Fig. 4

Changes in the Cobb angle and AVSI between postures. (a) In the total cohort, the Cobb angle is significantly greater in the habitual standing position (HSP) than the relaxed prone position (RPP), and the Cobb angle in the prone extension position (PEP) does not significantly differ from the Cobb angle in the RPP. (b) In group A (PEP-Cobb < RPP-Cobb), the Cobb angle is significantly greater in the HSP than the RPP, while the Cobb angle is significantly smaller in the PEP than the RPP. (c) In group B (PEP-Cobb > RPP-Cobb), the Cobb angles in the HSP and PEP are significantly greater than the Cobb angle in the RPP. (d) and (f) In the total cohort and group B, the symmetrical index of paraspinal muscle activity at the apex vertebra (AVSI) is close to 1 in the RPP. The AVSI values in the HSP and PEP are significantly greater than 1 and significantly greater than the AVSI in the RPP. (e) In group A, the AVSI values in the HSP and RPP are close to 1 and do not significantly differ, while the AVSI in the PEP is significantly greater than 1 and significantly greater than the AVSI in the RPP. *p < 0.05, **p < 0.01, ***p < 0.001, compared with that in the RPP