Urinary incontinence is worldwide a major problem. Stress urinary incontinence (SUI), defined as the complaint of involuntary loss of urine on effort or physical exertion (e.g. sporting activities), or on sneezing or coughing is the most common form of urinary incontinence especially among younger women. Female athletes report a prevalence of SUI up to 80%, depending on their sports activity, which is highest during high-impact activities, such as jumping or running (1). Ultrasound and magnetic resonance imaging is applicable to measure PFM displacement during voluntary contractions and reflexive tasks like coughing. During a voluntary PFM contraction a cranio-caudal elevation and with coughing a caudal-dorsal descent of the PFMs has been demonstrated (2). High intra-abdominal pressure occurs during sports activities. An intra-abdominal pressure increase will displace the PFMs caudally, which needs to be counteracted by a PFM activity. PFM displacement is increasingly explored during running (3), but has not been investigated during jumps. However, enhanced comprehension of PFM displacement and its related muscle action is clinically relevant for the development of specific approaches in rehabilitation.
The aim of the study was to describe and to compare PFM displacement between women who were continent and women with SUI during jumps before and after initial contact.

A cross-sectional, exploratory pilot design was applied. The study was approved by the Ethics Committee of the Canton of Bern, Switzerland (No. 391/14). PFM displacement was assessed in six degrees of freedom with an electromagnetic tracking system (ETS). Data were recorded during 3 drop jumps (DJ) and counter movement jumps (CMJ). An ETS sensor was attached to a vaginal probe. A referential ETS sensor was attached at the second sacral vertebrae. To detect impacts, i.e. ground reaction force (GRF) and related body weight force (BWF) during landing and take-off, a force plate was used. Cranial-caudal translation and forward-backward rotation of the vaginal probe was measured from 30 ms before to 150 ms after ground contact in six 30 ms-intervalls.

Twenty-six continent (CON: 39.3 ± 10.5 years, BMI: 21.5 ± 1.7 kg/m2) and twenty-one stress incontinent (SUI: 45.8 ± 9.9 years, BMI: 21.4 ± 2.0 kg/m2) women were included. Groups differed significantly for ICIQ-UIsf (CON: 1 ± 1; SUI: 7 ±2) and age, but not for Oxford grade and BMI. 
Cranial-caudal translation and BWF from 30 ms before to 150 ms after ground contact during first landing is shown in figure 1. Maximal caudal translation (CON: 10.3 ± 7.2 mm, SUI: 13.4 ± 11.8 mm) and maximal cranial translation (CON: 5.0 ± 5.5 mm, SUI: 4.9 ± 5.1 mm) was raised during the first landing of DJ. Maximal caudal translation (second landing DJ: CON: 5.4 ± 8.8 mm, SUI: 5.2 ± 6.1 mm; landing CMJ: CON: 8.3 ± 12.8 mm, SUI: 5.4 ± 5.7 mm) and maximal cranial translation (second landing DJ: CON: 12.2 ± 10.9 mm, SUI: 8.4 ± 7.6 mm; landing CMJ: CON: 9.1 ± 7.3 mm, SUI 11.6 ± 11.3 mm) during the second landing of DJ and landing of CMJ showed more cranial than caudal translation compared to the first landing of DJ, p<0.05 (Table 1). Contrary to the translational displacement no differences between jumps and groups could be found for the rotational aspects, showing forward rotation before and backward rotation after landing (before landing: 0.1 to 0.6°; after landing: 1.4 to 10.9°) this for all jumps and groups. The investigation concerning PFM displacement during vertical jumps for CON and SUI showed no significant difference between the groups.

PFM displacement has been explored during running and demonstrated caudal translation/forward rotation before and cranial translation/backward rotation after heel-strike (3). In this study this mechanism could be seen during the second landing of DJ and the landing of CMJ. During the first landing of DJ a caudal translation/backward rotation has been observed, this may be due to the higher BWF in the first landing of DJ. During coughing the bladder neck displacement has been described in dorso-caudal direction and the ano-rectal angle in ventro-caudal (CON) and dorso-caudal (SUI) direction (2). The ventro-caudal displacement of the ano-rectal angle may be compared to the backward rotation.

This study describes kinematic properties during vertical jumps and indicates that during jumps two opposite reactions of involuntary PFM displacement happen, which may provide a better understanding of PFM contraction behavior during impact loads.

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Leitner M, Moser H, Eichelberger P, Kuhn A, Baeyens JP, Radlinger L. Evaluation of pelvic floor kinematics in continent and incontinent women during running: An exploratory study. Neurourol Urodyn. 2017. https ://doi.org/10.1002/nau.23340