Upper Thoracic Segmental Acceleration Time-Series Analysis of Trunk Control During Sit-to-Stand in Adolescent Idiopathic Scoliosis: A Novel Individual-Level Analytical Approach

Adolescent idiopathic scoliosis (AIS) can alter movement strategies during functional tasks such as sit-to-stand (STS), yet sensitive biomechanical measures capable of detecting subtle motor control adaptations remain underexplored. This preliminary study examined phase-specific upper thoracic (UT) segment acceleration during STS before and after a one-week intensive Schroth exercise intervention in individuals with AIS. Seven adolescents with AIS (five female, two male; mean age 15.43 ± 2.37 years) underwent pre- and post-intervention three-dimensional motion capture during a standardised STS task. Peak UT accelerations and phase durations were extracted for the horizontal and vertical phases of the movement. Group-level vertical acceleration demonstrated the most substantial change, increasing from 1.81 m/s/s (SD 0.31) to 2.25 m/s/s (SD 0.40) post-intervention. Horizontal acceleration also increased (1.32 to 1.60 m/s/s), while phase durations remained broadly similar. Considerable inter-individual variability was observed, with P1 and P6 showing the most pronounced acceleration gains. Phase-specific UT acceleration analysis provides a sensitive and clinically informative means of detecting acute movement adaptations following Schroth therapy in AIS. Single-subject waveform analysis further highlights the potential of this approach for individualised intervention monitoring, warranting investigation in larger cohorts. These findings suggest that UT acceleration based STS assessment may offer clinicians a practical and objective tool for tracking neuromuscular responses to conservative scoliosis management in real-world rehabilitation settings.