This post was written by H&W instructor Allison Ariail PT, DPT, CLT-LANA, BCB-PMD. Allison will be instructing the Pelvic Floor Level 1 course Boston this October.
Several weeks ago some of my fellow faculty members and I were discussing the resting tone of the pelvic floor. These days we take it for granted that we know there is constant low-level activity in the pelvic floor and anal sphincter in order to provide continence. However, how did this information come about? I took it upon myself to do some research to find out the beginnings of this knowledge. What I found was interesting and thought I would share.
In the late 1940’s and early 1950’s the belief was held that the pelvic floor and external anal sphincters were inactive at rest, like other striated muscle throughout the body. Activity was believed to be initiated by afferent impulses from the rectal ampulla and anal canal. In 1953 Floyd and Walls found activity in the external anal sphincters at rest, even during sleep. In 1962 Parks, Porter, and Melzak published a study examining the pelvic floor muscles and the external anal sphincters using electromyography recordings. They also found activity in these muscles at rest. They hypothesized the activity was maintained by spinal reflex. These researchers looked at the activity in a healthy population, a paraplegic population, and a population that had undergone a rectal excision. When examining the paraplegic population (all subjects had complete SCI injuries above L3), they did identify activity of the pelvic floor at rest.