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Neurourology and Urodynamics 35:457–463 (2016)
Pattern of Activation of Pelvic Floor Muscles in Men Differs
With Verbal Instructions
Ryan E. Stafford,
1
James A. Ashton-Miller,
2
Chris Constantinou,
3
Geoff Coughlin,
4
Nicholas J. Lutton,
5
and Paul W. Hodges
1
*
1
The University of Queensland, Centre for Clinical Research Excellence in Spinal Pain, Injury and Health,
School of Health and Rehabilitation Sciences, Brisbane, Australia
2
Departments of Mechanical and Biomedical Engineering, Institute of Gerontology, The University of Michigan,
Ann Arbor, Michigan
3
Department of Urology, School of Medicine, Stanford University, Palo Alto, California
4
Department of Urology, Royal Brisbane and Womens Hospital, Brisbane, Australia
5
Department of Colorectal Surgery, Princess Alexandra Hospital, Brisbane, Australia
Aims: To investigate the effect of instruction on activation of pelvic floor muscles (PFM) in men as quantified by
transperineal ultrasound imaging (US) and to validate these measures with invasive EMG recordings. Methods:
Displacement of pelvic floor landmarks on transperineal US, intra-abdominal pressure (IAP) recorded with a nasogastric
transducer, and surface EMG of the abdominal muscles and anal sphincter were recorded in 15 healthy men during sub-
maximal PFM contractions in response to different verbal instructions: ‘‘tighten around the anus,’’ ‘‘elevate the bladder,’’
‘‘shorten the penis,’’ and ‘‘stop the flow of urine.’’ In three men, fine-wire EMG recordings were made from puborectalis
and bulbocavernosus, and trans-urethral EMG recordings from the striated urethral sphincter (SUS). Displacement data
were validated by analysis of relationship with invasive EMG. Displacement, IAP, and abdominal/anal EMG were
compared between instructions. Results: Displacement of pelvic landmarks correlated with the EMG of the muscles
predicted anatomically to affect their locations. Greatest dorsal displacement of the mid-urethra and SUS activity was
achieved with the instruction ‘‘shorten the penis.’’ Instruction to ‘‘elevate the bladder’’ induced the greatest increase in
abdominal EMG and IAP. ‘‘Tighten around the anus’’ induced greatest anal sphincter activity. Conclusions: The
pattern of urethral movement measured from transperineal US is influenced by the instructions used to teach activation
of the pelvic floor muscles in men. Efficacy of PFM training may depend on the instructions used to train activation.
Instructions that optimize activation of muscles with a potential to increase urethral pressure without increasing
abdominal EMG/IAP are likely ideal. Neurourol. Urodynam. 35:457–463, 2016.#2015 Wiley Periodicals, Inc.
Key words: electromyography; male; pelvic floor exercise; prostatectomy; ultrasound imaging; urinary incontinence
INTRODUCTION
Incontinence is a common problem for men after surgical
removal of a cancerous prostate.
1
Pelvic floor muscle exercises
are the cornerstone of conservative management of mild/
moderate incontinence but the efficacy has been questioned.
2
A
surprising feature of clinical trials, which have mixed results,
3,4
is the lack of consistency of the instructions used to teach men
to activate the pelvic floor muscles; however, ‘‘tighten around
the anus’’ is common.
4,5
This instruction targets muscles that
are anatomically remote from the urethra, but may encourage
activation of puborectalis (PR) which can modify urethral
pressure, at least in women.
6
There are two limitations. First, no
studies have identified the optimal instructions to activate the
muscles of the pelvic floor that have the potential to influence
urinary continence in men. Second, there is limited evidence
regarding which muscle(s) of the array of striated muscle
complexes related to continence should be targeted with
intervention. Although the efficacy of a pelvic floor muscle
exercise program for treatment of incontinence after prosta-
tectomy is likely to depend on if and how the muscles of urinary
continence are activated, optimal methods to achieve activa-
tion have received limited attention.
