Pelvic Floor Testing Methods Rarely Matched in Women With Stress Urinary Incontinence
In women with stress urinary incontinence, the tools used to judge pelvic floor strength did not line up as closely as clinicians might expect. A cross-sectional study comparing digital vaginal palpation with the Modified Oxford Scale and two forms of surface electromyography found only limited association between the bedside exam and electrical activity, while the two sEMG recording approaches performed poorly against each other.
The finding matters because pelvic floor assessment often guides rehabilitation decisions, patient counseling, and follow-up after training. When separate methods appear to measure different aspects of function, a single score can look reassuring while another modality tells a different story.
Limited Link Between Manual Grading and Electrical Signal
The study enrolled 25 women with SUI between December 25, 2025, and January 25, 2026. Each participant underwent sequential pelvic floor muscle evaluation using digital vaginal palpation with the Modified Oxford Scale, transperineal sEMG, and intravaginal sEMG. Investigators then examined how strongly the manual score tracked with the EMG parameters, using Spearman’s rank correlation coefficient.
During the 5-second contraction protocol, moderate positive correlations emerged between MOS scores and selected sEMG measures, with rho values ranging from 0.414 to 0.445 and p values below 0.05. Outside that narrow window, the associations fell apart. The remaining correlations were not statistically significant, which points to a modest and inconsistent relationship between what the examiner feels and what the electrodes record.
One-sentence clinical reality: a stronger palpation grade did not reliably translate into a stronger electrical signature.
That gap is biologically plausible. Digital palpation captures a composite of contraction force, timing, endurance, and examiner perception, while sEMG reflects muscle activation patterns influenced by electrode placement, tissue conductivity, and signal processing. In the pelvic floor, where anatomy varies and the target muscle group is compact and deep, two valid methods can still diverge if they are sensing different layers of performance rather than a single unified construct.
Poor Concordance Between Transperineal and Intravaginal sEMG
The larger mismatch came when the two EMG methods were compared directly. Agreement between transperineal and intravaginal recordings was poor across the evaluated parameters, with intraclass correlation coefficients ranging from -0.136 to 0.162. Those values sit far from the range that would support interchangeability in routine practice.
Bland–Altman analysis added another cautionary layer. Systematic bias appeared for selected parameters, and the limits of agreement were wide. In practical terms, the same patient could receive meaningfully different readouts depending on whether the signal was captured transperineally or intravaginally. For a clinician trying to track response to pelvic floor training over time, that kind of variability can obscure whether the patient is improving or whether the device is simply reading the contraction differently.
A second one-sentence takeaway follows from the data: the two sEMG setups cannot be treated as interchangeable based on these results.
Several reasons could explain the mismatch. Transperineal recording may be more vulnerable to skin and soft-tissue attenuation, while intravaginal recording may sample a slightly different muscular field and be more sensitive to placement consistency. Even subtle differences in probe positioning, contraction instruction, or signal filtering can alter amplitude and shape. In pelvic floor research, those technical details are not cosmetic; they can determine whether a measurement is clinically interpretable at all.
What the Small Sample Means for Pelvic Floor Practice
The cohort was small, and the design was cross-sectional, so the study cannot determine whether one method is superior for predicting symptoms, treatment response, or long-term function. It also does not establish whether the methods are capturing distinct physiological constructs or whether the observed discordance arises mainly from measurement noise. Those are separate questions, and they should not be collapsed into one.
Still, the pattern is hard to ignore. Manual palpation showed only partial alignment with sEMG, and the two EMG approaches showed poor mutual agreement. For clinicians managing SUI, that suggests caution when using one modality as a surrogate for another. A woman may demonstrate a reasonable MOS score while her EMG profile remains low, or vice versa, and either result could influence how progress is interpreted during pelvic floor muscle training.
The study also points to a broader problem in pelvic floor rehabilitation research: measurement standardization remains unfinished. Without validated reference methods, standardized acquisition protocols, and consistent processing rules, it is difficult to compare trials or decide whether one tool is tracking true physiologic change or simply producing a different number.
Why Measurement Consistency Matters for Stress Urinary Incontinence Care
SUI remains one of the most common reasons women are referred for pelvic floor rehabilitation, and treatment success often depends on repeated assessment. When measurement tools disagree, the risk is not only academic. Patients may be advanced too soon, held back unnecessarily, or labeled as nonresponders when the instrument, not the muscle, is responsible for the discrepancy.
This study adds a practical warning: pelvic floor assessment in SUI cannot assume that all strength measures speak the same language. The MOS and the two sEMG techniques each provide information, but the present data show that they do not consistently move together under the conditions tested.
Future work will need larger samples, standardized EMG acquisition and processing, and validated reference methods before clinicians can say with confidence whether transperineal and intravaginal recordings should be used side by side, separately, or not as substitutes at all. For now, the study leaves pelvic floor testing in a narrower but useful place: measurement is possible, but interchangeability is not established.