Perceived Risk of Low-Back Injury Among Four Occupations

Introduction

Occupational health and safety has been an integral part of labor acts for decades. Since the introduction of health and safety legislation around the world, significant advancements have been made in terms of required training as well as the understanding of actual risk factors in different occupational sectors. However, despite these advancements, injuries still occur, possibly due to lack of translation of knowledge from research to workers.

Low-back pain (LBP) is consistently one of the most common reasons for disability among workers and loss of work days (Hoy et al., 2014). As a result, various physical risk factors have been established and associated with LBP and injury, including awkward or sustained postures and heavy and/or repetitive lifting. In regard to lifting, authors of numerous studies have aimed to determine whether an individual should assume a squat position (lordotic spine with bent knees) or a stooped position (kyphotic spine with straight knees), with conflicting findings (see extensive review by van Dieën, Hoozemans, & Toussaint, 1999). Regardless, health and safety education programs (for example, the Canadian Centre for Occupational Health and Safety and the National Institute for Occupational Safety and Health) typically still recommend the traditional “lift-with-your-knees,” or squat, technique.

Also of concern in the workplace are prolonged static postures, such as sitting, as many modern occupations involve a high percentage of sitting during the workday (Kazi, Duncan, Clemes, & Haslam, 2014; Marshall, Duncombe, Robinson, & Kilbreath, 1997; Puig-Ribera et al., 2015; Visser & Straker, 1994). A study by Womersley and May (2006) showed that individuals who suffered from mild LBP tended to adopt a more kyphotic or slumped spinal posture than those without LBP. Further, slumped sitting is perceived by both the general public and clinicians to more likely to result in LBP (O’Sullivan, O’Sullivan, O’Sullivan, & Dankaerts, 2012; O’Sullivan, O’Keeffe, O’Sullivan, O’Sullivan, & Dankaerts, 2013). Interestingly, other studies have failed to demonstrate an association between sitting posture and LBP (Hartvigsen, Leboeuf-Yde, Lings, & Corder, 2000; Mork & Westgaard, 2009).

Although the knowledge of physical workplace hazards has been an integral part of occupational health and safety education for years, workers’ perception of these hazards has only recently been incorporated into procedure and regulation establishment. Individual perception of safe manual material handing has been used to set safe lifting limits (Snook, 1978; Snook & Ciriello, 1991; Yeung, Genaidy, Deddens, Shoaf, & Leung, 2003) and to determine compliance with health and safety regulations (Leiter, Zanaletti, & Argentero, 2009). More recently, workplaces are starting to recognize the potential benefit of knowing this type of information (Lee, Faucett, Gillen, Krause, & Landry, 2013; Leiter et al, 2009) and its influence on occupational injuries. Previous work has shown that worker perception of risk is affected by various psychosocial factors, such as satisfaction with safety regulations/procedures, safety training, and social support (Rundmo, 1992, 1994) and is also affected by the perceived level of safety compliance among coworkers (Leiter et al., 2009). Further, a great deal of research has shown a significant association between rates of injury and partaking in risky behaviors (Badri, Nadeau, & Gbodossou, 2012; Dawson, 1994; Gauchard et al., 2006; Macdonald et al., 2010). Kirscenbaum, Oigenblick, and Goldberg (2000) and Knuth, Kehl, Hulse, and Schmidt (2014) also found that those who had experienced an injury were also more likely to have a higher perception of risk.

It is unclear if having a higher perception of risk could protect or predispose an individual to becoming injured. For instance, if a worker has an appreciation for the potential risk of a certain exposure, would he or she be more likely to adhere to any safety procedures that pertain to such an exposure? Or could a heightened risk perception result in hypervigilance and/or fear avoidance? Although the answers to these questions are of significant importance, it is critical to first examine risk perception among workers in various occupations. Thus, the primary purpose of this study was to examine perception of low-back injury risk factors across four different groups: office employees, dental workers, firefighters, and students. Second, we aimed to determine if previous LBP history was associated with risk perceptions.

