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An investigation of posture and manual materials handling as risk factors for low back pain in delivery drivers.

1 Introduction

Encouraging the safety and health of occupational drivers through control of exposure to Whole-Body Vibration (WBV) has become a subject of growing concern (Hulshof, Verbeek, Braam, Bovenzi & Van Dijk, 2006). In this respect the European Directive (European Parliament and the Council of the European Union, 2002) places a duty on employers under general health and safety regulation to manage and minimise the risks from exposure to the physical agent (vibration), giving consideration to work equipment and methods. Although the link between WBV exposure and musculoskeletal problems (particularly Low Back Pain [LBP]), is now well demonstrated (Lings & Lebouf-Yde, 2000; Bovenzi, Pinto & Stacchini, 2002), no clear quantitative dose-response relationship has yet been established, which makes it difficult for safe levels of WBV exposure to be defined. Furthermore, exposure to other stressors (e.g., prolonged sitting, particularly, extreme and/or awkward positions, and Manual Materials Handling [MMH]), have also been shown to be associated with health problems among workers (Bovenzi, Rui, Negro, D'Agostin, Agotzi et al., 2006; Milosavijeric, Bergman, Rehn & Carman, 2010). Thus, depending on how the risk factors are presented, different control strategies may be required for different categories of drivers (Hannerz & Tuchsen, 2001).

Delivery drivers are subject to WBV and their work often always also includes prolonged sitting and MMH (van der Beek & Frings-Dresen, 1995; Friswell & Williamson, 2010). For them, the risks for musculoskeletal problems from WBV may be compounded, but the role of posture and MMH is not clear (Olson, Hahn, & Buckert, 2009). Indeed, epidemiological studies have often investigated exposure to postural stress and MMH stress in terms of self-reported and other subjective measures, which tend to correlate only weakly with observed measures and/or reality (Wiktorin, Karlqvist & Winkel, 1993; Leijon, Wiktorin, Harenstam, & Karlqvist, 2002). The purpose of this study was to investigate by questionnaire and direct observation, the prevalence of LBP symptoms, posture and MMH amongst delivery drivers.

2 Subjects and methods

The study was approved by the local ethics committee. 51 persons (49 males and 2 females) who did intra-city deliveries and drove such vehicles as trucks, vans, and lorries comprised the sample population. They were recruited through contact with management staff of haulage/delivery companies by telephone and press releases published in newspapers and professional newsmagazines to explain the purpose of the study. Large organisations or companies which agreed to include their driving staff, were supplied copies of the study questionnaire by hand (including free post envelopes) for distribution to drivers and return. In other instances, the questionnaire was posted out to volunteers or hand delivered (including a freepost envelope for their return when completed). 13 of the drivers were independent (self-employed) delivery drivers who had responded to one or other press release and 38 were employed drivers drawn from three haulage/delivery companies.

The Aberdeen Vibration Exposure (AVE) questionnaire (Pope, Magnusson, Lundstrom, Hulshof, Verbeek et al., 2002) was used to obtain information about health history (particularly LBP, neck and shoulder pain), driving experience, sitting (driving) posture and MMH. This is a validated questionnaire with the questions grouped into four sections, A-General information, B-Job satisfaction, C-Work environment and D-Musculoskeletal health. The questions concerning musculoskeletal health sought details on type of trouble experienced, number and typical duration of episodes, time off work and pain intensity and disability consequences. Presence or absence of LBP, i.e. pain in the past 12 months, was the health outcome of principal interest, but information about other health problems and specific medical conditions, which had been treated, was also included in the questionnaire. The questions regarding posture were in terms of five different possible configurations of the torso (torso against backrest, torso straight, torso bent, torso twisted, and torso twisted and bent simultaneously) and three possible frequencies of occurrence (never, occasionally, and often). Based on the indicated frequency of occurrence of the driving postures, a posture exposure score was computed for each respondent. MMH exposure was assessed in terms of the weight of load (light load < 5 kg, medium load 5-10 kg, heavy load > 10 kg) and frequency (self-reported) in a typical workday, for lifting and pushing, whether lifting was done in awkward postures (bent or twisted torso) and whether lifting was done immediately after driving (sometime, often).

