Reliability of dynamometric measurements of the pelvic floor musculature

The objective of this study was to evaluate the reliability of strength and endurance dynamometric measurements of the pelvic floor musculature (PFM).

Twenty-nine female participants, primipara and multipara, aged between 27 and 42 and presenting different severity levels of stress urinary incontinence (SUI), participated in the study. They were evaluated using a new pelvic floor dynamometer, an instrumented speculum based on strain-gauged technology. Strength and endurance evaluations were repeated in three successive sessions, each followed by a 4-week period. Maximal strength values were recorded at three dynamometer openings (5 mm, 1 cm, and 1.5 cm between the two dynamometer branches). The maximal rate of force development (MRFD) and percentage of strength lost after 10 and 60 sec were computed from the endurance trial. The generalizability theory was applied to estimate the reliability of the PFM measurements. The reliability was quantified by the index of dependability and the corresponding standard error of measurement (SEM) for one and the mean of three trials performed in one session for the strength measurements and one trial completed in one session for the MRFD and endurance measurements.

For the maximal strength measurements, the largest coefficient of dependability was obtained at the 1 cm opening, with a value of 0.88. The corresponding SEM reached 1.49 N. The reliability of the MRFD was also very good with a coefficient of 0.86 and an SEM of 0.056 N/sec. The reliability was minimally affected by the number of trials. The strength loss measurements at 10 and 60 sec were unreliable, with coefficient values of 0.38 and 0.10, respectively.

The results of the present study indicate that the reliability of the strength parameters (maximal strength and MRTD measurements) was high enough for future investigations on pelvic floor rehabilitation programs.