Method

Perception of Low-Back Injury

Following completion of the questionnaire, participants were presented with a series of seven standardized images (the same seven images were presented to all participants; Figure 1) depicting different postures, which included sitting (slumped versus upright), lifting (combinations of bent or straight knees and rounded [kyphotic] or straight back [lordotic]), and twisting followed by one occupation-specific image, which was unique for each group (Figures 1h through 1k). Participants were instructed to rate and record numerically on paper each individual image on a continuous scale from 0 to 10 according to their perceived magnitude of risk of injury to the low back. Zero represented no risk of injury to the low back, and 10 represented extreme risk of injury to the low back. The eight images were shown one at a time. Once the participant rated a posture, he or she was not permitted to go back to that previous image. The seven standardized images were randomly ordered at the start of the study such that no two similar images (e.g., lordotic lifting with bent knees and kyphotic lifting with bent knees) were presented one after another. Once the order was set, this order remained the same for all participants. The occupational-specific image was always the last image to be presented to the participant as to not influence any of the standardized images.

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Figure 1.

Images presented to each participant (see Method for description of image presentation order). (a) Lordotic lift with bent knees, (b) kyphotic lift with bent knees, (c) lordotic lift with straight knees, (d) kyphotic lift with straight knees, (e) upright sitting, (f) slumped sitting, and (g) trunk axial twist while standing. Each participant was also presented with an occupation-specific image based on which group they were in: (h) sitting on a stability ball (presented to office professionals), (i) cardiopulmonary resuscitation administration (presented to firefighters), (j) sitting in a lecture hall tablet seat (presented to students), and (k) working with a patient (presented to dental professionals).

Results

Demographic Questionnaire

Of the 232 individuals who participated, 190 (82% of participants) completed the questionnaire portion of the study. Of these participants, 93 (49% of participants) reported previous LBP, of which 50 (54% of those with a history of LBP) believed their pain was likely related to their job/daily tasks. A summary of the key findings is highlighted in Table 1. The one-way ANOVA did not reveal a significant main effect of sex on risk rating (p = .20). Further, Pearson correlations (R² values) ranged from .002 for bent-knee lordotic lifting to 0.10 for straight-knee lordotic lifting, indicating a lack of relationship between age and risk rating.

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Table 1:

Mean Demographic Statistics Obtained From the Questionnaire

Demographic	Office	Dental a	Student
Age in years	43.9 (1.7)	43.6 (2.1)	19.9 (0.1)
Body mass in kilograms	75.7 (2.4)	76.5 (2.8)	69.3 (1.3)
Height in meters	1.70 (0.02)	1.72 (0.02)	1.72 (0.01)
% Who reported LBP b	60 (30/50)	57 (4/7)	44 (59/133)
% Who reported LBP likely related to job b	43 (13/30)	100 (4/4)	56 (33/59)

Note. Demographic data not gathered for firefighters. Standard errors shown in parentheses except where otherwise indicated. LBP = low-back pain.

a

Only seven of the 23 dental professionals completed the survey.

b

Values in parentheses indicate the number of individuals who responded.

Differences Between Occupations

A main effect of group for risk rating was observed such that dental and office workers rated postures significantly higher and therefore were considered a high-risk-perception group compared with both students and firefighters (p < .0001; Figure 2), who were therefore considered a low-risk-perception group. No significant differences were found between students and firefighters or between dental and office professionals.

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Figure 2.

Average (+ SE) risk rating collapsed across the seven standardized images. Dental and office professionals, on average, rated all postures higher than both firefighters and students (p < 0.0001). Bars with different letters are significantly different from each other.

Interaction Between Group and Posture

A significant interaction was found between group and posture (p < .0001; Figure 3). There was full agreement in average risk rating across the four groups for bent-knee lifting with either a lordotic or kyphotic spine posture. However, for all other postures, significant differences between groups were observed. All differences are shown in Figure 3; however, of notable interest include the following observations: First, dental professionals were the only group to indicate no difference in risk between bent-knee and straight-knee lordotic lifting, whereas all other groups perceived the straight knee to be riskier to the low back. Second, although all individuals, on average, rated upright sitting as having the lowest risk, firefighters rated both upright and slumped sitting significantly lower compared to all other occupations. Further, in general, office and dental workers rated the seated postures similarly and highest among all groups, with students falling below (but above firefighters). Last, students rated axial twisted postures the lowest among the four groups.

