Massed versus spaced practice in vocology : effect of a short-term intensive voice training versus a longer-term traditional voice training

Background: In contrast with most medical and pharmaceutical therapies, the optimal dosage for voice therapy or training is unknown. Aims: The aim of this study was to compare the effect of a short-term intensive voice training (IVT) with a longer-term traditional voice training (TVT) on the vocal quality and vocal capacities of vocally healthy non-professional voice users. Methods & Procedures: A pre-/post-test randomized control group design with follow-up measurements was used. Twenty healthy female non-professional voice users with a mean age of 21.7 years (range = 20-24 years) were randomly assigned into a short-term IVT group (n = 10) or a longer-term TVT group (n = 10). Both groups received an identical 6-h lasting voice training. Only the distribution of practice varied between the groups: 2h a day for 3 consecutive days for the IVT group versus two 30-min sessions a week for 6 weeks for the TVT group. In both groups, a voice assessment protocol consisting of subjective (questionnaire, participant's self-report, auditory-perceptual evaluation) and objective (maximum performance task, acoustic analysis, voice range profile, dysphonia severity index) measurements and determinations was used to evaluate the participants' voice pre- and post-training and at 6 weeks follow-up. Groups were compared over time using linear mixed models and generalized linear mixed models. Within-group effects of time were determined using post-hoc pairwise comparisons with Bonferroni corrections. Outcomes & Results: No significant time-by-group interactions were found for any of the outcome measures, indicating no significant differences in evolution over time between the groups. Significant time effects were found for maximum phonation time, lowest intensity, lowest frequency, highest frequency and dysphonia severity index, all improving over time in both groups. More in-depth within-group analyses indicate a preference for the IVT group regarding the evolution of maximum phonation time, lowest frequency and dysphonia severity index, and a preference for the TVT group regarding the evolution of lowest intensity. Conclusions & Implications: Short-term IVT may be equally, or even more, effective in training vocally healthy non-professional voice users compared with longer-term TVT.