Steam and/or Semi-occluded Vocal Tract Exercise as Morning Vocal Warm-up Strategy

This study was designed to evaluate the effectiveness of either steam, semi-occluded vocal tract (SOVT) exercises, or a combination of both as a speaking voice warm-up strategy to be used at the start of the day.

This prospective study assessed the impact of three different vocal warm-up conditions on phonatory threshold pressure (PTP). The three conditions were: (1) Steam - breathing steam for 3 minutes; (2) SOVT exercise - blowing bubbles through a straw into a cup of water while phonating /u/ for 3 minutes; and (3) Steam + SOVT - both conditions 1 and 2. Participants were 12 females with a mean age of 24. They were assessed on three different mornings, with one condition being tested each morning. Condition order and combination order were counterbalanced. Each morning prior to arriving, participants were asked to be up for about an hour, with no shower, no hot drinks or food, minimal voice-use, and no exercise. PTP was measured prior to each condition and immediately after. Participants also qualitatively described the experience of each condition and provided their subjective impression of how their voice felt after each condition.

There were 36 data points, reflecting change in PTP from before to after each condition. Results reflected high variability within each individual and condition. Due to this variability, means and standard deviations for each separate condition are meaningless, requiring deeper investigation into trends in the data. The investigators eliminated all data points where the sound pressure level (SPL) in the pre-experimental measure exceeded 67 dB; this was interpreted as the participant not performing the PTP task as softly as possible. First, data were examined within each participant, excluding all data from any participant who exceeded 67 dB SPL in any of the three pre-experimental measures. Of the seven participants remaining, steam was the best condition for one, SOVT was the best for three, and Steam + SOVT was the best for three. Of these, only two people experienced an improvement in PTP of greater than or equal to 0.5 cm H 2 O, both under the SOVT condition. Of the same seven participants, steam was the worst condition for three, SOVT was the worst for one, and Steam + SOVT was the worst for two. The three participants for whom steam was the worst reported strongly disliking the condition. Only three people experienced a worsening of PTP greater than or equal to 0.5 cm H 2 O: one in the SOVT condition; and two in the Steam + SOVT. It is typically expected that increases or decreases in PTP and SPL will be systematically related. Since the goal of a warm-up is to increase phonatory efficiency, and improve the viscosity of the vocal folds, a reduction in PTP after any condition was interpreted favorably. For the 9 data points across all conditions where PTP and SPL both decreased, there was a mean decrease in PTP of 0.34 cm H₂O (SD = 0.28 cm H₂O ). Mean decrease in SPL was 2.00 dB (SD = 0.88 dB). This indicates that individuals were able to decrease PTP and SPL as expected after a warm-up strategy. Finally, a trend appeared in six data points, where despite an increase in SPL, PTP decreased, potentially indicating improvement in vocal efficiency. Of these data points the mean decrease in PTP was 0.36 cm H₂O ( SD = 0.17 cm H₂O ), with a mean increase in SPL of 1.70 dB (SD = 1.21 dB). Of these six data points, indicating increased efficiency, three were with steam, two with Steam + SOVT, and one with SOVT.

This study revealed that these strategies are not universally successful, and clinicians should recommend them only after assessing their effectiveness for their client. Clinicians need to be custom tailoring these exercises to their client's goals and proclivities. Another consideration is the importance of teaching proper SOVT technique, so it is done correctly without added tension. Even blowing bubbles into a cup of water with phonation can be done poorly, in some cases yielding counterproductive results. Another interesting trend suggests that the inclusion of steam in vocal warm-up may increase vocal efficiency. Future studies should explore how time of day and vocal condition impact each strategy's effectiveness, and which strategy may be most appropriate for different desired outcomes, such as vocal warmup versus vocal rescue.