title: Developing common metrics of mechanical exposures across aetiological studies of low back pain in working populations for use in meta-analysis.
abstract: OBJECTIVE
  One of the challenges of conducting meta-analyses on the relationship between workplace mechanical exposures and low back pain is that mechanical exposures are reported in a wide variety of ways. We aimed to develop common metrics to apply in the translation of literature-based workplace mechanical exposures for use in meta-analyses, and to test the metrics' measurement properties.
  
  
  METHODS
  We developed a set of 7-point scales to capture the intensity of important aspects of mechanical exposures that may be related to the development of low back pain in workers. The scales represented three dimensions of mechanical exposures at work: (1) trunk posture, (2) weight lifted or force exerted and (3) spinal loading, and estimated both peak and cumulative loads. Measurement properties of the scales were tested through a survey of experts in biomechanics and ergonomics who were asked to rate literature-based workplace exposure definitions using the scales and provide estimates of their confidence in their ratings.
  
  
  RESULTS
  For each dimension the ratings for peak loads tended to be higher than the cumulative load ratings. The inter-rater reliability for the scales ranged from 0.3 to 0.5; we would need to average the ratings of at least four expert raters to have an acceptable level of reliability (>0.7). Inter-expert reliability was positively related to the experts' level of confidence in their ratings. In most cases the ranking of intensity ratings from the experts matched the ranking of exposure intensity from the original articles.
  
  
  CONCLUSIONS
  This study provides insight into estimating the intensity of literature-based mechanical exposure metrics using a common set of scales which can be applied across epidemiologic studies. These metrics may be useful to quantify the relationship between workplace mechanical exposure and low back pain in a systematic review and meta-analysis.
authors.affiliation: Department of Clinical Epidemiology and Biostatistics, McMaster University, Hamilton, Canada. griffith@mcmaster.ca
authors.forename: L E
authors.initials: LE
authors.lastname: Griffith
authors.forename: R P
authors.initials: RP
authors.lastname: Wells
authors.forename: H S
authors.initials: HS
authors.lastname: Shannon
authors.forename: S D
authors.initials: SD
authors.lastname: Walter
authors.forename: D C
authors.initials: DC
authors.lastname: Cole
authors.forename: S
authors.initials: S
authors.lastname: Hogg-Johnson
mesh_terms: D016001:Confidence Intervals; D004576:Electromyography; D006804:Ergonomics; D006801:Humans; D017116:Low Back Pain / Q000209:etiology*; D015201:Meta-Analysis as Topic; D009784:Occupational Diseases / Q000209:etiology*; D016273:Occupational Exposure; D009787:Occupational Medicine / Q000379:methods*; D011187:Posture; D015203:Reproducibility of Results; D013314:Stress, Mechanical; D011795:Surveys and Questionnaires; D020711:Threshold Limit Values; D014940:Work Schedule Tolerance