Abstract
Objective
To assess pelvic floor muscle (PFM) strength and influencing factors among healthy women at different life stages.
Design
Multicentre cross-sectional study.
Setting
Fourteen hospitals in China.
Population
A total of 5040 healthy women allocated to the following groups (with 1680 women per group): premenopausal nulliparous, premenopausal parous and postmenopausal.
Methods
The PFM strength was evaluated by vaginal manometry. Multivariate logistic regression was used to determine the influencing factors for low PFM strength.
Main Outcome Measures
Maximum voluntary contraction pressure (MVCP).
Results
The median MVCP values were 36, 35 and 35 cmH2O in premenopausal nulliparous (aged 19–51 years), premenopausal parous (aged 22–61 years), and postmenopausal (aged 40–86 years) women, respectively. In the premenopausal nulliparous group, physical work (odds ratio, OR 2.05) was the risk factor for low PFM strength, which may be related to the chronic increased abdominal pressure caused by physical work. In the premenopausal parous group, the number of vaginal deliveries (OR 1.28) and diabetes (OR 2.70) were risk factors for low PFM strength, whereas sexual intercourse (<2 times per week vs. none, OR 0.55; ≥2 times per week vs. none, OR 0.56) and PFM exercise (OR 0.50) may have protective effects. In the postmenopausal group, the number of vaginal deliveries (OR 1.32) and family history of pelvic organ prolapse (POP) (OR 1.83) were risk factors for low PFM strength.
Conclusions
Physical work, vaginal delivery, diabetes and a family history of POP are all risk factors for low PFM strength, whereas PFM exercises and sexual life can have a protective effect. The importance of these factors varies at different stages of a woman’s life.
1 INTRODUCTION
Pelvic floor dysfunction (PFD), mainly including urinary incontinence, pelvic organ prolapse (POP), anal incontinence and sexual dysfunction, is a common disorder among middle-aged and older women.1, 2 The anatomical structure of the pelvic floor is complex, and the pelvic floor muscle (PFM) is an important part of it. Impaired function of the PFM can lead to changes in the position and function of the pelvic organs, leading to a variety of clinical symptoms.3–5
Nowadays, there are many methods to evaluate PFM strength, including vaginal palpation, pelvic floor imaging technologies and vaginal manometry. Vaginal palpation is simple and practical, but is subjective and cannot be used for quantification.6 Pelvic floor imaging technologies can directly observe the structural changes of the pelvic floor and provide an anatomical basis for the reconstruction of the pelvic floor tissue. However, ultrasound resolution decreases with increasing pelvic depth, and dynamic magnetic resonance imaging (MRI) is expensive, complex and has poor repeatability, which greatly limits the widespread application of these techniques in clinical practice. Vaginal manometry is a simple, non-invasive and direct method that objectively assesses PFM strength using a vaginal balloon.7 The difference between vaginal resting pressure and peak pressure during a maximum voluntary contraction is taken as the maximum voluntary contraction pressure (MVCP), which is proportional to the force of PFM.1, 8
Studies have compared PFM strength based on vaginal manometry between nulliparous and primiparous women,9 during different periods of gestation,10, 11 following different modes of delivery,12, 13 and in women with or without PFDs.4, 5 Many studies have shown that PFM function is closely related to childbirth, aging and menopause,14–17 which are important indicators of a woman’s life stage. However, few studies have assessed the normative values of PFM strength and the influencing factors among healthy women. Therefore, we conducted this multicentre, large-sample-size study to assess PFM strength, and the influencing factors for PFM strength, in healthy premenopausal nulliparous, premenopausal parous and postmenopausal women, for the purpose of providing a reference for PFM strength in healthy Chinese women at different life stages.
2 METHODS
2.1 Study design and sample
From May 2018 to June 2020, 5040 participants from 14 centres were recruited in three groups: premenopausal nulliparous, premenopausal parous and postmenopausal groups. In each of the 14 medical centres, 120 participants per group were recruited consecutively. Data on general characteristics, Pelvic Organ Prolapse Quantification System (POP-Q) values and indicators of PFM strength (measured by vaginal manometry) were obtained.
