Static pelvic asymmetry is not linked to activation asymmetry of the lateral abdominal muscles and body weight distribution asymmetry on lower extremities

Abstract

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.