Introduction

It is well established that regular physical activity provides systemic benefits such as lung function improvement, cardiovascular risk reduction and lowering the risk of progression of chronic illnesses including diabetes mellitus, hypertension and metabolic syndrome [1]. On the other hand, the influence of physical activity on pelvic floor function and dysfunction is controversial. While some report a positive influence, others report that physical activity is a risk factor for pelvic floor dysfunction (PFD). For example, pelvic floor muscle (PFM) contraction pressure presented significant correlations with physical and aerobic capacity [1]. It was also found that women exercising regularly at mid-pregnancy have stronger PFMs and better muscular endurance than their sedentary counterparts [2]. On the other hand, others have described decreased perineal pressure in female athletes compared with nonathletic women [3].

PFM have an essential role in sexual function in women [4]. Prior studies have shown that strong PFM were critical for proper sexual arousal and reaching orgasm [5]. PFM damage may cause a defect in the physiologic sexual function by insufficient vaginal friction and improper blood supply, which may delay the orgasm [6]. Another suggested explanation is that during the sexual act, the genital response that is mediated via the levator ani contractions that enhance sexual response in both sexes is faulty [7]. Another study found that PFM training improve quality of life (QoL) and sexual function in women suffering from stress urinary incontinence (UI) [8]. Another study showed an improvement in sexual desire, performance during coitus and achievement of orgasm in women who received PFM rehabilitation [9]. Additional research found that one third of women with stage III or IV pelvic organ prolapse (POP) who were sexually active felt that their prolapse affected their ability to have sexual relations [10]. Many women that suffer from UI report low libido, vaginal dryness and dyspareunia which lower orgasm intensity, lower sexual arousal and fewer chances to reach orgasm as well as their satisfaction from their sexual life [11]. Another study found that 20.1% of women who perform intensive physical activity suffer from dyspareunia compared with 9.4% in women who perform non-intensive sports [12].

The relationship between running and sexual function is not well investigated. We opted to assess the influence of running with different levels of effort on sexual function, considering the popularity of recreational running and the rising rates of PFD that may influence sexual function in women worldwide. Investigating this relationship is fundamental in promoting health, prevention of PFD and improving sexual function.

Methods

Settings

This study was an observational, cross-sectional study. This was a secondary analysis of a larger study investigating the impact of running on pelvic floor dysfunction and sexual function. The groups of comparison were the original study groups. Running group members and women who run individually were approached through social media. The respondents were invited to participate in the study. The study received the approval of the Ben-Gurion University of the Negev's institutional review board.

Study population

Non-professional athlete women runners, who had run at least once a week for the past 6 months or more, were included in the study and were divided into two groups. The 'High effort' group comprised women who ran at least three times a week, for an accumulated distance of at least 20 km. The comparison group, 'Moderate effort,' comprised the remainder (< three times a week or < 20 km). Women under the age of 18, pregnant or in puerperium, with past traumatic pelvic injuries, neurologic injuries, congenital pelvic defects or past pelvic operations and women with language difficulties were excluded from the study.

Study design

An observational, cross-sectional study was performed. Recruiting women for the study was carried out by contacting running groups and women who run individually through social media. The recruitment took place between November 2019 to May 2020. Each woman was approached by the research team and was offered to participate following an explanation on the study course and purpose. Women who gave their informed consent were requested to anonymously complete questionnaires regarding pelvic floor disorders and sexual function. Three validated questionnaires were used for assessment. The first questionnaire is PFDI-20 (Pelvic Floor Distress Inventory-20 questions), a tool validated in the Hebrew language. It is a condition-specific questionnaire developed to measure QoL and extent of injury to the pelvic floor in patient with all forms of PFD. The PFDI-20 is a short version of the PFDI that is composed of 20 questions. The questionnaire is divided into three subscales which evaluate the following symptoms: UDI-6 (Urinary Distress Inventory-6 questions), CRADI-8 (Colorectal and Anal Inventory-8 questions) and POPD-6 (Pelvic Organ Prolapse Distress Inventory-6 questions). Participants can answer either yes or no to questionnaire items. “No” is given a value of “0” whereas “yes” is followed by a ranking of the level of bother on a scale of 1 to 4 (1 = “not at all,” 2 = “somewhat,” 3 = “moderately” and 4 = “quite a bit”). For each participant, there is an option to calculate a Scale Score and a Summary Score. The Scale Score is the mean value of all questions answered per scale multiplied by 25, meaning that each scale (urinary distress, colorectal anal distress and pelvic organ prolapse) may receive a maximum score of 100. The Summary Score is the sum of all three Scale Scores (range 0–300).