The study protocol was approved by the Peking Union Medical College Hospital Ethics Committee (JS-1548, 03/27/2018). The study was registered with the ClinicalTrials.gov Protocol Registration and Results System (PRS) (https://register.clinicaltrials.gov: NCT03516266) and the Chinese Clinical Trial Registry (http://www.chictr.org.cn: ChiCTR1800015488). All participants provided signed informed consent before data collection.
The inclusion criteria were non-pregnant women without PFDs who attended the hospital for a health check-up and were: (i) premenopausal nulliparous women with no history of childbirth or abortion over 16 weeks of gestation; (ii) premenopausal parous women who had given birth (including caesarean section or vaginal delivery); or (iii) postmenopausal parous women who had undergone natural menopause. The exclusion criteria were: (i) history of PFD (such as urinary incontinence, anal incontinence or prolapse beyond the level of the hymen); (ii) radical surgery in pelvic cavity (for cervical cancer, rectal cancer, bladder cancer, etc.); (iii) pelvic floor surgery or radiotherapy; (iv) latex allergy; (v) pelvic, vaginal or urinary tract infection; (vi) pregnancy or breastfeeding; and (vii) never had sexual intercourse or could not tolerate vaginal examination.
2.2 Outcome measures
Pelvic floor muscle strength was evaluated using intravaginal manometry, using a vaginal balloon probe (filled with 15–20 mL of gas) connected to a PHENIX USB 8 Neuromuscular Electrical Stimulation Therapy System (Electronic Concept Lignon Innovation, Montpellier, France), which acted as a high-precision pressure transducer. Each participant was examined after emptying their bladder. They were assessed in the lithotomy position, with the head of the bed inclined at 30°. To reduce manual biases, the assessments were conducted by experienced personnel who had undergone standardised training, and each participant was taught how to contract the PFM without abdominal or hip muscle contraction or any movement of the pelvis.
The primary outcomes were MVCP in the three groups.1, 8 At present, there is no standard cut-off value for low PFM strength based on MVCP. In this study, we selected <20 cmH2O as the cut-off value to indicate low PFM strength.13 Previous studies have shown that PFM strength is related to factors such as age, number of deliveries, body mass index (BMI), menopause and genetics.14, 15 In addition to the above indicators, we included some other potential factors, such as family history (yes, no or unknown), with reference to whether the participant’s mother or sisters have a history of POP or SUI, toileting (squatting or sitting), work position (sitting, standing or other), occupation type (mainly mental, mainly physical or both), intensity of physical labor (light, moderate or heavy), sexual frequency in the last 3 months (none, less than twice per week or equal to or more than twice per week) and some related comorbidities, such as asthma, allergic rhinitis and diabetes. Moreover, we also detected the strength and muscle fatigue of type-I and -II muscle fibres,4, 18 and the ‘knack’ manoeuvre,1, 19 using intravaginal manometry. Type-I muscle fibre contractions lasting between 0 and 4 s at 40% or above of their maximum intensity are categorised as levels 0–4, respectively. If the contraction lasts for 5 s or more, it is classed as level 5. Similarly, for type-II muscle fibres, contractions repeated at or above 60% of their maximum intensity are categorised as levels 0–4 for 0–4 repetitions, respectively. Five or more repetitions are classed as level 5.18 The measurement for assessing muscle fatigue is based on the percentage decrease between the peak point of the contraction curve and the end point at 5 s. A normal value is 0, whereas a negative value indicates abnormality.4 Under physiological conditions, the PFM will undergo a prior reactive contraction to increase urethral pressure when there is a sudden increase in abdominal pressure, such as a cough. Miller first named the ‘counter-balancing PFM contraction prior to a cough’ as the ‘knack’ in 1998, and demonstrated its effectiveness in controlling urinary incontinence.20 We instruct the participants to contract the PFM according to a unified pattern, during which the participants are asked to cough and the contraction curve of the PFM is observed for the presence of a peak. If the peak does not precede the cough, it indicates an abnormal ‘knack’ and may suggest urinary control dysfunction in the participants.