For a subset of the sample of drivers (n = 12 persons), a combined approach consisting of direct observation of the working conditions and application of the revised NIOSH equation was used to determine risk associated with postural stress and MMH. These drivers were observed and videotaped during their work, i.e. for 4 hours in the morning before lunch break or 4 hours in the afternoon after lunch break. They were selected on the basis of their availability and willingness to be observed. Each of the drivers was observed for details of the frequency and duration of sitting postures adopted during driving, which were recorded once every minute for an accumulated 1-hour period of continuous driving, and the number of lifts and/or pushes performed; the weights of loads handled were also noted.

Data analysis was performed with the statistical package SPSS 10.1 for Windows. Continuous variables were summarised with the average (mean) as measure of central tendency and the standard deviation (SD) as measure of dispersion. Group differences in the continuous variables were analysed by Student's t-test and p < 0.05 was accepted as the minimum for significance. Univariate Odds ratios (OR) and Chi-square values were computed to assess the relationship between occurrence of LBP and exposure to posture and MMH.

3 Results

A total of 100 copies of the study questionnaire were provided to potential volunteers and 70 copies were returned. 19 of the returned questionnaires were subsequently excluded because they did not meet the inclusion criteria or had more than half of the questions left unanswered. The inclusion criteria were that a driver should have a minimum of 5 years in the present job or 5 years of delivery driving experience.

Regarding personal characteristics and habits, the included drivers were aged between 27 and 70 years (mean 44.6, SD 11.11); they weighed between 57.3 and 133.6 kg (mean 84.5, SD 15.14) and stood between 160.0 and 195.6 cm in stature (mean 176.5, SD 6.92). 33 of the drivers (64.7 %) were overweight, 37 (72.5 %) exercised regularly, 32 (62.7 %) smoked regularly (or had done so within the last five years) and 41 (80.4 %) drank alcohol regularly.

3.1 Prevalence of LBP

The questionnaire responses showed that 25 drivers (49.0 %) experienced LBP during the last 12 months (Table 1), 29 (58.0%) performed lifting tasks in their jobs and 27 (52.9%) performed pushing tasks (Figure 1), though, for 14 (27.4%) of these, pushing constituted force application to secure restraining straps. Three of the driving postures were identified by the drivers, as most commonly adopted i.e. the 'torso bent' posture (11 drivers-21.6%), the 'torso against backrest' posture (28 drivers-54.9%) and the 'torso straight' posture (34 drivers-66.7%).

Most of the drivers who reported LBP in the last 12 months, experienced more than 10 pain episodes, which each typically lasted between 1 and 6 days and most perceived their pain as severe (Figure 2). Back pain only and back-pain with radiating pain to the leg were the two types of symptoms reported and a medical diagnosis often identified sciatica and/or prolapsed/worn vertebral discs as the underlying problem. In these respects, the commonly prescribed treatments were pain relieving tablets and physiotherapy. Five of the drivers reported that their LBP resulted from an accident during force application to secure restraining straps and six reported that they had previously suffered injury during a major accident outside of work.

The drivers with LBP were on average significantly lighter (lower weight) but associated with higher posture scores than those without LBP. Drivers with LBP also lifted light loads more frequently than the drivers without LBP (Table 1).

3.2 Correlation of LBP with Posture and MMH

Regarding correlations between the qualitative data for posture and MMH and LBP, the prevalence of LBP was significantly higher among drivers who reported they sometimes adopted the 'torso twisted' driving posture (Odd's ratio of 5.343) than among the drivers who reported that they never did (Table 2). However, while all the drivers reported that they sometimes adopted the 'torso twisted and bent simultaneously' posture, only 19 drivers reported that they sometimes adopted the 'torso twisted ' posture (Figure 1). None of the MMH tasks considered showed significantly increased odds ratio for LBP, but a higher number of drivers reported handling heavy loads than light and medium loads, particularly during pushing.

