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Measurement of Blood Lactate as a Function of Vocal Loading and Neuromuscular Electrical Stimulation: Proof of Concept
Abstract
The goal of the current investigation was to establish proof of concept regarding measurement of blood lactate levels as an indicator of laryngeal muscle activity and fatigue, as well as to examine the relationship between blood lactate levels and NMES intensity. Fifteen participants completed a vocal loading exercise while blood lactate was measured prior to, during, and upon completion of the exercise. Acoustic measures of voice production and subjective reports of fatigue/soreness were obtained pre- and post-vocal loading task. The participants were divided into three groups: those who did not receive laryngeal neuromuscular electrical stimulation (NMES), those who received laryngeal NMES at a minimally perceivable level of intensity, and those who received laryngeal NMES at a maximum tolerable level of intensity. Changes in blood lactate levels were observed during the vocal loading task, thus indicating that blood lactate measurements are sensitive enough to reflect laryngeal muscle activity. No consistent pattern between blood lactate levels and NMES intensity or fatigue emerged. Several factors may account for these findings.
... Thus, its contribution is specific, and its information is nonredundant in comparison with other procedures commonly used in vocal clinical practice. In this context, this review identified the different acoustic measures that have been used in interventions in vocally healthy individuals, including fundamental frequency (f0) measures , intensity measures (18,22,23,25,(29)(30)(31)37,39,40,(43)(44)(45)(46)49,53,(56)(57)(58)61,63,66,67,(69)(70)(71)(72)(73) , cepstral/ spectral measures (25,(39)(40)(41)66,70,(73)(74)(75)(76)(77) , perturbation and noise measures ( (16,18,23,41,(43)(44)(45)49,50,52,72,73,79) , and descriptive analysis of narrowband spectrograms (15,(17)(18)(19)(20)(26)(27)(28)(43)(44)(45)(46)51,57,59,69,70,(75)(76)(77)83,86) . F0 variability stood out among the parameters in the articles that used acoustic assessment to measure the effects of interventions in vocally healthy individuals. ...
... The most used electroglottography measures were the glottal contact quotient (15,27,29,50,54,70,73,85,(88)(89)(90)(91) , glottal closure quotient (21,28,32,33,35,40,77,(92)(93)(94)(95)(96) , and opening quotient (21,40,92) . In most (14,33,39,42,49,53,58,59,61,67,71,81,86,97,99,102,105,106,109,110) Before-and-after (15, 17-22, 25-28, 31, 32, 34-36, 40, 41, 50-52, 54-57, 60, 62, 63, 70, 72-74, 76-80, 82-85, 89-93, 95, 101) Experimental (16, 23, 24, 37, 38, 43, 44-48, 64-66, 68, 69, 75, 87, 88, 94, 96, 98, 100, 103, 104, 107, 108) Case series (29,30) Case study -----Type of intervention Direct (14-21, 23-32, 34-58, 60-66, 70-74, 76-89, 91, 92, 94-97, 99, 101-105, 107-110) Indirect (22,106) Both (33, 59, 67-69, 75, 90, 93, 98, 100) TOTAL TIME OF INTERVENTION Less than 1 minute (14,23,26,27,60,103) 1-3 minutes (15, 16, 41-43, 45, 89) 4-10 minutes (20,29,35,40,44,45,50,52,73,81,82,87,91) 11-20 minutes (32,48,51,54,88,92,97) 21-30 minutes (15,25,46,61,63,66,78,90,95,96,99,105,106) ...
... In the studies approached in this review, the visual analog scale (16,30,38,41,51,53,74,81,98) was the most used tool to measure voice self-perception before and after the intervention. There was great variability in the construct measured with this scale, ranging from the intensity/frequency of symptoms to the perceived effort associated with voice production. ...
Purpose
to map the vocal assessment measures used to verify the effect of the intervention in vocally healthy individuals.
Research strategy
This is a scope review based on the research question: What vocal assessment measures are used to verify the effect of the intervention in vocally healthy individuals? The search was carried out electronically in MEDLINE (PubMed), LILACS (BVS), Scopus (Elsevier), Web of Science (Clarivate), Embase and Cochrane databases.