2.3 Sample size calculation
The primary outcome of this study was the value of MVCP. There were few studies focused on MVCP in healthy women, and we could not calculate the sample size separately for each group. Hence, we utilised data from a previous study involving 559 healthy women with a mean age of 48 years (range 35–64 years) to estimate the standard deviation of MVPC, which was found to be 19.7.21 We define one-fifth of the standard deviation as the value of allowable error (i.e. σ = 19.7, δ = 4). A sample size of 94 participants was calculated through PASS 15 (NCSS Statistical Software, East Kaysville, UT, USA), with a two-sided significance level of 0.05. Based on this, we aimed to recruit 120 participants per group per clinical centre, allowing for approximately a 20% nonresponse rate, giving a total of 5040 participants (1680 participants in each of the three groups).
2.4 Statistical analysis
The data were analysed using SPSS 22.0 (IBM, Armonk, NY, USA). Categorical variables are presented as proportions with frequencies, and were compared using the chi-square test. Continuous variables are presented as medians (interquartile ranges), and were compared using the Kruskal–Wallis test, as they were all non-normally distributed. When exploring the influencing factors of PFM strength, univariate analysis was conducted first to find out the indicators of difference between the low (MVCP <20 cmH2O) and normal (MVCP ≥20 cmH2O) PFM strength groups, and then the potential indicators (p < 0.1) were all included in the multivariate logistic regression to determine the influencing factors. The logistic regression results are presented as odds ratios (ORs) with 95% confidence intervals (95% CIs).
3 RESULTS
3.1 Participant characteristics
From May 2018 to June 2020, 5040 healthy women were enrolled in the study: 1680 women in each of the premenopausal nulliparous, premenopausal parous and postmenopausal groups. The general participant characteristics are shown in Table 1 and the POP-Q values are shown in Table 2. In the premenopausal nulliparous, premenopausal parous and postmenopausal groups, the median (range) age was 30 (19–51), 39 (22–61) and 57 (40–86) years, respectively, and the median (interquartile range) BMI was 20.8 (19.5–23.0), 22.3 (20.4–24.4) and 23.3 (21.5–25.4) kg/m2, respectively. TABLE 1. Sociodemographic characteristics of participants.
| Study characteristics | Premenopausal nulliparous (n = 1680) | Premenopausal parous (n = 1680) | Postmenopausal (n = 1680) |
|---|---|---|---|
| Age (years)a | 30 (27, 33) | 39 (34, 47) | 57 (54, 62) |
| BMI (kg/m2)a | 20.8 (19.5, 23.0) | 22.3 (20.4, 24.4) | 23.3 (21.5, 25.4) |
| Graviditya | 0 (0, 1) | 2 (1, 3) | 2 (2, 3) |
| Number of vaginal deliveriesa | – | 1 (0, 1) | 1 (1, 2) |
| Number of caesarean deliveriesa | – | 0 (0, 1) | 0 (0, 0) |
| History of instrumental deliveryb | – | 26 (2.73%) | 21 (2.22%) |
| Maximum fetal weighta | – | 3400 (3100, 3650) | 3300 (3000, 3600) |
| Number of years after menopausea | – | – | 5 (2, 9) |
| Family historyb | |||
| POP | 23 (1.4%) | 55 (3.3%) | 56 (3.3%) |
| SUI | 141 (8.4%) | 209 (12.4%) | 225 (13.4%) |
| PFM exerciseb | 71 (4.2%) | 194 (11.5%) | 83 (4.9%) |
| Smokerb | 44 (2.6%) | 24 (1.4%) | 16 (1.0%) |
