Reliability of speed of contraction and endurance dynamometric measurements of the pelvic floor musculature in stress incontinent parous women

Aims: To evaluate the test-retest reliability of dynamometric measurements of the pelvic floor muscles (PFM) during speed and endurance tests. Methods: Nineteen parous women suffering from stress urinary incontinence (SUI) participated in the study. Two PFM evaluation sessions were conducted using the dynamometric speculum. For the speed test, the women were instructed to contract maximally and relax as quickly as possible during a 15-s test period. The speed of contraction was quantified by the rate of force development of the first contraction and the number of contractions performed. The maximal strength value attained during the speed test was also extracted from the curves. For the endurance test, the subjects were asked to maintain a maximal contraction for 90 s. The normalized area under the force curve was utilized as the endurance parameter. The reliability of the data was evaluated using the generalizability theory. Two reliability estimates were calculated, the dependability indices (Phi) and the standard error of measurement (SEM), for one measurement session involving one trial. Results: The indices of dependability obtained indicate that the reliability of the speed of contraction and endurance parameters are good (Phi-0.79-0.92). The corresponding SEMs were 1.39 N/s, 1 contraction, 1.00 N, and 298%*s for the rate of force development, number of contractions, maximal strength and normalized area, respectively. Conclusion: This study indicates that the speed of contraction and endurance parameters possess good test-retest reliability. The inclusion of these parameters in the PFM assessment is therefore highly recommended for assessing changes in PFM in incontinent women.