Sitting posture affects pelvic floor muscle activity in parous women: an observational study.

QUESTION Do different sitting postures require different levels of pelvic floor and abdominal muscle activity in healthy women? DESIGN Observational study. PARTICIPANTS Eight parous women with no pelvic floor dysfunction. OUTCOME MEASURES Bilateral activity of pelvic floor muscles (assessed vaginally) and two abdominal muscles, obliquus internus abdominis and obliquus externus abdominis, during three sitting postures. RESULTS There was a significant increase in pelvic floor muscle activity from slump supported sitting (mean 7.2% maximal voluntary contraction, SD 4.8) to both upright unsupported sitting (mean 12.6% maximal voluntary contraction, SD 7.8) (p = 0.01) and very tall unsupported sitting (mean 24.3% maximal voluntary contraction, SD 14.2) (p = 0.004). Activity in both abdominal muscles also increased but did not reach statistical significance. CONCLUSION Both unsupported sitting postures require greater pelvic floor muscle activity than the supported sitting posture.