Evaluation of Pelvic Floor Muscle Strength Using Four Different Techniques

The aim of the study was to evaluate whether four different techniques were able to correctly measure pelvic floor muscle strength only. Sixteen volunteers performed a set of muscle contractions using the pelvic floor muscles (PFM) only, the abdominal muscles with and without PFM, gluteal muscles with and without PFM, adductor muscles with and without PFM and Valsalva maneuver with and without PFM. Pelvic floor muscle strength was evaluated by digital palpation, intravaginal EMG, pressure perineometry and perineal ultrasound. A “non-pelvic muscle induced” reading was defined as a significant increase even though the pelvic floor muscles were not contracted. Results were as follows: isolated abdominal muscle contraction: non-pelvic muscle induced readings in 3/8 women with EMG and in 3/8 with pressure perineometry; isolated gluteal muscle contraction: non-pelvic muscle induced readings in 1/2 women with EMG perineometry; isolated adductor muscle contraction: non-pelvic muscle induced readings in 6/11 women with EMG perineometry and in 2/11 women with pressure perineometry; Valsalva maneuver: non-pelvic muscle induced readings in 4/9 women with EMG perineometry and 9/9 women with pressure perineometry. It was concluded that EMG and pressure perineometry do not selectively depict pelvic floor muscle activity.     

Differences in muscle activation patterns during pelvic floor muscle contraction and Valsalva maneuver

AIMS: To investigate the different muscle activation patterns around the abdomino-pelvic cavity in continent women and their effect on pressure generation during a correct pelvic floor muscle (PFM) contraction and a Valsalva maneuver. METHODS: Thirteen continent women were assessed. Abdominal, chest wall, and PFM activity and vaginal and intra-abdominal pressure (IAP), were recorded during two tasks: PFM contraction and Valsalva whilst bladder base position was monitored on trans-abdominal ultrasound. A correct PFM contraction was defined as one that resulted in bladder base elevation and a Valsalva resulted in bladder base depression. RESULTS: Comparison of the mean of the normalized EMG activity of all the individual muscle groups was significantly different between PFM contraction and Valsalva (P = 0.04). During a correct PFM contraction, the PFM were more active than during Valsalva (P = 0.001). During Valsalva, all the abdominal muscles (IO (P = 0.006), EO (P < 0.001), RA (P = 0.011)), and the chest wall (P < 0.001) were more active than during PFM contraction. The change in IAP was greater during Valsalva (P = 0.001) but there was no difference in the change in vaginal pressure between PFM contraction and Valsalva (P = 0.971). CONCLUSIONS: This study demonstrates a difference in muscle activation patterns between a correct PFM contraction and Valsalva maneuver. It is important to include assessment of the abdominal wall, chest wall, and respiration in the clinical evaluation of women performing PFM exercises as abdominal wall bracing combined with an increase in chest wall activity may cause rises in IAP and PFM descent.     

Altered muscle activation patterns in symptomatic women during pelvic floor muscle contraction and Valsalva manouevre

AIMS: To investigate the muscle activation patterns of the abdomino-pelvic region used by incontinent women during a pelvic floor muscle (PFM) contraction and a Valsalva manouevre compared to healthy, asymptomatic subjects. METHODS: Thirteen incontinent (symptomatic) women, identified using ultrasound to be consistently depressing the bladder base during PFM contraction, and thirteen continent women (asymptomatic) able to perform an elevating PFM contraction were assessed using surface electromyography (EMG) of the PFM, abdominal and chest wall muscles and vaginal and intra-abdominal pressure (IAP) measurements during PFM contraction and Valsalva under ultrasound surveillance. RESULTS: There were no differences between groups in age, parity or BMI. There was a difference in muscle activation patterns between groups (P = 0.001). During PFM contraction the PFM were less active and the abdominal and chest wall muscles were more active in the symptomatic group. During Valsalva, the PFM and EO were more active in the symptomatic group but there was no difference in the activation of the other muscles between groups. There was a significant interaction (group x pressure) for change in IAP (P = 0.047) but no significant interaction for change in vaginal pressure (VP) (P = 0.324). CONCLUSIONS: The symptomatic women displayed altered muscle activation patterns when compared to the asymptomatic group. The symptomatic women were unable to perform a voluntary PFM contraction using a localized muscle strategy, instead activating all the muscles of the abdomino-pelvic cavity. The potential for muscle substitution strategies reinforces the need for close attention to specificity when prescribing PFM exercise programs.     

