Introduction: Systematic reviews have found that sitting at work is not associated with LBP, although the biomechanical evidence does offer plausible causative mechanisms. Indeed, exposure to lumbar postures has been assessed using imprecise tools that have limited epidemiological investigations. The aim of this study was to use new technology to measure the seated lumbar postures of sedentary (call centre) workers, and survey their current and future symptoms in order to determine associations with LBP.

Methods: A fibre-optic goniometer (FOG) system was attached to the lumbar spine and hip of 181 sedentary call centre workers at the start of their working shift. The lumbar FOG provides a continuous measure of sagittal lumbar curvature (lumbar position and movement), whilst the hip FOG enables quantification of sitting time. Baseline and 6-month follow-up questionnaires were used to collected symptom data, and logistic regression was used to determine associations between postural and symptom (yes/no) data.

Results: Workers spent a mean proportion of 83% of work-time sitting, with 17% sitting for more than 90 minutes without a break. Current LBP (symptoms lasting more than 24hrs) was associated with a kyphotic (mean lumbar angle> 180°) sitting posture (yes/no) (OR 2.1, 1.1–4.1), although movement (mean standard deviation and angular velocity °sec-1) in sitting was not. Sitting relatively static (AV< 4.26° yes/no) (OR 3.30, 1.06–10.25), using a small amount of range (SD< 10.2° yes/no) (OR 3.79, 1.2–11.7), and adopting a kyphotic posture (yes/no) (OR 2.75, 1.02–7.3) all significantly increased the risk of future LBP.

Discussion: Sitting postures at work are associated with current LBP and are statistically significant risks for recurrence. These results highlight the potential for ergonomic interventions to reduce current symptoms and the risk of future episodes. The findings from this study are novel, and the FOG system should now be used in larger investigations of sedentary risk factors for LBP.

Background: Many sedentary workers will experience low back pain (LBP) whilst sitting, and some will believe that work caused their symptoms. They also report that their symptoms can be aggravated or relieved by work. Little is known about sedentary workers’ beliefs about the causes of back pain or symptom modifying factors (SMFs), and this study sought to determine their influence on absence.

Methods: 600 call centre workers completed validated questionnaires concerning beliefs about work-related causes of LBP in sedentary work and SMFs. Three constructs for work-related causes of LBP (physical demands; work environment; work organisation), and three groups of SMFs (physical aggravating; movement relieving; and postural relieving factors) were measured. A 6-month follow-up survey identified workers who did and did not take absence due to LBP. Logistic regression was used to predict future absence.

Results: Results indicated that, on their own, beliefs about the work environment (OR 1.2, 95% CI 1.1–1.4), and work organisation (OR 1.2, 95% CI 1.0–1.3) were significant risks for future absence (P< 0.001). Physical aggravating factors also represented a significant risk (OR 1.3, 95% CI 1.1–1.4, P< 0.001). Perceived physical demands and relieving factors were not significant (P> 0.05). The multivariable model showed that physical aggravating factors accounted for 16% of the variance (OR 1.3, 95% CI 1.1–1.4).

Conclusions: Beliefs about the work environment/organisation and physical aggravating factors are significant risks for future absence, although when considered together, physical aggravating factors dominate. These results highlight the potential for ergonomic interventions to reduce symptom-aggravating aspects of work to reduce absence.

Background: Researchers have measured exposure to sitting using self-reported questionnaires and observational analysis. Such methods are not a reliable measure of daily exposure or sensitive enough to take into account lumbar posture when seated. Recent innovations have produced a fibre-optic goniometer (FOG) that can continuously measure sagittal lumbar posture, although this single sensor is unable to identify if the user is sitting, standing or walking.

Methods: A new system was developed utilising a second FOG attached to the hip. Movement characteristics of the hip and lumbar spine were described and used to develop software to predict activity (sitting, standing, walking). Subsequently 10 participants were asked to wear the FOGs for 8 minutes whilst their behaviour was recorded using a video camera. MPEG video sequences were produced and each activity was coded at a point in time and compared against the 2 FOG software model.