Sexual function was assessed using the Pelvic Organ Prolapse/Urinary Incontinence Sexual Questionnaire (PISQ-12) and QoL was assessed by the Incontinence Impact Questionnaire (IIQ-7). The PISQ-12 is the short version of PISQ-31, composed of 31 questions. The short form scores underwent correlation analysis with the long form, IIQ-7, Sexual History Form-12 (SHF-12) and Symptom Questionnaire (SQ) scores. The PISQ-12 is a validated and reliable short form that evaluates sexual function in women with UI and/or POP and correlates to the results of the PISQ-31 form. It can recognize women with poor sexual function as measured on the SHF-12.

Background variables assessed included demographic, medical and obstetrical data, lifestyle and description of the running characteristics of these women such as belonging to a running group, weekly running distance and duration of persistence.

Statistical analysis

Statistical analysis was performed with the SPSS package (SPSS, Chicago, IL).

The initial analysis was performed using descriptive statistics (mean, SD, graphs), followed by advanced analytical statistics using various parametric tests. Continuous variables with normal distribution were presented as mean ± standard deviation and compared between the study groups using t-tests. Continuous variables which were not normally distributed were presented as median with interquartile ranges, and statistical analysis was performed using the Mann-Whitney test. The correlation between the women's running characteristics and the scores of the questionnaires were examined by Spearman correlation. Categorical variables were presented in counts and percentages, and statistical analysis was performed using the chi-square or Fisher exact tests when appropriate. All analyses with two-sided p value of < 0.05 were considered significant.

Results

Of 223 women who completed the questionnaire, 180 (80.71%) were found eligible after applying the inclusion and exclusion criteria and were included in the study. The 'Moderate effort' group consisted of 87 women, and there were 93 women in the 'High effort' group. The demographic and clinical characteristics of the women are presented in Table 1. Women in the 'High effort' group were significantly older (42.93 + 8.65 vs. 38.81 + 9.36, p < 0.01) and had a lower BMI (22.43 + 2.53 vs. 23.39 + 3.66, p = 0.04).

Table 1 Baseline demographic and clinical characteristics of women in the 'Moderate effort' and 'High effort' groups
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Table 2 summarizes the running characteristics of the women in the two groups. Women in the 'High effort' group had a longer median duration of activity [90 (60–120) vs. 60 (60–90), p < 0.01], farther weekly running distance [34 (30–45) km vs. 15 (10–20) km, p < 0.01], a longer median duration of running persistence [24 (12–56) vs. 16 (11–30) months, p < 0.01] and a higher median number of training sessions per week [4 (3–6) vs. 3 (3–4), p < 0.01].

Table 2 Running characteristics of women in the 'Moderate effort' and 'High effort' groups
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Table 3 summarizes the differences between the median scores of the PFDI-20 and the three sub-scales POPDI-6, UDI-6 and CRADI-8. No significant differences were found between the two groups. Although there were no significant differences between the groups in the questionnaire scores or in any of the sub-scales scores, a higher incidence of PFD was found among 'High effort' runners compared to 'Moderate effort' runners. Additionally, a sub-analysis of item number 17 in the PFDI-20 that relates to stress urinary incontinence demonstrated no significant difference between the two groups.

