Ultrasound examination
CONTRACTION
After the initial learning session on how to correctly contract the PFM, the participants were examined with three- and four-dimensional transperineal ultrasound by one of two trained investigators (JSJ, FS). A GE Voluson E8 system (GE Medical Systems, Zipf, Austria), with a 4– to 8-MHz curved-array volume transducer (RAB4-8l/obstetric) was used. After voiding, the participant was positioned in a standardized supine lithotomy position, a position used throughout the whole study when acquiring ultrasound volumes. Ultrasound images were acquired at rest, during maximal PFM contraction and maximal Valsalva maneuver, using a previously described methodology [