Fatigue and low-back pain of freight-container tractor drivers. Correlation with ergonomic factors

An ergonomic checklist was prepared to examine safety and comfort of freight-container tractors. With this checklist, 533 tractor drivers were asked to evaluate the tractors to which they were exclusively assigned. In order to check the objectivity and the validity of the results, the correlation between the evaluation of the items on the checklist and the corresponding dimensions on 10 tractors was studied. Also, a multivariate analysis based on quantification theory was done to examine the correlation between the ergonomic items on the checklist and the drivers' low-back pain or fatigue symptoms of the upper and lower extremities. The main results were as follows: 1) A high correlation was observed between the evaluation of items on the checklist and the corresponding dimensions of the tractors. 2) Many items on the checklist received a poor evaluations, indicating that there are many ergonomic problems with freight-container tractors. 3) The analysis by the quantification theory showed high correlation ratios between the items in the checklist and the drivers' fatigue symptoms of the upper and lower extremities. These correlation ratios were: arm fatigue when holding the steering wheel (0.51), arm fatigue in operating the gearshift lever (0.65), arm fatigue from opening and closing the windows (0.46), leg fatigue from operating the pedals (0.58), and low-back pain during the last two months (0.31). These showed that more than 50% of the fatigue symptoms could be explained by the ergonomic aspects of the tractors. 4) The rate of dissatisfaction with the current tractors was 82.9%. According to the analysis by the quantification theory, the correlation ratio between the items in the checklist and the rate of dissatisfaction for the current tractors was 0.66. 5) The foregoing results indicate that ergonomic improvement of the freight-container tractors is a matter of urgency. This should reduce the drivers' fatigue and elevate the rate of satisfaction with the tractors. 6) However, for the prevention of the drivers' low-back pain and fatigue symptoms, improvement of the ergonomic conditions of the tractors and the drivers' working conditions must be undertaken at the same time.     

The labor of freight-container tractor drivers and low back pain. Correlation with whole-body vibration exposure

In order to determine the causal factors of low back pain (LBP) which prevails among freight-container tractor drivers, vibration measurements of the seat of ten freight-container tractors and one heavy truck, a survey on the daily working hours of 240 tractor drivers for a month, and a time study of work on 28 person-days were conducted. Vibration measurement was made under routine conditions on paved public roads for 40 km under laden and unladen conditions. For the evaluation of vibration exposure, ISO 2631 was used. With the freight-container tractors, the mean vibration levels were high in X and Z directions, particularly in X direction. In the heavy truck, the vibration level was consistently higher in Z direction. According to the evaluation made by ISO 2631, the X component of the vibration was found to be serious. The magnitude of the vibration level was greatly influenced by the condition of the road surface with bridges tending to produce a high level of vibration. Vibration levels of the new model tractors were not necessarily always lower than that of the old models. It was estimated from the foregoing results and the time study that in more than 90% of the drivers the daily exposure time (i.e. driving hours) exceeded the allowable exposure time of fatigue-decreased proficiency boundary (FDP), and in about one-third of the drivers the allowable exposure time of exposure limit (EL) was exceeded. These results suggest that long exposure to severe vibration during work is one of the possible causal factors of LBP of freight-container drivers.     

Self-reported back pain in tractor drivers exposed to whole-body vibration

Summary A postal questionnaire on symptoms of ill health and exposure to whole-body vibration was completed by 577 workers (response rate 79%) who were employed in certain functions by two companies 11 years before. The relation between the occupational history of driving vibrating vehicles (mainly agricultural tractors) and back pain has been analyzed. The prevalence of reported back pain is approximately 10% higher in the tractor drivers than in workers not exposed to vibration. The increase is mainly due to more pain in the lower back and more pain lasting at least several days. A vibration dose was calculated by assigning each vehicle driven a vibration magnitude, estimated on the base of vibration measurements. The prevalence of back pain increases with the vibration dose. The highest prevalence odds ratios are found for the more severe types of back pain. These prevalence odds ratios do not increase with the vibration dose. This might be due to health-related selection which is more pronounced for severe back pain than for back pain in general. The two components of the vibration dose, duration of exposure and estimated mean vibration magnitude, have also been considered separately. Back pain increases with duration of exposure but it does not increase with the estimated mean magnitude of vibration. This is probably due to the inaccuracy of this estimate. The higher prevalence of back pain in tractor drivers might be (partly) caused by whole-body vibration, but prolonged sitting and posture might also be of influence.     