Pelvic floor muscle exercise for the treatment of female stress urinary incontinence: II. Validity of vaginal pressure measurements of pelvic floor muscle strength and the necessity of supplementary methods for control of correct contraction

The present investigation comprises three methodological studies concerning vaginal pressure measurements of pelvic floor muscle (PFM) strength. Vaginal pressure was measured by a balloon (6.7 ± 1.7 cm) connected by a catheter to a pressure transducer. The balloon was placed with the middle of the balloon 3.5 cm inside the introitus vagina. In fourty-seven women, mean age 44.9 years (24–64), observation of movement of the vaginal catheter during PFM contraction verified 7 inconclusive results from perineovaginal palpation and was the most valid way to distinguish between correct and incorrect PFM contraction. Vaginal pressure rise was obtained regardless of correct or incorrect PFM contraction, showing that vaginal pressure is not specific for PFM contraction. However, as the action of the PFM is elevation, a simultaneous inward movement of the vaginal catheter is present only during correct PFM contraction. Degree of influence of various muscle groups on vaginal pressure was investigated in 14 women using two different balloons, one having a silicone reinforcement of the tip. It was found that the median contraction value of muscles other than the PFM did not exceed contraction of PFM alone. No significant difference was observed using the two types of balloons. In three physical therapists EMG activity of the lower m. rectus abdominis was recorded during maximal PFM contractions. A rise in EMG activity always occurred during maximal contractions even if the women actively tried to relax the abdominal muscles. It is concluded that vaginal pressure measurement of PFM strength is valid with simultaneous observation of inward movement of the balloon catheter. Vaginal pressure rise due to simultaneous contraction of other muscles is probably not larger than pressure rise due to intended PFM contraction. Reinforced balloon tip will not change pressure recording, and rise in EMG activity of lower abdominal muscles seems unavoidable during maximal PFM contraction.     

Effect of abdominal and pelvic floor tasks on muscle activity, abdominal pressure and bladder neck

Introduction and hypothesis  

Although the bladder neck is elevated during a pelvic floor muscle (PFM) contraction, it descends during straining. This study aimed to investigate the relationship between bladder neck displacement, electromyography (EMG) activity of the pelvic floor and abdominal muscles and intra-abdominal pressure (IAP) during different pelvic floor and abdominal contractions.     

Relationship between abdominal and pelvic floor muscle activation and intravaginal pressure during pelvic floor muscle contractions in healthy continent women

AIM: Activation of the abdominal muscles might contribute to the generation of a strong pelvic floor muscle contraction, and consequently may contribute to the continence mechanism in women. The purpose of this study was to determine the abdominal muscle activation levels and the patterns of muscle activity associated with voluntary pelvic floor muscle (PFM) contractions in urinary continent women. METHODS: Fifteen healthy continent women participated. They performed three maximal contractions of each of the four abdominal muscles and of their PFMs while in supine. Abdominal and PFM activity was recorded using electromyography (EMG), and intravaginal pressure was recorded using a custom modified Femiscan probe. RESULTS: During voluntary maximal PFM contractions, rectus abdominus was activated to 9.61 (+/-7.42)% maximal voluntary electrical activity (MVE), transversus abdominus was activated to 224.30(+/-47.4)% MVE, the external obliques were activated to 18.72(+/-13.33)% MVE, and the internal obliques were activated to 81.47(+/-63.57)% MVE. A clear pattern of activation emerged, whereby the transversus abdominus, internal oblique, and rectus abdominus muscles worked with the PFM in the initial generation of maximal intravaginal pressure. PFM activity predominated in the initial rise in lower vaginal pressure, with later increases in pressure (up to 70% maximum pressure) being associated with the combined activation of the PFM, rectus abdominus, internal obliques, and transverses abdominus. These abdominal muscles were the primary source of intravaginal pressure increases in the latter 30% of the task, whereas there was little increase in PFM activation from this point on. The external oblique muscles showed no clear pattern of activity, but worked at approximately 20% MVE throughout the PFM contractions, suggesting that their role may be predominantly in postural setting prior to the initiation of intravaginal pressure increases. CONCLUSIONS: Defined patterns of abdominal muscle activity were found in response to voluntary PFM contractions in healthy continent women.     

