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Losing Balance Upon Standing
Do Construction Workers Perceive the Problem?
By Angela T. DiDomenico, Raymond W. McGorry, Michael F. Blair and Yueng-Hsiang Huang
T he construction industry is one of the larg- est sectors of the U.S. economy, employing 7,439,000 people in 2009 (BLS, 2009). Al-
though worksite safety has improved, incidents continue to occur, causing numerous fatalities and injuries to workers.
Falls account for the most fatalities and are the sec- ond most common cause of nonfatal workplace injuries in the construction industry (CPWR, 2007). Loss of bal- ance often is a contributing factor in falls (Hsiao & Simeonov, 2001), although it is not always clear what factors cause the imbalance. One possible factor is the transitory na- ture of construction work activities that requires workers to
perform tasks in awkward postures and frequently transition to a standing posture before proceeding
to the next task and/or location. OSHA has requirements regarding fall protec-
tion ranging from training to personal fall protec- tion devices. Fall protection devices may be active [e.g., personal fall arrest systems (PFAS) such as horizontal and vertical lifelines] or passive systems (e.g., guardrails and safety nets).
In general, fall protection is used to react to a loss of balance and eliminate or minimize injury. A proactive approach is for workers to perceive situ- ations that place them at risk so they can employ techniques to maintain balance. At this time, it is unclear to what extent workers can perceive fall risks, particularly those associated with standing up after working in a nonerect posture.
What Factors Affect Balance? Maintaining balance is a critical factor for suc-
cessful task performance; it requires information from the visual, vestibular (detects motion of the head-in-space) and proprioceptive (senses relative position of body parts) systems (Danis, Krebs, Gill- Body, et al., 1998). Sensory input is integrated to provide the individual with information that influ- ences balance control and allows for compensatory movements necessary to maintain postural control (Cobb, 1999). These movements depend on the in- tegrity of the musculature and the effectiveness of processing within the central nervous system (Hor- ak, Shupert & Mirka, 1989). In general, stable con-
IN BRIEF •Falls are a serious concern within the construc- tion industry. This study explored factors affecting perceptions of balance upon standing from different working postures. •Data were collected on perceptions of balance upon standing, fall protection measures employed and factors affecting balance. Ratings of perceived balance were significantly affected by working posture, construction trade and age of worker. •Construction workers identified measures they use to maintain balance, including those that do not require additional equipment, such as transitioning to an intermediate posture prior to standing. •Findings may lead to recommendations for rede- sign of tasks or tools to reduce the use of certain working postures, and mitigate fall risks through a proactive approach of maintaining balance and reducing the occurrence of falls.
Angela T. DiDomenico, Ph.D., CPE, has been a research scientist at the Liberty Mutual Research Institute for Safety in Hopkinton, MA, since 2003. She holds a Ph.D. in Industrial and Systems Engineering/ Human Factors from Virginia Tech. DiDomenico conducts research within the slips and falls domain.
Raymond W. McGorry, M.S.B.E., PT, CPE, is a senior research scientist in the Center for Physical Ergonomics at Liberty Mutual Research Institute for Safety.
Michael F. Blair is a technical consultant for Liberty Mutual Group, currently working exclusively with United Parcel Service in the New England region.
Yueng-Hsiang Huang, Ph.D., is a senior research scientist at Liberty Mutual Research Institute for Safety. She holds a Ph.D. in Industrial/ Organizational Psychology from Portland State University. She is a member of Society for Industrial and Organizational Psychology, American Psychological Association, Society for Occupational Health Psychology, and editorial board of Accident Analysis and Prevention.
Construction Safety Peer-Reviewed
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trol of posture and balance is automatic for healthy individuals, although alterations to sensory inputs may make maintaining balance more challenging.
Transitions between postures can affect all three sensory systems involved in maintaining balance. Altering the orientation of the head influences vi- sual input and has been shown to challenge balance control in healthy working-age adults (age 22 to 50) due to a decreased ability to discern the orientation of the head and body with respect to gravitational vertical (Paloski, Wood, Feiveson, et al., 2006).
Changing proprioceptive feedback also can af- fect balance as shown in studies that examined the after-effects of standing on an inclined sur- face (Kluzik, Horak & Peterka, 2007; Mezzarane & Kohn, 2007); walking on an inclined surface (Ler- oux, Fung & Barbeau, 2002; Wade & Davis, 2005); and standing on compliant surfaces (Simeonov, Hsiao & Hendricks, 2009). The interaction of all these factors at an elevation make maintaining bal- ance control more difficult, yet critical in the pre- vention of falls.