Urinary continence in men is maintained by a combination of
active (activation of smooth and striated muscles) and passive
(e.g., elasticity of urethra, passive muscle tension, etc.) mecha-
nisms. In addition to smooth muscle (bladder neck and urethra),
multiple striated muscles influence urethral pressure. These
include the levator ani (LA) group of puborectalis, iliococcygeus,
and pubococcygeus,
7
the striated urethral sphincter (SUS),
8
and
the bulbocavernosus (BC).
7
Unlike smooth muscle, striated
muscles can be trained with voluntary activation. Training
generally targets strength, endurance, or timing of activation,
9
but the instructions used in clinical trials are variable (e.g.,
‘‘tighten around the anus’’
4,5
, ‘‘stop the flow of urine’’
10
or
‘‘elevate the penis’’
11,12
), or are not reported.
13,14
Recent studies
suggest deficits in activation of the LA (reduced bladder
elevation
15
) and SUS (reduced closure pressure
16
) in men with
incontinence. Furthermore, it is likely that an optimal training
program would be one that avoids excessive activation of
abdominal muscles and elevation of intra-abdominal pressure
Mickey Karram led the peer review process as the Associate Editor responsible for
the paper.
Funding for this study was provided by the Australian Research Council (ARC). PH
is funded by a Senior Principal Research Fellowship from the National Health and
Medical Research Council (NHMRC) of Australia.
Potential conflicts of interest: Nothing to disclose.
Correspondence to: Paul W. Hodges, Centre for Clinical Research Excellence in
Spinal Pain, Injury and Health, School of Health and Rehabilitation Sciences,
University of Queensland, Brisbane 4072, Queensland, Australia.
E-mail: p.hodges@uq.edu.au
Received 17 September 2014; Accepted 14 January 2015
Published online 1 March 2015 in Wiley Online Library
(wileyonlinelibrary.com).
DOI 10.1002/nau.22745
#2015 Wiley Periodicals, Inc.
(IAP), which would increase bladder pressure and challenge
continence. An understanding of how the activation of each
muscle is affected by different instructions is required.
This study investigated the effect of verbal instruction on
activation of pelvic floor and abdominal muscles. This was
achieved by estimation of muscle activation from urethral
movement acquired with transperineal ultrasound imaging
(US).
17
An additional aim was to use invasive electromyogra-
phy (EMG) recordings of the PR, SUS, and BC in a subset of
participants to validate the interpretation of urethral motion.
We hypothesized that verbal instructions which encourage the
recruitment of different muscle groups would achieve different
patterns of movement of anatomical landmarks
MATERIALS AND METHODS
Participants
Fifteen men aged 28–44 years with no history of urological or
neurological disease volunteered in response to advertisements
placed around the University, electronic newsletter, or within a
local paper. Men wereexcluded if they hada historyof pelvic floor
dysfunction, any urological dysfunction, any major respiratory or
neurological condition, or were more than 50 years of age. Six
participants were physiotherapists and had knowledge of the
pelvic floor. The remaining nine participants had no academic or
clinical training related to pelvic floor muscles.No participanthad
undergone previous training for the pelvic floor muscles. An a
priori power calculation using the mean (2.83mm) and SD
(1.34mm) of MU displacement reported in an earlier study of
healthy males
17
indicated that this sample size was sufficient to
detecta 25% differencein MU displacement between instructions
with an alpha of 5% and beta of 50%.Three participants
volunteeredfor an additionaldata collection session thatincluded
fine-wire EMG recordings of PR and BC,and trans-urethral surface
EMG recordings of SUS.
18
This component was added to validate
the measures madewith ultrasound imaging and the sample size
was limited due to the invasive nature of the methods.
Participants provided informed written consent and the Institu-
tional Medical Research Ethics Committee approved the study.
Measurement
All data were collected by the same assessor in a research
laboratory at the University of Queensland. Urethral displace-
ment was recorded using real-time US in video format with a
transducerplaced mid-sagittal on the perineum (M7C;Logiq9, GE
Healthcare, Sydney, Australia) as describedin detail elsewhere.
