Evaluation of female pelvic- floor muscle.pdf

Evaluation of Female Pelvic-Floor

Muscle Function and Strength

Evaluation of pelvic-floor muscle (PFM) function and strength is

necessary (1) to be able to teach and give feedback regarding a

woman’s ability to contract the PFM and (2) to document changes in

PFM function and strength throughout intervention. The aims of this

article are to give an overview of methods to assess PFM function and

strength and to discuss the responsiveness, reliability, and validity of

data obtained with the methods available for clinical practice and

research today. Palpation, visual observation, electromyography, ultra-

sound, and magnetic resonance imaging (MRI) measure different

aspects of PFM function. Vaginal palpation is standard when assessing

the ability to contract the PFM. However, ultrasound and MRI seem to

be more objective measurements of the lifting aspect of the PFM.

Dynamometers can measure force directly and may yield more valid

measurements of PFM strength than pressure transducers. Further

research is needed to establish reliability and validity scores for

imaging techniques. Imaging techniques may become important clin-

ical tools in future physical therapist practice and research to measure

both pathophysiology and impairment of PFM dysfunction. [Bø K,

Sherburn M. Evaluation of female pelvic-floor muscle function and

strength. Phys Ther. 2005;85:269–282.]

Key Words: Evaluation, Function, Measurement, Pelvic-floor muscles, Reliability, Strength, Validity.

Kari Bø, Margaret Sherburn

Physical Therapy . Volume 85 . Number 3 . March 2005

269

Physical therapists need to be aware

U rinary incontinence is defined by the Interna-

of the advantages and disadvantages

tional Continence Society (ICS) as the com-

plaint of any involuntary leakage of urine. 1

Urinary incontinence is more common in

women than in men and affects women of all ages.

Prevalence rates vary between 9% and 72% of women

aged 17 to 79 years living in the community. 2 The most

common type of urinary incontinence in women is stress

urinary incontinence (SUI), defined as the complaint of

involuntary leakage on effort or exertion, or on sneezing

or coughing. 1 Urinary incontinence is a socially embar-

rassing condition, causing withdrawal from social situa-

tions and reduced quality of life. 3,4 Stress urinary incon-

tinence may be an important barrier to regular physical

and fitness activities in women. 5–7 This withdrawal may

threaten women’s general health and well-being because

regular moderate physical activity is important in pre-

vention of osteoporosis, obesity, diabetes, high blood

pressure, coronary heart disease, breast and colon can-

cer, and depression and anxiety. 8

of current technology to become less

reliant on manual palpation alone.

Kegel 9 was the first to report training of the pelvic-floor

muscles (PFM) to be effective in management of urinary

incontinence in women. In uncontrolled, nonrandom-

ized studies, he claimed an 84% cure rate in a variety of

incontinence types. Since then, several randomized con-

trolled trials (RCTs) have supported the results of his

clinical series and have demonstrated that PFM training

is more effective than no treatment or placebo treatment

for SUI. 10 –15 Cure rates, measured as

The PFM form the floor of the pelvic basin and help

maintain continence by actively supporting the pelvic

organs and closing the pelvic openings with their ante-

rior and cephalad action when contracting. 17 The PFM

comprise the pelvic diaphragm muscles (pubococcy-

geus, puborectalis, and iliococcygeus, together known as

the levator ani), which can be referred to as the deep

layer of the PFM; the urogenital diaphragm muscles

(ischiocavernosus, bulbospongiosus, and transversus

perinei superficialis, together known as the perineal

muscles), which can be referred to as the superficial

layer of the PFM; and the urethral and anal sphincter

muscles (Figs. 1, 2). The PFM are encased in fascia,

which is connected to the endopelvic (parietal) fascia

surrounding the pelvic organs and which also assists in

Figure 1.

The pelvic-floor muscles form the floor of the pelvis and a structural

support for internal organs. Reprinted with permission from: Hahn I,

Myrhage R. Bekkenbotten: Bygnad, Funktion Och Traning . Goteborg,

pelvic organ support. 17–19 Although the deep and super-

ficial layers of the PFM comprise different anatomical

structures and innervation, clinically, they work as a

functional unit. The PFM normally contract simulta-

neously as a mass contraction, but the contraction

quality and contribution of the 2 layers may differ.

K Bø, PT, PhD, is Professor and Exercise Scientist, Norwegian University of Sport and Physical Education, PO Box 4014, Ullevål Stadion, 0806 Oslo,

Norway (kari.bo@nih.no). Address all correspondence to Dr Bø.

