Lumbopelvic Kinematics During Functional Tasks in a Chronic Low Back Pain Observational Cohort.

Background: The University of Pittsburgh Mechanistic Research Center, entitled, "Low Back Pain: Biological, Biomechanical, Behavioral Phenotypes (LB3P)," is part of the National Institutes of Health's Helping to End Addiction Long-term Initiative. LB3P conducted a prospective, observational cohort study to identify phenotypes from over 1000 participants with chronic low back pain (cLBP). This article reports findings from multi-level inertial measurement unit (IMU) kinematic data collected during performance-based tests obtained at the in-person LB3P enrollment visit. Methods: Participants with cLBP were recruited and performed self-paced and fast-paced movements while wearing inertial measurement units (IMUs) placed over T1/T2, T12/L1, L5/S1, and along the right femur. For self-paced tests: axial rotation (AR), lateral bending (LB), and flexion and extension (F/E), participants performed to their maximum range of motion (ROM), and for fast-paced tests: combined rotation/flexion (CRF), AR, LB, flexion, five times sit to stand (5STS), and postural lifting strategy (PLS), participants performed at their maximum speed. ROM, velocity, acceleration, and lumbopelvic rhythm (LPR) were calculated for tests using IMU data. LPR was calculated as the ratio of absolute lumbar to hip movement and was extracted for each motion quartile (0%-25%, 25%-50%, 50%-75%, and 75%-100%) during neutral-to-flexion and neutral-to-extension. Results: Analysis of sensor data of 954 participants (58.6 ± 16.4 years old; 40% male and 60% female) revealed variable kinematic patterns across spinal and hip regions during isolated and functional movements. Noticeable variations were observed based on movement type, with the trunk region demonstrating predominant mobility during self-paced movements like AR and LB, while the hip region played a critical role in functional tasks (CRF, 5STS, PLS). LPR evaluation indicated that individuals with cLBP typically adopt a hip-dominant movement pattern, with slightly greater lumbar contributions during the initial phase of flexion. Sex and age analyses unveiled females generally exhibit greater ROM and higher velocities compared to males. Younger participants (< 60 years old) show more dynamic movement patterns, except in the hip region during F/E, where older (≥ 60) participants exhibited greater excursion. Conclusions: This study characterized spinal and hip movement in individuals with cLBP, focusing on ROM, velocity, acceleration, and LPR across a variety of self-paced and functional tasks. The values established from this cohort provide a foundation for future cLBP phenotyping, offering insights to guide individualized treatment plans and inform clinical guidelines. These findings highlight the complex relationship between regional contributions, demographic factors, and movement demands in spinal and hip kinematics, emphasizing the need for person-specific approaches to understanding the biomechanics of individuals with cLBP. Future research will expand this analysis by collecting the same metrics in asymptomatic individuals, enabling a more robust comparison to differentiate movement patterns and further refine the understanding of cLBP biomechanics. Future analyses will integrate these comprehensive kinematic data with the other study domains (behavioral and biological) to identify distinct cLBP phenotypes, which may serve as a basis for predicting treatment response and guiding personalized interventions.