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Figure 3.

Average (+ SE) risk rating for each group for each posture. Different lowercase letters indicate a significant difference between groups within each image (p < 0.05).

Discussion

Numerous industrial sectors exist worldwide, suggesting that occupation-specific training may be valuable and may help to reduce work-related injuries. We examined the perceived risk of low-back injury with particular interest in the difference between four groups: office/administrative workers, dental professionals, firefighters, and undergraduate students. Unique levels of risk perception were observed between the four groups. This finding can most likely be explained by the differences that exist between these groups in terms of job demands/daily tasks.

When risk ratings were collapsed across the seven standardized postures examined, differences between the four groups were such that two subsets of individuals emerged: a high-risk-perception group, or those who tended to rate postures higher, and a low-risk-perception group, or those who tended to rate postures lower. Dental professionals and office workers had similar average risk ratings, which were higher than those of both students and firefighters. One reason for this finding may be due to the similarities and differences between the two subsets of groups. Office and dental workers, on average, spend the majority of their workday in a seated posture (Kazi et al., 2014; Marshall et al., 1997; Puig-Ribera et al., 2015; Visser & Straker, 1994) with minimal exposure to lifting or manual materials-handling postures. In contrast, firefighters are more likely to be exposed to strenuous tasks, including various lifting postures (Gledhill & Jamnik, 1992) that may alter how they perceive the level of risk associated with each of the standardized tasks examined in this study. Since firefighters are exposed to relatively riskier situations as part of their occupation, they likely perceive non-life-threatening situations, like the postures examined in this study, as less risky.

It is surprising that students did not fall into the same category as dental and office workers, as their daily tasks (sitting for long periods of time) are similar. One explanation for this finding is that students may lack the necessary experience (due to less or limited time spent in the workforce compared to the other groups examined) to perceive risk in a similar manner as office and dental professionals, similar to results previously shown by Cohn, Macfarlane, Yanez, and Imai (1995). Interestingly, age was not significantly correlated with risk rating, suggesting that age alone does not dictate level of perceived risk for low-back injury. Another possible explanation may lie in the type of training received by individuals in each group. Specifically, the health and safety training received by firefighters may not focus on tasks such as sitting, as such tasks may not be perceived as one of the greater risks of injury and may be perceived as redundant.

Regarding firefighters, the findings of the current study are somewhat contrary to previous work that has shown that job strain is significantly related to an increase in risk perception (Lee et al., 2013). However, in the work of Lee and colleagues (2013), nurses were studied and were asked to rate their perceived risk of injury for occupation-specific tasks rather than standardized tasks like the current study, which could explain why office/administrative workers and dental professionals rated sitting postures higher than did the other occupations, as sitting is a task they are required to do for a large proportion of their workday. This phenomenon has been documented previously (Knuth et al., 2014) in that exposure to a specific hazard increases one’s perception of the risk of that hazard. Interestingly, no significant relationship between previous LBP and risk rating was observed in this study. Although nearly 50% (93/189) of individuals who completed the demographic questionnaire reported a history of LBP, of whom 54% (50/93) believed their LBP to likely be related to their job/daily tasks, it appears that in this study, LBP did not affect injury risk perception. However, a relationship may have been found if the cause of the pain was ascertained (i.e., those who hurt their back while lifting may have had higher perceived risk rating for the lifting postures).