For the twelve drivers observed during their driving and delivery activities, excluding time for lunch and tea breaks, 35 % of the work time (average) was spent actually driving and 17 % was spent sitting in the parked vehicle with or without the engine running. 48% of the work time was spent performing MMH activities and/or walking about. The 'torso straight', 'torso bent' and 'torso against backrest' postures were the three postures most often adopted by the drivers (Figure 1) and the 'torso twisted' posture was the least often adopted. During MMH, the drivers handled light loads more frequently when lifting than they did medium and heavy loads, and the observed frequencies of lifting were considerably higher than the mean frequencies determined from the questionnaire responses. When pushing, the drivers handled only heavy loads, and the observed frequency of handling was considerably lower than the frequencies determined from the questionnaire responses. Furthermore, the drivers were seen to adopt awkward postures of the torso and arms often during lifting and pushing activities (Figure 3) but NIOSH equation analysis found that the weights handled under the different delivery conditions were well below the recommended weights limit for safety.

4 Discussion

MMH and posture were investigated using both questionnaire and objective observation for insights into how they occur for drivers in intra-city delivery jobs. Other studies that investigated these aspects were mainly concerned with drivers in inter-city delivery jobs, i.e. those who drove for long periods at a time (van der Beek & Frings-Dresen, 1995; Koda, Yasuda, Sugihara, Ohara, Udo et al. 2000). The intention was to determine how MMH and posture might present as risk factors for LBP among drivers who spend short periods at a time within their vehicles and frequently handle loads.

Concerning the driving postures adopted, the data indicate that occasional adoption of the torso twisted posture is a risk factor for LBP. This finding mirrors those of other studies (Lings & Lebouf-Yde, 2000; Magnusson, Wilder, Pope & Hansson, 1993; Xu, Bach & Orhede, 1997), and suggests that eliminating the need to twist the torso during driving could reduce the incidence of LBP among delivery drivers to some extent. However, less than half of the drivers (nineteen) in our questionnaire survey indicated that they adopted the torso twisted posture, compared to the torso twisted and bent simultaneously posture which was indicated by all the drivers. Secondly, the frequency of occurrence of the torso twisted posture was generally low for all drivers in the observation survey. Furthermore, an appreciable number of the drivers in the questionnaire survey (n = 6) indicated that they developed their LBP from a slip accident during force exertion. Since prolonged sitting during work has often been found to relate poorly with LBP incidence among occupational drivers, the results point to a need for better understanding of dynamic postures in sitting positions as has previously been suggested by Graf, Guggenbuhl & Krueger (1995).

Concerning the risks from MMH, the results showed that lifting was generally prevalent among the drivers, but none of the MMH tasks investigated showed significantly increased odds ratios for low back pain. This result can be attributed to the fact that the drivers handled light loads more frequently than moderate and heavy loads, or that some with LBP had moved to jobs with little or no MMH (their current job) due to severe LBP from previous heavy lifting, as has previously been suggested by Xu, Bach & Orhede (1997). These authors found that light and moderate lifting did not associate significantly with prevalence of LBP (though frequent bending and twisting did) and attributed the finding to an interaction between the risk factor heavy lifting and low back pain. In the present work, none of the drivers surveyed indicated that they had changed jobs due to back pain from previous heavy lifting. Secondly, the observed load handling frequencies were considerably higher than those reported by drivers, particularly for lifting, and handling of loads often occurred immediately after a period of driving. The risks for LBP may then have been grossly under-represented by the questionnaire data; an observation that buttresses the need for more objective assessments of MMH occurring in driving tasks. Furthermore, considering that some of the drivers identified their LBP occurred after a slip accident during force exertion to secure loads (n = 5 persons), for intra-city drivers the risks from MMH seem particularly attributable to sudden lumbar loading from undue rapid rate of task performance.

