gms | German Medical Science

Introduction: 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]. High intra-abdominal pressure occurs during sports activities. An intra-abdominal pressure increase has the potential to displace the PFMs caudally, which needs to be counteracted by a PFM activity. To date, PFM activity during whole-body movements that potentially provoke urinary leakage is increasingly explored. However, the importance of involuntary reflex activity of the PFM for continence has been recognized.

Ultrasound and magnetic resonance imaging are used to measure bladder neck/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]. 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 activity and displacement between women who were continent and women with SUI during jumps before and after initial contact.

Objective: The study investigated female PFM activity and displacement during jumps, by means of electromyographic (EMG) measurement to clarify the involuntary reflex activity of the PFMs and an electromagnetic tracking system (ETS) to assess the PFM displacement.

Methods: Twenty-six continent and twenty-one incontinent women aged between 18 and 60 years were included. A vaginal probe was used to record surface EMG activity and an ETS in six degrees of freedom to assess PFM displacement of the PFMs during three drop jumps (DJ) and counter movement jumps (CMJ). A referential ETS sensor was attached at the second sacral vertebrae. Cranial-caudal translation and forward-backward rotation of the vaginal probe was measured. Six time intervals of 30 ms were used to parameterize data from 30 ms before (pre-activity) to 150 ms after ground contact (reflex activity) on a force plate to detect impacts, i.e. ground reaction force (GRF) and related body weight force (BWF) during the landing and take-off phase. All EMG signals were normalized to the mean of the peak values of two maximal voluntary contractions (MVC) and expressed in percentage (%MVC). Cranial-caudal translation and forward-backward rotation of the vaginal probe was analyzed.

Results: 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. The measurement of PFM activation and displacement during DJ and CMJ for continent and incontinent women showed no significant difference between the groups (P < 0.05). EMG values exceeded 100 %MVC for all time intervals during all landing and take-off phases. The mean of PFM pre-activation (CON: 136.3 ± 87.5 %MVC, SUI: 171.2 ± 88.3 %MVC) and PFM reflex activation (CON: 171.5 to 211.9 %MVC, SUI: 192.6 to 230.4 %MVC,) was reached during the first landing of DJ. During the second landing of DJ the mean of PFM pre-activation (CON: 132.0 ± 53.1 %MVC, SUI: 158.6 ± 78.1 %MVC) and PFM reflex activation (CON: 103.4 to 151.4 %MVC, SUI: 126.8 to 182.1 %MVC,) was raised (Figure 1 [Fig. 1]). During the landing of CMJ the mean of PFM pre-activation (CON: 145.5 ± 56.8 %MVC, SUI: 187.1 ± 92.3 %MVC) and PFM reflex activation (CON: 144.3 to 174.5 %MVC, SUI: 160.9 to 205.0 %MVC,) was raised

Cranial-caudal translation and BWF from 30 ms before to 150 ms after ground contact during first landing of DJ are shown in Figure 2 [Fig. 2]. 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) were reached 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). 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.

Conclusions: This study describes kinematic properties during vertical jumps. Vertical jumps seem to stimulate pre-activity before and reflex activity after ground contact during the landing phase. A fast and high PFM activation occurs, which are good conditions for a reactive strength training / power training. Jumping stimuli inducing involuntary PFM contraction should be used for future investigations to consider a beneficial effect concerning continence and a better understanding of PFM contraction behaviour during impact loads.