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 lowerlevels 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.
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