Perception of Physical Demand, Mental Demand, and Performance: A Comparison of Two Voice Interventions for Parkinson's Disease.

Purpose: The purpose of the study was to examine the effect of two voice intervention approaches for hypophonia secondary to Parkinson's disease (PD) on self-reported measures of physical demand, mental demand, and vocal performance.

Method: Thirty-four persons with hypophonia secondary to PD were assigned to one of three groups: Lee Silverman Voice Treatment (LSVT) LOUD ( = 12), SpeechVive ( = 12), and nontreatment clinical control ( = 10). The LSVT LOUD and the SpeechVive participants received 8 weeks of voice intervention following the standardized protocol previously described for each approach. To confirm the effectiveness of each voice intervention, sound pressure level (dB SPL) data were analyzed for the experimental and control participants for a monologue sample obtained pretreatment, midtreatment, and posttreatment. During the voice intervention period, the LSVT LOUD and the SpeechVive participants were instructed to complete a modified version of the National Aeronautics and Space Administration Task Load Index rating scale to indicate the mental and physical demand required to complete the intervention activities, and to indicate how well they performed in completing the assigned vocal tasks.

Results: The LSVT LOUD and the SpeechVive participants demonstrated a significant posttreatment increase in SPL (dB), in comparison to the clinical controls, thus confirming a positive intervention effect. The LSVT LOUD participants reported significantly higher ratings of physical and mental demand over the course of treatment, in comparison to the SpeechVive participants.

Conclusion: Consideration of the mental and physical demand associated with two voice intervention approaches, commonly used for PD, may help to foster improved therapeutic compliance and treatment outcomes.