Metabolic Mechanisms of Vocal Fatigue.

Objective: This study aimed to identify potential metabolic mechanisms including (1) neuromuscular inefficiency, (2) cardiovascular recovery deficits, or (3) both, in individuals with complaints of vocal fatigue.

Study Design: Within- and between-subjects group design was used in this study.

Methods: Three groups of women participated in the study, including (1) individuals with complaints of vocal fatigue; (2) vocally healthy sedentary individuals; and (3) vocally healthy, cardiovascularly conditioned individuals. Group assignment was based on results from the Vocal Fatigue Index, laryngeal examination, and self-report regarding exercise regimens. Metabolic profiles were obtained using gas exchange measures monitored during vocal task performance (reading) at two different loudness levels, and during recovery from reading.

Results: Statistical analyses did not reveal reliable group differences in metabolic cost for or recovery from vocal tasks. However, descriptive review of oxygen uptake and recovery kinetics revealed patterns indicating reliance on differential energy resources for the vocal task in individuals with vocal fatigue compared with cardiovascularly trained, vocally healthy individuals in particular. Slow oxygen uptake kinetics at task onset was a characteristic of the vocal fatigue group, indicating a general reliance on anaerobic resources to meet the demands of the vocal task, pointing to possible neuromuscular inefficiency. Individuals with vocal fatigue also demonstrated an increase in oxygen consumption following vocal task compared with cardiovascularly trained individuals, suggesting possible cardiovascular recovery deficits.

Conclusion: This study provides initial data relevant to possible metabolic mechanisms of vocal fatigue and the potential relevance of aerobic conditioning in individuals with such fatigue.