Study aim: The aim of the study was to evaluate asymmetry of activation of lateral abdominal muscles (LAM) in response to neurodevelopmental traction technique in children with pelvic asymmetry. Material and methods: Measurements of LAM activation asymmetry were performed during traction with the force of 5% body weight in two experimental conditions: 1) in neutral position, 2) in 20° posterior trunk inclination. Twenty-three healthy children with pelvic asymmetry participated in the study. To evaluate LAM activation asymmetry ultrasound technology was employed (two Mindray DP660 devices (Mindray, Shenzhen, China)). Activation asymmetry indices for each individual LAM were calculated. Results: The magnitude of LAM activation asymmetry indexes formed a gradient, with the most profound transversus abdominis (TrA) showing the greatest asymmetry, and the most superficial obliquus externus – the smallest. The inter-muscle differences were most pronounced between the TrA and the two more superficial oblique muscles. There were no correlation between the magnitude of pelvic asymmetry and LAM activation asymmetry. Conclusions: During the neurodevelopmental traction technique there is a difference in individual LAM activation symmetry, with deeper muscles showing greater asymmetry. The activation asymmetry of the LAM does not seem to be associated with the pelvic asymmetry. Results are similar to those recorded in earlier studies in samples where no pelvic asymmetry were subjected to analysis.

Background: Pelvic, spinal and hips asymmetries constitute common phenomena. Pelvic asymmetry is usually perceived from two different points of view: as a causative factor in certain motor system dysfunctions or as a symptom of existing dysfunctions. Objective: This study aimed to evaluate the difference in activation asymmetry of lateral abdominal muscles (LAM) and the difference in body weight distribution on lower extremities during prolonged standing between subjects with and without pelvic asymmetry, and check if there is a correlation between the magnitude of pelvic asymmetry and activation asymmetry of lateral abdominal muscles as well as body weight distribution on lower extremities. Methods: A total of 66 subjects (34 women) participated in the study. LAM activation was measured using ultrasound technology. Body weight distribution asymmetry on lower extremities was measured during prolonged barefoot standing on the two scales equipped with digital readings. The activation asymmetry index and the weight distribution asymmetry index between the left and right sides of the body were calculated. Results: The recorded weight distribution asymmetry indexes were slightly higher in subjects with pelvic asymmetry; however, no significant inter-group differences were found. These subjects did not show any significant difference from subjects without asymmetry for activation asymmetry index recorded in all individual LAMs (obliquus externus abdominis p = .68, obliquus internus abdominis p = .34, transversus abdominis p = .55). Conclusions: No differences were found between subjects with and without pelvic asymmetry in activation asymmetry of lateral abdominal muscles and body weight distribution on lower extremities. Thus, there was no evidence gathered to prove that pelvic asymmetry constitutes an advantageous or disadvantageous phenomenon. It seems that it may play only a minor role, if any, in the energy expenditure optimisation process during prolonged standing. It is unlikely that pelvic asymmetry may lead to or stem from activation asymmetry of lateral abdominal muscles.