," Welch said. "We know back injuries are a major problem in this trade. Once a back is injured, it's vulnerable and can easily be re-injured. We want to prevent these types of injuries, which are all too common, from happening in the first place."

Since the lift team technique is more easily understood visually, the research team decided to create an instructional video. The four-minute piece uses motionsensor footage, which enabled the researchers to create a unique effect. Viewers get to see two bricklayers working together safely, as well as a digital simulation of the bricklayer's skeleton while working.

The video can be found on CPWR's Web site or on YouTube.com. When searching on YouTube, use the key words "masonry lift team" to find the video entitled "Two Mason Lift Technique." For more information, e-mail lead researcher Anton at dan.anton@ewu.edu.

More Findings to Share

The team's research has generated a number of findings. Hess soon will be releasing analyses of alternatives to traditional CMUs. She and her colleagues, including Dr. Marc Weinstein of Florida International University, have evaluated the benefits and barriers to using autoclaved aerated concrete, lightweight block, and H-block to reduce shoulder and low back stress.

"These materials provide excellent alternatives to handling heavy CMUs, which can mean reduced instances of strains and sprains, and other back and shoulder injuries," Hess said. "We recognize that enhancing use of these alternatives by contractors, architects, and engineers may be a challenge. We welcome like-minded safety and health professionals to contact us to help spread the message that MSDs don't 'just happen.' We know we can control them and keep our workforce healthy."

This article originally appeared in the November 2009 issue of Occupational Health & Safety.

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