Evidence for increased tone or overactivity of pelvic floor muscles in pelvic health conditions: a systematic review.

OBJECTIVE: Pelvic floor muscle tone, which includes active and passive components, is argued to be increased in many pelvic health conditions, including those involving pain. This study systematically reviewed evidence for increased pelvic floor muscle tone in pelvic health conditions. DATA SOURCES: Electronic databases (PubMed, CINAHL, and Embase) were searched up to May 31, 2021. The search strategy included variants of pelvic and/or floor, muscle, and tone using keywords and Medical Subject Headings (MeSH) terms. STUDY ELIGIBILITY CRITERIA: Studies were included if they investigated increased tone of the pelvic floor muscle and reported measures of active or mechanical properties of the pelvic floor muscle in humans with any pelvic health condition, including pain, bowel, urogenital, or sexual dysfunctions. Studies of any design were included, except systematic and narrative reviews. Reference lists of studies, reviews, and book chapters were searched for additional studies. METHODS: Data were extracted using a standardized form, including measurement tool and outcome measure. Risk of bias was analyzed using a modified ROBINS-I (Risk of Bias In Non-randomized Studies - of Interventions) tool, and a score was allocated to determine whether the study provided "convincing" interpretation (comparison with condition-free control group, valid measure, no application issues). RESULTS: In total, 151 studies were included, reporting 8 different tools (electromyography, dynamometry, manometry, digital palpation, defecography, ultrasound, magnetic resonance imaging, other). The most common pelvic health condition was pelvic pain (n=16 conditions), followed by bowel and urogenital conditions. Most studies (57%) were cross-sectional. A healthy control group was infrequently included for comparison (27%). Unvalidated methods or methods applied in a manner that precluded convincing interpretation were common (94%). Of the 15 measurement tools that provided convincing evidence, 10 demonstrated greater tone in a pelvic health condition (all pain) compared with controls, and 5 showed no difference. CONCLUSION: Despite the large literature, few studies provide convincing evidence for increased tone/overactivity of pelvic floor muscles in pelvic health conditions. Interpretation is hampered by design and measurement issues. Terminology was often inaccurate. Few studies investigate male, transgender, and pediatric groups.

The influence of prostatectomy and body position on location and displacement of pelvic landmarks with pelvic floor muscle contraction.

AIMS: To compare pelvic floor muscle (PFM) anatomy and function (i) between pre- and post-prostatectomy in standing, and (ii) between sitting and standing postprostatectomy. METHODS: Thirty-two men scheduled to undergo a prostatectomy volunteered to participate. Transperineal ultrasound imaging was used to visualize five anatomical pelvic landmarks that have been validated to reflex anatomy and activity of PFMs (pubic symphysis, anorectal junction [ARJ], mid-urethra [MU], bulb of penis [BP], and urethrovesical junction [UVJ]). Both before and after prostatectomy, participants performed three submaximal PFM contractions in sitting and/or standing positions while ultrasound data were recorded. RESULTS: Postprostatectomy the UVJ location was more caudal and dorsal, the ARJ (puborectalis) vector was longer, the BP was more ventral than preprostatectomy, and these landmarks moved less ventrally with contraction. After prostatectomy, the MU, BP, and ARJ were more ventral in standing than sitting. The UVJ was more caudal and elevated more with contraction in standing than sitting after prostatectomy. CONCLUSION: These data demonstrate differences in the anatomy and mechanics of PFMs post- versus pre-prostatectomy, and between sitting and standing positions postprostatectomy. Findings are consistent with surgical changes to the bladder and urethral anatomy. Reduced passive support for the urethra and bladder are likely to may contribute to differences between standing and sitting postprostatectomy.

The relationship between pre- and postprostatectomy measures of pelvic floor muscle function and development of early incontinence after surgery.

