A randomized controlled trial with female teachers:are there differences between and within the outcomes in voice therapy groups with and without carryover strategies?

Purpose: We investigated if outcomes differ between voice therapy groups systematically using carryover strategies (attempts to generalize new vocal skills outside the clinic) and voice therapy with no emphasis on any generalizing process (here referred to as traditional voice therapy). Method: A randomized controlled trial was conducted. Participants (53 female teachers with voice disorders) were randomly allocated into three groups: Carryover (a group receiving voice therapy using carryover strategies), Trad (a group receiving voice therapy with no emphasis on any generalizing process), Controls (a group on an eight-week non-therapy period). Prior to the trial a direct laryngoscopy was performed with a videolaryngostroboscopy system and/or nasofaryngofiberoscope with stroboscopy. Before and after therapy and at follow-up a voice evaluation protocol was implemented consisting of subjective assessments (Questionnaire on Voice Symptoms, and the Voice Activity and Participation Profile; VAPP), and objective measurements (voice sample recordings, acoustic analysis [SPL, sound pressure level; f₀, fundamental frequency; alpha-ratio, tilt of the sound spectrum slope]). Results: No differences were found between the groups. Several significant changes occurred within the groups between initial phase vs. post-therapy and initial phase vs. follow-up. In the Carryover group text reading the alpha-ratio became lower (P = 0.011) and spontaneous speech f₀ increased (P = 0.024) after the therapy and [a:] SPL increased (P = 0.042) at follow-up. In the Trad group post-therapy [a:] alpha-ratio became lower (P = 0.012) and spontaneous speech f₀ decreased (P = 0.034). After therapy VAPP scores showed improvement in voice-related quality of life in both therapy groups (Carryover P = 0.003; Trad P = 0.01) but only in Carryover at follow-up (P = 0.000). Voice symptoms decreased in the Carryover group post-therapy (P = 0.001) and at follow-up (P = 0.000) and after Controls’ eight