The influence of the low-frequency transcutaneous electrical nerve stimulation application moment in vocal quality of dysphonic women

Objective: to compare the immediate effects of low-frequency TENS employment on vocal quality in women with behavioral dysphonia before and after vocal exercises. Methodology: 30 women (mean = 31.3 years old), diagnosed with behavioral dysphonia received low-frequency TENS before (TENS + VE Group) and after vocal exercises (VE + TENS Group) with a 1-week washout. They had their sustained vowel/a/and running speech recorded before and after each procedure for auditory-perceptual analysis and acoustic measures. The low-frequency TENS parameters applied were symmetrical biphasic quadratic pulse, 200 mu s phase, 10 Hz frequency, intensity on the motor threshold, and the electrodes were positioned on the submandibular and superior fibers of the trapezius muscle region. The vocal exercises: tongue trill, humming, finger kazoo, and water resistance therapy were performed totalizing 20 min. Results: intragroup analysis of sustained vowel/a/showed reduction in both groups of strain parameter and increased the breathiness; only VE + TENS Group increased the instability parameter, decreased fundamental frequency, and increased in SPI values; the running speech analysis showed an increase in the overall degree, roughness, and breathiness parameters. However, in VE + TENS Group, there was a statistically significant decrease in the intensity of the strain and an increase in breathiness. The acoustic measures showed that VE + TENS Group had a higher variation than TENS + VE Group regarding NHR. Conclusion: vocal exercises followed by low-frequency TENS have more immediate positive effects on voice quality than the low-frequency TENS followed by vocal exercises. This is a preliminary immediate effects study, and these effects could be verified through long-term assessments.