Seat inclination, use of lumbar support and low-back pain of taxi drivers

OBJECTIVES: Epidemiologic evidence supporting optimal seating is limited and inconsistent. This cross-sectional study was conducted to examine the association between seat inclination, use of lumbar support, and the prevalence of clinically significant low-back pain among taxi drivers METHODS: A digital inclinometer was used to measure inclinations of seat surfaces (theta(seat)) and backrests (theta(back)), and calculate the back-to-thigh angle (theta(back-thigh)). Structured interviews were conducted to gather information on the use of lumbar support and the prevalence of low-back pain that had led to medical attention or absence from driving in the past month. A multiple logistic regression analysis was used to estimate the prevalence odds ratio (OR) with adjustment for age, body mass index, professional seniority, monthly driving hours, and the intensity of exposure to whole-body vibration. RESULTS: Among 224 drivers, the mean theta(seat), and theta(backrest) were 14.5 (SD 9.6) and 95.1 (SD 2.7) degrees, respectively, resulting in theta(back-thigh) of 80.6 (SD 9.3) degrees. Fifty-five percent used a lumbar support regularly, but 25% reportedly had significant low-back pain. The prevalence of low-back pain was 23% among those with theta(back-thigh) <86 degrees, 37% for those with a theta(back-thigh) of 86 approximately 91 degrees, and 9% for a theta(back-thigh) of >91 degrees. The adjusted OR comparing those with a theta(back-thigh) of < or = 91 degrees to those with a theta(back-thigh) of >91 degrees was 5.11 [95% confidence interval (95% CI) 1.07 approximately 24.4]. For regularly using drivers versus those not using lumbar support, the prevalence of low-back pain was 18% versus 34%, with an adjusted OR of 0.33 (95% CI 0.16 approximately 0.68). Neither theta(seat) nor theta(backrest) alone was significantly associated with low-back pain. CONCLUSIONS: The epidemiologic observation of this study was consistent with the results of prior biomechanical studies on appropriate seat inclinations and the use of lumbar support. Prospective studies are needed to confirm the true beneficial effects of these seating parameters.     

Clinical and psychological diversity of non-specific low-back pain. A new approach towards the classification of clinical subgroups.

This study explored the clinical and psychological features of non-specific low-back pain (LBP) using multivariate statistical methods including correspondence analysis, cluster analysis and discriminant analysis. An unselected population of subjects (n = 330) complaining of localized LBP to hospital rheumatologists during 1988 was studied. 41% of the subjects (n = 136) were classified as having a psychiatric disorder according to the DSM-III criteria (Axis I). A number of different organic syndromes were identified and the importance of psychological influences on the clinical presentation of LBP was demonstrated. Cluster analyses provided further evidence for a four-group typology of LBP, which may be interpreted through the relationships or interactions between psychological disturbances and the clinical features of LBP. This study highlights the need, in etiological research, to take into account the clinical diversity of non-specific LBP and to investigate further the complex relationships between psychological disturbances and back pain.     

Occupational causes of low-back pain

Associations between occupational activities and low-back pain (LBP) were examined in a retrospective postal survey of 545 randomly selected adults. Each subject gave a lifetime occupational history on six specified physical activities and also a lifetime history of LBP. Among the 436 subjects answering the questionnaire, the lifetime incidence of LBP was 63%. The occurrence of LBP was related by Cox's proportional hazards regression model to occupational activities in the year prior to the onset of symptoms. For the men the strongest associations were with heavy lifting and prolonged car driving. There was also an association with heavy lifting among the women. These risks were exaggerated in the subset of subjects whose LBP followed a chronic unremitting course. The findings are consistent with previous reports linking LBP with manual materials handling and driving at work. However, in this sample, less than 20% of the cases could be attributed to such activities.     