Results: All Participants found the system comfortable to wear. Validation of the software against the MPEG files showed high sensitivity for sitting (90%), standing (98%), and walking (95%). Positive predictive value was high for sitting (93%), standing (89%) and walking (94%). The overall agreement between video analysis and the FOG software was 92%

Conclusions: Developing the FOG has produced a practical system capable of continuously measuring sedentary workers basic activity in terms of sitting standing and walking. This novel tool will now be used in a prospective study of sedentary workers to determine the influence of seated lumbar posture on the development of LBP.

Work in the clinical environment led to the identification of the need for an instrument that was capable of continuously monitoring lumbar spinal curves of patients with back pain in order to establish degree of compliance with therapist advice regarding posture and activity during their normal day. Additionally, work by others in the laboratory setting has started to reveal some differences in motion parameters between those with and without back pain. Although there are changes of, in particular, maximum angular velocity associated with pathology of the spine, these changes may be considered the effects of the pathology. By looking at motion parameters taken over longer periods of time, more subtle differences, hopefully more related to possible causes of back pain, may be eventually identified. Factors such as time spent at extremes of range of motion and degree of activity or inactivity may have as great an affect on the production of back pain as vibration and heavy physical load. Unfortunately, even those factors thought most likely to contribute to the onset of back pain have only ever been proven to explain a small percentage of cases.

By logging lumbar spinal curves continuously over many hours, profiles of lumbar spinal usage can be calculated thus enabling study of the relationships between posture, activity and pain production. Conventional instrumentation can not be used in the users normal environment either because of bulk or interference from everyday appliances.

A small optical fibre goniometer (OFG) and data logger has been developed that is capable of continuously monitoring lumbar sagittal curves. It is robust and suitable for use in normal working environments. For use on the lumbar spine, the instrument’s stiffness was kept to a minimum to make it as comfortable to wear as possible. This has resulted in an instrument that is capable of reproduction of standard curves, in a jig, with a RMS error of 1°. A stiffer instrument would produce smaller errors. Comparative studies against other instruments have been carried out but are not yet published. The instrument takes the form of a small base plate, designed to be glued to the skin over the sacrum, and a flexible rod that is held in place over the lumbar spinous processes by two guide tubes also glued to the skin.

The OFG weighs 25g and the datalogger 250g. The OFG and logger can be run safely for over 30 hours at a maximum logging frequency of 50 Hz. The datalogger has a facility for entry of coded information via selector switches which allow the user to put markers on the data train which could be activity of pain behaviour related.

Initial trials have been carried out using the instrument to obtain motion profiles of 80 “normal” individuals, 10 males and 10 females from each of 4 age groupings; 20 to 29; 30 to 39; 40 to 49; 50 to 59. Logging duration was normally six hours during their working day. Data was collected at 25Hz. It was established that the instrument was able to produce basic motion parameters that were similar to other instruments. Although, no significant differences in ROM were found with age there were significant differences found between males and females in terms of end range flexion and extension. Additionally, the amplitude of oscillations of spinal curve during walking was found to significantly decrease with age. This may have been indicative of general stiffening of the lumbar spine with age or associated with a possible decrease in walking speed with age.

It is envisaged that the instrument will find use in both ergonomic analysis as well as the study of the management of back pain. Use of the instrument to investigate patient compliance with therapist advice is planned and will hopefully help to develop the management of patients with low back trouble.

Future development of the instrument is hoped to include incorporation of a sensor to monitor the angle of the base plate, as this will allow better interpretation of the data from the logger post data collection. Additionally information of base plate angle will allow some simple load calculations to be made.

Repeatability trials have been carried out using human subjects. Here, the major source of variability was found to be the subjects themselves. Reapplication error was found to be small, compared to subject variability.

Comparison with measurements taken using the flexicurve technique and also the Skill System (similar to Isotrak or Fastrak) has been undertaken. Here the two systems were found to follow each other achieving correlation coefficients of 0.99. However, more critical forms of analysis revealed relatively large differences, although these were no greater than others that have compared the inclinometer technique with the flexicurve.