Survey Development The research team developed a written pencil
and paper survey with assistance from subject- matter experts. Information from semistructured interviews was obtained from current construction workers (i.e., painter, mason, plumber) and loss prevention construction specialists (i.e., technical consultants) of an insurance company.
Cognitive interviews were conducted to examine the meaning of survey items (for clarification pur- poses) and the extent to which these items reflect the domain being investigated. This process was implemented to maximize content and face validity.
Participants were recruited for their expertise in and familiarity with the construction industry. Questionnaire items were revised based on sub- ject-matter experts’ comments and suggestions. The revised survey was completed by 10 current construction workers who represented the target participant population to ensure sufficient under- standing of the questions and determine an ex- pected range of responses. This feedback was used to finalize the survey questions and format.
Survey Topics The survey was divided into three main sec-
tions. The first section was used to evaluate the workers’ perceived sense of balance after stand- ing from a working posture. Photos of 10 different, nonerect working postures were presented (Figure 1). Standing was included as the 11th posture fol- lowing the nonerect postures and used as a point of comparison. General pictorial representations were intentionally used without specific tasks, tools, PPE, etc., to allow for generalizability across trades and tasks.
For each posture, the workers estimated how
much time each posture was used during a typi- cal month. If participants indicated that they used a given posture, they were asked to rate their per- ceptions of balance upon standing after working in that posture. Details regarding the five-point Lik- ert-type rating scale (1 = unstable, 2 = somewhat unstable, 3 = neither unstable nor stable, 4 = some- what stable, 5 = stable) used to obtain perceptions of balance can be found in DiDomenico, McGorry, Huang, et al. (2010).
The second set of questions examined the meth- ods that construction workers used to maintain balance when a threat to balance is perceived. The final set of questions explored contextual factors that
Pictorial representations of the 10 nonerect working postures included in the survey: a) reclined kneeling; b) lying on back; c) lying on stomach; d) sitting on level surface; e) upright kneel- ing—knee(s) on ground; f) lying on either side; g) sitting on el- evated surface; h) bent over at waist; i) forward kneeling—hand(s) on ground; j) squatting.
Figure 1
Nonerect Working Postures
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may increase risk of falling, includ- ing environmental, task and personal factors. Partici- pants were asked to indicate in the affirmative or neg- ative for each fac- tor. Data were also collected regarding each construction worker’s trade, age, gender and years of experience.
Survey Administration
Workers were recruited from 10 construction trades with an emphasis on trades directly involved in build- ing construction. All currently em-
ployed construction workers who comprehended English were eligible. Participation was completely voluntary and recruitment occurred at five jobsites and through local advertisements. Prior to taking the survey, all participants completed an informed consent procedure approved by the Liberty Mutual Research Institute for Safety’s Institutional Review Board.
One hundred and ninety-six workers in the northeastern U.S. participated in the study. An ef- fort was made to have a similar number of partici- pants from each construction trade complete the survey with a minimum of 10 workers from each trade taking part. Of participants, 97% were men, a proportion representative of the construction in- dustry as a whole. Workers surveyed averaged 15.9 (SD = 11.5) years’ experience within the construc- tion industry and 13.5 (SD = 11.1) years’ experi- ence within their current trade.
Table 1 summarizes participant demographics, including the distribution within the three age cat- egories used during analysis. Participants complet- ed the survey in approximately 15 to 20 minutes. Responses from seven participants were removed due to insufficient data, resulting in 189 usable sur- veys and a completion rate of 96.4%.
Results & Interpretation Ratings of Perceived Balance by Working Posture
Postures were ranked across all con- struction trades according to the fre- quency of use during a typical working month (Figure 2), although the rate of use for many postures was not the same across trades. Ratings of perceived balance (RPBs) averaged 4.1 [1.1] or “somewhat stable” when examining all postures and trades. RPBs provided were statistically different among the various postures, indicating that the working posture maintained prior to standing has a perceived influence on balance and the vulnerability to fall risk immediately fol- lowing the transition in posture.
Figure 3 illustrates the RPBs for each posture. Post-hoc testing indicated that bent over at waist, squatting and forward kneeling resulted in the lowest RPBs, whereas working while sitting on level surfaces and standing were associated with the highest RPBs.
Transitioning from one posture to another requires adjustment within multiple sensory systems during or im- mediately following the transition to return the body to balance equilibrium. Bending at waist, squatting and forward kneeling may create a heavier burden on multiple sensory systems, decreasing balance and resulting in lower RPBs.