Urethral pressure variations in women with neurourological symptoms: I. Relationship to urethral and pelvic floor striated muscle

Simultaneous urethrocystometry and electromyography (EMG) of the urethral and pelvic floor striated muscle were performed in 42 gynecological patients with neurourological symptoms. Their maximum urethral pressure varied between 20 and 124 cm H₂O. A correlation analysis was performed between the maximum urethral pressure and the integrated EMG of the urethral striated muscle and the pelvic floor striated muscle. The analyses were performed on results obtained in 1-min periods during bladder filling before first desire to void was reported, when first desire to void was reported, and when a strong desire to void was reported. In 21 patients no correlation was found between the urethral and pelvic floor striated muscle activity and the maximum urethral pressure at any stage of bladder filling. In the other 21 patients a correlation was found in at least 1 of the 3 stages. At all stages of bladder filling a correlation was found significantly more often between the maximum urethral pressure and the striated urethral muscle EMG than between the maximum urethral pressure and the striated pelvic floor muscle EMG. Thus, activity of the urethral striated muscle cannot be reliably studied in an EMG recording from the pelvic floor striated muscle. In the same patient, periods with a correlation could be succeeded by periods without a correlation. Thus, the urethral pressure variations may in the same patient sometimes be caused mainly by the urethral striated muscle and sometimes mainly by the urethral smooth muscle.     

Role of male pelvic floor muscles and anterior fibromuscular stroma in males on α1‐blocker treatment: A magnetic resonance imaging study

Dynamic motion of the pelvic floor muscles during voiding was analyzed using real‐time magnetic resonance imaging. To evaluate the contraction of the pelvic floor muscles, striated urethral sphincter distance, levator ani muscle thickness and anterior fibromuscular stroma distance were measured. The percent contraction of the striated urethral sphincter from before voiding to just before initiation of voiding was 14% in the normal group and 5% in the voiding dysfunction group. The percent contraction of the anterior fibromuscular stroma from before voiding to just before initiation of voiding was 11% in the normal group and 1% in the voiding dysfunction group; the percent contraction of the muscles was significantly greater in the normal group (P < 0.05). Striated urethral sphincter and anterior fibromuscular stroma contraction at initiation of voiding open the bladder neck and urethra. This plays an important role in the smooth initiation of voiding.     

The effect of abdominal and pelvic floor muscle activation on urine flow in women

Introduction and hypothesis

Interruption of urine flow during micturition has been used as an assessment of ability to voluntarily contract the pelvic floor muscles (PFM). However, the PFM are also activated during specific abdominal manoeuvres. This study aimed to assess the effect of similar abdominal manoeuvres on urine flow and compare this with the effect of PFM contraction.

Methods

Eight healthy women, of mixed parity, contracted the abdominal muscles and the PFM during urine flow on separate occasions. Differences in urine flow were compared using paired t tests.

Results

All participants were able to interrupt the urine stream using both muscle activation patterns. There was no difference in the time taken to interrupt urine flow (p?=?0.78) between the two patterns.

Conclusions

These data provide evidence that specific abdominal muscle manoeuvres influence urethral closure in continent women, and this is probably mediated by concurrent activation of PFM during the abdominal task.     

