Transversus abdominis and internal oblique muscles activation in standing and single leg standing among healthy adults

Abstract

Symmetrical activation of deep abdominal muscles such as transversus abdominis (TrA) and internal oblique (IO) induce the efficiency of spinal stability. Previous using ultrasound imaging have shown side symmetry in the deep abdominal muscles thickness at resting and during contraction in supine position in the healthy individuals which has the low load to the spine. However, it is unknown whether the symmetrical activation of TrA and IO muscle in the functional position which increases load to the spine such as standing and single leg standing position. Therefore, the purpose of this study was to examine the symmetrical of the TrA and IO muscle activation ratio between sides of the body in standing and single leg standing position among healthy participants. Fifty five healthy participants (twenty-five male and thirty female, mean age = 28.2 ± 7.9 years) were recruited for USI measurement of TrA and IO muscle thickness during resting and abdominal drawing in maneuver (ADIM) using ultrasound imaging (USI) in standing and single leg standing position. The activation ratio (AR) of TrA and IO muscle were calculated from the muscle thickness during ADIM divide by muscle thickness during rest in each condition. Repeated measures ANOVA was used to compare the AR of TrA and IO muscle between sides and between muscles. During both standing and single leg standing position, there were no significant differences in AR of TrA between sides (p > 0.05). But the AR of IO muscle on dominant side was significantly higher than non-dominant side (p < 0.05). Moreover, there was significantly higher AR of TrA muscle compared to IO muscle only in non-dominant side (p < 0.05). The present study indicated that there were symmetrical AR of the TrA muscle in dominant in healthy individuals but asymmetrical AR of the IO muscle with the higher AR in dominant side. Moreover, the AR of TrA muscle was higher than IO muscle only in non-dominant side in both functional standing and single leg standing positions which more load to the spine. This finding provided information for assessment deep abdominal muscles.