Pelvic floor muscle activity in different sitting postures in continent and incontinent women.

OBJECTIVE

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).

DESIGN

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.

SETTING

A research laboratory.

PARTICIPANTS

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

INTERVENTIONS

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.

RESULTS

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).

CONCLUSIONS

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