Urethral pressure variations in women with neurourological symptoms: III. Relationship to urethral wall venous plexus

Twenty-five women were investigated in order to find out if the urethral submucous venous plexus may influence urethral pressure variations. Urethral and bladder pressure were measured with a microtip transducer catheter. Electromyography (EMG) and integrated EMG from the urethral striated muscle were recorded using a concentric needle electrode. Blood volume in the urethral submucous venous plexus was measured with a urethral photopletysmograph probe. In 9 women without neurourological symptoms, during squeezing there was increased urethral striated muscle activity, increased urethral pressure and decreased blood volume. When they were asked to void the opposite was found. In 16 patients with marked urethral pressure variations a negative correlation was found between the maximum urethral pressure and the photopletysmograph tracing. In 7 of 8 patients a negative correlation was found also between the integrated EMG tracing and the photopletysmograph tracing, but a positive correlation was found between the maximum urethral pressure and the EMG of the urethral striated muscle. In 1 of the 8 patients no correlation was found between EMG activity and maximum urethral pressure and between EMG activity and the photopletysmograph tracing. The results demonstrate that the urethral venous plexus becomes emptied secondary to contractions of the urethral striated and/or smooth muscle and filled with blood secondary to relaxation of the same muscles. Hence, the urethral venous plexus does not influence the urethral pressure actively.     

Histochemical and contractile properties of striated muscles of urethra and levator ani of dogs and sheep

AIMS: To understand their possible importance in long- and short-term control of continence, some properties of the striated muscles of the urethra and pelvic floor (levator ani) of dogs and sheep were investigated, especially fiber types and contractile characteristics. MATERIALS AND METHODS: Striated muscles of urethra and levator ani of 29 male and 6 female dogs and 11 male and 6 female sheep were removed and cut into strips. Some strips were frozen and stained for ATPase at pH 9.4 and 4.3 for fiber typing; others were set up in an organ bath to study contractile responses to nerve stimulation. RESULTS: All muscles contained both type I (slow) and type II fibers, ranging from 97% type II in female greyhound urethra to 60% in female sheep levator ani. For each muscle, there were fewer type II muscles in sheep than in dog. The diameters of the urethral fibers were about 60% of the levator ani in dogs and 34% in sheep. Contraction of the urethral muscle was faster than for levator ani and declined to about 80% of the peak, 500 msec after the beginning of stimulation at 20 Hz. The levator ani contraction rose to a steady level as long as stimulation continued. CONCLUSIONS: Both the levator ani and urethral striated muscles contain slow and fast fiber types. The levator ani muscles are capable of sustained contraction with rapid onset which will produce long-term closure of the urethra. The circular urethral muscle contraction was faster but less well maintained.     

Women with SUI demonstrate motor control differences during voluntary pelvic floor muscle contractions

Introduction and hypothesis  To compare maximum abdominal and pelvic floor muscle (PFM) electromyographic (EMG) and intravaginal pressure (IVP) amplitudes and muscle activation patterns during voluntary PFM contractions between women with and without stress urinary incontinence (SUI). Methods  Twenty-eight continent women and 44 women with SUI performed single and repeated PFM contractions in supine. Surface EMG data were recorded simultaneously with IVP. Maximum EMG and IVP amplitudes and ensemble average IVP versus EMG curves were determined from the single contractions. Muscle activation timing was determined with cross-correlation functions from the repeated contractions. Results  The continent group produced higher PFM EMG amplitudes than the SUI group; there were no between group differences in IVP. The women with SUI delayed activating rectus abdominus. The IVP versus EMG curves’ shapes were similar between the groups, however the SUI group had higher abdominal muscle y-intercepts than the continent women. Conclusions  These findings suggest that women with SUI demonstrate altered motor control strategies during voluntary PFM contractions.     

