Investigation of Change in Thickness of Transverse Abdominis Under Voluntary Contraction

Abstract

Recently, so-called “core training” which focuses on muscles in the body trunk has attracted much attention. When discussing the stability of the body trunk, both Local muscles and Global muscles should be considered, but the importance of Local muscles has been studied more. Instructing a person verbally to halt urination is thought to prompt contraction of the transversus abdominis, one of the Local muscles. However, there has been no research that shows if this method is appropriate to prompt contraction of the transversus abdominis or what position is most effective. The purpose of this study was to investigate the appropriateness of this method and to determine what position is most effective to induce contraction. The participants were 61 male students (average age 18.1±1.8). They were instructed to halt urination in both supine and standing positions, and the thickness of the transversus abdominis were measured using an ultrasonograph. The thickness of those muscles at rest in both positions was also measured. The results showed that instructing a person to halt urination in order to prompt contraction of deep muscles in the body trunk was in fact effective to voluntary contraction of the transversus abdominis and adliquus internus abdominis, and the supine position was more effective. The result also showed that the standing position is effective to induce contraction of the transversus abdominis if it cannot be achieved voluntarily because when standing these muscles contract unconsciously.