The impact of state of bladder fullness on tonic and phasic activation of the pelvic floor muscles in women

PurposeWe aimed to determine if state of bladder fullness affects pelvic floor muscle activation in healthy women without urogenital symptoms.Materials and methodsTwenty-three nulliparous, continent female participants were recruited to participate. Women were randomized to begin the protocol with either an empty (EF) or a full (FE) bladder. Tonic and maximal voluntary pelvic floor muscle electromyographic activity were measured in three states of bladder fullness (empty, full and uncomfortably full). Electromyographic signal amplitudes were compared among bladder states using separate two-way repeated-measures analyses of variance including bladder state and test order as main effects as well as the interaction between bladder state and test order.ResultsTonic activity of the pelvic floor muscles was significantly higher in the full and uncomfortably full bladder states compared to when the bladder was empty (p < 0.005). Maximum voluntary electromyographic activation was unaffected by state of bladder fullness (p = 0.713).ConclusionsConsistent with studies in which the bladder was filled through saline infusion, these results suggest that tonic activity of the PFMs is higher when the bladder is full compared to when it is empty. However once the bladder is moderately full, tonic PFM activity does not increase with increases in bladder volume.