Urethral sphincters response to cavernosus muscles stimulation with identification of cavernoso-urethral reflex

The functional activity of the urethral sphincters during cavernosus muscles' contraction at coitus has been poorly addressed in the literature. We investigated the hypothesis that cavernosus muscles' contraction affects reflex contraction of the urethral sphincters to guard against semen reflux into the urinary bladder or urine leakage from the bladder during orgasm and ejaculation. The electromyographic (EMG) response of the external (EUS) and internal (IUS) urethral sphincters to ischio- (ICM) and bulbo- (BCM) cavernosus muscle stimulation was studied in 15 healthy volunteers (9 men, 6 women, age 39.3 +/- 8.2 SD years). An electrode was applied to each of ICM and BCM (stimulating electrodes) and the 2 urethral sphincters (recording electrodes). The test was repeated after individual anesthetization of the urethral sphincters and the 2 cavernosus muscles, and after using saline instead of lidocaine. Upon stimulation of each of the 2 cavernosus muscles, the EUS and IUS recorded increased EMG activity. Repeated cavernosus muscles' stimulation evoked the urethral sphincteric response without fatigue. The urethral sphincters did not respond to stimulation of the anesthetized cavernosus muscles nor did the anesthetized urethral sphincters respond to cavernosus muscle stimulation. Saline infiltration instead of lidocaine did not affect the urethral sphincteric response to cavernosal muscle stimulation. Results were reproducible. Cavernosus muscles' contraction is suggested to effect EUS and IUS contraction. This action seems to be reflex and mediated through the 'cavernoso-urethral reflex.' Urethral sphincters contraction upon cavernosus muscles contraction during sexual intercourse presumably prevents urine leak from the urinary bladder to urethra, prevents retrograde ejaculation, and propels ejaculate from the posterior to the penile urethra. The cavernoso-urethral reflex can act a diagnostic tool in the investigations of patients with ejaculatory disorders.     

Co-activation of the abdominal and pelvic floor muscles during voluntary exercises

The response of the abdominal muscles to voluntary contraction of the pelvic floor (PF) muscles was investigated in women with no history of symptoms of stress urinary incontinence to determine whether there is co-activation of the muscles surrounding the abdominal cavity during exercises for the PF muscles. Electromyographic (EMG) activity of each of the abdominal muscles was recorded with fine-wire electrodes in seven parous females. Subjects contracted the PF muscles maximally in three lumbar spine positions while lying supine. In all subjects, the EMG activity of the abdominal muscles was increased above the baseline level during contractions of the PF muscles in at least one of the spinal positions. The amplitude of the increase in EMG activity of obliquus externus abdominis was greatest when the spine was positioned in flexion and the increase in activity of transversus abdominis was greater than that of rectus abdominis and obliquus externus abdominis when the spine was positioned in extension. In an additional pilot experiment, EMG recordings were made from the pubococcygeus and the abdominal muscles with fine-wire electrodes in two subjects during the performance of three different sub-maximal isometric abdominal muscle maneuvers. Both subjects showed an increase in EMG activity of the pubococcygeus with each abdominal muscle contraction. The results of these experiments indicate that abdominal muscle activity is a normal response to PF exercise in subjects with no symptoms of PF muscle dysfunction and provide preliminary evidence that specific abdominal exercises activate the PF muscles.     

Excitatory effect of propiverine hydrochloride on urethral activity in rats

Objectives: To investigate the effects of the antimuscarinic agent, propiverine, on the bladder and urethra in rats. Methods: A total of 54 female rats were given propiverine, imidafenacin (an antimuscarinic agent), or distilled water by gavage once or twice daily. After 2 weeks, bladder and urethral activity were recorded under urethane anesthesia. In the propiverine group, the changes of bladder and urethral activity before and after intravenous injection of α₁‐adrenergic antagonists (prazosin, silodosin and naftopidil) were also recorded. Furthermore, the leak point pressure after electrical stimulation of abdominal wall muscles was measured in rats with vaginal distension from the control and propiverine groups. Results: Intravesical baseline pressure was significantly lower in the propiverine and imidafenacin groups compared with the control group, whereas the urethral baseline pressure was significantly higher in the propiverine group compared with the control or imidafenacin groups. Intravenous injection of prazosin (an α₁‐receptor antagonist) significantly decreased the urethral baseline pressure in both of the propiverine and control groups. Intravenous injection of silodosin and naftopidil (α_1A‐ and α_1D‐receptor antagonists, respectively) significantly decreased the maximum contraction pressure and the urethral baseline pressure in the propiverine group. The leak point pressure of the propiverine group was significantly higher than that of the control group. Conclusions: An increase of catecholamines after propiverine administration might activate smooth muscle of the proximal urethra via α_1A‐ and α_1D‐adrenergic receptors, as well as activating urethral and pelvic floor striated muscle via the spinal motoneurons.     

