Stephanie Both PhD, Rik van Lunsen PhD, Philomeen Weijenborg PhD, Ellen Laan PhD
ONLINE: August 27, 2012 – The Journal of Sexual Medicine, DOI: 10.1111/j.1743-6109.2012.02910.x
Dyspareunia in women, characterized by recurrent and persistent genital pain at intercourse, is believed to be associated with pelvic floor hyperactivity and decreased sexual arousal. At present, no device exists that can measure pelvic floor activity and genital arousal simultaneously. This study reports on a new vaginal device that can take both measurements at the same time.
Spano and Lamont’s explanatory model of dyspareunia suggests that pain with intercourse leads to anticipatory pain in later situations, resulting in decreased vaginal lubrication and increased activity in the pelvic floor muscles. This perpetuates a cycle of pain. Other researchers believe that pelvic muscle activity may increase when a woman is anxious, but it may also increase because of comorbidities such as urological, gynecological, and gastrointestinal conditions. These hypotheses and similar ones separate the roles played by pelvic floor activity and genital arousal in dyspareunia.
Vaginal surface electromyography (EMG) has been used to measure pelvic floor activity in women with sexual pain issues. Related studies have focused on provoked vestibulodynia (PVD) and vaginismus and consider “deviant pelvic floor functioning” to be the main culprit in these conditions.
Vaginal photoplethysmography has been used to assess genital sexual arousal in studies evaluating women’s responses to erotic films or the suggestion of a pain stimulus. A study by Brauer et al. supports Spano and Lamont’s theory of diminished genital response caused by a fear of pain.
Fear of pain may lead to decreased arousal and increased pelvic floor activity as “part of a defense reaction.” It’s possible that that pelvic floor muscles may react to emotional stimuli because of a connection to the limbic system.
To learn more about how anxiety and fear of pain affects genital response and pelvic floor muscle activity, it would be helpful to measure genital blood flow and vaginal surface EMG at the same time. To this end, the researchers created a device for this purpose. The aim of this study is to test a second version of this device.
Vaginal pulse amplitude (VPA) and vaginal surface EMG were monitored while study subjects watched four film clips described as neutral, sexual, anxiety-evoking, and sexually threatening.
Vaginal surface EMG was also measured as participants did pelvic floor contractions independent of the film clips.
In accordance with previous research, the authors expected to see increased vaginal surface EMG during the anxiety and sexually threatening clips and increased VPA during the sexual film. They also looked at the relationship between vaginal surface EMG and VPA.
Pelvic floor contractions were used to test the sensitivity of the device to voluntary pelvic floor activity. “Flick” contractions lasting 1-2 seconds and “sustained” contractions of 10 seconds were measured. Contractions included those of the pelvic floor muscles alone and with other muscle groups. The authors expected to see higher EMG ratings for contractions of pelvic muscles alone compared to a resting state. They also expected to see higher EMG ratings for contractions that involved other muscle groups when compared to contractions of only the pelvic floor muscles.
Thirty-six heterosexual women with a mean age of 23 years participated in the study. Most of the women were students in the Netherlands. All of the women were sexually active and all had had sexual intercourse before.
Each participant viewed four 5-minute film clips. A neutral clip depicted a Dutch village. A sexual clip showed heterosexual petting, cunnilingus, and intercourse. An anxiety clip was from the movie “Cujo” and showed a woman and child being threatened by a dog. A sexually threatening clip was from the movie “Extremities” and depicted a woman being chased into her house by a man who then forces her into a sexual situation.
After the film, the women received instructions on the pelvic floor contractions. The first block of contractions involved the pelvic floor muscles only using the flick and sustained techniques. In the second block, the women were told to repeat these steps using other muscles along with the pelvic floor muscles.
Vaginal photoplethysmography was used to measure VPA, which involved using a light source. Electrodes mounted on the photoplethysmograph measured pelvic floor activity. Each participant was instructed to insert the sterilized device into her vagina until a metal plate touched her labia.
Participants completed subjective sexual arousal and emotional experience questionnaires before the film presentation and after each film clip. Researchers also collected data on sexual function, pelvic floor function, and sexual abuse history.
