gms | German Medical Science

Introduction: Stress urinary incontinence (SUI), defined as involuntary loss of urine during effort or physical exertion or upon sneezing or coughing, has also been attributed to a lower speed of contraction of the pelvic floor muscles (PFM). Therefore, it was suggested that PFM assessment and training also implement fast voluntary contractions (FVC) [1], [2]. For this, women are instructed to ‘contract-relax’ as quickly and strongly as possible. However, up to date, the feasibility of electromyography (EMG) as well as the reduction and parametrization of data and the comparison between continent and incontinent women has not been reported. The purpose of the study was to explore FVC regarding the feasibility of EMG-measurements, the on-/offset and rate of activity determination as well as differences between continent (CON) and stress urinary incontinent (SUI) women.

Methods: Fifty women were included in this exploratory cross-sectional study (CON: n=28; SUI: n=22) and examined by means of PFM EMG during rest, maximum voluntary contractions (MVC) and five FVCs. MVC-peak activity was used to normalise EMG-data. On-/offset of muscle activity was determined as mean of rectified rest activity plus 1 standard deviation [3]. Linear regression was calculated for rate of activity from onset to peak, peak to offset and within 200ms after both onset and peak. Peak activity and time variables related to onset, peak, and offset were calculated. Descriptive statistics, parametric t-tests and nonparametric Mann-Whitney-U-test were computed for all respective variables.

Results: On-/offsets were evaluable for 234/222 of 250 FVCs by a computer-based algorithm, 16/28 on-/offsets had to be determined manually. There was no significant difference between groups (CON/SUI) regarding FVC peak (92.1/99.3 %MVC), time to peak (514.2/525.6 ms) and increase of activity (182.8/182.1 %MVC/s). The SUI group showed a significantly slower activity decrease (-120.7/-74.4 %MVC/s). The regression model fitted well for linear function onset+200ms and peak+200ms (median R2: CON: .954, SUI: .936; median R2: CON: .806, SUI: .900).

Conclusions: FVC measurements and analyses were shown to be feasible and the introduced parametrisation of the activity time curve can be recommended for future investigations. Although rate of force development measured by dynamometry is known to be lower in women with SUI, rate of activity could not support these results. The significant difference observed between the groups did not refer to activity increase but instead to a prolonged relaxation phase in the SUI group. This prompts to reconsider the interpretation of FVC in PFM testing and training.

Figure 1 [Fig. 1]