Concerning prevalence of LBP, the results reflect those of studies that have focused on drivers who are exposed to WBV from a specific kind of vehicle. Lenos, Marqueze, & Moreno (2014) for example, reported that 264 out of 460 truck drivers (53.5 %) from a large freight company suffered musculoskeletal spinal pain in the preceding one month, most of whom identified the lumbar spine area as the most affected part of the trunk. Rob & Mansfield (2007) reported that 60.0% of 192 HGV truck drivers reported suffering LBP in the previous 12 months, and that, contrary to expectation, vibration exposure was significantly lower among those who suffered musculoskeletal symptoms when distance travelled was used as exposure measure. Luoma, Riihimaki, Luukkonen, Raininko, Viikari-Juntura et al., (2000), however, found that LBP was common among machine (vehicular) operators (drivers) and construction carpenters with distinctively different occupational loads and that sciatica was the most commonly identified problem for the drivers, while local LBP was the most commonly identified problem for the construction carpenters. The results here suggest that in a typical workday short haul delivery drivers tend to spend less time actually driving compared to performing MMH; generally, less than 15 minutes. It may be that, for intra-city delivery drivers, LBP is more likely the result of postural and MMH stresses rather than of stresses derived from exposure to WBV.

5 Conclusion

In a typical workday, intra-city delivery drivers are continuously exposed to WBV (i.e., from the vehicles they drive) for only relatively short periods. For them, postural stress, from twisting of the torso and MMH stress from frequent handling of loads, appears to be the main contributors for LBP.


This work was part of research to understand the role of posture, whole body vibration and manual handling as risk factors for low back pain, which was sponsored by the Health and Safety Executive, UK.


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Olanrewaju O Okunribido

Department of Industrial and Production Engineering

University of Ibadan


epxoook@hotmail .com

Caption: Figure 1. Prevalence of MMH reported by the drivers, i.e., weight of loads handled in lifting/carrying and pushing and pulling tasks, and prevalence of driving postures.

Caption: Figure 2. Episodes and intensity of low back pain suffered in the last 12 months by the drivers.

Caption: Figure 3. Awkward arm and torso postures adopted during lifting of loads from the vehicle.
Table 1. The number of drivers and summarised values of personal and
risk factors (mean and standard deviation [SD]) for those with and
without LBP.

Variable                                Drivers         Drivers
                                        with LBP        without LBP

Number of drivers                       25 (49.0 %)     26 (51.0 %)
Age (yrs)                               45.7 (10.68)    43.1 (11.57)
Height (cm)                             176.0 (7.13)    176.8 (6.93)
Weight (kg) *                           81.4 (11.48)    89.4 (17.08)
U.S. Total
BMI                                     28.3 (3.57)     28.6 (5.11)
Driving postures (frequency score) *    15.8 (1.96)     14.3 (1.97)
MMH--lifts< 5 kg (freq) *               30.0 (11.40)    16.4 (13.14)
MMH--lifts between 5-10 kg (freq)       13.3 (7.53)     11.4 (9.88)
MMH--lifts > 10 kg (freq)               12.5 (9.35)     6.7 (2.79)

* significant (p < 0.05), freq = number of lifts per day

Table 2. Odds ratios (OR) and Chi-square test results concerning
relationship between reports of LBP and driving postures, and
MMH activities.

Factors                      Frequency of occurrence/
                                    Odds ratios

                          Never    Sometimes    Often

Driving postures
Torso bent                             1        1.326
Torso twisted               1        5.343
Torso against backrest      1          1        1.667
Torso straight                       1.265        1
MMH activities
Any handling task           1          2
Lifting                   1.477        1
Lifting after driving     2.333        1        2.622
Pushing                   1.076        1

Factors                     Chi-square test

                          Value    Probability

Driving postures
Torso bent                0.171       0.679
Torso twisted             7.371       0.007
Torso against backrest    1.851       0.396
Torso straight            0.157       0.692
MMH activities
Any handling task         0.314       0.575
Lifting                   0.473       0.492
Lifting after driving     1.363       0.506
Pushing                   0.017       0.895
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Author:Okunribido, Olanrewaju O.
Publication:Ergonomics SA
Date:Dec 1, 2016
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