In October I had the privilege of presenting at the International Pelvic Pain Society’s annual meeting. During one of the presentations, a discussion ensued regarding the term contracture. The discussion was centered on whether or not the pelvic floor could ever be in a state of contracture. Given the confusion that was evident during this discussion, I thought a review of the muscle physiology associated with skeletal muscle contracture would be useful to our membership.
First, one should review the definition of contracture. Central to the definition is that a muscle or group of muscles remains in a persistent state of shortening to the point that complete range of motion of the muscle is limited and is resistant to stretching. Kendall et al defines a contracture as a marked decrease in muscle length where the range of motion in the direction of elongation of the muscle is markedly limited. Of course there are neuromuscular and ischemic pathological conditions where contractures can develop. Contractures associated with pathological conditions are usually considered irreversible.
An additional skeletal muscle phenomenon is the length-tension curve of muscle. The maximal force generated by a muscle contraction is when the muscle is at some midpoint in its range of motion. A muscle that is too short or too long will have a decreased force generation. Therefore, a muscle in a state of contracture will be weak when assessed for strength.
Given the definitions above, can the pelvic floor be in a state of contracture? The pelvic floor, with its supportive function, is considered a postural muscle composed of predominately slow twitch muscle fibers. Slow twitch muscle fibers trigger more easily and are capable of sustained contraction therefore are more inclined to become shortened and tight. Even though there are fast twitch muscle fibers within the pelvic floor muscles it is possible that they can be transformed from fast twitch to slow twitch. The neural impulse transmitted by the nerve conditions the fiber type. A contracture develops slowly but is maintained by constant continued neural stimulation. Postural muscles are known to shorten in response to stress. With pain or a constant sense of urinary urge, there is psychological stress but there is also the physical response of protective guarding. Guarding is the additional recruitment of the pelvic floor in response to pain or to inhibit urge. Initially there will be active shortening, but it will lead to a shortening of the muscle(s) without any electrical activity.
Therefore, it appears that the pelvic floor should respond as any other skeletal muscle in the body, and is capable of developing a reversible contracture. The next question to answer is how best to evaluate the pelvic floor for contracture – is it short and weak or long and weak?
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Article by Rhonda Kotarinos on behalf of the ICS Physiotherapy Committee