17
IAP was recorded with a naso-gastric pressure transducer (CTG-2,
Gaeltec Ltd, Isle of Skye, UK). EMG recordings were made from
the right obliquus externus (OE), internus abdominis (OI), and
rectus abdominis (RA) muscles using surface electrodes (Nor-
axon, Inc., Scottsdale, AZ, USA; 2 cm electrode spacing) with a
reference electrode (9160F, 3M Ltd, Glen Waverley, Australia)
over the iliac crest. Anal sphincter (AS) EMG was recorded from
nine participants with a rectal electrode (Neen, Huthwaite, UK).
Abdominal and AS EMG was filtered (10–1000 Hz), amplified
2000(Neurolog, Digitimer Ltd, Welwyn Garden City, UK), and
sampled at 2 kHz using a Power1401 and Spike2 software
(Cambridge Electronic Design, Cambridge, UK).
In three participants who volunteered for the additional
experiment, fine-wire electrodes (2 Teflon-insulated 75 mm
stainless steel wires [A-M Systems, Inc., Sequim, WA] inserted
into a 23Gx7 0mm hypodermic needle; 1 mm of insulation
removed; tips bent at 1 and 3 mm to form hooks) were inserted
into PR and BC with guidance of ultrasound and palpation by a
colorectal surgeon. Recordings of SUS EMG were made with a
transurethral catheter electrode as described elsewhere.
18,19
Fine-
wire/catheter EMG was filtered (10–2000 Hz), amplified 2000
(Neurolog, Digitimer Ltd, Welwyn Garden City, UK), and sampled
at 10 kHz using a Power1401 and Spike2 software (Cambridge
ElectronicDesign,Cambridge,UK).EMGandpressuredatawere
synchronized with ultrasound via a footswitch.
Experimental Protocol
Participants sat upright on a plinth (backrest reclined at 208
from vertical) with knees extended. Prior to commencement of
data collection, a brief period of familiarization was provided to
educate participants of the anatomy of the pelvic floor muscles
and how contraction of these muscles relates to movements
observed in the US image. No specific instructions were
provided regarding how to contract the muscles and partic-
ipants did not use the US for feedback of activation. Three
repetitions of voluntary pelvic floor contractions were per-
formed with guidance of specific verbal instructions to a
standardized effort of 3/10 on a modified Borg scale (‘‘no
activity’’ – zero, ‘‘maximal voluntary contraction’’ – ten).
Contractions were sustained for 3 sec and separated by
10 sec rest. Four instructions were tested: ‘‘tighten around
the anus’’—predicted to target the anal sphincter, ‘‘elevate the
bladder’’—predicted to target PR; ‘‘shorten the penis’’—pre-
dicted to target SUS; and ‘‘stop the flow of urine’’—predicted to
target SUS and PR. Instructions were performed in random
order and separated by 2 min rest. No instruction was
provided regarding the abdominal muscles.
Data Analysis
Individual frame images were exported from the US video
data and analyzed by a single assessor to calculate pelvic floor
landmark displacements associated with activation of SUS
(motion of the midurethra [MU]), PR (motion of the urethra-
vesical junction [dorsal – dUVJ; ventral – vUVJ] and anorectal
junction [ARJ]), and BC (compression of the bulb of the penis
[BP]) muscles, as described previously
17,20
(Fig. 1). The
experimenter was blinded to the identity of the participant
and the task during analysis. Displacement of each landmark
was averaged over the three repetitions for each instruction.
Averaged displacement data (for each anatomical location)
were normalized to the maximum value for each participant
across all instructions to optimize comparison between tasks.
The number of participants who demonstrated maximum
displacement (at each location) was determined for each
instruction, and expressed as a proportion of the number of
participants (n ¼15). Root-mean-square (RMS) EMG amplitude
and average IAP amplitude were calculated for 1 sec (500 ms
before and after the time of maximum landmark displacement
[Fig. 1]) in each task and expressed as a change from baseline
(1 sec prior to instruction). EMG and IAP data were averaged
over the three repetitions and normalized to the maximum
value across all instructions.
