Three-Dimensional Spinal and Pelvic Alignment as Determinants of Anticipatory Core Muscle Activation

Background/Objectives: Three-dimensional (3D) spinal and pelvic alignment plays a critical role in maintaining anticipatory postural control. However, the extent to which specific multiplanar alignment parameters influence feedforward activation of trunk stabilizing muscles remains unclear. This study aimed to determine whether sagittal, coronal, and transverse postural deviations predict anticipatory muscle activation patterns during externally induced perturbations. Methods: Surface electromyography (EMG) was recorded from bilateral external oblique (EO), lumbar multifidus (LM), and transversus abdominis/internal oblique (TrA/IO) muscles in 100 asymptomatic young adults (18-25 years) performing dynamic right-leg raises. Spinal and pelvic alignment was quantified using rasterstereography, including sagittal and coronal imbalance, pelvic tilt, torsion, rotation, vertebral rotation, and spinal curvatures (kyphotic and lordotic angles). Regression models examined how these parameters predicted EMG onset latency and activation amplitude. Results: Distinct alignment patterns were associated with altered anticipatory control. Increased vertebral rotation and greater sagittal imbalance were linked to delayed activation of EO and LM, while asymmetries in pelvic torsion and tilt were related to less efficient TrA/IO recruitment. Conversely, more balanced spinal curvatures corresponded with earlier, more coordinated muscle activation across the trunk. Conclusions: Multiplanar spinal and pelvic alignment significantly influences anticipatory neuromuscular strategies. Identifying how specific postural deviations disrupt feedforward activation provides a functional basis for targeted rehabilitation programs aiming to restore alignment, enhance trunk stability, and prevent recurrent postural dysfunction.