Table 3 Comparison of the scores of the questionnaire and the sub-scales between the two groups (Mann-Whitney U test)
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Women who reported having any PFD were requested to complete the PISQ-12 questionnaire. It was completed by 136 women, 67 from the 'High effort' group and 69 from the 'Moderate effort' group.

Table 4 presents the scores of the PISQ-12 questionnaire in the two groups. No difference in the overall sexual function was found between the two groups. The median score in the 'High effort' group was 39 and in the 'Moderate effort' group was 37 (p = 0.04). However, in item number 12 in this questionnaire (compared to orgasms you have had in the past, how intense are the orgasms you have had in the past 6 months?), we found a significant difference between the two groups (median score 2 (IQR: 2–2) vs. 1.5 (IQR: 1–2) in the 'High effort' and the 'Moderate effort' groups, respectively; p < 0.01). In the 'High effort' group, 10.4% of women reported 'much more intense' orgasms compared to their orgasms in the past with only 8.1% of women in the 'Moderate effort' group. Moreover, 6.0% and 11.3% of the 'High effort' and 'Moderate effort' groups, respectively, reported having 'much less intense' orgasms then the ones they had in the past. A correlation was found between the weekly running distance and the orgasm intensity (rS = 0.25, p = 0.004). A significant difference between the two groups (p = 0.03) was also found in item number 8 in this questionnaire [Do you avoid sexual intercourse because of bulging of the vagina (either the bladder, rectum or vagina falling out?)].

Table 4 Comparison of the scores of the PISQ-12 questionnaire between the two groups (Mann-Whitney U test, chi-square test)
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Table 5 compares sexual function between the groups stratified by the median score of the PFDI questionnaire and the sub-scales (above and below the median score). Women with a higher score suffered from a more severe impairment in their sexual function, and this finding was statistically significant.

Table 5 Comparison of sexual function between the groups above and below the median score of the PFDI questionnaire and the sub-scales (Mann-Whitney U Test)
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Table 6 compares sexual function in women stratified by BMI (above and below the median) and by parity (primiparity vs. multiparity). No significant differences in sexual function scores were found between women above and below the median BMI (p = 0.26). Nevertheless, a significant difference was found between primiparous and multiparous women regarding their sexual function (p = 0.018), with multiparous women having a better sexual function score.

Table 6 Comparison of sexual function in women with BMI above and below the median found in the study and between primiparity and multiparity
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Discussion

We aimed to investigate the association between sexual function and PFD including symptoms of urinary disorders, anorectal disorders, pelvic organ prolapse and pain in sexual intercourse and different characteristics of amateur running (weekly running distance, number of trainings per week, length of each training and belonging to a running group). We divided the participants according to the running characteristics into two groups: 'Moderate effort' and 'High effort.' We did not find significant differences in the sexual function between women in the 'High effort' and 'Moderate effort' groups. Significant differences in sexual function were found between women above and below the median score of the PFDI-20 questionnaire and its sub-scales. Women above the median score who suffered from UI, AI and POP had higher rates of sexual disfunction (SD).

