What is the Knack and why does it work to prevent urine leakage?

In Pelvic Floor Dysfunction, Urinary Incontinence by Lisa ThompsonLeave a Comment

By: Lisa Thompson, PT, DPT

The saying “getting the knack of it” refers to acquiring a skill to perform a specific task. In the world of pelvic floor rehabilitation, the Knack refers to performing a pelvic floor muscle contraction prior to an increase in intra abdominal pressure. This technique is most commonly used to prevent stress urinary incontinence (SUI), such as when a person experiences leakage of urine with coughing and sneezing. We use the term the Knack to describe this voluntary, preliminary muscle contraction to hone in on the fact that the skill of coordination is the most important component of this activity. The strength of the muscle contraction can play a role in the success of the technique but the timing of the action really determines how successful a person will be at preventing leakage.

Lets first dive into a brief discussion of SUI so that we can better understand why and how the Knack works. Stress urinary incontinence occurs when an increase in intra abdominal pressure exceeds the capacity of our continence maintaining systems, one of which is the pelvic floor musculature, and leakage of urine ensues. Dysfunction of the pelvic floor can include muscles that are too tight, muscles that are weak, and/or muscles that lack motor control (more on motor control a bit further down). It is important to make an appointment with a pelvic floor physical therapist to determine which of these impairments could be contributing to your SUI. It is also important to note that the Knack is not a pelvic floor strengthening program, it is a specific technique to be used only during the exact moment before a cough or sneeze. It does not require you to perform kegels during the day outside of the precise moment before leakage occurs, and specifically I would advise against a regimen that includes regular kegels unless your pelvic floor PT has assessed you and determined that a pelvic floor strengthening program is right for you. More often than not most people would actually benefit from pelvic floor relaxation exercises so it is important to recognize that the Knack is a skill to be used only immediately before that cough or sneeze, and should be followed up with diaphragmatic breathing and pelvic floor relaxation techniques.

During a cough or sneeze, the force of increased intra abdominal pressure bears down on our bladder, urethra, and pelvic floor muscles. This is where a properly timed pelvic floor muscle contraction, the Knack, can come into play. Picture a garden hose running along the ground spouting water. If you wanted to stop the water from coming out of the hose you could step on it, pinching the house shut and preventing more water from exiting. Now picture the same hose laying on top of a trampoline, if you step on the hose now it will not be pinched shut because both the hose and the trampoline will move under the weight of your foot, and the water will continue to flow. In this analogy the hose is your urethra, the ground or trampoline is your pelvic floor, and your foot is the increased intra abdominal pressure bearing down from the force of a cough or sneeze. With a properly functioning pelvic floor, your body will automatically perform a preliminary pelvic floor muscle contraction immediately prior to the cough or sneeze so that the increased intra abdominal pressure will press down on the urethra closing it against a firm pelvic floor to maintain continence. With a dysfunctional pelvic floor, your body is not performing that preliminary pelvic floor muscle contraction automatically so when the increased pressure comes from the cough or sneeze both the urethra and the pelvic floor are displaced inferiorly (as with the trampoline analogy) so the urethra is not pinched shut and leakage occurs.

In the absence of your body performing this preliminary pelvic floor muscle contraction automatically, you can perform the Knack to voluntarily contract those pelvic floor muscles. A study by Ben Ami et al1 discovered that the most effective verbal instruction for correctly contracting the pelvic floor muscles was asking participants to “squeeze your anus.” That said, it is important to recognize that many people perform pelvic floor muscle contractions incorrectly, even after adequate verbal instructions. Therefore, it is important to have this skill assessed by a physical therapist to ensure that you are performing the contraction correctly. Once you and your PT have determined that you are contracting those pelvic floor muscles properly, then the emphasis should be on timing. You need to contract those muscles right before that increase in intra abdominal pressure, if you perform the Knack too soon the muscles may start to fatigue and lose power and if you perform it too late you may not have given those muscles enough time to perform a maximal contraction to meet that increased intra abdominal pressure as it bears down on your urethra and pelvic floor.

The efficacy of performing the Knack has been demonstrated in a study by Miller et al. titled “A Pelvic Muscle Precontraction Can Reduce Cough‐Related Urine Loss in Selected Women with Mild SUI.2” The study revealed that within one week of learning the Knack, where patients were instructed to contract their pelvic floor muscles one second before they cough, subjects leaked 98.2% less with a medium cough and 73.3% less with a deep cough (see Figure 1, reproduced from the study below). No increase in pelvic floor muscle strength was found during the one week time period. This reinforces the notion that the skill of properly learning the timing of the Knack, rather than improving pelvic floor muscle strength, is an important and effective component in reducing SUI with coughing.

Figure 1. The effect of the Knack on the total volume of urine leaked in three separate medium coughs (left) and three separate deep coughs (right) at 1‐week follow‐up. Each line joins total leakage in each of the 27 women observed without the Knack (denoted by “w/o Knack”) with that observed with using the Knack (denoted “w/Knack”).

Following performing the Knack you’ll want to do some diaphragmatic breathing. This will provide a gentle stretch to those pelvic floor muscles that were tightened during contraction. Diaphragmatic breathing also helps to improve motor control, which is your ability to initiate and direct muscle function and voluntary movements. By learning to better control these muscles with relaxation you’ll improve your coordination and have better success with the Knack. This post is meant to give you a quick summary and how to for performing the Knack, but now that you’re aware of how this technique could help you it’s important to go see a physical therapist. Your PT will help to determine the underlying cause of your stress urinary incontinence, check your form with the Knack, and determine what other interventions you’ll benefit from to come up with a more permanent fix for your leakage.

If you would like to come see us, please visit www.pelvicpainrehab.com/locations to find which office is closest to you.

References:

  1. Ben Ami, N, Dar, G. What is the most effective verbal instruction for correctly contracting the pelvic floor muscles?. Neurourology and Urodynamics. 2018; 37: 2904– 2910. https://doi-org.ucsf.idm.oclc.org/10.1002/nau.23810
  2. Miller, J. M., Ashton‐Miller, J. A. and DeLancey, J. O. (1998), A Pelvic Muscle Precontraction Can Reduce Cough‐Related Urine Loss in Selected Women with Mild SUI. Journal of the American Geriatrics Society, 46: 870-874. doi:10.1111/j.1532-5415.1998.tb02721.x

 

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