AIMS: The aim of this study is to investigate (i) whether pelvic floor muscle (PFM) shortening can be enhanced by provision of training focused on striated urethral sphincter (SUS) with feedback before prostatectomy, (ii) whether PFM shortening during voluntary efforts and coughing before and after prostatectomy differs between men who do and do not report symptoms of urinary incontinence 1 month after prostatectomy, and (iii) the relationship between severity of incontinence after prostatectomy and features of pelvic floor function (muscle shortening) and urethral length before and after prostatectomy. METHODS: Sixty men referred for preoperative PFM training before radical prostatectomy participated. The International Continence Society Male Short Form questionnaire was used to quantify continence status. Transperineal ultrasound (US) imaging was used to record pelvic displacements related to activation of striated urethral sphincter, bulbocavernosus (BC) and puborectalis muscles during cough, "natural" voluntary contraction following pamphlet instruction, and trained voluntary contraction after formal physiotherapist instruction including US feedback. RESULTS: Pelvic floor displacements following training differed between continent and incontinent men; continent participants demonstrated increased SUS shortening after training (compared with "natural"), but no difference was observed between trained and "natural" contractions for incontinent participants. Motion at ano-rectal junction during cough was reduced following surgery, but voluntary and involuntary activation of SUS or BC was not consistently affected by surgery. CONCLUSIONS: Participants' capacity to improve function of the SUS with training appears related to postprostatectomy continence outcome.

Validation of shear wave elastography as a noninvasive measure of pelvic floor muscle stiffness.

OBJECTIVES: To investigate the validity of shear wave elastography (SWE) as a measure of stiffness of the puborectalis muscle by examining: (1) the relationship between puborectalis muscle stiffness and pelvic floor muscle (PFM) activation at different intensities; and (2) the relationship between puborectalis stiffness and pelvic floor morphometry during contractions at different intensities. METHODS: Fifteen healthy asymptomatic women performed 6-s isometric PFM contractions at different intensities (0, 10%, 20%, 30%, 50%, 75%, and 100% of maximal voluntary contraction) guided by intravaginal electromyography (EMG). Stiffness of the puborectalis muscle was measured using SWE by calculating the average shear modulus in regions of interest that contained puborectalis muscle fibers parallel to the transducer. Pelvic floor morphometry was assessed in the mid-sagittal plane using transperineal B-mode ultrasound imaging. Shear modulus, EMG (root mean square amplitude) and pelvic floor morphometry parameters were normalized to the value recorded during maximal voluntary contraction. To assess the relationship between stiffness and pelvic floor activation/morphometry, coefficient of determination (r2 ) was calculated for each participant and a group average was computed. RESULTS: Shear modulus and EMG were highly correlated (average r2 ; left 0.90 ± 0.08, right 0.87 ± 0.15). Shear modulus also strongly correlated with bladder neck position (x-axis horizontal coordinates relative to the pubic symphysis), anorectal rectal angle and position, levator plate angle, and antero-posterior diameter of the levator hiatus (average r2 : range 0.62-0.78). CONCLUSIONS: These findings support the validity of SWE to assess puborectalis muscle stiffness in females. Stiffness measures were strongly associated with PFM EMG and pelvic floor morphometry and may be used to indirectly assess the level of activation of the puborectalis muscle without the use of more invasive techniques. By overcoming limitations of current assessment tools, this promising noninvasive and real-time technique could enable important breakthrough in the pathophysiology and management of pelvic floor disorders.

The repeatability of measurements of male pelvic floor anatomy and function made from transperineal ultrasound images of healthy men and those before and after prostatectomy.

