The reliability of surface EMG recorded from the pelvic floor muscles

The neuromuscular function of the pelvic floor muscles (PFMs) is frequently evaluated using surface electrodes embedded on vaginal probes. The purpose of this study was to determine the between-trial and between-day reliability of EMG data recorded from the PFM using two different vaginal probes while subjects performed PFM maximum voluntary contractions and a coughing task. The Femiscan and the Periform vaginal probes were used to acquire EMG data while the subjects performed the tasks. Peak RMS amplitudes were computed for each instrument, task, and side of the pelvic floor using a sliding window technique. The between-trial reliability was evaluated using intraclass correlation coefficients (ICCs) and coefficients of variation (CV). Between-trial reliability was determined using ICCs, Pearson's correlation coefficients, computing the mean absolute difference between days, and calculating the standard error the measurement (SEM) for each instrument and task. EMG amplitude differences were detected between the left and right PFM (p<0.05), therefore all of the analyses were performed separately for each side. Overall, between-trial reliability was fair to high for the Femiscan (ICC((3,1))=0.58-0.98, CV=8.5-20.7%) and good to high for the Periform (ICC((3,1))=0.80-0.98, CV=9.6-19.5%), however between-day reliability was generally poor for both vaginal probes (ICC((3,1))=0.08-0.84). The results suggest that although it is acceptable to use PFM surface EMG as a biofeedback tool for training purposes, it is not recommended for use to make between-subject comparisons or to use as an outcome measure between-days when evaluating PFM function.