Pelvic floor and abdominal muscle interaction: EMG activity and intra-abdominal pressure

Pelvic floor muscle exercises prescribed for the treatment of incontinence commonly emphasize concurrent relaxation of the abdominal muscles. The purpose of this study was to investigate the interaction between individual muscles of the abdominal wall and the pelvic floor using surface and intramuscular electromyography, and the effect of their action on intra-abdominal pressure. Four subjects were tested in the supine and standing positions. The results indicated that the transversus abdominis (TA) and the obliquus internus (OI) were recruited during all pelvic floor muscle contractions. It was not possible for these subjects to contract the pelvic floor effectively while maintaining relaxation of the deep abdominal muscles. A mean intra-abdominal pressure rise of 10 mmHg (supine) was recorded during a maximum pelvic floor muscle contraction. These results suggest that advice to keep the abdominal wall relaxed when performing pelvic floor exercises is inappropriate and may adversely affect the performance of such exercises.