Original article| Volume 89, ISSUE 9, P1741-1747, September 2008

Pelvic Floor Muscle Activity in Different Sitting Postures in Continent and Incontinent Women


      Sapsford RR, Richardson CA, Maher CF, Hodges PW. Pelvic floor muscle activity in different sitting postures in continent and incontinent women.


      To determine whether resting activity of the pelvic floor muscles (PFMs) and abdominal muscles varied in different sitting postures in parous women with and without stress urinary incontinence (SUI).


      PFM and abdominal muscle activity was recorded in 3 sitting postures: slump supported, upright unsupported, and very tall unsupported. Spinal curves were measured in slump supported and upright unsupported.


      A research laboratory.


      Women (N=17) with a history of vaginal delivery, 8 who were symptomatic of SUI and 9 who were asymptomatic.


      Not applicable.

      Main Outcome Measures

      Electromyographic activity of (1) the resting PFM recorded per vaginam with surface electrodes and (2) superficial abdominal muscles using surface electrodes. Changes in spinal curves were measured with a flexible ruler.


      Electromyographic activity of the PFM increased significantly from slump supported to upright unsupported postures in both groups (P<.001) but with lower levels of activity in women with SUI (P<.05). PFM activity increased further in very tall unsupported sitting in comparison with slump supported sitting (P<.001). Obliquus internus abdominis electromyographic activity was greater in upright unsupported than in slump supported sitting (P<.05), and electromyographic activity of other abdominal muscles was greater in very tall unsupported than slump supported. Women with SUI had a trend for greater activity in the abdominal muscles in upright unsupported than asymptomatic women. Asymptomatic women had a greater depth of lumbar lordosis in upright unsupported sitting than women with SUI (P=.04).


      More upright sitting postures recruit greater PFM resting activity irrespective of continence status. Further investigation should consider the effect of sitting posture in rehabilitation.

      Key Words

      List of Abbreviations:

      ANOVA (analysis of variance), BMI (body mass index), PFM (pelvic floor muscle), SUI (stress urinary incontinence)
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