From The Ergoweb® Learning Center

Researchers Look Upstream to Mitigate Ergonomic Risk Factors for Residential Carpenters

The slump in housing starts in 2008 and 2009 in the United States has put many residential carpenters out of work, which means they are out of harm’s way for the ergonomics-related perils of their trade. But who would describe a recession as a constructive way to combat risk?  Political ideology has stymied at least one effort to mitigate the risk constructively. The complexities of work-related muscular disorders (WMSDs) and typical construction projects undermine other efforts. One recent study reveals the taxing nature of the research. Another sees potential ways to reduce hazards for carpenters—upstream of the construction site.   
Residential building construction can only be described as a vast industry – the National Association of Home Builders describes it as the seventh largest. And it’s a hazardous line of work.
In August 2008 the American National Standards Institute (ANSI) described musculoskeletal injuries as the most common and costly health and safety issue in the construction industry. Evaluating data from over 30,000 respondents, Guo et al. (1995, 1999) found that construction laborers and carpenters had the highest prevalence of back pain within the construction industry.
Initiatives to Mitigate Risk

To address the hazards, OSHA launched an initiative called “Ergonomics Programs in Construction (Part 1926): Preventing work-related musculoskeletal disorders among construction workers.” Many work-related MSDs are preventable, the agency noted in its abstract, and “many low-cost methods of reducing worker exposure to ergonomic risk factors are now available for the construction industry.”
The well-intentioned initiative didn’t survive beyond the early days of the George W. Bush presidency. The administration’s ideological aversion to federal regulation also doomed the child of the initiative—the Ergonomics Standard of January 21, 2001. Talk of federal rule-making for the workplace has started up again under the Barak Obama administration, but it is likely to be nudged off the agenda for the present by issues as diverse as the recession and piracy in the Indian Ocean.
In the meantime, ANSI has picked up the ergonomics ball that OSHA set aside. In July 2008 the Institute published a standard on sprain and strain injuries in construction. “For the first time since Congress voided OSHA’s ergonomics standard in 2001,” ANSI wrote in a news release, “the construction industry has guidance for limiting MSDs.”
Though the standard is voluntary and imposes no specific employer obligations, other than the responsibility to assess dangers and involve workers in their mitigation, the Construction Employers Coalition slammed it.  In a letter dated 22 July 2008, the National Association of Home Builders (NAHB) expressed its “strong disappointment” with the standard, arguing it “would not help reduce workplace injuries.” NAHB complains that rather than providing workplace safety instructions, the standard offers “vague suggestions for employers to examine activities that involve such things as ‘force,’ ‘pushing,’ or ‘lifting.’”
Challenges of Combating Ideology

Despite decades of research into almost every aspect of the problem, WMSDs still bedevil the residential construction industry. The intrinsic complexity of WMSDs and construction work make both difficult to study, and, arguably, undermines the robustness of the findings; the research literature has yielded few irrefutable findings that could turn the tide for regulation.
There is not even a reliable figure for the number of carpentry contractors in the country, much less the number of carpenters. The last US Census, in 2000, put the figure for carpenters in the country at 1.2 million, but a report from the North American Industry Classification System (NAICS), an arm of the Census Bureau, implicitly disputes the accuracy of the figure: “It is difficult to determine exactly how many carpentry contractors exist in the United States because carpentry contractors generally are small establishments, and many self-employed carpenters serve as their own contractors. Plus, the housing industry is highly fragmented, lacking national general contractors or specialty trade contractors.”
The United Brotherhood of Carpenters, which describes itself as North America’s largest construction trade union, offers another reason to doubt the numbers—the informal or underground economy. Writing about the situation in New York City, which can be extrapolated for the whole country, the union observes the underground construction industry is concentrated in residential construction, and estimates that nearly one in four of New York City’s 50,000 construction workers is either misclassified as an independent contractor or employed completely off the books.
It follows that any official WMSD figures are unlikely to reflect the true scale of the problem.
Recent Studies

Two recent studies make a valuable contribution to the body of knowledge about WMSDs in residential carpenters. Both studies were presented at National Occupational Research Agenda (NORA) conferences in Utah. The first, in 2003, was, “Occupational Low Back Pain in Residential Carpenters: OWAS Categories and Forces of Compression and Shear,” by David P. Gilkey and a team at Colorado State University and the University of Utah. The second, in 2009, was “Development of a decision support system for residential construction using panellised walls: Approach and preliminary results,” by Maury A. Nussbaum and a team from Industrial and Systems Engineering at Virginia Tech.

