Figure 1

Generalized schema of the musculoskeletal arrangement. Different geometric arrangements of the spinal column (blue dots) and global muscles (red). First row (A, B): symmetrical arrangement of the spinal segments (as for example in the coronal plane). Second row (C, D): asymmetrical arrangement with an eccentric spinal column (e.g. the mid-sagittal plane). Third row (E, F): asymmetrical arrangement with an eccentric spinal column and a spinal curvature (e.g. a lumbar lordosis). Left column (A, C, E): global muscles acting in parallel to the spine (e.g. m. rectus abdominis, m. erector spinae). Right column (B, D, F): global oblique muscles (e.g. m. obliquus externus abdominis, m. obliquus internus abdominis, m. multifidus). A, B, C: A muscular activity pattern exists in which all segments are in equilibrium. D, E, F: Local counter torques are necessary which may be minimized by a spinal curvature (E, F).