AIMS: To investigate the inter- and intratester repeatability of measurement of the location and displacement of five pelvic landmarks related to pelvic floor muscles with transperineal ultrasound (TPUS) imaging recorded from healthy men and men before and after prostatectomy. METHODS: TPUS images were selected from four different participant groups: healthy men, men awaiting prostatectomy, men 2 weeks after prostatectomy, and men 12 months after prostatectomy. On two separate occasions, two assessors with different levels of experience performed analysis of location and displacement of five pelvic landmarks in images made at rest and during voluntary contraction. A two-way mixed effects, single measurement, absolute agreement intraclass correlation coefficient (ICC) was used to investigate the repeatability. RESULTS: Intertester reliability of all locations at rest for all groups was excellent (ICCs > 0.8) except for the craniocaudal coordinate of the ventral urethrovesical junction for men 2 weeks postprostatectomy and the anorectal junction for men with a cancerous prostate. Intertester reliability of the measurement of landmark displacement was acceptable (>0.5) for the dorsoventral axis of motion but not for the craniocaudal axis of motion for all landmarks across all groups. The more experienced assessor was consistently more repeatable. More deeply placed landmarks were more often excluded from analysis and had poorer reliability. CONCLUSIONS: Analysis of TPUS images across clinical groups is repeatable for both location and displacement of pelvic landmarks related to pelvic floor muscles when measures are made twice. Analysis experience, landmark depth and optimization of ultrasound settings appear to be important factors in reliability.

Influence of body position on dynamics of the pelvic floor measured with transperineal ultrasound imaging in men.

AIMS: This paper aims to evaluate the feasibility of transperineal ultrasound imaging (TPUS) for visualizing the motion of pelvic landmarks associated with striated pelvic floor muscle contraction in men in standing; to compare the locations of pelvic landmarks between sitting and standing; and to compare the effects of different body positions on measures of pelvic floor muscle contraction. METHODS: Thirty-five men awaiting prostatectomy volunteered to participate. Participants performed three repetitions of submaximal pelvic floor contraction in sitting and again in standing. Movement of pelvic landmarks with contraction was recorded using an ultrasound imaging transducer placed on the perineum. RESULTS: The feasibility of TPUS in men in standing was demonstrated through the visualization of three out of four pelvic landmarks in more than 95% of images in the standing position. Analysis of pelvic landmarks and their respective relationships with muscle shortening demonstrated that the anorectal junction and urethrovesical junction were lower and the estimated length of puborectalis was shorter in standing than sitting. The mid-urethra (striated urethral sphincter) and anorectal junction (puborectalis) landmark displaced further cranially in standing than sitting. CONCLUSIONS: TPUS can be used to visualize three pelvic landmarks in men with cancerous prostates. Puborectalis is shorter at rest in standing than sitting, and elevation of the mid-urethra and the anorectal junction is more in standing than sitting. Together these findings indicate that feedback for pelvic floor muscle training is possible in both positions, but the position needs to be standardized for a comparative assessment.

Comparison of dynamic features of pelvic floor muscle contraction between men with and without incontinence after prostatectomy and men with no history of prostate cancer.

AIM: To compare features of pelvic floor muscle function between men with and without incontinence after prostatectomy and men with no history of prostate cancer. METHODS: The study included men with incontinence postprostatectomy (PPI; n = 20), continent men postprostatectomy (PPC; n = 23) and a control group (CC; n = 20). Transperineal ultrasound imaging recorded motion associated with contraction of the striated urethral sphincter (SUS), puborectalis (PR) and bulbocavernosus (BC) muscles during maximal voluntary contraction (MVC), submaximal efforts, evoked coughing and bearing down. Anatomical landmark displacements were compared between groups and receiver operating characteristics were calculated to determine the threshold displacements that best differentiated PPI and PPC. RESULTS: PPC demonstrated greater SUS, PR, and BC displacement than PPI during MVC (All: P < .01). During cough, PPC had less bladder neck descent (PR lengthening), and greater BC shortening (P = .003) than both PPI and CC. PPC also achieved greater SUS displacement (P = .025) than PPI during cough. The best discrimination between PPI and PPC was achieved when men exceeded threshold displacement for both SUS (≥4.1 mm) and PR (≥2.4 mm) during MVC. The urethral length was not different between PPC and PPI. CONCLUSIONS: Men who were continent postprostatectomy achieved greater shortening of the SUS, PR, and BC muscles than incontinent men during voluntary contractions and demonstrated better PR and BC function than control participants during coughing. The capacity to shorten the SUS ≥4.1 mm and the PR ≥2.4 mm best distinguished between PPI and PPC and might be a useful clinical target for conservative treatment programs.