Also of interest in this study were the rating differences observed between postures. Individuals from all groups indicated that kyphotic lifting postures were associated with the highest risk of injury to the low back regardless of knee positioning. Previous work has shown that typically kyphotic/stooped lifts compared to lordotic/squat lifts increase the bending moment (Dolan, Earley, & Adams, 1994; Dolan, Mannion, & Adams, 1994) as well as increase spinal loading (Anderson & Chafffin, 1986; Leskinen, Stalhammar, Kuorinka, & Troup, 1983; Potvin, McGill, & Norman, 1991). However, of particular interest was that in all groups, with the exception of dental professionals, individuals reported that a straight-knee lordotic lift was significantly riskier than a bent-knee lordotic lift, despite a similar spine posture. A possible explanation for this finding could be due to the way employees are trained within the workplace. A common training technique in workplace health and safety programs often recommends to “bend with the knees.” This common recommendation has persisted likely due to its simplicity in employee training to promote a lordotic back positioning rather than a stooped posture during a lift. This finding suggests the need for a more thorough training program with respect to safe lifting within the workplace, particularity in situations when bending at the knee is not feasible (Kingma, Faber, & van Dieën, 2010). Further, risk perception could also be used as a way of identifying individuals who may be fearful of lifting with their back (i.e., if lordotic lifting postures are perceived as much less risky than kyphotic postures), which could lead to fear avoidance and, potentially, LBP/disability (Fritz, George, & Delitto, 2001).

In addition to lifting postures, key findings between seated postures were observed. When compared, on average, individuals from all groups rated the risk of slumped sitting higher than that of upright sitting. Although slumped sitting is perceived as riskier than upright sitting by both clinicians (O’Sullivan et al., 2012) and the general population (O’Sullivan et al., 2013), there is little evidence to suggest that sitting posture does influence LBP (Hartvigsen et al., 2000; Mork & Westgaard, 2009). Despite this lack of evidence, individuals from all groups perceived slumped sitting (greater flexion) as riskier than upright sitting.

In this paper we have generally considered higher risk perception as being a positive attribute and potentially protective. However, a heightened level of risk perception may be indicative of, or may lead to, negative situations, such as fear avoidance beliefs and associated disability (Fritz et al., 2001; Leeuw et al., 2007; Sions & Hicks, 2011; Vlaeyen & Linton, 2000). Although it is possible that certain individuals may benefit from a higher level of risk perception (i.e., it is protective), others may actually be negatively affected by heightened risk perception. Future work is necessary to determine how to decipher between these two types of individuals. Additionally, it is possible that the lower rating of risk perception observed in students and firefighters may be a more accurate assessment of the actual risk of the postures examined in this study. Although it is not possible to determine the true level of risk (as it is subjective), it should not be ignored that these occupations (students and firefighters) may be less likely to suffer from disability as a result of fear avoidance or hypervigilance.

There were some limitations in this study that should be addressed. First, only 82% of participants fully completed the demographic questionnaire portion of the study, including no firefighters due to uncontrollable circumstances (outlined in the Method section), and therefore some valuable information was not obtained. Second, unequal numbers of participants from each occupation were collected: dental (n = 23), firefighter (n = 26), student (n = 133), and office (n = 50). Third, perception of risk is likely affected by personal experience (i.e., previous involvement in risky activities/behaviors or a history of injury; Badri et al., 2012; Dawson, 1994; Gauchard et al, 2006; Macdonald et al., 2010); however, participant experiences were not controlled for within and between each group in this study. Authors of future studies should examine the effect of such previous experiences in order to determine if such information would be a valuable addition to health and safety training. Fourth, individuals’ perception of injury, rather than pain or discomfort, was assessed. Injury was chosen as it generally is a more objective measure than pain. Last, the images used have not been tested for validity, which should be incorporated into future studies. Further, only static images were presented with no indication of how long or how often each posture was assumed or, in the case of lifting, how heavy the load was in the hands. Certainly duration, repetition, and load would all have a significant effect on the perception of low-back injury risk; however, the scope of this study was to examine static posture. Future studies should focus on various combinations of the aforementioned variables to determine how they affect injury risk perception.

In terms of recommendations based on the findings of this study, it is recommended that occupational health and safety training include more detail regarding safe lifting postures, particularly emphasizing that a neutral/lordotic spine posture can be achieved with bent or straight legs, which is important when bending at the knees is not possible (wide load, obstruction between person and load). However, training should also educate workers on the potential concerns associated with an overly high level of perceived risk, including fear avoidance and altered movement patterns that may lead to disability as a result of their fear of injury.

Key Points