Purpose <p>Paraspinal muscle imbalances in teenagers with adolescent idiopathic scoliosis (AIS) are well-documented, but their metabolic characteristics remain unclear. This study assessed oxygen recovery asymmetry (TrAsy) in paraspinal muscles during isometric trunk extension in teenagers with and without AIS and explored its correlation with spinal curvature.</p> Methods <p>Fifty-one AIS participants with primary right thoracic curves (40 females; 13.5 ± 1.7 years; thoracic Cobb angles: 22.9°±6.8°; 28 mild [Cobb angles 10°–24°], 23 moderate-to-severe [≥ 25°]) and 51 non-AIS controls (33 females; 13.2 ± 1.7 years) performed prone isometric trunk extensions. Bilateral paraspinal oxygen recovery times (Tr) at T9 and L3 were measured using near-infrared spectroscopy. TrAsy (between-side Tr difference) was analyzed using mixed-design ANOVA with group (AIS vs. controls) and side (convex vs. concave) factors; Welch’s ANOVAs assessed TrAsy differences by curve severity and location. The association between thoracic Cobb angles and TrAsy was evaluated using multiple linear regression, adjusting for covariates.</p> Results <p>AIS cases (Cobb angles: 22.9°±6.8°) showed significantly longer Tr on the concave side at T9 (74.6s ± 10.1s vs. 50.1s ± 16.8s; <i>p</i> &lt; 0.001), with no significant between-side difference at L3 in both groups analyzed collectively (<i>p</i> = 0.31). Tr was longer at T9 than L3 (<i>p</i> &lt; 0.001) Single curves exhibited greater TrAsy than double curves at T9 (mean difference: 25.0s ± 8.60s; <i>p</i> = 0.004), with moderate-severe AIS showing larger concave-side Tr. The regression model showed that greater TrAsy was associated with larger thoracic Cobb angles (R² = 0.46, <i>p</i> &lt; 0.001).</p> Conclusion <p>Teenagers with AIS showed greater TrAsy at T9, predominantly on the concave side, which correlated with curve severity. Further research should investigate causal relation between metabolic response and curvature progression.</p>