Reliability of pelvic floor muscle strength assessment using different test positions and tools

The aims of this study were to determine the intra-therapist reliability for digital muscle testing and vaginal manometry on maximum voluntary contraction strength and endurance. In addition, we assessed how reliability varied with different tools and different testing positions.

Subjects included 20 female physiotherapists. The modified Oxford scale was used for the digital muscle testing, and the Peritron perineometer was used for the vaginal resting pressure and vaginal squeeze pressure assessments. Strength and endurance testing were performed. The highest of the maximum voluntary contraction scores was used in strength analysis, and a fatigue index value was calculated from the endurance repetitions. Bent-knee lying, supine, sitting, and standing positions were used. The time interval for between-session reliability was 2-6 weeks.

Kappa values for the between-session reliability of digital muscle testing were 0.69, 0.69, 0.86, and 0.79 for the four test positions, respectively. Intra-class correlation coefficient (ICC) values for squeeze pressure readings for the four positions were 0.95, 0.91, 0.96, and 0.92 for maximum voluntary contraction, and 0.05, 0.42, 0.13, and 0.35 for endurance testing. ICC values for resting pressure were 0.74, 0.77, 0.47, and 0.29.

Reliability of digital muscle testing was very good in sitting and good in the other three positions. vaginal resting pressure demonstrated very good reliability in all four positions for maximum voluntary contraction, but was unreliable for endurance testing. Vaginal resting pressure was not reliable in upright positions. Both measurement tools are reliable in certain positions, with manometry demonstrating higher reliability coefficients.