M Sherburn, PT, M Women’s Health, is Lecturer and Researcher, The University of Melbourne, School of Physiotherapy, Melbourne, Australia.

Dr Bø provided concept/idea/project design. Both authors provided writing.

270 . Bø and Sherburn

Physical Therapy . Volume 85 . Number 3 . March 2005

2 g of leakage on

pad weigh tests after PFM training, vary between 44%

and 67% in RCTs comparing PFM training with

untreated controls or other treatment modalities. 13,14,16

vascular plexi, and intact ligaments and fascia support-

ing the bladder and urethra in their optimal position

during an increase in abdominal pressure. 27,28 If factors

other than the function of the PFM are the cause of

incontinence (eg, if urethral ligaments are totally rup-

tured during childbirth), PFM training may be unsuc-

cessful. However, because the PFM are untrained in

most people, training these muscles has a great potential

for improvement, and well-functioning PFM may com-

pensate for other factors unrelated to function.

Figure 2.

Inferior view of the pelvic-floor muscles, showing the pelvic diaphragm

(levator ani muscles) and urogenital diaphragm (perineal muscles).

Muscle strength can be defined as the maximal force that

a muscle can generate and is often referred to as the

weight the muscle can lift once, or the one repetition

maximum (1RM). 29 When assessing muscle strength, the

person being tested is asked to attempt to perform a

maximum voluntary contraction of the specific muscle.

This force can be measured by different instruments,

each with its own qualities. Pelvic-floor muscle training

may be beneficial for pelvic-floor dysfunctions other

than urinary incontinence (eg, fecal incontinence, blad-

der outlet obstruction, pelvic organ prolapse, pain,

sexual disorders). However, to date, there is evidence

from RCTs and systematic reviews to support PFM train-

ing for women with stress and mixed urinary inconti-

nence only. 30

Correct action of the PFM has been described as a

squeeze around the pelvic openings and an inward lift. 9

Measurement of the PFM muscle action becomes com-

plicated by its diaphragmatic form and its attachments to

the endopelvic fascia and pelvic organs.

The International Classification of Impairments, Disabilities,

and Handicaps (ICIDH) , 31 lately changed to International

Classification of Functioning, Disability and Health (ICF) , 32 is

a World Health Organization (WHO)–approved system

for classification of health and health-related states.

According to this system, the causes of a nonoptimally

functioning pelvic floor (eg, muscle and nerve damage

after vaginal birth) can be classified as the pathophysio-

logical component. A nonfunctioning PFM (reduced

force generation, incorrect timing or coordination) is

the impairment component, and the actual leakage is a

disability. How it affects the woman’s quality of life and

participation in fitness activities is an activity and partic-

ipation component.

In people without urinary incontinence, the PFM con-

tract simultaneously with, or precede, the increase in

abdominal pressure as an unconscious automatic

co-contraction. 20,21 A voluntary contraction is a simulta-

neous contraction of all muscles of the pelvic floor and

can be described as an inward movement and closure

around the pelvic openings. 22 Magnetic resonance imag-

ing (MRI) studies have demonstrated that, during vol-

untary contraction, the coccyx is moved ventrally toward

the pubic symphysis. Thus, the PFM contract concentri-

cally. 23 A true PFM contraction does not involve any

visible movement of the pelvis. Submaximal PFM con-

tractions may be performed as isolated contractions;

however, a maximum PFM contraction does not seem to

be possible without a co-contraction of the abdominal

muscles, 24 especially the transversus abdominis and

internal oblique muscles. 25 This abdominal contraction

can be observed as a small inward movement of the

lower abdomen.

Pelvic-floor muscle training aims to make changes in all

these components, and therefore all components should

be measured in physical therapy. The theory for strength

training is that, by changing PFM impairment (structural

support, timing, and strength of automatic contraction),

leakage will be stopped or markedly reduced. Thus, the

patient can function adequately and have enhanced

quality of life. DeLancey 33 suggested that cure rates after

PFM training could be even higher than shown so far, if

treatment could be based on a better understanding of

the pathophysiology associated with incontinence symp-

toms in individual patients . The purposes of this article

are to give an overview of evaluation methods available

to measure PFM function and strength and to discuss the

Normal continence is maintained by the complex inte-

gration of pelvic, spinal, and supraspinal factors. The

PFM are one of many factors contributing to the urethral

closure mechanism for continence and are the target

tissue in physical therapist management of incontinence

and other pelvic-floor dysfunctions. 26 Other important

pelvic factors for continence are contraction of smooth

and striated muscles within the urethral wall, patent

Physical Therapy . Volume 85 . Number 3 . March 2005

Bø and Sherburn . 271

advantages and disadvantages of the different methods

as they relate to clinical practice and research. For the

purposes of this article, PFM function is defined as ability

to perform a correct contraction, meaning a squeeze

around pelvic openings and an inward movement (lift)

of the pelvic floor, and PFM strength is defined as

maximum voluntary contraction, meaning that a person

attempts to recruit as many fibers in a muscle as possible

for the purpose of developing force.