Statistical Analysis
To investigate the relationship between urethral displace-
ment (US imaging) and pelvic floor muscle activity (EMG), we
assessed the linear regression and Pearson’s coefficient of the
correlations between pelvic floor EMG (SUS, BC, and PR;
proportion of peak EMG across the tasks) and displacement
measured from US data (dorsal MU displacement, BP
458 Stafford et al.
Neurourology and Urodynamics DOI 10.1002/nau
compression, and UVJ elevation/ventral ARJ displacement;
proportion of the peak motion across the tasks).
Displacement of landmarks measured from US, change in AS
(n ¼9) and abdominal muscle EMG, and IAP amplitude were
compared between instructions using repeated measures
analysis of variance (ANOVA) (repeated measures; Instruction
[‘‘elevate the bladder,’’ ‘‘shorten the penis,’’ ‘‘stop the flow of
urine’’ vs. ‘‘tighten around the anus’’]). For trials in which AS
EMG was recorded, the ‘‘stop the flow of urine’’ instruction was
not used and thus omitted from the ANOVA model. Post-hoc
testing was performed with Duncan’s multiple range test. The
fine-wire/catheter EMG recordings (n ¼3) were also interpreted
but these data are presented individually and the pattern is
considered qualitatively without statistical analysis because of
the small number. Data for the main trial are presented as
mean 95% confidence intervals throughout the text and
figures.
RESULTS
In the three participants with fine-wire/catheter EMG
recordings, displacement at the five pelvic landmarks was
most strongly correlated (highest mean R
2
coefficients) with the
change in EMG activation of the appropriate muscle (SUS-MU;
PR-vUVJ/dUVJ/ARJ; BC-BP)(Table I). Figure 2 shows the relation-
ships between US and EMG for each participant and each
muscle across instructions.
Figure 3 shows the group data for US landmarks, IAP, and
surface EMG with each instruction. Displacement at the MU
differed between instructions (Main effect: P¼0.018). Peak MU
displacement was greater during ‘‘shorten the penis’’ than
‘‘elevate the bladder’’ (Post hoc: P¼0.017) and ‘‘tighten around
the anus’’ (Post hoc: P¼0.007) but not ‘‘stop the flow of urine’’
(Post hoc: P¼0.187). Instruction had no differential effect on
displacements at vUVJ (Main effect: P¼0.879), dUVJ (P¼0.910),
BP (P¼0.975), or ARJ (P¼0.815) that was systematic for the
group. Table II shows the proportion of participants who
demonstrated their largest displacement of the US landmarks
for each instruction. When these data were considered for
individual participants, the instruction that achieved the
greatest MU displacement for most participants was ‘‘shorten
the penis,’’ then ‘‘stop the flow of urine.’’ More variation was
observed for movements related to activation of PR. The
instruction that achieved maximum displacement for individ-
ual participants was distributed between ‘‘elevate the bladder,’’
‘‘shorten the penis,’’ and ‘‘stop the flow of urine.’’ Most
participants achieved maximum displacement of ARJ with
A
B C
BC EMG
PR EMG
SUS EMG
500 ms
PS
MU BP
vUVJ
ARJ
Bladder dUVJ
PS PS
D
Fig. 1. (A) Representative EMG recording of striated urethral sphincter (SUS), puborectalis (PR), and bulbocavernosus (BC) during voluntary contraction with
associated transperineal ultrasound images during rest (B) and contraction (C). Overlaid traces of the different pelvic floor structures from (B) and (C) are shown
in (D). Arrows and associated dashed lines on the EMG traces indicate the time point of image capture. In the contracted image (C), the initial position of each
point of interest is indicated by a shaded circle. EMG calib ration: BC – 200 mV, PR – 50 mV, SUS – 20 mV.