| Asthmab | 13 (0.8%) | 26 (1.5%) | 34 (2.0%) |
| High abdominal pressureb | 132 (7.9%) | 123 (7.3%) | 210 (12.5%) |
| Frequency of sexual intercourse (in past 3 months)b | |||
| None | 217 (12.9%) | 216 (12.9%) | 841 (50.05%) |
| <2 times per week | 1167 (69.5%) | 1277 (76.0%) | 809 (48.15%) |
| ≥2 times per week | 296 (17.6%) | 187 (11.1%) | 30 (1.8%) |
| Toiletingb | |||
| Squatting | 639 (38.0%) | 573 (34.1%) | 528 (31.4%) |
| Sitting | 1044 (62.1%) | 1107 (65.9%) | 1152 (68.6%) |
| Work positionb | |||
| Sitting | 1264 (75.2%) | 1052 (62.6%) | 950 (56.55%) |
| Standing | 237 (14.1%) | 418 (24.9%) | 417 (24.82%) |
| Other | 179 (10.7%) | 210 (12.5%) | 313 (18.63%) |
| Occupation typeb | |||
| Mainly mental | 1086 (65.4%) | 903 (53.8%) | 744 (44.3%) |
| Mainly physical | 116 (6.7%) | 284 (16.9%) | 478 (28.5%) |
| Both | 478 (27.9%) | 493 (29.3%) | 458 (27.3%) |
| Intensity of physical labourb | |||
| Light | 1119 (64.6%) | 970 (57.7%) | 1019 (60.7%) |
| Moderate | 332 (19.8%) | 649 (38.6%) | 600 (35.7%) |
| Heavy | 20 (1.2%) | 61 (3.6%) | 61 (3.6%) |
| Level of educationb | |||
| Primary school | 6 (0.3%) | 84 (5.0%) | 302 (17.98%) |
| Middle or high school | 332 (19.8%) | 618 (36.8%) | 878 (52.26%) |
| University or higher | 1342 (79.9%) | 978 (58.2%) | 500 (29.76%) |
- Note: High abdominal pressure includes long-term chronic cough, constipation or other high-risk factors.
- Abbreviations: PFM, pelvic floor muscle; POP, pelvic organ prolapse; SUI, stress urinary incontinence.
- a Data were not consistent with normal distribution, and are presented as median (P25, P75).
- b Data presented as n (%).
TABLE 2. Pelvic organ prolapse quantification (POP-Q) values of study participants.
| POP-Q (cm) | Premenopausal nulliparous (n = 1680) | Premenopausal parous (n = 1680) | Postmenopausal (n = 1680) |
|---|---|---|---|
| Aa | −2.5 (−3, −2) | −1.5 (−2, −1) | −1.5 (−2, −1) |
| Ba | −2.5 (−3, −2) | −1.5 (−2, −1) | −1.5 (−2, −1) |
| C | −6 (−6,−5) | −5 (−6, −4.5) | −5 (−6, −4) |
| gh | 3 (2.5, 4) | 3.5 (3, 4) | 3.5 (3, 4) |
| pb | 3 (3, 3.5) | 3 (3, 3) | 3 (3, 3) |
| TVL | 8 (7.5, 9) | 8 (8, 9) | 8 (7, 9) |
| Ap | −3 (−3,−2.5) | −2.5 (−3, −2) | −2 (−3, −1.5) |
| Bp | −3 (−3,−2.5) | −2.5 (−3, −2) | −2 (−3, −1.5) |
| D | −7 (−8, −6) | −7 (−7.5, −6) | −7 (−7, −6) |
- Note: Data were not consistent with normal distribution and are presented as median (P25, P75).
- Abbreviations: C, cervix or vaginal cuff; D, posterior fornix (if cervix is present); gh, genital hiatus; pb, perineal body; TVL, total vaginal length.
3.2 PFM strength values
The PFM strength values, evaluated by vaginal manometry, are shown in Table 3. In the premenopausal nulliparous, premenopausal parous and postmenopausal groups, the median (interquartile range) MVCP values were 36 (22–52), 35 (20.5–52) and 35 (20–50) cmH2O, respectively. The proportions of women with low PFM strength in the groups were 20.6% (346/1680), 22.9% (384/1680) and 24.3% (409/1680), respectively. Moreover, the proportions with an abnormal ‘knack’ manoeuvre were 31.0% (520/1680), 40.3% (677/1680) and 46.2% (677/1680), respectively, which are relatively high. TABLE 3. Objective assessment of pelvic floor muscle (PFM) strength using vaginal manometry.
