Background: We believe that the M. levator ani plays little or no role in obstructed defaecation, and that the concept of "paradoxical" puborectalis muscle activity is misleading. The main aim of the study was to investigate the function of the pubococcygeal muscle during simulated defaecation and to compare this with the electromyographic activity of the puborectal muscle.
Methods and results: In a prospective electromyographic study of 18 women (average age 53 years) with obstructive defecation disorder the activity of the pubococcygeal muscle and the puborectal muscle was investigated at rest, during contraction and straining. The control group consisted of 18 healthy women with an average age of 54 years. The function of the pubococcygeal muscle and the puborectal muscle was largely the same in both, study and control group. No statistically significant differences in the amplitude were found between the two groups at rest during contraction and maximum strain.
Conclusion: We therefore conclude that the increase in activity of the voluntary muscle of the pelvic floor observed on electromyography during defaecation does not indicate automatically a pathologic condition but is a possible functional state at this moment.