Impact of External Load on Spinal Kinematics in Individuals with Chronic Low Back Pain with Lumbar Disc Degeneration: A Cross-Sectional Study

Low back pain (LBP) remains a leading cause of disability globally, with a particularly high burden in low- and middle-income countries. It is evident from the literature that up to 84% of the population experience LBP during their lifetime, and among them nearly 23% develop chronic low back pain (CLBP). CLBP is associated with significant functional limitations and a substantial impact on quality of life.

Postural adaptations are commonly observed in individuals with CLBP. Conversely, poor posture itself can contribute to the development or persistence of LBP by adversely affecting spinal alignment and flexibility. Structural alterations in spinal curvatures—particularly in the lumbar and thoracic regions—have been shown to increase mechanical stress on vertebrae and lumbopelvic structures. These changes may lead to intersegmental instability and further degeneration of the spine, particularly at the intervertebral disc level.

Spinal alignment (SA) can be further influenced by external factors such as lifting or holding weight. While the spine employs various compensatory mechanisms to maintain sagittal balance in static conditions, these mechanisms may be challenged or become insufficient during load-bearing activities. The response of the spine to such mechanical loading is particularly relevant in individuals with CLBP, where age-related spinal degeneration and reduced paraspinal muscle strength may impair compensation and exacerbate kinematic disturbances.

Although some studies have explored the effects of external load in healthy or military populations under static conditions, there is limited research investigating its impact in individuals with CLBP. Moreover, little is known about how these responses vary across age groups, particularly in older adults who may experience more pronounced degenerative changes.

Recent advanced technologies such as the DIERS formetric 4D system (DIERS Medical Systems, Chicago, IL) allow for accurate, non-invasive assessment of spinal posture and movement. This radiation-free system uses surface topography to capture spinal curvature, vertebral rotation, and pelvic alignment over a six-second scan, providing reliable data for evaluating static postural alignment under different loading conditions.

Given the lack of evidence in biomechanical changes in the spine in individuals with CLBP, this study aims to:

-  Evaluate the effects of external load on spinal alignment parameters (including spinal curvature angles, trunk inclination, pelvic tilt, and lumbar vertebral rotation),

• Compare these parameters between younger and older adults with CLBP

- Investigate the influence of age, disc degeneration, physical activity, and functional disability on spinal kinematic responses to load.