Trunk posture exposure as a risk factor for low back disorders in farmers

Abstract

Introduction Low back disorders (LBD) are the most prevalent type of musculoskeletal disorder in farm worker. Farm workers have a unique employment context with physical tasks that may expose them to awkward posture, but the link between exposure and LBD has never been summarized. The objectives of this thesis were to: 1) conduct a systematic literature review on trunk posture as a risk factor for LBD in farmers; and 2) measure the patterns of trunk posture exposure in Saskatchewan farm workers.

Methods Objective 1: Comprehensive electronic searches were conducted in six data bases with two conceptual groups of search terms: ‘farming’ and ‘LBD.’ Screening, data extraction, and risk of bias assessment were performed by two reviewers independently. Objective-2: A one-year field-based study with three repeated farm visits directly measured working posture for 49 farm workers (91 measurements total). Individual and farm characteristics were obtained via questionnaire. Trunk posture angles and velocity were measured with motion-tracking inertial sensors and summarized as 10th, 50th, and 90th percentile and time spent in neutral or extreme postures. Work tasks on farms were categorized in to driving, manual, and mixed activities. The variability between the farms tasks was analyzed with Generalized Estimation Equations (GEE).

Results Objective 1: Out of 1394 titles identified in the search, nine articles met the inclusion criteria. The included studies were diverse in terms of employment context, region, and commodity; all used self-report to measure exposure. Two studies showed no association, one showed a protective effect, and six showed a positive association between awkward working posture and LBD in farm workers (OR from 1.3 to 3). Despite the diversity, the weight of evidence supports a relationship between awkward posture and LBD. Objective-2: The 90th percentile trunk flexion-extension angle was significantly higher for manual as compared to driving tasks, and the 90th percentile flexion-extension velocities were also significantly higher for manual than driving tasks. Participants spent 38% of their working time in trunk forward flexion ≥ 20°, which according to previous epidemiological studies may increase their risk for LBD.