| Muscle strength | Premenopausal nulliparous (n = 1680) | Premenopausal parous (n = 1680) | Postmenopausal (n = 1680) |
|---|---|---|---|
| VRP (cmH2O)a | 46 (36, 61) | 45 (34, 61) | 45 (35, 59) |
| MVCP (cmH2O)a | 36 (22, 52) | 35 (20.5, 52) | 35 (20, 50) |
| MVCP (cmH2O)b | |||
| <20c | 346 (20.6%) | 384 (22.9%) | 409 (24.3%) |
| ≥20c | 1334 (79.4%) | 1296 (77.1%) | 1271 (75.7%) |
| The strength of type-I muscle fibrea | 3 (1, 5) | 1 (1, 3) | 1 (1, 3) |
| The strength of type-II muscle fibrea | 3 (2, 5) | 2 (1, 5) | 2 (1, 4) |
| Muscle fatigue of type-I muscle fibrea | −1 (−3, 0) | −2 (−3, 0) | −2 (−3.75, 0) |
| Muscle fatigue of type-II muscle fibrea | 0 (−1, 0) | 0 (−1, 0) | 0 (−1, 0) |
| Abnormal ‘knack’ manoeuvrec | 520 (31.0%) | 677 (40.3%) | 776 (46.2%) |
- Abbreviations: MVCP, maximum voluntary contraction pressure; VRP, vaginal resting pressure.
- a Data were not consistent with a normal distribution, and are presented as median (P25, P75).
- b Data presented as mean ± standard deviation.
- c Data presented as n (%).
3.3 Potential influencing factors for low PFM strength
In the premenopausal nulliparous group, low PFM strength was related to age, BMI toileting, occupation mode and school education level (Table S1). Multivariate regression analysis demonstrated that occupations primarily involving manual labor (OR 2.05, 95% CI 1.32–3.19, p = 0.001) was an independent risk factor (Table 4). TABLE 4. Multivariate analysis of the influencing factors of low pelvic floor muscle (PFM) strength in healthy women of the premenopausal nulliparous, premenopausal parous and postmenopausal groups.
| Group | Influencing factor | OR (95% CI) | p |
|---|---|---|---|
| Premenopausal nulliparous | Occupation mode | – | 0.006 |
| Physical work mainly vs. Brainwork mainly | 2.05 (1.32, 3.19) | 0.001 | |
| Both vs. Brainwork mainly | 1.08 (0.82, 1.42) | 0.588 | |
| Age | 0.98 (0.96, 1.00) | 0.077 | |
| BMI | 0.97 (0.93, 1.01) | 0.191 | |
| Toileting (sitting vs. squatting) | 0.83 (0.65, 1.07) | 0.16 | |
| School education | – | 0.55 | |
| Middle or high school vs. primary | 1.48 (0.17, 13.18) | 0.73 | |
| University or higher vs. primary | 1.25 (0.14, 11.12) | 0.84 | |
| Premenopausal parous | Number of vaginal deliveries | 1.28 (1.09, 1.51) | 0.003 |
| Frequency of sexual intercourse (in past 3 months) | – | 0.001 | |
| <2 times per week vs. none | 0.55 (0.40, 0.76) | <0.0001 | |
| ≥2 times per week vs. none | 0.56 (0.36, 0.89) | 0.0014 | |
| PFM exercise | 0.50 (0.32, 0.78) | <0.0001 | |
| Diabetes | 2.70 (1.74, 4.18) | <0.0001 | |
| Gravidity | 1.02 (0.93, 1.12) | 0.65 | |
| Asthma | 1.62 (0.71, 3.69) | 0.254 | |
| School education | – | 0.253 | |
| Middle or high school vs. primary | 0.84 (0.48, 1.48) | 0.547 | |
| University or higher vs. primary | 1.19 (0.92, 1.53) | 0.18 | |
| Postmenopausal | Number of vaginal deliveries | 1.32 (1.14, 1.53) | <0.0001 |
| Family history of POP | – | 0.014 | |
| Yes vs. none | 1.83 (1.03, 3.24) | 0.039 | |
| Unknown vs. none | 1.34 (1.05, 1.71) | 0.019 | |
| Number of caesarean deliveries | 1.04 (0.70, 1.53) | 0.852 | |
| Toileting (sitting vs. squatting) | 0.90 (0.70, 1.17) | 0.433 |
- Abbreviations: MVCP, maximum voluntary contraction pressure; VRP, vaginal resting pressure.
