Postural and respiratory functions of the pelvic floor muscles

AIMS: Due to their contribution to modulation of intra-abdominal pressure (IAP) and stiffness of the sacroiliac joints, the pelvic floor muscles (PFM) have been argued to provide a contribution to control of the lumbar spine and pelvis. Furthermore, as IAP is modulated during respiration this is likely to be accompanied by changes in PFM activity. METHODS: In order to evaluate the postural and respiratory function of the PFM, recordings of anal and vaginal electromyographic activity (EMG) were made with surface electrodes during single and repetitive arm movements that challenge the stability of the spine. EMG recordings were also made during respiratory tasks: quiet breathing and breathing with increased dead-space to induce hypercapnoea. RESULTS: EMG activity of the PFM was increased in advance of deltoid muscle activity as a component of the pre-programmed anticipatory postural activity. This activity was independent of the direction of arm movement. During repetitive movements, PFM EMG was tonic with phasic bursts at the frequency of arm movement. This activity was related to the peak acceleration of the arm, and therefore the amplitude of the reactive forces imposed on the spine. Respiratory activity was observed for the anal and vaginal EMG and was primarily expiratory. When subjects moved the arm repetitively while breathing, PFM EMG was primarily modulated in association with arm movement with little respiratory modulation. CONCLUSIONS: This study provides evidence that the PFM contribute to both postural and respiratory functions.     

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.     

Deformation of the pelvic floor muscles during a vaginal delivery

Pelvic floor dysfunction is a hidden problem with a magnitude unknown to many. Statistics show that one in every ten women will have pelvic floor dysfunction so severe that it will require surgery. Several studies have shown that pelvic floor injuries during a vaginal delivery can be considered a significant factor in the development of urinary incontinence, fecal incontinence, and pelvic organ prolapse. The objective of the present work is to contribute to the clarification of the mechanisms behind pelvic floor disorders related to a vaginal delivery. For this purpose, a numerical simulation based on the finite element method was carried out. The finite element model intends to represent the effects that the passage of a fetal head can induce on the muscles of the pelvic floor, from a mechanical point of view. The model used for the simulation represents the pelvic bones, with the attached pelvic floor muscles and the fetus. In this work, we simulated the movements of the fetus during birth, in vertex position. We simulated the engagement, descent, flexion, internal rotation, and extension of the fetal head. Results for the pelvic floor stretch values obtained during the passage of the fetus head are presented; the deformation field is also shown. The results were obtained using the finite element method and a three-dimensional computer model of the pelvic floor and fetus. The maximum deformation obtained was 0.66 for a vertical displacement of the fetal head of approximately 60 mm.     

A new concept of the anatomy of the anal sphincter mechanism and the physiology of defecation: Mass contraction of the pelvic floor muscles

We have previously demonstrated both anatomically and physiologically that the external anal (EAS) and urethral (EUS) sphincters and the bulbocavernosus muscle (BC) originate from the puborectalis muscle (PR). It is hypothesized that stimulation of any of these muscles would lead to contraction of all the others. Because the levator ani (pubococcygeus) muscle (LA) also has the same innervation as the above-mentioned muscles, it is further suggested that it, too, contracts reflexly upon stimulation of any of those muscles. The purpose of this study was to test this hypothesis. The study comprised 18 healthy volunteers (mean age 36.6±8.4 years; 10 men, 8 women). The EAS was stimulated and the response of the EUS, PR, LA and BC was determined. Each muscle was thereafter stimulated separately and the response of the other pelvic floor muscles registered. Stimulation of any of the pelvic floor muscles effected an increased EMG activity of the rest of the muscles. The muscle contraction was instantaneous with no latency in all the muscles except the LA EMG activity, which showed a mean latency of 21.3±6.6 ms. The pelvic floor muscles' response seems to be attributable to muscle stimulation both directly and indirectly through activation of pudendal nerve fibers in the muscles. The study demonstrated that the pelvic floor muscles behave as one muscle: they contract or relax en masse. This mass contraction might explain some of the physiologic phenomena that occur during pelvic organ evacuation. However, besides this mass contraction, a voluntary selective individual muscle activity exists by which each individual muscle acts independently of the others.Editorial Comment: Assuming that the data in this paper are confirmed by other investigators, they have farreaching implications for the mechanisms hypothesized to cause bladder neck opening and closure. The pressure equalization components of Enhorning's and DeLancey's hypothesis appear valid for urethral closure, but are difficult to sustain during micturition. Any straining during micturition would immediately cause pelvic floor spasm and urethral closure, rendering bladder evacuation impossible. The integral theory of Petros and Ulmsten is consistent with these data. It specifies a generalized pelvic floor contraction for both urethral closure and micturition, the only difference between them being relaxation of a single muscle during micturition, that controlling the external urethral sphincter.     