the participants have had inadequate adherence. It is

likely that such programs have not followed muscle

training recommendations. 41

In general, when measuring muscle strength, 42 it can be

difficult to isolate the muscles to be tested, and many test

subjects need adequate time and instruction in how to

perform the test. In addition, the test situation may not

reflect the whole function of the muscles, and the

generalizability from the test situation to real-world

activity (external validity) has to be established. 38 There-

fore, when reporting results from muscle testing, it is

important to specify the equipment used, position dur-

ing testing, testing procedure, instruction and motiva-

tion given, and the parameters that are tested (eg, ability

to contract, maximum force generation, duration of

contraction). When testing the PFM, additional chal-

lenges are present because muscle action and location

are not easily observable.

Methods

A computerized search was conducted in PubMed with

the terms “pelvic floor”/“pelvic-floor muscles”/“pelvic

muscles” AND “measurement”/“evaluation”/“assess-

ment,” with the limitation of English language. In addi-

tion, a hand search of the abstract books of the Interna-

tional Continence Society annual meetings from 1987 to

2004 and the World Confederation of Physical Therapy

meetings from 1991 to 2004 was conducted.

The main reasons for physical therapists to conduct

high-quality measurement of PFM function and strength

are:

Measurement Tools to Evaluate PFM Function

and Strength

Methods for evaluating PFM function and strength can

be categorized as:

1. Without proper instruction, many women are unable

to volitionally contract these muscles on demand

because the PFM are situated at the floor of the pelvis

and are seldom used consciously. Several studies 9,34 –37

have shown that more than 30% of women do not

contract their PFM correctly at their first consulta-

tion, even after thorough individual instruction. The

most common error: contracting the gluteal, hip

adductor, or abdominal muscles instead of the PFM.

Some women also stop breathing or try to exaggerate

inspiration instead of contracting the PFM. Some

studies 36,37 have demonstrated that many women

strain, causing PFM descent, instead of actively

squeezing and lifting the PFM upward. For proper

contraction of the PFM, it is mandatory that women

receive precise training with appropriate monitoring

and feedback. Hay-Smith et al 30 found that, of the 43

RCTs they reviewed, only 15 stated that a correct PFM

contraction was checked before training began.

1. Methods to measure ability to contract (clinical obser-

vation, vaginal palpation, ultrasound, MRI, electro-

myography [EMG]).

2. Measures to quantify strength (manual muscle test by

vaginal palpation, manometry, dynamometry, cones).

These methods measure different aspects of PFM activ-

ity, anterior and cephalad movement, squeeze pressure,

and electrical activity. All of these methods have their

place in physical therapist evaluation, but all have their

limitations. Measurement of PFM performance is an

evolving science, which is changing as new technologies

become available.

Ability to Contract

Clinical observation. Observation of a correct PFM con-

traction can be done clinically, 9 by ultrasound, 43– 45 or

with dynamic MRI. 23,46 In 1948, Kegel described obser-

vation of a correct PFM contraction as squeeze around

the urethral, vaginal, and anal openings and an inward

lift that could be observed at the perineum. 9,22 Shull

et al 47 stated that, by clinical observation, a person is

generally observing superficial perineal muscles. From

this observation, however, it can be assumed that the

levator ani muscles are responding similarly due to their

co-contraction with the superficial perineal muscles.

However, to be certain, more than external observation

of the skin must be undertaken.

