Foley Balloon Pull Test of Pelvic Floor Muscle Strength

Methods for pelvic floor muscle (PFM) strength testing are limited by their subjective nature, prohibitive cost, training burden, or lack of validation.

The objectives of this study are to validate a new, inexpensive, and accessible method for PFM strength testing using a 30-mL Foley balloon inserted into the vagina, the Foley Balloon Pull Test (FPT), and to demonstrate external validity by comparing the subjective Oxford Muscle Grading Scale (OMGS) scores to measurements obtained with the FPT. Secondary objectives include demonstrating repeatability and internal validity of the FPT.

Participants underwent PFM strength testing with the OMGS on a 0 to 5 scale. A gauge was attached to the Foley balloon to measure the force required to remove the balloon from the vagina. Three measures at rest and 3 measures during maximal muscle contraction were recorded. Cross-sectional data were analyzed.

One hundred one participants were included; there were no adverse events. The ratio of contraction FPT measurements to at-rest measurements revealed moderate linear and rank order correlation with the OMGS ( R2 = 0.54, P < 0.001, and R2 = 0.58, P < 0.001). The reliability of repeated measurements was highly correlated, with intraclass correlation coefficients >0.95. An FPT ratio of 1.75 discriminated between weak (0-2) and strong (3-5) OMGS scores with an area under the curve of 0.86.

The FPT is an internally reliable, simple, and externally valid method of PFM strength testing.