TABLE I. Pearson’s Coefficient of Determination (R
2
) (Range[Mean]) for
Pelvic Floor Landmark Displacement and Muscle Activity
Location SUS EMG PR EMG BC EMG
MU 0.51–1.00 (0.77) 0.05–0.58 (0.34) 0.26–0.53 (0.36)
vUVJ 0.21–0.56 (0.38) 0.58–0.96 (0.72) 0.17–0.86 (0.42)
dUVJ 0.13–0.37 (0.26) 0.57–0.72 (0.63) 0.12–0.82 (0.42)
ARJ 0.17–0.67 (0.43) 0.97–0.99 (0.98) 0.03–0.92 (0.38)
BP 0.05–0.67 (0.41) 0.01–0.97 (0.33) 0.84–0.96 (0.92)
Shading – indicates the pelvic landmark predicted to have the strongest
relationship to each muscle’s activity based on anatomy and predicted direction
of muscle shortening.
Pattern of Activation of Pelvic Floor Muscles 459
Neurourology and Urodynamics DOI 10.1002/nau
‘‘tighten around the anus’’ and ‘‘stop the flow of urine,’’ and
greatest movement at BP was most commonly observed for
‘‘tighten around the anus,’’ then ‘‘shorten the penis.’’ OI RMS
EMG and IAP amplitudes were higher with ‘‘elevate the
bladder’’ than ‘‘tighten around the anus’’ (Main effect: OI
EMG – P¼0.044; IAP – P¼0.004; Post hoc: OI EMG – P¼0.014;
IAP – P¼0.007), ‘‘shorten the penis’’ (Post hoc: OI EMG –
P¼0.038; IAP – P¼0.003) and ‘‘stop the flow of urine’’ (Post hoc:
OI EMG – P¼0.045; IAP – P¼0.003) and did not differ between
the latter three conditions (Post hoc all: P>0.05). No differences
were observed between instructions for RA and OE RMS EMG
amplitudes (Main effect all: P>0.05). AS EMG amplitude was
higher during instruction to ‘‘tighten around the anus’’ than
‘‘elevate the bladder’’ (Main effect: P¼0.041; Post hoc:
P¼0.034) and ‘‘shorten the penis’’ (Post hoc: P¼0.029).
Fine-wire/catheter EMG data from the additional experiment
are shown for the three participants in Figure 4. EMG
amplitudes generally follow the observations reported above
for US recordings in the larger experiment. Key observations are
SUS EMG was greatest with ‘‘shorten the penis’’ for 2/3
participants, greatest activation of PR with either the ‘‘shorten
the penis’’ or ‘‘elevate the bladder’’ instructions; and no
systematic pattern for BC. The main difference between the
fine-wire/catheter EMG and US data was that SUS EMG was
consistently lowest during ‘‘stop the flow’’ but this was
commonly associated with peak US displacement.
DISCUSSION
These data from healthy continent men show that verbal
instructionsused to encourage voluntarycontraction of different
pelvic floor musclesinfluences the pattern of urethralmovement
observed with US, and that these movements can determine the
degree of activation of specific muscles. These observations have
two key implications. First, if the aim of a pelvic floor exercise
program is to optimize activation of SUS with limited increase in
IAP, this is best achieved with the instruction to ‘‘shorten the
penis’’ or ‘‘stop the flow or urine.’’ Second, the relationship
between movement on US and EMG provides evidence for the
validity of interpretation of activity of specific pelvic floor
muscles from motion of pelvic landmarks. This supports the
potential clinical utility of this non-invasive method.
Optimal Instructions to Train Muscles of Continence in Men
Clinical trials of pelvic floor exercise for treatment of
incontinence after prostatectomy use a variety of instructions
to encourage patients to contract pelvic floor muscles, including
‘‘tighten aroundthe anus,’’
4,21
‘‘elevate the scrotum,’’
22
and ‘‘stop
flow of urine.’’