Pediatric urodynamics: a clinical comparison of surface versus needle pelvic floor/external sphincter electromyography.

Urodynamic evaluations were done on 37 children to diagnose voiding pattern abnormalities and/or recurrent urinary infections. Each of 25 children had 2 sets of testing to judge a practical method of urodynamic evaluation. Bipolar anal skin electrodes were compared to bipolar perianal muscle needle electrodes as a means of monitoring the urethral sphincter/pelvic floow electromyographic activity. In addition, the urethral catheter was compared to the suprapubic catheter as a means of monitoring intravesical pressure. The results were similar and statistically significant (p less than 0.001). The remaining 12 children were evaluated based only on the results of bipolar anal skin electrodes and uroflowmetry. The results of both groups clearly demonstrated that surface perianal electrodes are practical, accurate and reliable for the diagnosis and treatment of children with voiding pattern abnormalities. We recommend the use of surface electrodes and a urethral catheter as techniques for the urodynamic evaluation of voiding pattern abnormalities of children without overt neuropathology or extensive urethral operation. Preoperative surface electromyography of the urinary sphincters may prove to be a useful screening test to detect occult dyssynergia in patients who have had failed ureteral reimplants.     

Urethral sphincter EMG activity registered with surface electrodes in the vagina

Transvaginal registration of urethral sphincter EMG with surface electodes at the anterior vaginal wall has been compared to simultaneous registrations of urethral ring electrode EMG and anal surface electrode EMG in 12 patients. We found that the transvaginal EMG was almost identical to the intraurethral EMG during different pelvic floor muscle activities but differed considerably from the perianal EMG. The clinical applicability was investigated during medium-fill water cystometry followed by pressure-flow studies, and in 21 out of 25 patients, a satisfactory EMG was registered.     

Electromyographic evaluation of pelvic floor muscles in pregnant and nonpregnant women

Introduction and hypothesis

We compared the maximal voluntary contraction (MVC) and strength of pelvic floor muscles (PFM) of pregnant and nonpregnant women using surface electromyography (SEMG).

Methods

Fifteen pregnant primiparous women and 15 nulliparous nonpregnant women were evaluated. The healthy pregnant women were in the third trimester of pregnancy with a single fetus and did not have any neuromuscular alterations. The nonpregnant women did not present with PF dysfunctions and, as with the pregnant women, did not have any previous gynecological surgeries or degenerative neuromuscular alterations. The evaluation methods used were digital palpation (Oxford Grading Scale, which ranges from 0 to 5) and SEMG. In the EMG exam, MVC activity was evaluated, and the better of two contractions was chosen. Before the evaluation, all women received information about PFM localization and function and how to correctly contract PFM.

Results

In the EMG evaluation, MVC was significantly greater in the nonpregnant group (90.7 μv) than in the pregnant group (30 μv), with p?p?=?0.005).

Conclusion

In comparison to nulliparous women, pregnant women demonstrated worse PFM function with decreased strength and electrical activity.     

Development of the pelvic floor muscles of murine embryos with anorectal malformations

Background/Purpose: Recent biological studies have elucidated the molecular mechanism of muscle development, in which various regulatory molecules play key roles during embryogenesis. To determine possible myogenic abnormalities in anorectal malformations (ARM), the authors investigated the pelvic muscle development in murine embryos affected with ARM. Methods: ARM embryos were induced by all-trans retinoic acid (ATRA) on the ninth gestational day (E9.0). Embryonal specimens were obtained from the uteri between E10.5 and E16.0, and the frozen sections were prepared for immunohistochemistry using antibodies specific for MyoD, myogenin, and PGP9.5 molecules. Results: In ARM embryos, the neural tube was irregularly branched and formed an anomalous mass in the sacral region. Embryonal caudal somites differentiated into myogenic cells to form proper myotubes in the pelvis corresponding to the developmental stages between E12.5 and E15.0 both in affected embryos and the controls. Conclusions: In ARM embryos, an impaired anatomic framework of the pelvis was caused by neural maldevelopment, whereas muscle development proceeded physiologically. These results support the hypothesis that pelvic floor muscles may function in ARM children, in whom neural abnormalities such as meningomyelocele or tethered spinal cord have been ruled out, if the surgical correction is appropriately completed.     