膀胱出口梗阻所致逼尿肌过度活动的神经电生理研究

目的 从膀胱传入神经以及盆底相关神经肌肉角度探讨神经因素及肌源性因素在膀胱出口梗阻所致的逼尿肌过度活动发生中的作用.方法 采用耻骨上膀胱颈梗阻的方法建立逼尿肌过度活动大鼠模型,测定不稳定收缩时盆神经传入电位信号,并同步测定阴部神经运动支电位、尿道外括约肌肌电及腹肌肌电的反射反应.并观察T8段脊髓截断、双侧盆神经截断、腹交感干截断以及双侧阴部神经截断后大鼠膀胱充盈测压不稳定收缩的变化.结果 成功制作了膀胱出口梗阻逼尿肌过度活动大鼠模型,成功率62.5%.充盈性膀胱测压神经肌电生理同步记录结果显示,允盈期逼尿肌过度活动可分为两种类型,一种为收缩幅度高于10 cmH2O(1 cmH2O=0.098 kPa)的逼尿肌过度活动(B-DO),伴有同步盆神经传入的信号明显增强,且能引发阴部神经、尿道外括约和腹肌肌电图出现显著变化;一种为收缩幅度低于10 cmH2O的逼尿肌过度活动(S-DO),没有上述盆神经传入及相关神经肌电变化.T8脊髓截断后,膀胱充盈-排尿收缩周期消失,膀胱基础压显著升高,B-DO消失,S-DO仍然存在,且收缩幅度较截断前略有上升,但差异无统计学意义.依次截断控制膀胱的盆神经、交感神经和阴部神经后,膀胱失去充盈-排尿收缩周期,基础压显著升高,不稳定收缩中B-DO消失,S-DO仍然存在.结论 膀胱出口梗阻所致的逼尿肌过度活动存在不依赖于中枢和周围神经的膀胱源性因素.     

Role of the transversus perinei profundus muscle on voiding: The meaning of UPmax in patients with paralyzed urethral sphincter

Urodynamic study of 66 patients with caudal injury and of 7 patients who underwent saddle block was evaluated by putting emphasis on the maximal pressure of the urethra (UPmax). The static pressure of 49.7 ± 10.8 cm H₂O in the membranous urethra of the patients with completely paralyzed sphincter raised the question that some active muscle that functions to open the membranous urethra must have been working during physiological urination. Urodynamic findings of detrusor sphincter relationship, monitored by pressure and electromyogram (EMG) measurement, suggested that the combined reflections of the pelvic floor muscle and urethral sphincter are present. We concluded that this would be induced by the transversus perinei profundus muscle contraction and the urodynamic interpretation would be re-integrated on the role of this muscle on active urethral opening mechanism. © 1996 Wiley-Liss, Inc.     

Diagnostic discordance of electromyography (EMG) versus voiding cystourethrogram (VCUG) for detrusor-external sphincter dyssynergy (DESD)

AIMS: Detrusor sphincter dyssynergia (DSD) is defined as: "a detrusor contraction concurrent with an involuntary contraction of the urethral and/or periurethral striated muscle." In neurogenic etiology, this usually refers to involuntary contraction of the external striated sphincter and has classically been termed detrusor-external sphincter dyssynergia (DESD). There is currently no consensus regarding diagnosis [specifics of electromyographic (EMG) or voiding cystourethrographic (VCUG) determination], and little data on how well these modalities correlate. We explore the diagnostic congruence for DESD between needle EMG and VCUG in the neurogenic population. METHODS: Consecutive studies performed by a single urodynamicist at a major neurologic center were reviewed. Presence of DESD was determined by increased wire needle EMG activity and/or by dilated bladder neck and proximal urethra during detrusor contraction, in the absence of valsalva or attempt to inhibit voiding. Minimal acceptable criterion for agreement between the two tests was set at 70%. RESULTS: Fourty nine patients were diagnosed with DESD, had a videourodynamic study available, and had no history of sphincterotomy or stent. Binomial testing demonstrated significant disagreement (P < 0.000) in observed proportions. There was 60% agreement (28 patients) and 40% disagreement (21 patients) between EMG and VCUG for diagnosis of DESD. CONCLUSIONS: We found significant disagreement between needle EMG and VCUG for a positive diagnosis of DESD. A combination of EMG and VCUG may identify more cases of DESD than either modality alone and underscores the need for more strict criteria when defining this entity from a urodynamic standpoint.     