10,23
The present data suggest that outcome of
instructions differs and some may be better than others for
several reasons. First, instructions that emphasize dorsal
movement/retraction of the penis (‘‘shorten the penis’’) or that
Fig. 2. Relationship between EMG activation and displacement at the appropriate anatomical location for three participants. Different shapes are used for
each participant. Each data point for a participant refers to the response for a different instruction. Lines represent the best linear fit of the data with the
coefficient of determination (R
2
) shown for each. Relationship between dorsal urethra-vesical junction and puborectalis omitted due to similarity with that
shown for the ventral urethra-vesical junction. SUS, striated urethral sphincter; PR, puborectalis; BC, bulbocavernosus; MU, mid-urethra; UVJ, ventral urethra-
vesical junction; ARJ, ano-rectal junction; BP, bulb of penis; and prop. peak, proportion of the peak value.
460 Stafford et al.
Neurourology and Urodynamics DOI 10.1002/nau
Fig. 3. Mean (SD) amplitudes of movement, EMG, and IAP displayed as a proportion of the peak value across the four instructions. RA, rectus abdominis; OE,
obliquus externus; OI, internus abdominis; IAP, intra-abdominal pressure; MU, mid-urethra; vUVJ, ventral urethra-vesical junction; dUVJ, dorsal urethra-
vesical junction; ARJ, ano-rectal junction; and BP, bulb of penis. Differences between instructions (P<0.05) are indicated with an asterisk.
TABLE II. Proportion of Participants With the Greatest Amplitude of Displacement at Each Pelvic Landmark in Response to Each Instruction
Location ‘‘Elevate the bladder‘‘ ‘‘Shorten the penis‘‘ ‘‘Stop the flow of urine‘‘ ‘‘Tighten around the anus‘‘
MU 6.7% 53.3% 40.0% 0.0%
vUVJ 26.7% 26.7% 26.7% 20.0%
dUVJ 33.3% 26.7% 26.7% 6.7%
ARJ 13.3% 20.0% 33.3% 33.3%
BP 20.0% 26.7% 20.0% 33.3%
MU, mid-urethra; vUVJ, ventral aspect of the urethra-vesical junction; dUVJ, dorsal aspect of the urethra-vesical junction; ARJ, ano-rectal junction; BP, bulb of the
penis.
Pattern of Activation of Pelvic Floor Muscles 461
Neurourology and Urodynamics DOI 10.1002/nau
target contraction related to urethral closure (‘‘stop the flow of
urine’’) encourage activation of the SUS. Second, anal-focused
instruction (‘‘tighten around the anus’’) targets activation of the
anal sphincter muscle, and although there is co-concomitant
activation of the musclesthat can affect the urethra (PR and SUS),
activation of those muscles was less than for other instructions.
Third, the instruction that emphasized ‘‘elevation’’ caused a
counter-productive increase in abdominal muscle activity and
IAP that was greater than the other instructions. This would
increase demand on the continence mechanism.
The present results provide a basis to re-examine the recent
systematic review of pelvic floor exercise for treatment of post-
prostatectomy incontinence that reported inconsistency of
outcomes between trials and an overall interpretation of lack of
efficacy.
2
It is plausible that the variability in results between
seemingly similar clinical trials might be influenced by the
strategies used to train the muscular mechanisms for urinary
continence. An extrapolation of the present findings is that
trials that used the instruction ‘‘interrupt the flow of urine’’
have a greater probability of success (e.g.,
10,23
) than trials that
focus on anal-based instructions, feedback, or stimulation.
4,24
Although there are examples where this distinction is
supported, that is not always the case (i.e., poor outcome
with ‘‘urethral’’ instructions
25
and good outcome with ‘‘anal-
focused’’ instructions
26
). However, a factor that prevents
determination of the potential influence of specific instructions
on the outcomes of pelvic floor muscle training is that
treatment efficacy is also likely to be influenced by the targeted
feature of muscle function (e.g., strength, endurance, timing of
activation) and potential differences in patient phenotypes.
20
Further studies are required to determine whether better
outcomes can be achieved with instructions tailored to the
male continence mechanism.
Interpretation of Muscle Activity From Displacement of
Landmarks in Transperineal Ultrasound Images
To overcome the issue of invasiveness of direct EMG
recordings from the pelvic floor muscles, we estimated
activation from movement of landmarks on transperineal US.
