BMI was higher in the older age range, compared with younger women, and there was a progressive increase in BMI with aging. Other authors have also observed an increase in weight with aging and this factor could be correlated with menopause [17,18]. Different studies have demonstrated the presence of PFM dysfunction related to aging, parity, and vaginal deliveries [19,20]. Interestingly, in our series of continent women, despite the higher BMI and the higher number of pregnancies and vaginal deliveries in older women, there was no statistically significant difference in PFM strength in the different age ranges, showing that the aging process in continent women generally did not influence PFM strength. There was a positive linear relationship between PFM weakness, BMI, and vaginal deliveries though, and considering this, probably the interaction of these factors may have contributed to the decrease in PFM strength encountered in some of these continent women.
The International Continence Society (ICS) has defined by consensus, the diagnosis and treatment of pelvic floor dysfunctions . They standardized the terminology of pelvic floor muscle function and acknowledged that assessing it by vaginal digital palpation is easy to perform, but emphasized that quantification of PFM contraction is problematic [21,22]. In our study, we used a scale of four grades, varying from 0 to 3, as described by Amaro et al. , with the objective to facilitate the understanding and reproducibility in clinical practice. However, different authors do not consider digital palpation of the vagina as a sensitive and reproducible method for the assessment of PFM function [11,23,24]. On the other hand, others have reported that this would be the best qualitative method to assess the contraction and muscular strength of PFM [11,25,26].
In our study, there was no correlation between muscle weakness and age. This finding is in agreement with the literature where the physiological aging "per se" in continent women does not correlate with decrease of PFM strength . However, in incontinent women the PFM strength was significantly lower than continents and worsens during the aging process [3,28].
Our results are consistent with the literature that reports the difficulty of assessing PFM function by vaginal digital palpation, due to variability of its anatomy. This assessment still depends on the skill and experience of examiners. The examiners who participated in our study had 4–5 years of work experience after graduation and, despite that, there were some different interpretations of PFM contraction degree. Our find are in agreement with the literature, that shows reproducibility of the TDP method, with some restrictions [26,28-30]. Slieker-ten Hove et al. , conducted a reproducibility study with 4 different examiners by TDP, demonstrating high intra-observer rates of reproducibility, and low inter-examiner rates. According to the authors, the classifications used in the studies may not have enough accuracy to properly distinguish between individuals.
Morin et al.  reported that it is not possible to establish any correlation between TDP and objective methods of evaluation, such as dynamometer or perineometer. In another study of our group, we also observed that the correlation with objective methods of evaluation of PFM and its reproducibility are questionable [3,13].
The intra-rater reliability refers to the concordance of each anterior and posterior TDP assessment of pelvic floor contractions, for each subject and for each examiner. Our results objectively revealed a good level of concordance, indicating that the TDP assessment is accurate for evaluating the pelvic floor muscular strength in either position. However, when we take in consideration the inter-rater reliability between each two examiners, the concordance varied between moderate to good. Inter-rater reliability refers to the concordance of PFM grading on the same subject, by different examiners. This fact is in agreement with the findings of other authors that have highlighted the differential profile of vaginal pressure distributed along the vaginal canal , and that this is a subjective evaluation, dependent of examiners’ training . Consequently, the accuracy of this assessment test depends on the skill and experience of the examining physical therapist.
Different measurement tools assess different aspects of PFM function, and it is important to look at them as complementary in a thorough PFM evaluation, not mutually exclusive. Further studies are necessary to evaluate the concordance between tests using different classifications and their inter-rater reliability.