Effect of body position on reflex and voluntary pelvic floor muscle contraction during a distraction task.

AIMS: To explore the impact of body position (sitting vs standing) on voluntary and reflex pelvic floor muscle (PFM) contraction during a mental distraction task (DT). METHODS: Informed consent was obtained from 19 healthy women. The electromyographic (EMG) activity of the external anal sphincter (EAS) was recorded during voluntary and reflex contraction. Reflex contraction of the EAS was induced by means of coughing. The trials were carried out with and without a mental DT (paced auditory serial additional test). PFM contraction was recorded in two different postures: standing and sitting. During voluntary PFM contraction, reaction time (RT1), defined as latency between the stimulus and the onset of EAS EMG activity, was measured. During reflex PFM contraction, latency between the onset of external intercostal (EIC) muscle EMG activity and EAS EMG activity was measured (RT3). RESULTS: Concerning voluntary pelvic floor muscle contraction, there was no difference between the two positions with and without DT, except for RT1 without DT. RT1 was shorter (353.99 mv/s; 263.89-425.03) in a standing position than in a sitting position (409.86 mv/s; 361.86-461.90) (ratio 0.86, P = 0.014). Concerning reflex PFM contraction, there was no difference between standing position RT3 (-96 ms; IQR: -114: -62) and sitting position RT3 (-80 ms; IQR: -100; -51) (ratio 1.2, P = 0.225) without DT. With DT, reflex PFM was also not different (-36 vs -34 ms, ratio 1.06, P = 0.86). CONCLUSIONS: Body position did not influence the timing of voluntary and reflex PFM contraction during DT.