Evaluation of trunk acceleration in healthy individuals and those with low back pain

Aims: The aim of this study was to investigate trunk acceleration as a measure of performance in both healthy individuals and those with low back pain (LBP). The study explored the difference in behaviour of trunk acceleration during flexion-extension movements between these two groups. This study investigated the test-retest reliability of the Lumbar Motion Monitor (LMM) using a single task protocol. Methods: Trunk acceleration of a group of healthy participants (M = 5, F = 5) and a group of participants with LBP (M = 4, F = 6) was evaluated using the LMM. Two sets of measurements were obtained from participants performing trunk flexion-extension movements for 8 seconds. Each participant had a 10 minute rest period between measures. Data were analysed using a two-way mixed model for an intra-class correlation (ICC) analysis to investigate the reliability of the measure, and a Bland-Altman graph was used to demonstrate the levels of agreement between those repeated measures. Results: The LBP group of participants demonstrated a slower three dimensional performance than the healthy group. The ICC for average sagittal acceleration (0.96, 95% confidence interval (CI) 0.90-0.98) and peak sagittal acceleration (0.89, 95% CI 0.75-0.96) with a 95% limit of agreement for the repeated measures of between - 100.64 and + 59.84 degrees/s(2) demonstrates the reliability of the measure. The higher ICC and its narrow confidence interval suggest that average rather than peak acceleration is more reliable. Within group measures for both the healthy and LBP groups demonstrated similar reliability for average acceleration (ICC 0.98, 95% CI 0.92-0.99) and for peak acceleration (healthy group ICC 0.94, CI 0.76-0.99; LBP group ICC 0.92, 95% CI 0.67-0.98). Conclusions: Low back pain may reduce trunk acceleration. The LMM may be used to measure trunk acceleration as a descriptor of trunk performance in response to an onset of LBP. However, the Bland-Altman limits suggest that its reliability is dependent upon the harness upon which the LMM is secured remaining in a fixed position.