Purpose: Pelvic floor exercises are invaluable for regaining continence but mechanisms are not fully understood. To contribute to the understanding of these mechanisms we investigated the contraction sequence of superficial vs deep pelvic floor muscles in 6 positions in continent and incontinent women.
Materials and methods: The onset of contraction of the superficial and deep pelvic floor muscles was recorded by perineal and intravaginal surface electromyography in 32 continent and 50 incontinent women. The agreement between perineal and intravaginal recordings was calculated with the kappa statistic and the percent of agreement. Differences in onset between superficial and deep pelvic floor muscle contractions are reported as the median and IQR.
Results: Perineal and intravaginal electromyography recordings used to define the onset of muscle activity showed a high level of agreement. In the continent group the superficial muscles almost always contracted before the deep muscles in all 6 positions. In the incontinent group the reverse sequence was observed in 3 of 6 positions. Higher and less consistent time differences in the onset of contraction of the 2 muscle layers were found in incontinent vs continent women.
Conclusions: Contractions of the superficial and deep pelvic floor muscles can be recorded by intravaginal or perineal electrodes. A consistent contraction sequence can be found in continent women but it is lacking in incontinent women. This might be a possible explanation for incontinence. Including differentiated muscle contraction exercises in pelvic floor muscle exercise programs may further optimize treatment outcomes.