In their cross-sectional investigation of framing carpenters in the Denver Metro area for low back pain (LBP), the Gilkey team measured the prevalence of occupational LBP, and evaluated ergonomic factors that might have contributed to the problem. Ninety-four individuals were chosen randomly from a population of 5,500 framing carpenters.
The 94 carpenters were selected from participating general contractors within the HomeSafe Pilot Program. The team collected their data using video samples of selected job-tasks and a 91-question self-report survey focused at identifying prevalence and risk factors for LBP. Subjects rated perceived lower back strain while performing the 44 major job-tasks required to build a wood-framed house. Using the subjective strain scores, a subset of 10 job-tasks were identified and analyzed using The Ovako Working Posture Analysis System (OWAS). And they used ErgoMaster 2-D software to evaluate risk of injury and compression and shear forces to the lumbar spine during routine carpentry work.

The team examined the validity of their research methods and findings against an array of studies that document characteristic research challenges. The collection stands out as a compendium of the difficulties of obtaining irrefutable data about WMSDs in an occupation where they flourish—residential carpentry. Evaluated in the context of these other researchers’ findings, the Gilkey team concluded that their study “has certain limitations in its design and conclusions.”

The design was a nested cross-sectional study within a larger cohort of volunteers. Gilkey et al cited studies that questioned whether the testing could be random with this approach, and whether the subjects are truly representative. Several studies noted that the use of a cross-sectional design is inherently limiting as the findings represent a slice in time and cannot establish causation. Again referring to the experiences of other researchers, the team questioned whether they job-tasks they sampled were representative of the most common methods of work.
Survivor bias, it appears, is another typical obstacle for researchers in this field. “Men and women who cannot manage the stresses and strains inherent in this work leave the industry,” the authors wrote, suggesting the framers they evaluated may not represent the average population. “Mean anthropometric measures for stature/height and weight suggest that the average residential framer is slightly larger and heavier than the average American citizen or military personnel, and the subset of people may have additional features or characteristics not measured that further influence findings in ways not recognized.”
Some of the studies indicated that self-report survey instruments can also skew results. And writing about their own study, the Gilkey team noted that the workers sampled may have been affected by the presence of the onsite investigator collecting video recordings of their work. “Workers may in fact be exposed to greater stresses through common work practice not seen or sampled during filming,” they concluded.
The collection of studies also reveals that:
• Job-task sampling time can be limited in many cases due to the fragmented nature of construction work, erratic building schedules, lack of materials supply, weather and lack of cooperation by workers or management
• Many phases of building facilitate parallel job-tasks, making it very difficult to separate specific job-tasks from the overall work activity
• Materials or equipment availability, tool operations, job-task skills, authority, interest, or management factors may result in job-task changes moment by moment
• Framing carpenters follow a building plan but may have many divergent paths to achieve the overall goal of building a house, with little regard for investigational activities on site
• Carpenters performing job-tasks are not necessarily doing so in a linear systematic fashion, but tend to maneuver between job-tasks—a factor that complicates the sampling of some job-tasks and can result in inaccuracies
• The major job-task of interest can be a multi-step process not fully assessed.
Writing about their own study in the context of other researchers’ difficulties, Gilkey et al wrote that “decisions were made … about the representative sampling necessary to capture the job-task demands through whole-task or sub-task sampling. These decisions may not have been adequate to describe all the actual elements of posture and loading associated with each job-task evaluated.” They note that inadequate exposure assessment has been identified as a significant limiting factor in studies looking at ergonomic risk factors for LBP and other musculoskeletal disorders.
Some researchers found that the nature of 2-D sampling is inherently limited in its ability to assess real-life activities and motions. “Only those images at or near perpendicular to the subject can be used for assessment and may not represent the actual forces being generated,” the authors wrote. “This type of assessment makes no effort to describe torsional forces, which may also pose significant risk.” They noted that the investigator can be limited by hazards on the jobsite, as well as the need to be inconspicuous and non-disruptive to the usual work process.
The authors described ErgoMaster as “fairly friendly,” but added that it requires the height and weight of the subject and the weight of load values. Carpenters consenting to be filmed were asked for this personal information, they said, and may not have provided accurate information. 

Software use requires placement of the cursor on specific body parts to determine moment arms and vectors in the calculation of compression and shear forces, according to Gilkey et al, creating the potential for human error. “The OWAS software does classify twisting and bending postures, but is limited to 30 second observation intervals for predominant posture and load classifications, and the sensitivity of OWAS is still limited to 30 second captures. They observed that construction work is dynamic and changing. “Postures, loads, and activities may change dramatically from moment to moment. The sensitivity of OWAS may not have captured this dynamic work as it is actually performed.”
Researchers cited by Gilkey et al note that the multi-dimensional nature of factors attributable to LBP cannot all be measured. “Not fully understanding all exposure elements and their relationships limits the quality of the data and the inferences drawn,” the Gilkey team concludes.
The team pointed out that the inexact nature of symptomatic complaints such as LBP has been recognized as a source of potential bias by many investigators. Concluding with the observation that carpenters appear to be a group of workers exposed to greater levels of risk relating to LBP, and that no clear job-task associations can be made, the authors noted that their study did not possess “the scope and depth to thoroughly compare job-tasks of residential framing carpentry to that of the general population.
Moving “Upstream”