Activity of Deep and Superficial Pelvic Floor Muscles in Women in Response to Different Verbal Instructions: A Preliminary Investigation Using a Novel Electromyography Electrode.

INTRODUCTION: Verbal instructions are used clinically to encourage activation of the pelvic floor muscles (PFM). Whether separate layers of PFM activate differently in response to instructions remains unknown. AIM: To test the hypotheses that (i) instructions that aimed to bias activity of a specific muscle layer would increase activation of the targeted layer to a greater extent than the other layer, (ii) activity of individual PFM layers would differ between instructions, and (iii) PFM activity would be symmetrical for all instructions. METHOD: PFM electromyography (EMG) was recorded using custom-designed surface electrodes in 12 women without PFM dysfunction. The electrode included 4 pairs of recording surfaces orientated to measure EMG from deep and superficial PFM on each side. 3 submaximal contractions were performed for 5 seconds in response to 7 verbal instructions. Root-mean-squared EMG amplitude was calculated for 1 second during the period when participants most closely matched the target activation level. A repeated-measures anova was used to test whether PFM EMG differed between instructions and between regions. The EMG increase of individual muscles relative to that of the reference muscle [deep/right PFM] was compared to no change with t-tests for single samples. MAIN OUTCOME MEASURE: PFM EMG amplitude. RESULTS: Superficial PFM EMG was greater than deep PFM for all instructions (P = .039). 2 instructions induced the greatest amplitude of EMG for the superficial PFM: "squeeze the muscles around the vaginal opening as if to purse lips of your mouth" and "draw the clitoris in a posterior direction" (P = .036). Asymmetry was found in the deeper PFM in 3 instructions designed to bias the superficial PFM. STRENGTH & LIMITATIONS: This preliminary study recorded activation of deep and superficial PFM layers in females with a custom-designed novel electrode. Some cross-talk of recording between muscle layers is possible but unlikely to impact the major findings. CONCLUSION: Verbal instructions used to teach PFM contractions can influence their pattern of activity. This study provides preliminary evidence that, in a selection of verbal instructions, the superficial PFM activates more than the deep PFM, and that the deep PFM can have asymmetrical activation. Aljuraifani R, Stafford RE, Hall LM, et al. Activity of Deep and Superficial Pelvic Floor Muscles in Women in Response to Different Verbal Instructions: A Preliminary Investigation Using a Novel Electromyography Electrode J Sex Med 2019;16:673-679.

Female striated urogenital sphincter contraction measured by shear wave elastography during pelvic floor muscle activation: Proof of concept and validation.

AIMS: Investigation of the function of the striated urogenital sphincter (SUS) is challenging because it is difficult to access and requires invasive measures. Ultrasound shear wave elastography (SWE) is a non-invasive real-time technique used to estimate tissue stiffness. As muscle stiffness can be used as an estimate of muscle force, SWE provides an opportunity to study contraction of the peri-urethral musculature. Validation of SWE to study SUS during functional tasks, such as pelvic floor muscle contractions, is required prior to application in clinical populations. METHODS: Ten healthy females (34[5] years) participated. Stiffness in a region expected to contain the SUS was quantified using SWE at rest and during a pelvic floor muscle contractions performed at 10%, 25%, and 50% of maximal voluntary contraction (MVC). Two repetitions were performed for 10 s. RESULTS: During contraction, stiffness increased in the region of the SUS in all participants and at all contraction intensities. Multiple regions of increased stiffness were detected, with 95.8% of regions situated ventral to the mid-urethra within the anatomical area of the SUS. The increase in stiffness was greater for 50% MVC than both 10% and 25% MVC contraction intensities (P < 0.01). CONCLUSIONS: Stiffness increased within the anatomical region of the SUS during voluntary pelvic floor muscle contractions with predictable response to changes in contraction intensity. These observations support the potential for ultrasound SWE to study SUS function non-invasively.