Selection criteria
The selection of studies was based on reading the titles, abstracts, keywords and full texts, applying the eligibility criteria. Data related to the publication’s bibliographic information, sample and intervention characteristics, the effects of the intervention on self-assessment, auditory-perceptual, acoustic, aerodynamic, electroglottographic measures, laryngeal examination results, among others, were extracted. The data were summarized and presented in a quantitative and descriptive way.
Results
97 articles were selected, among the 979 studies mapped in this review. Acoustic analysis was the most used measure (n=70, 72.3%) to verify the effects of vocal training in the selected studies, followed by electroglottography (n= 55, 56.7%), self-assessment (n= 38, 39 .2%), aerodynamics (n= 33, 34.0%), auditory-perceptual judgment (n= 22, 22.7%) and laryngeal examination (n= 16, 16.5%).
Conclusion
Acoustic analysis is the measure used in most studies to verify the effect of the intervention in vocally healthy individuals.
Keywords:
Voice; Voice quality; Voice training; Results study; Review; Healthy volunteers
... One prior study quantified La − from a fingertip blood draw following neuromuscular electrical stimulation (NMES) to the laryngeal region, with surface electrodes placed on the laminae and inferior horns of the thyroid cartilage (Gorham-Rowan et al., 2019). A detectable change in blood La − was found; however, while this approach may have stimulated the laryngeal muscles (the degree to which would be uncertain with this model), it is unlikely that the methodology imposed vocal loading and demand in an ecologically valid manner, given the absence of the respiratory and articulatory components of phonation (Fowler et al., 2011;Gorham-Rowan et al., 2019). ...
... One prior study quantified La − from a fingertip blood draw following neuromuscular electrical stimulation (NMES) to the laryngeal region, with surface electrodes placed on the laminae and inferior horns of the thyroid cartilage (Gorham-Rowan et al., 2019). A detectable change in blood La − was found; however, while this approach may have stimulated the laryngeal muscles (the degree to which would be uncertain with this model), it is unlikely that the methodology imposed vocal loading and demand in an ecologically valid manner, given the absence of the respiratory and articulatory components of phonation (Fowler et al., 2011;Gorham-Rowan et al., 2019). The vocal folds ad/abduct rapidly during conversational speech, and the ILSMs are constantly engaged in creating tension or laxness of the vocal folds for changes in pitch, intonation, and vocal intensity during connected speech. ...
Purpose
The purpose of this tutorial is threefold: (a) present relevant exercise science literature on skeletal muscle metabolism and synthesize the limited available research on metabolism of the adult human speech musculature in an effort to elucidate the role of metabolism in speech production; (b) introduce a well-studied metabolic serum biomarker in exercise science, lactate, and the potential usefulness of investigating this metabolite, through a well-established exercise science methodology, to better understand metabolism of the musculature involved in voice production; and (c) discuss exercise physiology considerations for future voice science research that seeks to investigate blood lactate and metabolism in voice physiology in an ecologically valid manner.
Method
This tutorial begins with relevant exercise science literature on the basic cellular processes of muscle contraction that require energy and the metabolic mechanisms that regenerate the energy required for task execution. The tutorial next synthesizes the available research investigating metabolism of the adult human speech musculature. This is followed by the authors proposing a hypothesis of speech metabolism based on the voice science literature and the application of well-studied exercise science principles of muscle physiology. The tutorial concludes with a discussion and the potential usefulness of lactate in investigations to better understand the metabolism of the musculature involved in vocal demand tasks.
Conclusion
The role of metabolism during speech (respiratory, laryngeal, and articulatory) is an understudied yet critical aspect of speech physiology that warrants further study to better understand the metabolic systems that are used to meet vocal demands.
... Na área de voz a utilização da corrente excitomotora ainda é restrita, com poucas pesquisas sobre o tema (3)(4)(5)(6)(7)(8)(9) . ...
... O laringoespasmo é um reflexo de fechamento glótico intenso e prolongado, potencialmente fatal se não diagnosticado ou tratado a tempo (26) . Dos estudos pesquisados que realizaram eletroestimulação com eletrodos em região de laringe nenhum fez referência à presença de espasmos glóticos independentemente do tipo de corrente e intensidade aplicada (1)(2)(3)(4)(5)(6)(7)(8)(9)18,19,(27)(28)(29)(30) . ...
