Background: Semi-occluded vocal tract (SOVT) exercises are a mainstay in current voice therapy practice. When performing these exercises, the patient’s breathing pattern is similar to that of slow breathing techniques, with a much longer expiratory than inspiratory time. Slow breathing markedly reduces respiratory frequency and is known to maximize vagal tone and facilitate an optimal parasympathetic-sympathetic balance.

Objective: The objective of this investigation was to determine the physiological impact of slow breathing and SOVT exercises and to determine if there is a differential benefit between these exercises on physiology.

Methods: This prospective study included 14 participants who completed six minutes of SOVT (straw phonation in water) and slow breathing conditions on separate days. Heart Rate (HR) and blood pressure (BP) were measured at various intervals throughout the study following a modified Systolic Blood Pressure Intervention Trial (SPRINT) protocol for each measure of BP. Following the intervention, participants completed a 100mm visual analog scale (VAS) to rate their degree of enjoyment of each condition.

Results: There was no significant effect of time or group on mean arterial pressure (a combined measure of systolic and diastolic BP). While there was no significant effect of group on HR, there was a significant effect of time on HR (p = 0.0002). This suggests that HR changed significantly across the different time points measured and was similar between both groups. The distribution of degree of enjoyment was right-skewed, with a significant number of respondents reporting high enjoyment of both activities with a combined mean of 76.86/100. The t-test results suggest that there was no significant difference in degree of enjoyment between slow breathing and SOVT conditions (p = 0.8439).

Conclusion: SOVT and slow breathing conditions were similarly enjoyable for participants, shared similar patterns of HR over time, and revealed no significant effect of group on BP measures. This may suggest that the well-documented benefits of slow breathing techniques on vagal tone could also be expected from SOVT exercises. Further research is warranted to better elucidate the physiological impact of these exercises and differentiate possible benefits of each individually.