2. In intervention studies evaluating the effect of PFM

training, the training is the independent variable

meant to cause a change in the dependent variable,

SUI. 38 Thus, measurement of PFM function and

strength before and after training is important to

determine whether the intervention has made chang-

es. 13,39 Even in the presence of tissue pathology

(eg, neuropathy), if there is no change in PFM

function or force development after a training pro-

gram commensurate with that pathology, the training

program has been of insufficient dosage (intensity,

frequency, or duration of the training period) 40 or

272 . Bø and Sherburn

Physical Therapy . Volume 85 . Number 3 . March 2005

resonance imaging can be conventional (2-dimensional

image acquisition), ultrafast image acquisition, or

3-dimensional image acquisition. 56 Bø et al, 23 using

dynamic MRI, could not confirm displacement of 2 to

4 cm of the PFM estimated by Kegel after vaginal

palpation in a supine position. 22 With the subjects in a

sitting position, a mean inward lift of the PFM of

10.8 mm (SD

7.2–15.3) was visualized with the subjects

positioned supine. 59 Further testing of responsiveness,

reproducibility, and validity of data obtained with these

methods needs to be done, particularly to understand

the implications of subject position on the different

displacement values, but there is consensus that both

ultrasound and MRI should be considered an investiga-

tional imaging technique in the evaluation of female

urinary incontinence and pelvic-floor dysfunction. 56

Ultrasound is increasingly being used clinically because

this technology is becoming more economically available

to physical therapists.

Figure 3.

Most physical therapists use vaginal palpation to evaluate and give

feedback on ability to contract the pelvic-floor muscles.

Vaginal palpation. This is the technique currently used

by most physical therapists to evaluate a correct PFM

contraction and was first described by Kegel as a method

to evaluate PFM function. 9,22 He placed one finger in the

distal one third of the vagina and asked the woman to lift

inward and squeeze around the finger. Kegel did not use

this method to measure PFM strength. He used vaginal

palpation to teach women how to contract their PFM

and classified the contraction qualitatively as correct or

not correct. For measuring PFM strength, he developed

the “perineometer,” a pressure manometer, which mea-

sured the ability of the PFM to develop vaginal squeeze

pressure. 9

EMG. Electromyography can be used to measure the

electrical activity of skeletal muscles and is a direct

representation of the outflow of motoneurons in the

ventral horn in the spinal cord to the muscles as a result

of either voluntary or reflex PFM contraction. Electro-

myographic measurement can be conducted with either

surface or intramuscular electrodes. 60,61 Surface elec-

trodes are recommended to measure the activity of

large, superficial muscles, whereas the use of intramus-

cular electrodes (needle or wire) is the method of choice

to detect activity from muscles that are small or located

deep within the body (eg, the PFM). 60 In clinical prac-

tice, however, surface electrodes on a vaginal probe are

most commonly used due to the high sensitivity of the

perineal region and skills required for using wire or

needle electrodes (Fig. 5).

Van Kampen et al 48 reported that since Kegel first

described vaginal palpation as a method to evaluate PFM

function, more than 25 different vaginal palpation meth-

ods have been developed. Some examiners use one

finger, and others use 2 fingers. Worth et al 49 and Brink

et al 50 have evaluated pressure, duration, muscle “rib-

bing,” and displacement of the examiner’s finger in a

specific scoring system.

Several types of apparatus and different techniques of

surface EMG, 62– 64 wire EMG, 21,25,65 and concentric nee-

dle EMG 66–68 have been used to measure PFM activity. In

general, the number of activated motor units increases

with increasing force when the muscle force is low,

whereas frequency of firing of motor units increases at

high force levels. It is reasonable, therefore, to expect

that electrical activity may represent the level of force

developed by the muscle. 60 However, Turker 60 recom-

mended that researchers be cautious about using the

EMG information as the absolute measure of force

because most muscles give nonlinear responses.

Turker 60 also stated that comparison of single motor

unit data among and within subjects on different occa-

sions is highly unlikely, but that it is possible to compare

firing and synaptic characteristics of motor units that

There has been no systematic research to determine the

best method of vaginal palpation to assess the ability to

contract. This may be because, in the context described

here, vaginal palpation is used only to determine quali-

tatively whether or not there is a muscle contraction

(Fig. 3).

Ultrasound and MRI. More recently, real-time diagnos-

tic ultrasound and MRI have been used to evaluate PFM

action during contraction. 23,43– 49,51–55 Ultrasound can be

performed either with the probe placed suprapubically

or at the perineum (curved-array ultrasound probe, 3.5

and 5 MHz, and vaginal probe, 7.5 MHz) or with the

probe inserted into the vagina or rectum (linear or

end-firing probe, 5 and 7.5 MHz) 56 –58 (Fig. 4). Magnetic

Physical Therapy . Volume 85 . Number 3 . March 2005

Bø and Sherburn . 273

6.0) was measured by MRI. This finding

corresponds with results from a recent study using

ultrasound where a mean lift of 11.2 mm (95% confi-

dence interval

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