Physical activity to prevent low back pain in an occupational cohort

Low back pain (LBP) is an expensive and common occupational health problem. Physical activity has been implicated as effective treatment for LBP, however its utility in prevention is unclear. This nested prospective cohort study utilized objective measure of physical activity via accelerometers in 68 participants. These participants were subsequently followed for 17 months for a total of 92.7 person years and developed 30 incident cases of LBP. Total minutes of light, moderate, and vigorous activity per day from accelerometer data were measured and divided into quartiles of total minutes. Univariate and multivariate Hazard Ratios (HR) were calculated. Multivariate analyses were performed, adjusting for personal and occupational factors, and demonstrated similar associations. There were statistically significant differences in risk of development of LBP for the first (lowest) and fourth (highest) quartile as compared with the third quartile, with HR estimates of 5.53 [Confidence Interval (CI) 1.19, 25.59] and 9.48 (95% CI 2.11, 42.51), respectively. When comparing the second quartile of total minutes of activity with the third quartile the results were not statistically significant with an RR of 3.58 (95% CI 0.74, 17.23). Moderate levels of physical activity were protective for the development of subsequent LBP of any intensity in this cohort, including after adjustment for other known and suspected risk factors. This study suggests the relationship between activity and LBP is nonlinear indicating higher levels of activity do not confer increased protection from incident LBP, although increasing from the lowest level of activity does appear to provide protection.