Transabdominal Ultrasound Measurement of Pelvic Floor Muscle Activity When Activated via a Transversus Abdominis Muscle

Aims of Study This study aimed to investigate the relationship of pelvic floor muscle and transversus abdominis (TA) muscle activity during a pelvic floor (PF) muscle contraction. Sapsford et al (1) investigated this relationship using EMG and found there to be consistent co-contraction between these two muscles. Due to this finding, it has been hypothesised that the pelvic floor muscles can be trained indirectly via the transversus abdominis muscle. This is despite the fact that randomised controlled trials have shown that specific training of the pelvic floor muscles is effective in the treatment of stress urinary incontinence (2,3). It has also been shown that a strong pelvic floor contraction is required for effective closure of the urethral sphincter (4). However, a transversus abdominis contraction is a moderate strength, stabilising contraction. To understand the activity of the pelvic floor muscles when performing abdominal tightening of the deep abdominal muscles, transabdominal ultrasound was used to measure the displacement of the pelvic floor muscles, a reflection of a contraction, during this manoeuvre. Transabdominal diagnostic ultrasound has previously been shown to be a valid and reliable measure of pelvic floor muscle activity (5).It was hypothesised that the pelvic floor muscles can be activated more strongly when instructed specifically to contract the pelvic floor rather than indirectly via the transversus abdominis muscle, as measured by a greater displacement of the pelvic floor when imaged on ultrasound.