Interface Between Sensorimotor Dynamics and Trunk-Hip Movement Control: Implications for Movement Assessment in Low Back Pain
Abstract
Low back pain is the leading cause of activity limitation and work absence and results in billions of dollars in healthcare expenditures. Impaired trunk-hip movement control is associated with the development of back pain and the persistence of symptoms. Theories suggest a causal relationship between altered sensorimotor dynamics, including altered afferent somatosensory information from the periphery and neuroplastic central nervous system adaptations, and impaired trunk-hip movement patterns. We characterized trunk-hip movement patterns and their associated sensorimotor brain dynamics in people with and without chronic low back pain (cLBP). Supine, atop an instrumented system, 48 individuals with cLBP and 37 healthy controls (HC) performed a left unilateral bridge task while undergoing functional brain imaging. We performed partial correlations and multiple regression using functional connectivity weights to predict movement patterns for each group. Sensorimotor functional connectivity explained a significant amount (30-46%) of the variance in trunk-hip movement patterns in both groups, but the relationships between brain dynamics and movement control were in opposite directions. The observed relationships suggest an interesting and important aspect of how the brain adapts and responds to chronic pain, disrupted proprioception, and their interaction. Additionally, we characterized the effects of vibration-induced altered trunk extensor muscle (TEM) proprioception on trunk postural control. We compared trunk control between HC undergoing vibration and persons with cLBP without vibration to explore the relationship between altered TEM proprioception and impaired postural control in cLBP. Twenty HC performed active joint reposition error (AJRE) testing to determine personalized vibration parameters. Participants then underwent trunk postural control testing, in which they maintained balance atop an unstable chair under eyes open and closed conditions, with and without TEM vibration. To explore the role of altered proprioception in cLBP, we compared postural control data from the back-healthy participants with data from twenty matched cLBP participants. Muscle vibration altered position sense during AJRE testing, and personalizing vibration parameters amplified the size of this effect. However, we measured trivial to small effects of TEM vibration on seated trunk postural control in back-healthy adults, which did not result in performance degradation equivalent to that observed in cLBP.