SD is defined as a disorder in sexual arousal and in the psychophysiologic changes that cause personal distress and interpersonal difficulty [13]. Sexual disfunction may be caused by numerous circumstances that prevent women from being a part of a sexual relationship as they used to be in the past [14]. SD in females is estimated to affect 30–50% in the general population, while in women who suffer from PFD it is estimated to be higher, reaching 50–83% of patients [15]. The PFMs are directly responsible for the sensation a woman feels during intercourse and for the amount of grip felt by her partner. Rhythmic contractions of the pelvic floor contribute to arousal and many women's ability to achieve orgasm [16]. PFM training improves muscle tone and circulation and thereby improves or even enables engorgement of the clitoris when women get aroused [16]. A study that investigated the impact of PFD on sexual function found that women with UI suffer from dyspareunia, sexual arousal disorder, orgasmic deficiency and hypoactive sexual desire. Women with AI were found to have decreased sexual desire, sexual satisfaction, arousal lubrication and orgasm compared to those without. Other factors that decrease sexual experiences in women suffering from PFD include embarrassment, worries about the image of their vagina, concerns about the partner satisfaction, discomfort related to their POP, fear of worsening the prolapse and reduced genital sensation [15]. A recent study conducted in 2018 showed that nulliparous athletes had a high prevalence of UI and SD. Problems with orgasm and lubrication were the most prevalent. The relative risk demonstrated that incontinent athletes have 2.74 times the risk to develop desire problems than their continent athlete counterparts [17].

Our study did not find significant differences in the sexual function between 'High effort' and 'Moderate effort' groups. It may be related to the relatively small sample size. Interestingly, there was a significant difference in the orgasmic intensity between the two groups. Women in the 'High effort' group reported having more intense orgasms, and a correlation was found between the weekly running distance and the intensity of orgasms that they experienced.

The importance of PFM was confirmed by studies using magnetic resonance imaging as well as surface electromyography during sexual arousal and sexual intercourse. The levator ani muscles surround the distal vaginal canal and thus support the vaginal walls. During penetration, these muscles are slightly stretched, and during orgasm they contract [18]. Weak and misfunctioning PFM may cause insufficient contraction, which may contribute to an orgasmic disorder [6]. Studies have found that training and rehabilitation of the PFM positively affect sexual function and especially orgasm [9, 19].

We expected to find that women who perform intense physical activity and may suffer from PFD will have higher rates of orgasmic dysfunction. However, the 'High effort' group in our study reported the opposite.

Evaluation of sexual function is complicated and is composed of multiple factors including biologic, psychologic, physiologic, environmental and interpersonal factors [20]. Exercise augments the secretion of endogenous opioid peptides in the brain causing a beneficial effect on mood and general euphoria [21] and psychologic benefits including better self-esteem and body image [22]. A study that investigated the relationship between physical activity of several degrees of effort and the sexual function of middle-aged women found that 57.6% of women that perform physical activity had sexual disorders while 78.9% of women of sedentary lifestyle had such problems. Women that perform physical activity had a significantly higher score in orgasmic reaction than women who did not [23]. This may be explained partly by the fact that physically active women have better self-esteem and better body image, which positively influence their sexual function [20]. Another study demonstrated better clitoral blood flow and better sexual function in elite athletes compared with sedentary subjects [24].

Our study's main limitation is the use of self-reported questionnaires without an objective clinical assessment of the PFD symptoms or sexual function. Some of the women did not respond to all the items on the questionnaire, probably because of embarrassment or discomfort. The PISQ-12 is a PFD condition-specific sexual function instrument. The PISQ-9 is an instrument that should be used for a population without PFD. In our study only those who reported PFD completed the PISQ-12 (67 and 69 women). Although normally item analysis is not valid for the PISQ-12, a single item difference on orgasm was a major finding in our study. This may represent an area needing further investigation. Another important limitation was a relatively small sample size that limits the possibility of finding significant differences and performing multivariate analyses. Finally, the use of subjective report regarding running distance and length of each training may be a limitation. Use of proper quantitative equipment such as running smartphone apps or running watches would have been more accurate and objective but would have increased the risk for selection bias.

In conclusion, regular physical activity is important for the health and wellbeing of women at any age. Our study found that women who perform intense physical activity and belong to the "High effort' group experienced more intensive orgasms compared with the 'Moderate effort' group. This may be explained by better clitoral circulation, better function of PFMs, better self-esteem and body image or a combination of the above. Health professionals who treat symptoms related to PFD can raise awareness of the advantages of physical activity and PFM training and rehabilitation, which might improve PFM tone and circulation and hence sexual function.