In the premenopausal parous group, low PFM strength was related to gravidity, number of vaginal deliveries, PFM exercise, asthma, diabetes, frequency of sexual intercourse and school education level (Table S2). Multivariate regression analysis demonstrated that the number of vaginal deliveries (OR 1.28, 95% CI 1.09–1.51, p = 0.003) and diabetes (OR 2.70, 95% CI 1.74–4.18, p < 0.0001) were independent risk factors, whereas sexual intercourse (<2 times per week vs. none, OR 0.55, 95% CI 0.40–0.76, p < 0.0001; ≥2 times per week vs. none, OR 0.56, 95% CI 0.36–0.89, p = 0.0014) and PFM exercise (OR 0.50, 95% CI 0.32–0.78, p < 0.0001) may have protective effects (Table 4).
In the postmenopausal group, low PFM strength was related to the number of vaginal deliveries, the number of caesarean deliveries, family history of POP and toileting (Table S3). Multivariate regression analysis demonstrated that the number of vaginal deliveries (OR 1.32, 95% CI 1.14–1.53, p < 0.0001) and a family history of POP (OR 1.83, 95% CI 1.03–3.24, p = 0.039) were independent risk factors (Table 4). In addition, we explored the relationship between the number of vaginal deliveries and MVCP, observing that MVCP decreased as the number of vaginal deliveries increased in both premenopausal parous women (Figure S1A) and in postmenopausal women (Figure S1B).
4 DISCUSSION
4.1 Main findings
In the present study, we established PFM strength values and determined influencing factors for low PFM strength in women at different life stages. Occupations primarily involving physical work was an independent risk factor for low PFM strength in the premenopausal nulliparous group. The number of vaginal deliveries was an independent risk factor for low PFM strength in both the premenopausal parous group and the postmenopausal group, and MVCP decreased as the number of vaginal deliveries increased in both these groups. Diabetes was also an independent risk factor for low PFM strength in premenopausal parous women, whereas a family history of POP was an independent risk factor in postmenopausal women. Sexual intercourse and PFM exercise may have protective effects on PFM strength in premenopausal parous women.
4.2 Strengths and limitations
Our study has several strengths. First, our sample size was relatively large and consisted of participants from multiple regions. Second, this is the first study to provide a reference for PFM strength in healthy Chinese women at different stages of life by grouping participants into premenopausal nulliparous, premenopausal parous and postmenopausal groups. Third, compared with previous studies, we detected more potential factors that may affect PFM strength and explored the specific influencing factors of PFM strength in the three groups mentioned above.
One of the most noteworthy limitations of this study is that its sample was non-randomised and inadequately sized to comprehensively represent the complete demographics of healthy Chinese women. Additionally, the data suffer from a considerable interquartile range, which could undermine the validity of the results.
4.3 Interpretation
4.3.1 PFM strength values in women at different life stages
Previous studies on PFM strength have largely focused on individuals with pelvic floor disorders or women during pregnancy and postpartum.4, 5, 10–13 However, there have been relatively few studies examining PFM strength in healthy women. The present study is unique in its focus on PFM strength in healthy Chinese adult women, and found that the median (interquartile range) MVCP values were 36 (22, 52), 35 (20.5, 52) and 35 (20, 50) cmH2O in the premenopausal nulliparous, premenopausal parous and postmenopausal groups, respectively. Previous studies conducted in Brazil and Iran showed that the mean MVCP values were 45.6 and 55.62 cmH2O, respectively, in nulliparous women, values that are both higher than our findings.9, 22 Another study conducted in India reported mean MVCP values of 40.04 and 37.69 cmH2O in premenopausal nulliparous and parous women, respectively, which are roughly similar to our results (39.45 and 38.20 cmH2O respectively), whereas the value in postmenopausal women (34.93 cmH2O) was significantly lower than our finding (37.25 cmH2O).15 The differences in PFM strength among the above three groups did not seem to be very significant. Our study differs from previous studies in several ways, which may help to explain the observed discrepancies. First, our study had a larger sample size and covered a wider age range compared with previous studies, in which participants tended to be younger. Additionally, ethnic differences may also be a contributing factor, given that previous literature has indicated that ethnicity can impact PFM strength.23, 24 Lastly, differences in the vaginal manometry instruments used across studies may also introduce bias into the data and contribute to differences in findings.
