## 4 Discussion
Increased bioelectrical activity on the side of the protruding curvature is a synonym of progressivity for some researchers, because in compensated scoliosis and after spondylodesis, bioelectric activity disappears. Meanwhile, [PERSON] and [PERSON] [26] found differences of bioelectrical activity in the paravertebral muscles in the case of non-aggressive curvatures during static and dynamic loading of the upper limbs. When performing maximal isometric work, the differences in bioelectrical activity between the convex and concave sides are smaller, which suggests that in idiopathic scoliosis, the etiological agent must not be muscle weakness on the side of the concave curvature. [PERSON] et al. [27] concluded that the cause of idiopathic scoliosis is excessive activity of the deep erector spinae muscles on the side of the convex curvature. The activity of the back muscles during constant loading is greater in children with scoliosis than in healthy subjects. In both cases, the bioelectrical activity of the muscles in the thoracic segment was higher than in the lumbar region and the asymmetry of the tension was stronger in the chest segment on the right side [28; 29]. [PERSON] [30] presented another approach to neuromuscular imbalance as a cause of scoliosis. This author emphasizes the role of neuromuscular functional unity in the process of blastomere formation. Congenital disorders in the differentiation of nerve structures or myotomes can cause muscular-nerve imbalance on both sides of the spine, resulting in its segmental structural changes. According to some researchers, dysfunction of the peripheral neuron underlies idiopathic scoliosis. [PERSON] [23] found the occurrence of fibrillation, especially in curves below 20\({}^{\circ}\) Cobb angle and multiphase potentials in 30% of subjects on both the concave and convex sides. [PERSON] et al. [31], and [PERSON] and [PERSON] [32] describe fibrillation on the side of curvature convexity. [PERSON] [33] reports that in idiopathic scoliosis, where the pathological potentials in the form of fibrillation were electromyographically observed, degenerative changes were found in the erector spinae muscle junctions of on the side of curvature convexity. Other authors, including [PERSON] et al. [34], [PERSON] and [PERSON] [26], and [PERSON] et al. [35], did not notice idiopathic resting activity in the form of fibrillation, fasciculation, or positive waves in scoliosis. In addition, [PERSON] and [PERSON] [26] believe that these phenomena are not evidence of de-innervation unless they are found in many places in the muscle under examination. In another study, the effect of a several-week long rehabilitation programme using the Schroth method on erector spinae tone in children with scoliosis was evaluated. Significant reductions in muscle activity by 6.85% in the thoracic convex region and totaling 14.2% on the lumbar convex side were found. The activity quotient (convex/concave) was reduced by 11.99% in the thoracic region and by 7.91% in the lumbar region. These findings confirm the improvement of postural performance capacity after the intensive in-patient Schroth rehabilitation programme. As the imbalance of electromyographic activity may be influenced by scoliosis-specific exercises leading to a highly significant reduction of the Cobb angle, it is assumed to be secondary to the development of the scoliotic curve and may not be a primary factor in the etiology of idiopathic scoliosis [36]. On the other hand, in the given study, EMG responses of the erector spinae to postural perturbation have been described and interpreted as unloading reflex. Moreover, these responses have been found to be clearly and constantly abnormal in subjects presenting progressive idiopathic scoliosis when compared to responses observed in subjects presenting non-progressive scoliosis or in normal subjects.