Input to the vestibular system is affect- ed by movement of the head, and devia- tions of the head from a neutral position
Table 1
Participant Demographics
Note. n = 189. aOne value missing for age.
Percentage of time each working posture was reported to be used during a typical month.
Reclined kneeling 17.3%
Bent over at waist 12.2%
Forward kneeling 7.3%
Upright kneeling 7.2%
Squa�ng 5.7%
Si�ng on elevated surface
4.4%
Si�ng on level surface 1.7%
Lying on stomach 1.6%
Lying on side 1.3%
Lying on back 0.7%
Figure 2
Working Postures Use
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affect neck proprioception (Norre, 1995). When maintaining and transitioning be- tween postures, the sensory organs with- in muscles, ligaments and joints of the lower extremities respond to static and dynamic stimuli associated with load- ing and stretching of the musculoskeletal system. In addition, the cardiovascular and peripheral vascular systems may be affected after maintaining certain work- ing postures for prolonged periods .
Ratings of Perceived Balance by Construction Trade
RPBs provided by the various trades were significantly different when aver- aged across all postures. Floor installers and sheet metal workers reported sig- nificantly lower RPBs as compared to carpenters and drywall installers, who reported the highest RPBs overall.
Further investigation identified spe- cific postures which differed for each trade that were perceived to be more problematic. Sheet metal workers per- ceived lower levels of balance associated with forward kneeling (RPB = 3.3) and lying on back (RPB = 3.0), whereas floor installers provided significantly lower RPBs for bent over at waist (RPB = 2.7). Furthermore, plumbers recog- nized lying on stomach (RPB = 2.7) and sitting on level surface (RPB = 3.0) as precursors to potential imbalance, and iron workers provided lowest RPBs for squatting (RPB = 3.2).
Even though the utilization of postures is not identical among trades due to the diversity of the work performed, results suggest that no inherent difference exists between construction trades in self-reported RPBs upon standing. Differences in RPBs averaged across postures seem to stem from the differences in the tasks performed and the pos- tures required to complete those tasks.
Ratings of Perceived Balance by Age Groups RPBs among the three age categories were sig-
nificantly different, with older workers reporting higher RPBs. Construction workers age 48 and older reported higher levels of balance upon stand- ing (mean RPB = 4.4) as compared to younger col- leagues (mean RPB = 4.0).
The 10% shift in RPBs may not reflect a greater ability to maintain balance. Differences in tasks performed, survivor effect and adaptation of tasks for the older workers may account for the variations in perceptions. Older workers may have had more opportunities to identify potentially risky situations and have learned how to adapt their behavior.
These adaptations to the performance of tasks may help explain why the two postures with the lowest balance ratings (bent over at waist and squatting) had the largest disparity in balance rat- ings between younger and older workers. Famil- iarity with the tasks and feelings of imbalance also may lessen the effect and perceptions over time as
a worker’s tenure increases. These ideas are substantiated by the fact that
no significant effect of age was found when each posture was evaluated separately. Over time and with experience, workers may reduce the use of certain postures that cause imbalance either by re- designing the task or altering the tools necessary to complete the task (e.g., using a drill extension that allows the employee to stand while working at ground level). Another adaptation to reduce imbal- ance after transitioning from a “risky” posture (e.g., bent over at waist or squatting) may be to reduce the speed of the movement or utilize visual cues.
Fall Prevention Measures Fall prevention and protection measures avail-
able and used were dependent on the trade and the task being performed. Of the construction workers surveyed, only 21.7% reported using fall protection devices. As expected, the responses varied across trades, with electricians, masons and plumbers indicating almost no use of such devices. When available, 53.8% of workers indicated that they hold on to an object or work surface to help maintain balance. These results did not vary sub- stantially across trades.
When workers must maintain balance without external assistance, 34.6% of respondents indicated that they pause in an intermediate posture before standing up completely from an awkward or un- comfortable posture, and 47.5% pause after stand- ing up to regain balance before continuing to work or moving to the next location. Results indicate that many workers are aware of the potential imbalance created by transitioning to a standing position and alter behavior to mitigate the risk of falling.
Mean balance ratings (1 = unstable; 5 = stable) for each working posture are averaged across all construction workers.
0
1
2
3
4
5
R a�
n gs
o f
p er
ce iv
ed b
al an
ce
Figure 3
Mean Balance Ratings
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Factors Affecting Balance Contextual factors can influence a worker’s
ability to maintain balance upon standing and in general. Table 2 lists several of these factors and indicates the percentage of construction workers who believe balance is more difficult to maintain under these conditions. Overall responses and those for each construction trade are presented.
