The effect of abdominal and pelvic floor muscle activation patterns on urethral pressure.

PURPOSE: Urethral pressure increases during voluntary pelvic floor (PF) muscle contractions in healthy women. As PF and abdominal muscle activity is coordinated, this study aimed to determine whether specific abdominal muscle actions also change urethral pressure. METHODS: Urethral pressures were measured in seven healthy women during lower abdominal in-drawing, abdominal bulging and PF muscle contractions, with the bladder empty and filled to 250 ml. A repeated measures multiple analysis of variance compared vesical, rectal and urethral pressure changes between bladder volumes and the three tasks. RESULTS: Urethral pressures increased by a similar amount during PF muscle contractions and abdominal in-drawing (p = 0.94) and did not differ between bladder status. During abdominal bulging, urethral pressures decreased by 12.6 (18.2) cmH2O (full bladder) and 18.1 (11.5) cmH2O (empty bladder) and were different from the other two manoeuvres (p < 0.001). CONCLUSIONS: This study shows that specific abdominal actions are associated with increased or decreased urethral pressures, consistent with strategies for continence and voiding.

The effect of abdominal and pelvic floor muscle activation on urine flow in women.

INTRODUCTION AND HYPOTHESIS: Interruption of urine flow during micturition has been used as an assessment of ability to voluntarily contract the pelvic floor muscles (PFM). However, the PFM are also activated during specific abdominal manoeuvres. This study aimed to assess the effect of similar abdominal manoeuvres on urine flow and compare this with the effect of PFM contraction. METHODS: Eight healthy women, of mixed parity, contracted the abdominal muscles and the PFM during urine flow on separate occasions. Differences in urine flow were compared using paired t tests. RESULTS: All participants were able to interrupt the urine stream using both muscle activation patterns. There was no difference in the time taken to interrupt urine flow (p = 0.78) between the two patterns. CONCLUSIONS: These data provide evidence that specific abdominal muscle manoeuvres influence urethral closure in continent women, and this is probably mediated by concurrent activation of PFM during the abdominal task.

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.

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.