Dynamic MRI of the pelvic floor muscles in an upright sitting position

Since the pelvic floor muscles are situated inside the pelvis, the actual function is difficult to observe. Magnetic resonance imaging (MRI) is a new method that may prove to give additional information about pelvic floor muscle function during contraction. The purpose of the present study was to assess pelvic floor muscle function during contraction and straining in an upright sitting position by use of MRI. Sixteen women, nine continent and seven with urodynamically and clinically proven genuine stress incontinence participated in the study. MRI was performed in an open-configured GE Signa SP, 0.5 T Tesla magnet. With the participants sitting in an upright position on a pelvic RF-coil, sagittal, coronal and axial T1 weighted spin echo images of the pelvic floor were obtained. During contraction and straining a scan time of 2 seconds per image for 150-250 images, was performed in a mid-sagittal plane. The results showed that the mean inward lift during contraction was 10.8 mm (SD 6.0) for all women. During straining the mean downward movement was 19.1 mm (SD 7.4). The coccyx moved in a ventral, cranial direction during contraction and was pressed in a caudal, dorsal direction during straining. It is concluded that contraction of the pelvic floor muscles is concentric, moving the coccyx in a ventral, cranial direction. The movement measured by MRI in upright sitting position is less than that concluded after clinical observation in supine position. The coccyx is pressed dorsally during straining.     

The effect of training with vaginal weighted cones and pelvic floor exercises on the strength of the pelvic floor muscles: A pilot study

A pretest-post-test design (n=14) was used to investigate pelvic floor muscle (PFM) strength over a 2-month training period using vaginal cones with pelvic floor exercises in the treatment of female stress incontinence, and to correlate any changes in muscle strength with objective and subjective measures of stress incontinence. PFM strength was assessed by vaginal examination and the ability to retain the cones. The symptom of stress incontinence was assessed using rating scales, and measured objectively by the extended pad test. The results showed a significant increase in muscle strength (P<0.05). An unexpected finding was that most of the improvement in PFM function occurred in a 1-week baseline assessment period before training was commenced. It is therefore suggested that the increase in force generation occurred due to a process of neural adaptation rather than muscle hypertrophy. No significant correlations were found between muscle strength and objective or subjective measures of stress incontinence.Editorial Comment: Vaginal cones are gaining in popularity as a method of therapy for stress incontinence. As in this study, the symptom of stress incontinence was enough to begin treatment and objective documentation of the diagnosis was not undertaken. The therapy has no side-effects and only requires that the patient is motivated enough to put the cone in the vagina and take it out after a prescribed time period. Everything else is automatic. Biofeedback from the perception of the cone falling out provides the stimulus for pelvic floor contraction. Success rates are high, with 21% cured and 29% improved for an overall improvement rate of 50%. Such therapies may be tried before diagnosis, and certainly before expensive surgical treatment.     

The importance of leg support for relaxation of the pelvic floor muscles. A surface electromyograph study in healthy girls

The ability of relaxation is a necessary component for a good function of the pelvic floor muscles (PF). The importance of a relaxation technique for the PF has not been paid much attention in children either in urological examinations or treatments. The aim was to seek postures with optimal relaxation of the PF for use in clinical practice with girls. The relaxation of the PF and adjacent hip and abdominal muscle groups was studied by using surface electromyography (EMG) and a polygraph writer in 20 healthy volunteer girls, 6 and 10 years of age. They were placed in three different postures with their legs supported and unsupported. In postures with supported legs, the relaxation was observed in 94% recorded from the PF and in 97% from the adjacent muscles. EMG amplitudes from the PF and adductor muscles were significantly higher in postures with unsupported legs compared to postures with supported legs (p less than 0.05). The present study indicates that the optimal relaxation of the PF can be achieved by adequate leg support. This can be important to apply particularly in clinical situations such as urodynamic investigations, in uro-biofeedback training and for the design of pelvic floor exercises for girls.