Objetivo
Verificar o efeito imediato da corrente elétrica excitomotora, denominada FES, na qualidade vocal e no tempo máximo de fonação (TMF), e possíveis desconfortos, em mulheres sem alteração vocal, com aplicação em intensidade máxima suportada (IMS) e associada à fonação.
Método
Estudo experimental com 20 mulheres adultas normofônicas. Elas emitiram a vogal /a/ sustentada e depois foi aplicada a FES durante emissão da mesma vogal. Foram cinco séries com três minutos de emissão cada, intercaladas com descanso passivo; o estímulo elétrico foi na IMS pela participante, ajustado por série. Antes e após as emissões as vozes foram gravadas e coletados os TMF e a intensidade dos estímulos. A qualidade vocal foi classificada por juízes. Foram comparados os dados pré e pós emissão/eletroestimulação em cada fase. A análise qualitativa foi realizada a partir de sintomas autorreferidos.
Resultados
Não houve diferença na qualidade vocal e nos TMF entre os momentos pré e pós nas duas fases. A diferença entre a IMS e a intensidade de percepção do estímulo foi maior na série 1 em relação à série 2. Houve aumento da IMS na série 5 em relação à série 1. Não foram relatados sintomas negativos imediatos ou em até 48 horas após os procedimentos.
Conclusão
A corrente FES em IMS, associada à fonação, não gerou mudança imediata na qualidade vocal, nos TMF ou desconfortos autorreferidos pelas mulheres sem alteração vocal, mesmo com aumento gradual do estímulo.
... The emission of the sustained vowel/a/allows the source analysis, while the connected speech allows the understanding of the filter functions, representing the daily usage of voice [24][25][26]. Thus, this study considered two different voice samples to complement the auditory-perceptual analysis. ...
Objective: to compare the immediate effects of low-frequency TENS employment on vocal quality in women with behavioral dysphonia before and after vocal exercises.
Methodology: 30 women (mean = 31.3 years old), diagnosed with behavioral dysphonia received low-frequency TENS before (TENS + VE Group) and after vocal exercises (VE + TENS Group) with a 1-week washout. They had their sustained vowel/a/and running speech recorded before and after each procedure for auditory-perceptual analysis and acoustic measures. The low-frequency TENS parameters applied were symmetrical biphasic quadratic pulse, 200 µs phase, 10 Hz frequency, intensity on the motor threshold, and the electrodes were positioned on the submandibular and superior fibers of the trapezius muscle region. The vocal exercises: tongue trill, humming, finger kazoo, and water resistance therapy were performed totalizing 20 min.
Results: intragroup analysis of sustained vowel/a/showed reduction in both groups of strain parameter and increased the breathiness; only VE + TENS Group increased the instability parameter, decreased fundamental frequency, and increased in SPI values; the running speech analysis showed an increase in the overall degree, roughness, and breathiness parameters. However, in VE + TENS Group, there was a statistically significant decrease in the intensity of the strain and an increase in breathiness. The acoustic measures showed that VE + TENS Group had a higher variation than TENS + VE Group regarding NHR.
Conclusion: vocal exercises followed by low-frequency TENS have more immediate positive effects on voice quality than the low-frequency TENS followed by vocal exercises. This is a preliminary immediate effects study, and these effects could be verified through long-term assessments.
Background
Neuromuscular electrical stimulation (NMES) offers a potential adjuvant to traditional voice therapy for individuals with dysphonia. The type of vocal task to implement in conjunction with electrical stimulation to achieve maximal therapeutic benefit is unknown. The purpose of this study was to elucidate the impact of tasks on voice outcomes.
Methods
Nineteen vocally-healthy adult females, between 23 and 27 years of age (Ave: 23.8, SD: 1.13), participated in the study. 15 participants completed all three 30-minute sessions, and four completed at least one session. NMES was paired with three different voice conditions: high-pitched hum, low-pitched hum, and comfortable-pitched hum. Acoustic (average fundamental frequency and loudness; perturbation (jitter, shimmer, noise to harmonic ratio); Cepstral Spectral Index of Dysphonia; pitch range), perceived phonatory effort, and discomfort (delayed onset muscle soreness) measures were compared across conditions.
Results
Eight participants experienced discomfort following NMES. Three participants withdrew from the study due to discomfort, and one withdrew due to an unrelated oral surgery. NMES paired with high-pitch humming resulted in increased average fundamental frequency during sustained phonation and reading tasks, and increased Cepstral Spectral Index of Dysphonia during sustained phonation. Low-pitch humming resulted in a decreased noise to harmonic ratio. No statistically significant changes in perceived phonatory effort were noted.
