Quantitative dynamic measures of physical exposure predict low back functional impairment.

STUDY DESIGN: Prospective field study of work exposure and changes in back function. OBJECTIVE: Quantify dynamic physical exposures in the workplace and their association with decreases in kinematic back function (indicative of low back pain [LBP]). SUMMARY OF BACKGROUND DATA: Previous epidemiologic studies of work have measured gross categories of exposure and found moderate relationships with LBP. More precise quantitative measures of exposure and spine function were hypothesized to increase the chances of identifying any significant associations. METHODS: Three hundred and ninety real-time physical exposure measures were collected from distribution center workers performing repetitive manual materials handling tasks. Low back health effect measures were quantitatively measured prospectively for workers performing each of the jobs using a kinematic measure of function. RESULTS: Significant decreases in spine function were observed in workers associated with 40% of the jobs sampled. Numerous significant univariate odds ratios were identified that indicated an association between physical exposure and decreased function. A multivariate model including right lateral trunk velocity, timing of the maximum dynamic asymmetric load moment exposure, and the magnitude of the dynamic sagittal bending moment predicted reduced spine function well. The model resulted in excellent sensitivity (85%) and specificity (87.5%) as well as excellent positive predictive value (89.5%) and negative predictive value (82.4%). CONCLUSION: This study suggests that with proper quantification of job exposure and spine function, it is possible to identify which dynamic physical exposures are associated with reduced spine function and increases in LBP.