A new study, published in Translational Exercise Biomedicine (ISSN: 2942-6812), an official partner journal of International Federation of Sports Medicine (FIMS) , has found that adolescents with idiopathic scoliosis (AIS) show fundamental differences in how their paraspinal muscles coordinate during trunk movement ( DOI:10.1515/teb 2026 000 7 ).
Researchers from the University of Hong Kong recorded surface electromyography (EMG) from 16 bilateral paraspinal muscles in 13 AIS patients with a mean Cobb angle 30°and 13 age-matched healthy controls during a seated flexion-extension task. Instead of comparing individual muscle pairs, they applied non-negative matrix factorization (NMF) to extract muscle synergies, compact neural-motor modules that represent co-activated muscle groups.
The results were striking. While healthy controls performed the task with a median of only 2 synergies, achieving ≥90% variance accounted for (VAF), AIS patients required a median of 3 synergies ( p =0.005). More importantly, the synergy most relevant to the primary task muscles, the lumbar and thoracic erector spinae and multifidus, accounted for only 42% of total muscle activation in AIS, compared to 62% in controls ( p =0.006). This means the main coordination pattern was significantly weakened in scoliosis patients.
In healthy individuals, this target-related synergy showed stable, repeatable activation peaks aligned with flexion and extension phases. In AIS, however, temporal profiles were more variable across movement cycles, with wider interquartile ranges, indicating less consistent multi-muscle coordination. Additionally, AIS participants frequently recruited extra synergies driven by non-target muscles such as the trapezius, often active only during specific movement phases. These extra synergies varied considerably between individuals, suggesting personalized compensatory strategies rather than a single stereotyped deficit.
" Traditional pairwise comparisons, concave versus convex side, have told us about muscle imbalances, but they miss the bigger picture of how muscles work together as a system, " said Dr. Teng Zhang from The University of Hong Kong, the corresponding author . " Our synergy-based approach reveals that AIS fundamentally reorganizes trunk motor control, and this reorganization is highly individual. These metrics could become objective tools for tailoring rehabilitation to each patient's specific coordination profile ."
The study’s lead author, Yifan Huang noted that the reduced dominance of the target-related synergy might serve as a quantitative marker of coordination integrity. " If we can track this VAF over time during exercise therapy, we may see whether a patient is actually improving their core coordination or just relying on compensatory patterns " Dr. Huang explained.
The findings align with earlier synergy studies in stroke, cerebral palsy, and chronic low back pain, where increased synergy numbers and reduced primary-synergy dominance have been interpreted as adaptive but inefficient motor strategies. In AIS, persistent reliance on compensatory synergies could alter spinal loading patterns and potentially contribute to curve progression, although the authors caution that longitudinal studies are needed to confirm this link.
Clinically, the heterogeneity of additional synergies may explain why standardized exercise programs often yield inconsistent outcomes. Two patients with similar Cobb angles may use entirely different compensatory muscles, meaning a one-size-fits-all rehabilitation protocol is unlikely to work equally well for both. Synergy analysis could identify which non-target muscles are overactive in a given patient, guiding targeted training to suppress compensatory recruitment and reinforce the primary coordination pattern.
The researchers acknowledge several limitations. The sample size is modest,13 per group, only moderate curves 20°–40°were included, and only one functional task was tested. Whether these synergy-based measures are modifiable through intervention, and whether they predict clinical outcomes such as curve progression, remains to be determined. Future work will require larger cohorts, multiple movement tasks and longitudinal designs.
Translational Exercise Biomedicine
News article
Characterization of muscle synergy organization in adolescents with idiopathic scoliosis
28-Jul-2026