4.3.2 Influencing factors of PFM strength
The relationship between age and low PFM strength remains controversial. Ilić et al. demonstrated that increasing age was positively associated with decreasing PFM strength,14 whereas another study demonstrated no significant differences in PFM strength among nulliparous women in different age groups.25 Pandey and Batra15 found that age is a risk factor for low PFM strength only in premenopausal nulliparous women, whereas years after menopause, rather than age, had a negative effect on PFM strength in postmenopausal women. In the present study, age was not found to be an independent risk factor for low PFM strength, which needs to be investigated further in future studies.
Consistent with previous studies, we found that the number of vaginal deliveries,14, 15, 26 and a family history of POP,24, 27 were independent risk factors for low PFM strength, and that MVCP decreased as the number of vaginal deliveries increased in both premenopausal parous women and postmenopausal women. Previous research has shown that taking part in physical work, which causes increased stress on the PFM, can also decrease PFM strength,14 which is consistent with the results of the present study.
There is no doubt that PFM exercise has a certain protective effect on PFM strength. However, the protective effect is only detected in premenopausal parous women in the present study. The reason for this could be because most premenopausal nulliparous women have normal PFM strength, and the protective effect was diminished in postmenopausal women. Moreover, the proportion of PFM exercise in the other two groups was relatively lower than that in the premenopausal parous women. As speculated by Kanter et al.,28 sexual intercourse can be considered an activity involving PFM contraction. Kanter et al. showed that sexually active women were more likely to have a strong PFM.28 We also found that sexual intercourse was a protective factor for PFM strength, but only in premenopausal parous women. However, the causal relationship between sexual intercourse and PFM strength is difficult to determine, as impaired PFM strength may also cause sexual dysfunction.29
4.3.3 ‘Knack’ manoeuvre
In our study, the proportion of participants with an abnormal ‘knack’ manoeuvre was approximately one-third to one-half in each group (31.0%, 40.3% and 46.2% in the premenopausal nulliparous, premenopausal parous and postmenopausal groups, respectively), which are relatively high proportions. The ‘knack’ manoeuvre has generally been included in treatment concepts as part of PFM training, and the symptom of urine leakage has been reported to be effectively improved by ‘knack’ manoeuvre training.30 However, the impact of the ‘knack’ manoeuvre on PFM strength varies among different studies.30, 31 In any case, the high rates of abnormal ‘knack’ manoeuvre suggest that we need to pay attention to the correct exercise method when recommending PFM exercise for high-risk groups with low PFM strength.
5 CONCLUSION
The median (interquartile range) MVCP values were 36 (22, 52), 35 (20.5, 52) and 35 (20, 50) cmH2O, respectively, and the influencing factors for low PFM strength varied among women at different life stages. In premenopausal nulliparous women, taking part in physical work was an independent risk factor for low PFM strength. In premenopausal parous women, the number of vaginal deliveries and diabetes were independent risk factors for low PFM strength, whereas sexual intercourse and PFM exercise may have protective effects. In postmenopausal women, the number of vaginal deliveries and a family history of POP were independent risk factors for low PFM strength. The knowledge of PFM strength and the main risk factors for low PFM strength in women at different life stages will be beneficial for identifying women at high risk of impaired PFM strength and encouraging the early protection of PFM strength.
ARYAN'S BLOG 