Original article Ultrasound measurement of abdominal muscles activity during abdominal hollowing and bracing in women with and without stress urinary incontinence q Amir Massoud Arab a, * , Mahshid Chehrehrazi b a Department of Physical Therapy, University of Social Welfare and Rehabilitation Sciences, Evin, Koodakyar Ave., P.O Box 1985713834, Tehran, Iran b Isfahan University of Medical Sciences, Isfahan, Iran article info Article history: Received 3 March 2010 Received in revised form 28 April 2011 Accepted 6 June 2011 Keywords: Abdominal muscles Stress urinary incontinence Ultrasound Hollowing Bracing abstract Synergistic co-activation of the abdominal and pelvic floor muscles (PFM) has been reported in the literature. Considering that PFM dysfunction is present in women with stress urinary incontinence (SUI), altered abdominal muscle activation may also occur in incontinent women. The purpose of this study was to investigate the abdominal muscle activity during abdominal hollowing and bracing maneuver in women with and without SUI using ultrasound. Convenience sample of 20 non-pregnant female participated in the study. Subjects were categorized into two groups: continent females (N ¼ 10) and females with SUI (N ¼ 10). The percentage of change in thickness of right transverse abdominals (TrA) and internal obliques (IO) was measured during abdominal hollowing and bracing maneuver in both groups. The result of two-way mixed-design ANOVA revealed no significant health status by maneuver interaction effect for ultrasound measurement of the percentage of change in thickness of TrA (P ¼ 0.66) and IO (P ¼ 0.36). The main effect of health status on the percentage of the change in thickness of TrA (P ¼ 0.52) or IO (P ¼ 0.84) was not statistically significant. In overall, no significant difference was found in the percentage of changes in thickness of TrA and IO muscles during abdominal hollowing or bracing maneuver between women with and without SUI. Ó 2011 Published by Elsevier Ltd. 1. Introduction Stress urinary incontinence (SUI) is a common health related problem in women, involving 50% of women with urinary inconti- nence (Abrams et al., 2003; DeLancey and Ashton-Miller, 2004). SUI is defined as “the complaint of involuntary leakage on effort or exertion, or on sneezing or coughing” (Abrams et al., 2003). For urinary continence to be maintained, urethral pressure must be greater than bladder pressure at all times. Under normal circum- stances, pelvic floor muscles (PFM) contract to increase the pressure of the urethra during the tasks that increase intra-abdominal pres- sure. There is substantial evidence indicating PFM dysfunction in women with SUI (Bø, 2003; Morin et al., 2004; Amaro et al., 2005). Synergistic co-activation of the abdominal and PFM has been reported in the literature with electromyographic (EMG) evidence of this synergistic relationship (Sapsford et al., 2001; Sapsford and Hodges, 2001; Neumann and Gill, 2002; Madill and McLean, 2006, 2008). It is probable that this contributes to urinary continence. Investigators attributed the generation of intra-vaginal pressure in continent women to co-activation of PFM and abdominal muscles (Madill and McLean, 2006). Neumann and Gill (2002) showed that continent women were unable to fully perform PFM contraction without simultaneous contraction of the transverse abdominals (TrA) and the internal obliques (IO). A significant difference in abdominal EMG amplitude during maximal voluntary PFM contraction was found between healthy continent women and those with severe SUI (Madill et al., 2009). Some reports have also demonstrated less PFM activity and more abdominal muscle activity during PFM contraction in the inconti- nent women compared with asymptomatic women (Thompson et al., 2006). It is thought that incontinent women can not perform a correct PFM contraction using a localized muscle strategy and use muscle substitution strategies and activate all the muscles of the abdomino-pelvic cavity (Thompson et al., 2006). EMG studies have found delayed abdominal muscle activity during arm movement (Smith et al., 2007a), greater external oblique activation during postural tasks (Smith et al., 2007b), and greater abdominal activa- tion during balance tasks (Smith et al., 2008) in women with SUI. Real-time ultrasound imaging is a reliable and valid technique recently used by physical therapists to evaluate muscle structure, q This research was reviewed and was approved by the Human Subject Committee at University of Social Welfare and Rehabilitation Sciences. * Corresponding author. Tel./fax: þ98 21 22180039. E-mail addresses: arabloo_masoud@hotmail.com, amarab@uswr.ac.ir (A.M. Arab). Contents lists available at ScienceDirect Manual Therapy journal homepage: www.elsevier.com/math 1356-689X/$ e see front matter Ó 2011 Published by Elsevier Ltd. doi:10.1016/j.math.2011.06.002 Manual Therapy 16 (2011) 596e601