Background. The most commonly used method to measure pelvic floor muscle (PFM) strength is vaginal squeeze pressure. There are, however, several apparatuses available for this purpose, and sizes of the probes differ significantly. The aim of the present investigation was to assess whether the size of two commonly used vaginal probes influences measurement of PFM strength.
Methods. Twenty female physical therapy students, mean age 25.1 years (range 21–38), participated in the study. All were able to contract the PFM, as assessed by means of vaginal palpation and observation of inward movement of the perineum. Two measuring devices with different lengths and diameters, the Peritron and the Camtech, were used in order to assess vaginal squeeze pressure. Each woman performed six contractions with each apparatus.
Results. Mean maximum squeeze pressure for the whole group with the Camtech was 19.7 cm H2O (95% CI: 16.5–22.9) and with the Peritron 36.5 cm H2O (95% CI: 31.7–41.3), P < 0.01. Nine women preferred the Camtech, four preferred the Peritron, and seven did not have any specific preferences.
Conclusions. Measurements of vaginal squeeze pressure differ depending on the vaginal probe used. Results from published studies using various probes should, therefore, not be compared or combined in systematic reviews or meta-analysis.