Overactive bladder inhibition in response to pelvic floor muscle exercises

A recent study by the senior author demonstrated that striated urethral sphincter contraction effected the inhibition of vesical contraction and suppression of the desire to micturate, an action suggested to be mediated through the "voluntary urinary inhibition reflex". We hypothesized that the effect of pelvic floor muscle (PFM) exercises on the overactive bladder was mediated through this reflex action. The current communication investigates this hypothesis. A total of 28 patients (mean age 44.8+/-10.2 years, 18 men, 10 women) with overactive bladder and 17 healthy volunteers (mean age 42.6+/-9.8 years, 12 men, 5 women) were enrolled in the study. The vesical and posterior urethral pressures were determined before and after vesical filling reached the volume at which urge in control subjects, and involuntary voiding in the patients, occurred. Intra-abdominal pressure was recorded to obtain detrusor pressure readings. The bladder was refilled to the above volume and the subject asked to hold PFM contractions for 10 s during which the vesical and posterior urethral pressures were recorded. In healthy volunteers, the mean detrusor and posterior urethral pressures at urge to void were 30.6+/-4.8 SD and 18.7+/-3.3 cm H(2)O, respectively. On PFM contraction, the detrusor pressure declined to 11.6+/-1.4 cm H(2)O (P<0.01) and urethral pressure increased to 139.8+/-17.4 cm H(2)O (P<0.001). In patients, the mean detrusor and posterior urethral pressure readings when the bladder was filled to the volume which induced involuntary incontinence, were 28.2+/-4.2 and 17.3+/-3.4 cm H(2)O, respectively; on PFM contractions, the detrusor pressure decreased to 10.6+/-2.1 cm H(2)O (P<0.01), while urethral pressure increased to 86.6+/-7.9 cm H(2)O (P<0.001) and voiding did not occur. In conclusion, PFM contractions led to a decline of detrusor and increase of urethral pressures and suppressed the micturition reflex. These contractions appear to induce their effect by preventing internal sphincter relaxation produced by the micturition reflex. Failure of the internal sphincter to relax seems to cause reflex detrusor relaxation, an action presumably mediated through the "voluntary urinary inhibition reflex". The results of the current study encourage the treatment of overactive bladder with PFM contractions.     

Continence and some properties of the urethral striated muscle of male greyhounds

OBJECTIVE: To determine the properties of the striated muscle of the greyhound (dog) urethra and to consider its role in maintaining continence. Materials and methods The thickness of the muscle layers and the muscle types were determined by examining sections stained with haematoxylin and eosin or Masson's trichrome. These factors were correlated with the mechanical and electrical responses of muscle strips to nerve stimulation, and compared with muscle from other breeds of dog and other parts of the animal. RESULTS: The striated muscle formed approximately 70% of the membranous urethra and was predominantly (68%) type IIa muscle (i.e. fast but fatigue-resistant). The mean resting membrane potential was -74 mV; nerve stimulation produced an action potential with a mean amplitude of 97 mV and contraction lasting about 200 ms. All responses were abolished by D-tubocurarine. The contractions were well maintained with continuous or intermittent stimulation. The properties were intermediate between those of the anconeus (slow) and the extensor carpi radialis (fast) muscles. CONCLUSIONS: The distribution, fibre type and contractile characteristics would enable the striated urethral muscle to maintain tension for continence at rest and provide additional continence during sprints.