Model for the work-relatedness of low-back pain

OBJECTIVES: This study aimed at developing a model for determining the work-relatedness of low-back pain for a worker with low-back pain using both a personal exposure profile for well-established risk factors and the probability of low-back pain if the worker were unexposed to these factors. METHODS: After a systematic review of the literature, the pooled prevalence of low-back pain in an unexposed population and the pooled odds ratio (OR) for each risk factor was calculated in a meta-analysis using a random effect model. An unbiased risk estimate for each risk factor was obtained by correcting the pooled OR for confounding by other risk factors. The probability of low-back pain was calculated with a logistic regression model. The input was (i) the age-dependent prevalence when not exposed and (ii) the unbiased risk estimates per risk factor of low and high exposure. The etiologic fraction was calculated to determine the level of work-relatedness. RESULTS: The pooled prevalence for low-back pain among unexposed subjects was 22%, 30%, and 34% for the <35-year, 35-to-45-year, and >45-year age categories, respectively. The pooled OR was 1.51 [95% confidence interval (95% CI) 1.31-1.74] for manual materials handling, 1.68 (95% CI 1.41-2.01) for frequent bending or twisting, 1.39 (95% CI 1.24-1.55) for whole-body vibration, and 1.30 (1.17-1.45) for job dissatisfaction. For high exposure to manual materials handling, frequent bending or twisting, and whole-body vibration, the pooled OR was 1.92, 1.93, and 1.63, respectively. CONCLUSIONS: The model is the first that estimates the probability of work-relatedness for low-back pain for a given worker with low-back pain seen by a general practitioner or an occupational health physician.     

Role of psychosocial risk factors in work-related low-back pain.

The experience of low-back pain and its psychosocial associates were directly compared among sufferers drawn from three populations, a blue-collar working group, a white-collar working group, and a patient group. Sufferers drawn from the patient population revealed the expected psychological disturbance. There was no evidence of such involvement for sufferers still at work. Disability resulting from low-back pain was positively linearly related to severity of pain for sufferers drawn from working groups, irrespective of psychological disturbance. For patients, on the other hand, the presence of psychological disturbance modified the relationship between severity and disability such that no simple linear relationship existed between the two variables. Work dissatisfaction was not found to be related to the presence of, and did not account for disability resulting from, low-back pain in working subjects.     

煤矿工人腰背痛休工率分析

本文对7225名煤矿工人腰背痛休工率分析表明,该矿1990年腰背痛体工率为5.5%,因腰背痛缺勤1.7万天,缺勤率为7.5‰。并下工人腰背痛休工率明显高于井上,其中掘进工休工率最高。并下阴冷、潮湿、作业环境狭窄、劳动负荷较大、外伤等可能是腰背痛高发的原因。     

Interaction of height and mechanical loading of the spine in the development of low-back pain.

The relation of low-back pain to height and physical activity was examined among 2667 British men and women aged 20-59 years and selected from the general population. Information about occupational activities, height, and lifetime history of low-back pain was obtained from a postal questionnaire. The lifetime prevalence of low-back pain was 58.3%. After allowance for other occupational activities, the onset of low-back pain was strongly associated with heavy lifting at work (men: relative risk (RR) 2.0, 95% confidence interval (95% CI) 1.4-2.8; women: RR 2.2, 95% CI 1.3-3.5). For the men there was also an association with digging (RR 1.6, 95% CI 1.1-2.3). Risk of low-back pain increased with height among the men but not among the women. The risks associated with heavy lifting and digging were greater for the short than for the tall men. Thus the data provide no justification for excluding tall men from heavy manual tasks, despite their greater susceptibility to back problems.     

Physiological effect of vibrations on tractor drivers under variable ploughing conditions

The vibration conditions to which tractor operators are subjected are complex and varied with multi axis translation and rotational vibration inputs to different parts of the body. Working under such conditions may lead to human fatigue and other driving related hazards. The present research was carried out to study the operators under varying conditions of vibration while driving a tractor with and without farm equipment on different fields. Test runs were conducted in wet and dry fields to determine the levels of vibration generated at different engine speeds. On the basis of this study three levels of vibration namely 2.5, 3.5 and 5.0 m/s(2) were selected. Five subjects, all males, with no experience in the field of tractor driving participated in the study. The data were analyzed on the basis of three factor repeated measure kind of experimental design. The results showed that the main effects of farm equipment and the vibration level were statistically significant but the effect of field type was found to be statistically non-significant. The results of the study call upon the ergonomists to design and develop a tractor where the driver may be relieved of vibration induced stresses. Front loading of farm equipment is recommended for improved visibility and better working posture.     

Physiological-hygienic aspects of the work of tractor drivers engaged in open-soil vegetable planting

The labour conditions of tractor drivers engaged in open soil vegetable planting in subtropical zones were characterized by the unfavourable influence of weather, noise and vibration, dust and exhaust contamination, and by static tension. The physiological studies performed revealed considerable tensions of the CVS, CNS, thermoregulatory and muscle systems in the drivers. The specificity of the identified changes confirmed marked decrease in the functional resources of the organism, which should be taken into account when providing medical services to the drivers.     