Interpretation of movements was based on the motion
expected from muscle shortening.
20
In this study, motion
that was consistent with ‘‘shortening’’ was observed with each
instruction and the relationships between urethral displace-
ment and EMG were strongest for the anatomically appropriate
comparisons. That is, movement at MU by SUS activation,
movement at ARJ/UVJ by PR activation.
Although we observed a moderate linear relationship
between EMG and displacement with low effort contractions,
this relation will not be straightforward and will be dependent
on contraction type. Studies of other muscles show a non-linear
relationship during isometric contractions, with greater short-
ening during low-level contractions explained by tendon
stretch.
27
During eccentric contraction, the muscle would
lengthen despite activation, and interpretation of activity
from US would be impossible. In the pelvic floor, interpretation
will be complicated and the potential for shortening will
depend on many factors including IAP.
28
Despite these issues,
under the appropriate conditions, the technique provides a
valid measurement of muscle activation that would otherwise
require invasive techniques.
Limitations
Although participants were instructed to perform efforts of
similar intensity across instructions, we cannot be certain this
was achieved. This would not be possible to confirm from EMG
of any individual muscle as all tasks involved a different
pattern of muscle activation. The additional study involved few
participants because of the highly invasive nature of the EMG
recording techniques. Although normalization of EMG ampli-
tude to maximum voluntary activation is recommended, the
generally poor volitional control of pelvic floor muscles
29
precludes the reliable performance of maximum contraction by
verbal instruction, hence, the analysis strategy used. All
measurements were performed during static contraction in
siting, whereas leakage episodes often occur during dynamic
upright activities such as coughing. Whether physical activity
“Shorten
Penis”
BC
“Elevate
Bladder”
“Stop
Flow”
Participant 1
Participant 2
Participant 3
0
1
PR
“Shorten
Penis”
“Elevate
Bladder”
“Stop
Flow”
SUS
0
1
Fig. 4. EMG amplitudes of the striated urethral sphincter (SUS), puborectalis (PR), and bulbocavernosus (BC) muscles during three different verbal instructions:
‘‘shorten the penis,’’ ‘‘elevate the bladder,’’ and ‘‘stop the flow of urine.’’ Data are presented as a proportion of the peak EMG/displacement across tasks.
462 Stafford et al.
Neurourology and Urodynamics DOI 10.1002/nau
and posture affect the outcome of verbal instruction requires
exploration. Despite the small sample size, consistent relation-
ships between EMG amplitude and movement were observed.
Implications for Clinical Populations
These data have potential clinical utility for management of
men with incontinence but interpretation is not straight-
forward. It remains unclear how anatomical changes from
prostatectomy affect urethral dynamics and stiffness and this
may affect the relationship between urethral movement and
EMG. Further, concomitant activation of abdominal muscles
during pelvic floor muscle contraction may be more prevalent
in men with incontinence, as shown in women.
30
This would
increase IAP and challenge continence. It is necessary to
determine which aspect of muscle activation is most important
to train in men with incontinence and whether this differs
between patient phenotypes.
The optimal instructions to activate pelvic floor muscles are
likely those that induce the greatest amplitude of pelvic floor
muscle shortening with minimal increase in abdominal muscle
activity and IAP. From the current data, the best instruction to
shorten SUS is ‘‘shorten the penis’’ or ‘‘stop the flow of urine.’’ If
the anal sphincter is targeted, ‘‘tighten around the anus’’ would
provide the most optimal activation. As instructions to ‘‘elevate
the bladder’’ induced the largest increase in OI EMG and IAP, this
may not be ideal unless the intervention aims to increase
continence demand. Bladderbase movement occurred with each
instruction and didn’t differ between them, indicating similar
activation of PR. The optimal instruction for PR may be best
determined by the instruction that limits the increase in IAP.
Overall, these data show that verbal instructions can elicit
different amplitudes of pelvic floor displacement at specific
locations, but one instruction does not achieve the same pattern
of activation for all men. The search for the optimal strategy
would be assisted by biofeedback from transperineal US imaging.
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