Metabolic Mechanisms of Vocal Fatigue

Abstract

Vocal fatigue is among the most debilitating conditions affecting individuals with voice disorders. Impressions about mechanisms potentially underlying vocal fatigue have varied depending on how fatigue is defined, participants studied, and measures made, thereby impacting the selection of treatment strategies that may alleviate the condition. However, little is currently known about actual metabolic mechanisms of vocal fatigue. The current study aimed to address this issue by investigating the hypothesis that neuromuscular inefficiency, cardiovascular recovery deficits, or both, may play a role in fatigue. The approach replicated well-vetted approaches in exercise physiology.Metabolic profiles of subjects with vocal fatigue were assessed using gas exchange measures in comparison to two non-fatigue groups: vocally healthy and cardiovascular trained individuals, recruited based on results from a newly vetted questionnaire, the Vocal Fatigue Index (VFI) and laryngeal examination. Participants read out loud at two different loudness levels for a duration of 5 minutes for each task with periods of rest between tasks. Metabolic cost for and recovery time from reading were same across all groups. Oxygen uptake and recovery kinetics (EPOC), ratings of perceived exertion revealed interesting patterns in individuals with vocal fatigue compared to cardiovascular trained individuals in particular.Specifically, slow oxygen uptake kinetics in the vocal fatigue compared to the cardiovascular iv trained group pointed to utilization of anaerobic energy source to meet the demands of the reading task in the vocal fatigue group, suggesting neuromuscular inefficiency. In contrast, rapid oxygen uptake kinetics in the cardiovascular trained group pointed to utilization of aerobic energy sources and greater neuromuscular efficiency. Similarly, a greater number of individuals in vocal fatigue and vocally healthy groups showed an increase in oxygen consumption post reading (EPOC) compared to the cardiovascular trained group, indicating possible cardiovascular recovery deficits in the former groups.In addition to uncovering potential mechanisms underlying vocal fatigue, including neuromuscular inefficiency and cardiovascular recovery deficits, results from the present study highlight the potential importance of aerobic training to generate aerobic energy required for vocal task demands for both ease of task performance and recovery from it. In sharp contrast to the situation for voice, fatigue as a common physical phenomenon more generally has received extensive attention in the physical therapy, sports medicine, and exercise physiology literature. Three broad schools of thought identify mechanisms pertaining to the origins of physical fatigue: (1) peripheral mechanisms (Allen, Lamb, & Westerblad, 2008;Asmussen, 1979;Edwards, 1981;Fitts, 1994;Westerblad, Allen, & Lannergren, 2002;Westerblad, Lee, Lannergren, & Allen, 1991), (2) The next pages and chapters provide pertinent background information on vocal fatigue, fatigue as understood ...

Vocal Change Patterns During a Teaching Day: Inter- and Intra-subject Variability

“…Intrinsic factors relate to the subject's voice use (phonation type, voice quality, duration of phonation, fundamental frequency (F0), and intensity of voice), 1 biological factors (gender, age, genetics, hormones, and vocal fold biochemistry), 1 and aerobic conditioning. 14 Extrinsic factors relate to the environment influencing the voice, for instance room acoustics, humidity, 15 and background noise. 4 Two main approaches have been used in previous studies to investigate the appearance of and recovery from changes because of vocal load in both healthy and dysphonic individuals.…”

“…4 Two main approaches have been used in previous studies to investigate the appearance of and recovery from changes because of vocal load in both healthy and dysphonic individuals. First, most such studies were conducted under laboratory conditions 2,11,12,14,[16][17][18][19][20][21] and used endurance tasks believed to challenge the vocal mechanism, such as prolonged speaking, speaking against background noise, sustaining vowels, and singing. 1 These tasks are referred to as vocally fatiguing tasks, vocal loading tasks, or vocal-loading tests.…”

“…As presented in a recent review, 1 previous studies aiming to describe voice conditions following vocal demand, which used a variety of methods, populations studied, and measurements, yielded mixed and contradictory observations. 13,14 For instance, some studies showed a significant increase in F0 after prolonged voice use, whereas others reported a significant decrease. 1,2,5,6,17,19,25 A similar discrepancy between studies has been observed for other voice descriptors such as HNR, 1,2,17,25 jitter, 1,2,6,17,19 and shimmer.…”

Fadiga vocal em professores universitários no início e ao final do ano letivo

“…Thus, the insufficient oxygen supply would cause performance decrements over time. Two factors can explain this: neuromuscular inefficiency and cardiovascular recovery deficit (3) . Regarding VF, neuromuscular inefficiency could involve the recruitment of more muscles than needed for task performance or "incorrect pattern" of muscle activation, considering that both will lead to greater energy demands.…”

“…Regarding VF, neuromuscular inefficiency could involve the recruitment of more muscles than needed for task performance or "incorrect pattern" of muscle activation, considering that both will lead to greater energy demands. On the other hand, the inadequate cardiovascular recovery is related to the time course that physiological functions return to the baseline homeostatic state after vocal use (3) , which could be affected by lack of training, as well as the possibility of a genetic disposition that could cause low efficiency of laryngeal repairing mechanism (4,5) .…”