Postprostatectomy incontinence is related to pelvic floor displacements observed with trans-perineal ultrasound imaging.

AIMS: To investigate the relationship between post-prostatectomy incontinence and dynamic features of activation of specific pelvic floor muscles in addition to anatomical parameters of the urethra. METHODS: Forty-two men aged 66 (7) years (incontinent [N = 19] and continent [N = 23]) who had undergone prostatectomy participated. Transperineal ultrasound imaging was used to record sagittal images of pelvic structures during involuntary coughing and sustained maximal voluntary contractions. Imaging data were analyzed to calculate displacements of pelvic floor landmarks associated with activation of the puborectalis, striated urethral sphincter, and bulbocavernosus muscles. Anatomical features of functional urethral length and the resting position of the ano-rectal and urethra-vesical junctions were calculated. A principal component analysis and multiple logistic regression were used to consider which combinations of variables best distinguish between men with and without incontinence. RESULTS: Five principal components were identified that together explained 72.0% of the data. Two principal components that represented (i) striated urethral sphincter activation and (ii) bulbocavernosus and puborectalis muscle activation were significantly different between participants with and without incontinence. Together these components correctly identified 88.1% of incontinent men, with a specificity and sensitivity of 91.3% and 84.2%, respectively. Poor function of the bulbocavernosus and puborectalis muscles could be compensated by good striated urethral sphincter function, but the bulbocavernosus and puborectalis muscles had less potential to compensate for poor striated urethral sphincter function. CONCLUSIONS: Dynamic features of pelvic floor muscle activation, particularly shortening of the striated urethral sphincter during cough and voluntary contraction, are related to continence status after prostatectomy.

Application of shear-wave elastography to estimate the stiffness of the male striated urethral sphincter during voluntary contractions.

OBJECTIVES: To investigate whether increases in stiffness can be detected in the anatomical region associated with the striated urethral sphincter (SUS) during voluntary activation using shear-wave elastography (SWE); to identify the location and area of the stiffness increase relative to the point of greatest dorsal displacement of the mid urethra (i.e. SUS); and to determine the relationship between muscle stiffness and contraction intensity. SUBJECTS AND METHODS: In all, 10 healthy men participated. A linear ultrasound (US) transducer was placed mid-sagittal on the perineum adjacent to a pair of electromyography electrodes that recorded non-specific pelvic floor muscle activity. Stiffness in the area expected to contain the SUS was estimated via US SWE at rest and during voluntary pelvic floor muscles contractions to 5%, 10% and 15% maximum. Still image frames were exported for each repetition and analysed with software that detected increases in stiffness above 150% of the resting stiffness. RESULTS: Pelvic floor muscle contraction elicited an increase in stiffness above threshold within the region expected to contain the SUS for all participants and contraction intensities. The mean (SD) ventral-dorsal distance between the centre of the stiffness area and region of maximal motion of the mid-urethra (caused by SUS contraction) was 5.6 (1.8), 6.2 (0.8), and 5.8 (0.7) mm for 5%, 10% and 15% maximal voluntary contraction, respectively. Greater pelvic floor muscle contraction intensity resulted in a concomitant increase in stiffness, which differed between contraction intensities (5% vs 10%, P < 0.001; 5% vs 15%, P < 0.001; 10% vs 15%, P = 0.003). CONCLUSION: Voluntary contraction of the pelvic floor muscles in men is associated with an area of stiffness increase measured with SWE, which concurs with the expected location of the SUS. The increase in stiffness occurred in association with an increase in perineal surface electromyography activity, providing evidence that stiffness amplitude relates to general pelvic floor muscle contraction intensity. Future applications of SWE may include investigations of patient populations in which dysfunction of the SUS is thought to play an important role, or investigation of the effect of rehabilitation programmes that target this muscle.

Pattern of activation of pelvic floor muscles in men differs with verbal instructions.

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.

Pelvic floor muscle length changes with breathing in males: A preliminary report.