Each woman was tested by a trained female experimenter. After emptying her bladder, each woman inserted the vaginal device privately. After each film clip, women spent 1 minute returning to baseline by completing an arithmetic task. A 2-minute baseline period followed before the next film clip was shown.
After the film portion of the experiment, the women had a 5-minute rest period and a 2-minute EMG baseline measurement before starting the pelvic floor contractions following the procedure described above.
EMG and VPA readings were taken throughout the baseline and film segments in the first portion of the experiment. EMG was also measured throughout the second portion.
An exit interview with each woman was conducted at the end of the experiment.
Ninety-seven percent of the participants reported feeling comfortable during the experiment and 94% said that the pelvic floor exercises were “not difficult at all or only a little bit difficult to perform.”
It was determined that sexual functioning for all the women was in the normal range. “Hardly any” of the women had pelvic floor complaints. Four participants revealed past sexual abuse.
In terms of subjective sexual arousal, the films had their intended effects on the subjects.
For emotional experience, feelings of lust were more common during the sexual film than the others. Threat and anger were more common during the anxiety and sexually threatening films than during the sexual or neutral films.
VPA readings during baseline segments showed that there were no carry-over effects between the films. VPA was significantly higher during the sexual film when compared to the other three.
EMG readings also showed that there were no carry-over effects between film clips. EMG readings increased during the anxiety film.
There were no significant correlations between EMG scores and emotional experience ratings, although the correlation between EMG during the anxiety film and associated feelings of threat and anger approached significance. Stronger feelings of threat and anger correlated with stronger EMG response. Stronger VPA scores correlated with stronger feelings of lust.
Significant negative correlations within subjects were found as expected. During the anxiety film, there was an increase in EMG and a decrease in VPA.
For the second part of the experiment, it was determined that pelvic floor muscle activity returned to baseline after each set of contractions. EMG readings were higher than baseline when the women contracted pelvic muscles alone and when they contracted pelvic muscles along with other muscles.
This study, a test of a new device measuring pelvic floor activity (EMG readings) and female genital arousal (VPA readings), generally achieved the expected results. As expected, VPA readings were higher during the erotic film clip, indicating increased vaginal blood flow caused by sexual stimulation. The device was able to detect changes in pelvic floor activity in response to the anxiety-provoking clip, “a threatening emotional stimulus.” EMG readings during the voluntary contractions showed that the device was sensitive to these changes.
Emotional experience indicated that the films achieved the intended emotional states (neutral, sexual, anxious, and a mixed sexual-anxious state).
VPA readings increased during erotic content and pelvic floor activity increased during threatening film clips. With this in mind, the authors concluded, “These results support the idea that the pelvic floor musculature is highly reactive to emotional stimuli…and specifically to anxiety…and show that the new version of the probe, in contrast to the first version…is highly sensitive to this reactivity.”
The authors suggested that “increased pelvic floor muscle activity may be associated with reduced blood flow to the vagina” but more research is needed.
From the results of the second part of the experiment, the researchers concluded that the new device was sensitive enough to measure voluntary pelvic floor activity.
Further research may also analyze the position of the EMG electrodes on the device.
The authors identified four limitations to this study.
First, beginning pelvic floor function was measured through a questionnaire on the physical complaints common to pelvic floor hypertonia. An actual physical examination by a doctor or physical therapist may provide a more accurate assessment.
Second, the women were instructed to perform contractions of their pelvic muscles and their pelvic muscles along with other muscle groups. However, the researchers did not test whether the women were actually able to do this. “In fact, it is questionable whether it is in itself possible to contract pelvic floor muscles in isolation,” the authors noted.
Third, the device tested does not differentiate between the different pelvic floor muscle groups (puborectalis, bulbocavernosus, and levator ani). It may be helpful to analyze these independently. However, doing so would involve placing needle electrodes into the muscles themselves, which may be threatening to study subjects.
Finally, pelvic floor activity in response to anxiety was prompted by an anxiety-provoking film clip. However, a woman with dyspareunia may experience anxiety differently when in an actual sexual situation.
The authors concluded that the device tested is “suitable for simultaneous measurement of VPA and pelvic floor EMG” and can be a “valuable tool” in further research.