Activities of daily living (ADL) accompanied by increasing intra-abdominal pressure can provoke urine loss in women with stress urinary incontinence. The affected can therefore complain involuntary loss of urine associated with change of body position (1). For preventing stress urinary incontinence involuntary pelvic floor muscle activity is important.

Therefore, the aim of the current study was to investigate 
a) whether there is pelvic floor muscle activity, i.e. involuntary response, in healthy nulliparous women during moderate ADL such as using stairs, rising from a chair and lifting of loads, and, 
b) whether there is a difference in pelvic floor muscle activity between three different speeds of stair using, two different speeds of chair rising and the lifting of two different loads.

This investigation was conducted as an exploratory, cross-sectional pilot study to determine pelvic floor muscle activity during ADL, namely during three different speeds (slow, medium, fast) of stair use, up and down, two different speeds of chair rise (slow, fast) and lifting of two different loads (10 kg, 15 kg).
Electromyographic (EMG) activity of the pelvic floor muscles of 16 healthy nulliparous women was determined using vaginal probes while participants lifted loads, went up and down stairs and rose from a chair, with different weights and speeds, respectively. Root mean square (RMS) values of the EMG signals were analyzed before and after onset of load. EMG values were normalized to the peak activity during maximum voluntary contractions (%MVC). Pelvic floor muscle activity-onset threshold was determined as the mean of rest activity plus two standard deviations (SD). Descriptive statistics are presented parametrically as mean ± SD for ratio scale data or non-parametrically as median with 25. & 75. percentiles for ordinal scale demographic variables. The pelvic floor muscle activities were analyzed by ANOVA for within each variable for repeated measures and by ANOVA between three different speeds (slow, medium, fast) and adequate post hoc t-test. Additionally, t-test between the different speeds (slow, fast) and different loads (10 kg, 15 kg) for paired samples was calculated. Level of significance was set to α = 0.05.

The 16 included participants had a mean (± SD) age of 26.8 (± 5.2) years and body mass index of 22.3 (± 2.4) kg/m2. The mean threshold of PFM activity onset could be determined at 32.4 ± 12.4 %MVC. In all measured ADL, pelvic floor muscle activity was higher than during rest. Stair up and down showed long lasting pelvic floor muscle activity and activity tended to increase with higher speed (66.2 - 152.1 %MVC). Load lifting (159.1 - 194.1 %MVC) and chair rise (86.7 - 94.2 %MVC) also showed higher activity with increasing weight and speed, respectively. See Figure 1, exemplarily showing pelvic floor muscle activity during chair rise.

EMG measurements showed involuntary pelvic floor muscle activity in healthy nulliparous women in ADL, namely during stair use, chair rise and load lifting.
The increase of involuntary pelvic floor muscle activity with speed and ground reaction force during stair use and chair rise is comparable to findings during other whole-body impact activities such as running (2, 3).

This study showed involuntary pelvic floor muscle activity during stair use, lifting loads and rising from a chair. These ADL can presumably be applied to provoke involuntary pelvic floor muscle activity in healthy nulliparous women. However, future studies should clarify if or how ADL could be helpful as training methods in preventing or treating stress urinary incontinence. Further research on involuntary pelvic floor muscle activity in women who suffer from stress urinary incontinence is needed to differentiate possible pathological changes of the involuntary pelvic floor muscle activity and to improve training concepts with focus on involuntary pelvic floor muscle activity.

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