The study aimed to identify whether pelvic floor muscles modulate length with breathing, and if any length changes induced by breathing relate to abdominal cavity displacement and intra-abdominal pressure. To investigate these relationships, displacement of pelvic landmarks that related to pelvic floor muscle length using transperineal ultrasound imaging, breath volume, intra-abdominal pressure, abdominal and ribcage displacement, and abdominal and anal sphincter muscle electromyography were measured during quiet breathing and breathing with increased dead-space in ten healthy men. Pelvic floor muscle landmark displacement modulated with ribcage motion during breathing. This relationship was stronger for: i) motion of the urethrovesical junction (puborectalis muscle length change) than the mid-urethra landmark (striated urethral sphincter muscle length change), and ii) dead-space breathing in standing than dead-space breathing in supine or quiet breathing in standing. In most (but not all) participants, the urethrovesical junction descended during inspiration and elevated during expiration. Striated urethral sphincter length changes during the respiratory cycle was independent of intra-abdominal pressure. In summary, breathing involves pelvic floor muscle length changes and is consistent with the role of these muscles during respiration to aid maintenance of continence, lung ventilation and/or provision of support to the abdominal cavity. Clinicians who train pelvic floor muscles need to be aware that length change of pelvic floor muscles is expected with breathing.

Novel insight into the dynamics of male pelvic floor contractions through transperineal ultrasound imaging.

PURPOSE: Transperineal ultrasound imaging enables the minimally invasive assessment of pelvic floor muscle function. Although commonly used in women, the approach has rarely been reported in men. This approach has advantages because the midsagittal view visualizes a bony landmark and the entire urethral length. This allows investigation of the displacement of multiple points along the urethra and the unique mechanical actions of multiple muscles that could influence continence. We used a new transperineal ultrasound technique to compare the relative displacement of urethrovesical junction, anorectal junction and distal urethra during voluntary pelvic floor muscle contractions in continent men. MATERIALS AND METHODS: We performed measurement and comparison of urethral displacement at specific urethral regions in 10 continent men (age range 28 to 41 years). Measures made on 2-dimensional midsagittal plane ultrasound images included the displacements of specific points along the urethra. Anatomical considerations suggest that these are caused by contraction of the levator ani, striated urethral sphincter and bulbocavernosus muscles. Pearson's correlation coefficient was used to investigate the relationship between displacements of pairs of points. RESULTS: Data show individual variation in displacement of the distal urethra (striated urethral sphincter contraction) and urethrovesical junction (levator ani contraction). A strong inverse linear relationship (0.723) between displacements of these points indicates 2 alternative strategies of urethral movement. CONCLUSIONS: Transperineal ultrasound imaging allows the simultaneous investigation of multiple pelvic floor muscles by measuring urethral displacement. The data provide evidence of different but coordinated strategies of urethral displacement in men.

Activation of the striated urethral sphincter to maintain continence during dynamic tasks in healthy men.

AIMS: Function of the striated urethral sphincter (SUS) in men is debated. Current evidence is limited to electromyographic (EMG) recordings made with concentric needle electrodes in supine. Understanding of SUS function requires investigation of SUS EMG activity using new recording techniques in dynamic tasks. The aim of this study was to evaluate timing and amplitude of SUS EMG at rest and during dynamic tasks that challenge continence by increasing intra-abdominal pressure (IAP). METHODS: Investigative study of five healthy men aged 25-39 years. Measurements included SUS, anal sphincter (AS), and transversus abdominus (TrA) EMG, and IAP (recorded with a nasogastric pressure catheter). Participants performed four tasks that challenged postural control in standing (single and repetitive arm movement, stepping and load catching). RESULTS: IAP amplitude and SUS activity were linearly correlated during repetitive arm movement (R(2): 0.67-0.88). During stepping SUS EMG onset preceded the IAP increase, but followed it with rapid arm movements. When the trunk was loaded unpredictably onset of SUS generally followed the increase in IAP. The modest sample size meant only younger men were tested. Future studies might investigate healthy older men or those with certain pathologies. CONCLUSIONS: Data show that SUS activity increases proportionally with IAP. This provided evidence that SUS contributes to continence when IAP is increased, and that postural control of the trunk involves activation of this muscle.