More than half of the respondents (57.4%) indi- cated that maintaining balance was more difficult when they were tired. In addition, 56% indicated that it was more difficult to maintain balance after standing up quickly. Construction workers must perform tasks in a wide variety of environments under diverse conditions, and different factors may be more important to different workers depending on their trade.
Considerations & Limitations The measures within this study were derived
from self-reports of current construction workers. Previous research has indicated limitations in ob- taining valid self-report exposure estimates from individual workers, especially those involved in highly variable tasks (Hunting, Haile, Nessel, et al., 2010). Level of physical effort and manual mate- rial handling can be collected, but assessments are only accurate for detecting the absence or presence of an exposure with minimal accuracy regarding intensity, duration or frequency (Stock, Fernandes, Delisle, et al., 2005).
Therefore, it is not known whether RPBs cor- related to direct quantitative measures of balance, such as postural sway, or whether participants were able to accurately recall feelings of imbalance associated with various working postures, espe-
cially those that are not used frequently (Unge, Hansson, Ohlsson, et al., 2005).
An attempt was made to ad- equately sample workers from a variety of construction trades to provide a general descrip- tion of perceptions; however, no observational data of indi- vidual construction workers were collected to link to spe- cific ratings. In addition, no considerations were made for differences in body mass index, footwear, loads, PPE or other job-specific factors that may influence balance.
Personality traits (e.g., ma- chismo) and psychosocial fac- tors associated with the largely male-dominated construction industry also may have influ- enced responses. Several con- struction workers expressed a
Potential Threats to Balance Upon Standing From a Working Posture It may not be possible to improve balance perception through training, but it is possible to inform workers about safer postures that they can utilize and factors that may make it more difficult to maintain balance in the workplace. The postures investigated in this study are listed below in rank order with those creating the most perceived imbalance at the top.
Working Posture •Bent over at waist •Squatting •Forward kneeling •Reclined kneeling •Upright kneeling •Lying on stomach •Lying on back •Sitting on level surface •Lying on either side •Sitting on elevated surface •Standing
Factors Affecting Balance •Fatigue •Standing up very fast •Working on uneven or irregular surface •Carrying a load •Extreme temperatures •Adverse weather conditions (e.g., fog) •Glare •Working at elevation •Working with arms overhead •Dim lighting
Table 2
Difficulty Maintaining Balance Percentage of participants who indicated the listed task or environmental factors made it more difficult to maintain bal- ance while working.
Note. n = 189.
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belief that providing lower balance ratings indi- cated a weakness or potential problem with their ability to successfully perform their job. Such beliefs could inflate RPBs; however, such a bias would likely be systematic across conditions and, thus, would not change the effects of the factors investigated.
Summary & Application Contextual demands on a construction site make
it beneficial, if not necessary, for workers to have good balance, especially those who are required to work on physically constrained surfaces or at heights (e.g., I-beams and roof tops) where a fall can result in serious injury or death. Maintaining balance on a level surface also is critical, especially when workers must contend with debris or con- struction materials nearby that may cause a slip or trip hazard. It is possible that individuals with good balance self-select into these trades and only those who can mitigate fall risks and perform tasks safely remain for long tenures.
Many factors can influence worker perceptions of balance upon standing from a working posture. One such factor is the working posture used to perform the task. This will depend on the trade, job within the trade, task being performed and the individual performing the task. Survey results sug- gest that perception of balance differs depending on the posture, with bent over at waist, squatting and forward kneeling causing the most imbalance upon standing.
Ongoing research will evaluate potential asso- ciations between workers’ perceptions and force- plate-measured changes in postural sway, an indicator of balance. The effect of age also will be investigated experimentally to determine whether balance improves with age or whether other fac- tors, such as a survivor effect or adaptation of task performance, contribute to the difference.
Recommendations for Practitioners This survey revealed that postural transitions may
present a risk of loss of balance. The results identify simple and common techniques used to minimize imbalance following transitions to standing.
When a threat to balance occurs, workers who are able to perceive the risk may be able to mitigate it by transitioning to more stable postures before standing or pausing for a few seconds after stand- ing to regain balance. Understanding how task and environmental factors affect balance also is important to minimizing loss of balance. Maintain- ing balance was reported by more than half of the construction workers surveyed to be more difficult when tired or after standing up fast.
If workers can perceive a threat to balance pri- or to a fall, proactive maneuvers may be able to prevent falls and minimize risk of injury, includ- ing redesigning tasks or tools to reduce the use of working postures associated with higher self- reported levels of imbalance upon standing or minimize exposure to contextual factors that may increase imbalance. PS
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