Incidence and risk factors of low-back pain in middle-aged farmers

A 12-year follow-up study was carried out to evaluate the riskfactors for unspecified low-back pain and sciatic pain. Middle-agedfarmers who did not report any low-back or neck-shoulder painduring the previous year in a postal questionnaire in 1979 wereincluded in the follow-up study in 1992 (n = 537). In total,366 (68%) of these farmers were interviewed by telephone. In1992, the one-year prevalence rates of unspecified low-backpain (13.3%) and sciatic pain (9.6%) were low. Full-time farmershad a significantly higher prevalence of sciatic pain than didpart-time or retired farmers. In the logistic regression modellingof sciatic pain in men, the odds ratio was 9.6 (95% CI: 2.7–65.2)for current smokers and 13.1 (95% CI: 1.7–53.0) for ex-smokersas compared to never smokers. Mental stress, body height, bodymass index and production factors did not predict unspecifiedlow-back pain or sciatic pain. Farmers who are free of backproblems in middle age seem to stay well in the long run despitethe heavy work. The close association between smoking and theprevalence of sciatic pain found in men is in line with thehypothesis that smoking is a causal risk factor for lumbar discdisease.     

Effectiveness of a return-to-work intervention for subacute low-back pain

The effectiveness of return-to-work intervention for subacute low-back pain on work absenteeism, pain severity, and functional status was examined by means of a systematic review of randomized controlled trials. Publications in English that met the selection criteria were identified in a computer-aided search and assessed for methodological quality. A best-evidence synthesis was performed instead of statistical data pooling, because of the heterogeneity of the interventions and study populations. Five of nine studies comparing return-to-work intervention with usual care were identified as methodologically high-quality studies. Strong evidence was found for the effectiveness of return to work intervention on the return-to-work rate after 6 months and for the effectiveness of return-to-work intervention on the reduction of days of absence from work after > or = 12 months. It can be concluded that return-to-work interventions are equal or more effective regarding absence from work due to subacute low-back pain than usual care is.     

Prognostic factors related to recurrent low-back pain and sickness absence

OBJECTIVES: This study aimed at determining the prognostic factors related to the recurrence of low-back pain and future sickness absence due to low-back pain. METHODS: Data were used from a prospective cohort study in a working population with a 3-year follow-up period. They were collected with annual questionnaires. A generalized estimating equation model was used to study the relation between pain characteristics, individual characteristics, and work-related factors and the recurrence of low-back pain or sickness absence due to low-back pain in the following year. Adjustments were made for potential confounders. RESULTS: All the pain characteristics [odds ratios (OR) varying from 1.4 to 2.4], flexion and rotation of the upper part of the body [OR 1.6, 95% confidence interval (95% CI) 1.1-2.5], low decision authority (OR 1.6, 95% CI 1.0-2.6), and low job satisfaction (OR 1.5, 95% CI 1.0-2.3), increased the risk of recurrent low-back pain. High disability due to low-back pain (OR 2.6, 95% CI 1.2-5.7), low co-worker support (OR 4.1, 95% CI 1.6-10.5), and low job satisfaction (OR 2.4, 95% CI 1.3-4.5) were predictors of sickness absence due to low-back pain. Lifting weights did not influence the risk of recurrences or sick leave. CONCLUSIONS: According to this study, high disability due to low-back pain is a prognostic factor for recurrent low-back pain and future sickness absence due to low-back pain. In addition, the following work-related factors predict a poor prognosis of low-back pain: flexion or rotation of the trunk, low job satisfaction, low decision authority, and low social support.     

Use of ultrasound in occupational risk assessment of low-back pain

The aim of the study was to evaluate ultrasound technique in preemployment medical assessment of the risk for low-back pain. Volunteers for the study were recruited among agricultural workers employed in the "Agraria Department" of the University of Bologna, Italy. The group consisted of 90 subjects, 52 male and 38 female, aged 25 to 58 years. The subjects filled in a questionnaire on medical history of low-back pain and were examined using an ultrasonograph equipped with a high linear frequency probe (3.5 MHz). The oblique parasagittal diameter of the lumbar spinal canal was measured by transabdominal ultrasonic imaging in the lumbar (L4-L5) and lumbosacral (L5-S1) region. Individuals with significantly narrower canals (< 14 mm) had an increased risk of low-back pain. The paper concludes that ultrasound imaging could become a valuable screening tool in industry, permitting selective job placement for workers at high risk for disorders of the back.