Anal sphincter fatigue: is the mechanism peripheral or central?

AIMS: Striated muscles of continence appear to exhibit marked fatigue during voluntary efforts. This is counterintuitive considering the high proportion of slow twitch muscle fibers. One explanation is that fatigue is due to central, rather than peripheral mechanisms. Here we examined the contribution of reduced voluntary activation (central fatigue) to the decline in anal sphincter (AS) and elbow flexor muscle force during voluntary contractions. METHODS: Ten healthy subjects participated. Fatigue was induced using 10 maximal voluntary contractions sustained for 20 s. During each fatiguing contraction, transcranial magnetic stimulation (TMS) was delivered over the motor cortex at 5 s intervals. Central fatigue was assessed using the superimposed twitch force elicited by TMS. Peripheral fatigue was measured using brachial plexus (elbow flexors) or sacral plexus (AS) stimulation during contraction and at rest. RESULTS: Ability to maximally activate AS (75.9%) was less than for the elbow flexors at baseline (91.6%). Voluntary activation declined in both muscles, but the decline was greater in AS (AS 28%; elbow flexors 12%). There was no change in the amplitude of the twitch evoked by peripheral nerve stimulation in either muscle. CONCLUSIONS: AS exhibits a greater decline in voluntary activation during fatiguing contractions than elbow flexor muscles. This is not accompanied by peripheral changes, which implies central mechanisms are responsible. Thus, we conclude that AS is susceptible to central fatigue during maximal voluntary activations. We propose this may be a protective mechanism to conserve contractile potential of the anal sphincter for function.

A novel transurethral surface electrode to record male striated urethral sphincter electromyographic activity.

PURPOSE: Concentric needle and current transurethral surface recording techniques are unlikely to accurately record electromyography activity of the male striated urethral sphincter during dynamic tasks. Thus, we developed a novel transurethral surface electrode that could be fixed to the urethral mucosa with optimal orientation to record striated sphincter electromyography. MATERIALS AND METHODS: Four recording surfaces were placed at equal intervals circumferentially around the tip of a 6Fr pediatric urinary catheter. This configuration provides optimal electrode-to-muscle fiber orientation for differential amplification. The electrode was fixed by gentle suction via the urine ports. Intra-abdominal pressure was monitored with a gastric pressure transducer. Five healthy male subjects participated in the validation study. Electromyography recordings were made of voluntary and involuntary striated sphincter contractions to investigate the quality of recordings and electrode stability. Tasks included maximal voluntary contractions of the striated sphincter and intra-abdominal pressure, submaximal contractions, ramped intra-abdominal pressure efforts and voluntary coughs. RESULTS: Data indicated high quality electromyography recordings. Energy in the frequency spectrum was between 50 and 500 Hz, typical of human striated muscle surface electromyography. The median signal-to-noise ratio was 16.1 db (range 11.9 to 18.6) for striated sphincter maximal voluntary contractions. Motor unit action potentials could be discriminated during gentle contractions. Overlaid motor unit action potentials showed consistent morphology. Energy associated with motion artifact during a cough was less when suction was applied, indicating improved electrode stability. CONCLUSIONS: The new electrode provides high quality surface electromyography recordings of the male striated sphincter during dynamic tasks, such as coughing.

Novel insight into pressurization of the male and female urethra through application of a multi-channel fibre-optic pressure transducer: Proof of concept and validation.