In their LBP-residential construction study, which was funded by the National Institute for Occupational Safety and Health (NIOSH), as part of the Construction Safety Center at Virginia Tech, the Nussbaum team’s “upstream” focus provided a measure of control over some of the taxing research issues noted in the other studies. Prefabricated walls (panels) were central to the study, and the team developed a decision support system (DSS) for the proactive control of exposures. The tool allows the panel designers to consider ergonomic risk when developing their designs. The approach has particular value, they wrote, “since the centralized panel designer can impact a large number of construction sites and workers ‘downstream.’”

The authors note that existing evidence suggests “a substantial fraction of injury-causing accidents stem from conditions ‘upstream’ of the actual construction process, at the stages of planning, scheduling and design.” They said studies suggest “more than half of construction accidents can be eliminated, reduced or avoided with more attention during design.” 

In a recent communication with The Ergonomics Report®, Professor Nussbaum explained that the team’s approach “involves using custom algorithms for designing wall panels starting from an architect’s plan and specifying how panels are stacked and delivered to the work site. Subsequently,” he added, “we simulate the construction process starting from stacked panels to completing the building structure. The simulation includes estimates of worker ergonomic exposures and risks for each of the physically-demanding tasks involved, [so] we can simulate any number of alternatives and find the best approach to minimize the impact on workers, while also ensuring high levels of productivity.”
The authors describe the DSS as a novel attempt to address a fairly difficult problem, and note several inherent advantages to the tool:
• Use of the software will facilitate a more proactive approach to ergonomics in one aspect of residential construction, and addresses the need expressed by designers for appropriate tools
• By addressing ergonomics aspects early in the construction process, and facilitating input by designers, the overall impact is expected to be more efficient and effective than more reactive, site-based interventions
• The DSS is scalable and can incorporate a range of additional tasks or processes involved with panelized wall construction, assuming requisite input data are available. Use of laboratory-based tasks simulations will provide quite detailed and extensive information on exposures. Such data allow for ergonomic risk assessment using a range of contemporary tools, but the DSS can also be easily adapted in the event that more advanced tools are developed.
•  A primary advantage in this approach could be the inclusion of both ergonomics and productivity as basic components. Thereby, a designer (or other user) can quantify the effects of modifications on both fundamental aspects, perhaps by determining a weighting or balance between the two
• As upstream work is expended in the factory, where working conditions are controlled and modern equipment and practices employed, substantial time/cost savings in the field can be realized for relatively little time/cost in the facility. Additionally, while ergonomic risk is reduced in the field, it does not increase at the facility, as the same modern equipment and practices (designed to address ergonomics) can be used.
In his communication with The Ergonomics Report®, Professor Nussbaum described the team’s approach as a different way to look at assessing worker exposures and designing and testing ergonomic interventions. “An approach like this, which is similar to what has been done in the manufacturing sector, has the potential to address some of the challenges inherent in construction,” he explained.
OSHA 1987. Ergonomics Programs in Construction (Part 1926): Preventing Work-related Musculoskeletal Disorders Among Construction Workers

ANSI Adopts Sprain and Strain Standard: (Aug 2008; Vol. 5, Num. 3 American National Standards Institute 

Guo, H.R., Tanaka, S., Cameron, L.L., Seligman, P.J., Behrens, V.J., Ger, J., Wild, D.K., Putz-Anderson,
V. (1995). Back pain among workers in the United States: National estimates and workers at high
risk. American Journal of Industrial Medicine, 28, 591-602. 

Guo, H.R., Tanaka, S., Halperin, W.E., Cameron, L.L. (1999). Back pain prevalence in the US and estimates of lost workdays. American Journal of Public Health, 89, 1029-1035.
Building Up New York, Tearing Down Job Quality: A Fiscal Policy Institute Report (Dec 2007)

Occupational Low Back Pain in Residential Carpenters:  OWAS Categories and Forces of Compression and Shear (2003). David Gilkey; Thomas J. Keefe; Philip L. Bigelow; Robin E. Herron; Kirby Duvall; Jacob E. Hautaluoma; Richard F. Sesek  

Development of a decision support system for residential construction using panellised walls: Approach and preliminary results (Jan 2009). Maury A. Nussbaum; John P. Shewchuk; Sunwook Kim; Hyang Seol; Cheng Guo


This article originally appeared in The Ergonomics Report™ on 2009-04-29.