Reliability of pelvic floor muscle electromyography tested on healthy women and women with pelvic floor muscle dysfunction.

Objectives
Electromyography (EMG) is a well-established method to quantify the relative pelvic floor muscle (PFM) activity. PFM EMG has shown good reliability in healthy women. However, its reliability has not been tested in women with PFM dysfunction. The reliability of EMG analysis methods concerning EMG normalization needs to be determined to assess specific therapeutic interventions. Therefore, the aim of this study was to investigate the intra-session reliability of PFM EMG variables by using 3 different analysis methods in women with PFM dysfunction.

Methods
EMG data analysis involved women who were healthy, had weak PFM and had stress urinary incontinence (SUI). We evaluated the reliability of EMG during rest and maximum voluntary contraction and compared muscle activity onset by visual determination and by calculation. All variables were checked for normality (Shapiro-Wilk). Descriptive statistics (mean, SD), systematic error within repeated measures (Wilcoxon) and reliability indexes were tested and presented descriptively (intraclass correlation coefficient [ICC], standard error of measurement [SEM], SEM%, minimal difference [MD], MD%).

Results
For 20 women who were healthy, 17 with weak PFM and 50 with SUI, ICC values were high for all variables (0.780–0.994), and SEM and MD values were relatively high (SEM%: 7.5–15.7; MD%: 21.0–43.8).

Conclusion
We need reliable methods to analyse clinical intervention studies. PFM EMG variables had high ICCs, but relatively high SEM and MD values modified the reliability. All EMG analysis methods were comparable in healthy women, but only the visual-onset determination was dependable in women with PFM dysfunction.