PURPOSE: To confirm feasibility of recording pressure along the length of the urethra using a multi-sensor fibre-optic pressure catheter; to identify the spatial and temporal features of changes in pressure along the urethra at sites related to specific striated pelvic floor muscles; and to investigate the relationship between urethral pressures and activation of individual pelvic floor muscles estimated from ultrasound imaging. MATERIALS AND METHODS: Proof-of-concept study including one male (47 years old) and one female (33 years old). A multi-sensor fibre optic pressure catheter (10 mm sensor separation) was inserted into the urethra. Pressure data were recorded simultaneously with trans-perineal ultrasound imaging measures of pelvic floor muscle activity during sub-maximal and maximal voluntary contractions and evoked coughs. RESULTS: Pressure changes along the urethra were recorded in all tasks in both participants. Face validity of interpretation of pressure measures with respect to individual muscles was supported by correlation with ultrasound-measured displacements induced by the relevant muscles. Onset of pressure increase occurred in a distal to proximal sequence in the urethra of the male but not the female during voluntary contraction. Peak urethral pressures varied in location, timing and amplitude between tasks. Evoked cough induced in the greatest urethral pressure increase across all tasks for both participants. CONCLUSIONS: The high spatial resolution pressure catheter provide viable and valid recordings of urethral pressure in a male and female. Data provide preliminary evidence of sex differences in spatial and temporal distribution of urethral pressure changes.

Reconsideration of pelvic floor muscle training to prevent and treat incontinence after radical prostatectomy.

Urinary incontinence is common after radical prostatectomy. Pelvic floor muscle training provides a plausible solution. Although early trials provided promising results, systematic reviews have questioned the efficacy of this intervention. A major consideration is that most clinical trials in men have applied principles developed for pelvic floor muscle training for stress urinary incontinence in women, despite differences in anatomy between sexes and differences in the mechanisms for continence/incontinence. Literature regarding continence control in men has been conflicting and often based on erroneous anatomy. New understanding of continence mechanisms in men, including the complex contribution of multiple layers of striated pelvic floor muscles, and detailed consideration of the impact of radical prostatectomy on continence anatomy and physiology, have provided foundations for a new approach to pelvic floor muscle training to prevent and treat incontinence after prostatectomy. An approach to training can be designed to target the pathophysiology of incontinence. This approach relies on principles of motor learning and exercise physiology, in a manner that is tailored to the individual patient. The aims of this review are to consider new understanding of continence control in men, the mechanisms for incontinence after radical prostatectomy, and to review the characteristics of a pelvic floor muscle training program designed to specifically target recovery of continence after prostatectomy.

Task-specific differences in respiration-related activation of deep and superficial pelvic floor muscles.

The female pelvic floor muscles (PFM) are arranged in distinct superficial and deep layers that function to support the pelvic/abdominal organs and maintain continence, but with some potential differences in function. Although general recordings of PFM activity show amplitude modulation in conjunction with fluctuation in intra-abdominal pressure such as that associated with respiration, it is unclear whether the activities of the two PFM layers modulate in a similar manner. This study aimed to investigate the activation of the deep and superficial PFM during a range of respiratory tasks in different postures. Twelve women without pelvic floor dysfunction participated. A custom-built surface electromyography (EMG) electrode was used to record the activation of the superficial and deep PFM during quiet breathing, breathing with increased dead space, coughing, and maximal and submaximal inspiratory and expiratory efforts. As breathing demand increased, the deep PFM layer EMG had greater coherence with respiratory airflow at the frequency of respiration than the superficial PFM (P = 0.038). During cough, the superficial PFM activated earlier than the deep PFM in the sitting position (P = 0.043). In contrast, during maximal and submaximal inspiratory and expiratory efforts, the superficial PFM EMG was greater than that for the deep PFM (P = 0.011). These data show that both layers of PFM are activated during both inspiration and expiration, but with a bias to greater activation in expiratory tasks/phases. Activation of the deep and superficial PFM layers differed in most of the respiratory tasks, but there was no consistent bias to one muscle layer. NEW & NOTEWORTHY Although pelvic floor muscles are generally considered as a single entity, deep and superficial layers have different anatomies and biomechanics. Here we show task-specific differences in recruitment between layers during respiratory tasks in women. The deep layer was more tightly modulated with respiration than the superficial layer, but activation of the superficial layer was greater during maximal/submaximal occluded respiratory efforts and earlier during cough. These data highlight tightly coordinated recruitment of discrete pelvic floor muscles for respiration.