Background and Aim: The Transversus Abdominis Muscle (TrA) is the deepest abdominal muscle which contributes to lumbo-sacral 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. Materials & Methods: 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. Results: 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 & 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). Conclusion: 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.

Introduction: Back muscles fatigue is one of the risk factors in workplace and throughout daily activities. Under fatigue conditions, loads will be redistributed among active and passive tissues in a non-optimal manner, where a single tissue may become overloaded and thus increasing the risk of injury with minimal loads. Because of the importance of abdominal muscles in producing and maintaining spinal stability in unstable conditions, it was necessary to investigate the response of these muscles in the presence of back muscles fatigue. Since it is not possible to study deep muscles with surface electromyography (EMG) techniques, in this study the function of abdominal muscles after lumbar extensor fatigue was investigated by ultrasound imaging technique.Materials and Methods: Fifteen healthy women participated in this experimental study. Abdominal muscles thickness was measured from the lateral abdominal wall (Transverse abdomen (TrA), Internal oblique abdomen (IO), External oblique abdomen (EO)) using ultrasound imaging technique before and after the back extensor muscles fatigue protocol in upright standing with and without axial loading equal to 25% of the participants’ body weight. Repeated measure ANOVA was used to test the main effects of the load and back extensor muscle fatigue on the thickness of the abdominal muscles.Results: Although, symmetric axial loads equal to 25% of each participant weight had no significant effect on the thickness of abdominal muscles, back extensor muscles fatigue increased IO thickness significantly (P=0.009).Conclusion: The results showed that abdominal muscles response changes with back extensor muscles fatigue. By increasing the thickness of abdominal muscle, the stability of the spine could be maintained.

The purpose of this study was to investigate both relative muscle activity levels and ratios of local to global muscle activity in health (normal lumbar lordose) and hyperlordose groups, during prone bridging stabilization exercise on stable and labile surfaces. Twenty-five healthy volunteers’ males were recruited from a convenience sample of collage students and divided to 2 groups. Surface electromyography activity were recorded from the abdominal muscles – rectus abdominis (RA), external oblique (EO) and internal oblique-transverse abdominis (IO-TA) – while performing prone bridge on the matt as well as on a Swiss ball and normalized to maximum voluntary isometric contraction (MVIC). The results were analyzed by t-test. In both groups during the prone bridge the addition of a Swiss ball resulted in significant increased myoelectric activity in the RA, EO and IO-TA muscles (P<0.05). Furthermore, the ratios of local to global abdominal muscle activity (IO-TA/RA and IO-TA/EO) were about 1 in normal lumbar lordose group on both surfaces. However, these ratios in hyperlordose group were about 1.5 principally on the Swiss ball. Results of the study suggest that prone bridge on a Swiss ball when compared with a matt is possible to be an useful exercise to restoration of the patterns correct contractions of abdominal muscles, particularly local muscles in hyperlordose group.

Up until now it was considered that the abdominal and hip extensor muscles weakness is the cause of pelvic anterior tilt and lumbar spine curvature rate (LSCR) increase. But it became dubiousness by some of recent research. The aim of the current study was determine the relationship between abdominal and hip extensor muscles strength with LSCR. This research accomplished on 90 healthy and un-athlete men. The average age, weight and stature of the men were 21.9±1.79 year, 70.44±10.54kg, and 176.86±6.07cm. LSCR, abdominal, and hip extensor muscles strength was measured by flexible ruler, double leg lowering test (DLLT) and digital dynamometer respectively.Collective data were analyzed using descriptive statistic and correlation between parameters. The outcome did not indicate a significant relationship between the muscles strength and LSCR (0.11). Also coefficient of correlation between right foot extensor muscles strength with LSCR and left foot extensor muscles strength with LSCR was 0.07,0.00 respectively. On the base of collected data, it seems that the muscle strength and weakness (abdominal and hip extensors) cannot be considered as only factor of lumbar curvature variation.