ABSTRACT
The Transversus Abdominis Muscle [TrA] is the deepest abdominal muscle which contributes to lumbosacral stability. Abdominal Hollowing [AH] maneuver is a clinical way to activate the TrA muscle in an isolated fashion. The aim of this study was to investigate the effects of AH maneuver on External Oblique [EO], Internal Oblique [IO], and Transversus Abdominis [TrA] muscles in supine and standing positions in both healthy men and women. This clinical trial study was conducted on 43 asymptomatic volunteers aged 19-44 years. After collecting demographic information, the participants were instructed to activate their TrA muscle in standing position. Then Rehabilitative Ultrasonic Imaging [RUSI] was performed for measuring thickness of all above muscles in both supine and standing positions and before and during doing AH. At the same time activation of the TrA was controlled by Pressure Biofeedback [PBF]. ANOVA, paired t-test and Pearson correlation tests were used to analyze the data. Values of p<0.05 were considered to be significant. During AH, the thickness of TrA increased significantly in both supine and standing positions [p<0.0001]. Also, thickness of the IO muscle increased in both men and women groups after AH [p<0.0001]. Generally, we observed that both IO and TrA thickness increased in standing position compared to supine position [p<0.003, p<0.0001] but advanced analysis indicated that TrA had increased only in its rest thickness [p<0.02]. There was no effect of AH or changing position on EO muscle's thickness [p<0.2]. It appears that performing AH in standing position can be effective on TrA thickness, although the PBF has been introduced as a clinical and available device for monitoring TrA activity, RUSI showed that both TrA and IO muscles were activated after AH. We recommend performing further investigations using electromyography and RUSI at the same time