Investigating Occupational Factors Linked to Back Pain: Repetitive Lifting Strategies and a Method for Examining Effects of Vibration

Abstract

Low back pain results in a significant burden to industrial nations worldwide from the medical costs and the loss of work productivity. The objective of the current work was to investigate repetitive lifting with high torso flexions and vibration, all factors linked to low back pain. In the first study, lumbar-pelvic coordination was examined in novice and experienced lifters. It was hypothesized that novice lifters would select a lumbar-pelvic coordination that reached the kyphotic limits of their lumbar range of motion (ROM) while experienced lifters would select a more neutral strategy. Twenty-seven subjects participated in a repetitive lifting experiment to examine the kinematics and energetics of different lifting strategies. Three lifting strategies were examined using individual lumbar ROM for normalization. The first was a self-selected strategy followed by two strategies trained with a biofeedback. The trained strategies included a strategy approaching the kyphotic limits of ROM and a neutral strategy maintaining near the middle of ROM. The results demonstrate novice lifters select a lumbar-pelvic coordination approaching the kyphotic limits of their range of motion while experienced lifters remain near the middle. The energetics of the lifting task were also examined, but found no significant differences between the trained lifting strategies. In another study, seven subjects participated in a study attempting to design a proprioceptive measurement acceptable for the occupational setting. The design criteria the task need to meet included: 1) portable, 2) minimal set up, 3) easy for subjects to understand, 4) minimal data collection time, and 5) able to identify effects of vibration exposure. A seated sway target pursuit task was designed to examine four tasks of increasing complexity to identify the most appropriate task for the occupational setting. The target pursuit tasks included stable sway, linear tracking in ML and AP directions, and tracking a circle. Limited detected effects of vibration in these tasks suggest that further development is required. In both efforts, dynamic control of lumbar motion was examined using repetitive trunk motion tasks. In the lifting study, experienced lifters chose a more neutral lumbar-pelvic coordination strategy, suggesting training such a strategy could reduce injury incidence.