Conclusion
Almost half of the participants reported temporary discomfort. Task-specific differences in some outcomes were noted indicating that the nature of voice task performed with NMES must be considered when examining the impact of NMES on voice. Vocal tasks can impact discomfort and acoustic vocal outcomes of NMES.
Eccentric exercise continues to receive attention as a productive means of exercise. Coupled with this has been the heightened study of the damage that occurs in early stages of exposure to eccentric exercise. This is commonly referred to as delayed onset muscle soreness (DOMS). To date, a sound and consistent treatment for DOMS has not been established. Although multiple practices exist for the treatment of DOMS, few have scientific support. Suggested treatments for DOMS are numerous and include pharmaceuticals, herbal remedies, stretching, massage, nutritional supplements, and many more. DOMS is particularly prevalent in resistance training; hence, this article may be of particular interest to the coach, trainer, or physical therapist to aid in selection of efficient treatments. First, we briefly review eccentric exercise and its characteristics and then proceed to a scientific and systematic overview and evaluation of treatments for DOMS. We have classified treatments into 3 sections, namely, pharmacological, conventional rehabilitation approaches, and a third section that collectively evaluates multiple additional practiced treatments. Literature that addresses most directly the question regarding the effectiveness of a particular treatment has been selected. The reader will note that selected treatments such as anti-inflammatory drugs and antioxidants appear to have a potential in the treatment of DOMS. Other conventional approaches, such as massage, ultrasound, and stretching appear less promising.
Background:
Obese people have abnormal deposition of fat in the vocal tract that can interfere with the acoustic voice. Aim : To relate the fundamental frequency, the maximum phonation time and voice complaints from a group of morbidly obese women.
Methods:
Observational, cross-sectional and descriptive study that included 44 morbidly obese women, mean age of 42.45 (± 10.31) years old, observational group and 30 women without obesity, control group, with 33.79 (± 4.51)years old. The voice recording was done in a quiet environment, on a laptop using the program ANAGRAF acoustic analysis of speech sounds. To extract the values of fundamental frequency the subjects were asked to produce vowel [a] at usual intensity for a period in average of three seconds. After the voice recording, participants were prompted to produce sustained vowel [ a] , [ i] and [ u] at usual intensity and height, using a stopwatch to measure the time that each participant could hold each vowel.
Results:
The majority, 31(70.5%), had vocal complaints, with a higher percentage for complaints of vocal fatigue 20(64.51%) and voice failures 19(61.29%) followed by dryness of the throat in 15 (48.38%) and effort to speak 13(41.93%). There was no statistically significant difference regarding the mean fundamental frequency of the voice in both groups, but there was significance between the two groups regarding maximum phonation.
Conclusion:
Increased adipose tissue in the vocal tract interfered in the vocal parameters.
To analyze the impact of body weight and body fat volume on selected parameters of vocal quality, phonatory range, and aerodynamics in females.
Based on measurements of body mass index in combination with body fat volume, 29 normophonic female subjects were classified as normal weight, underweight, and obese. Voice quality was investigated via auditory-perceptual ratings of breathiness, roughness, and overall dysphonia severity, via various acoustic measures and a multiparametric index. Phonatory range performance was examined using selected measures of the voice range profile and speech range profile. Measures of vocally relevant aerodynamics included vital capacity (i.e., VC), expected VC, phonation quotient, and maximum phonation time (i.e., MPT).
Significant differences between the three weight groups were found across several measures of intensity, VC, MPT, and shimmer. As compared to the other groups, significantly higher values of maximum and minimum intensity levels, as well as sound pressure level during habitual running speech were observed for the obese group (all p-values<0.05); whereas, the underweight group had significantly lower values for VC and ratio of expected to measured VC (p-values<0.01). Furthermore, underweight subjects differed significantly as compared to normal weight subjects with lower MPT (p=0.025) and higher lowest-F0 (p=0.035). Finally the obese group showed significantly lower shimmer values than the normal weight subjects (p<0.05).
Body weight and body fat volume appear to influence select objective measures of voice quality, vocal aerodynamics, and phonatory range performance.
A study of effects of squatting exercise on heart rate and blood lactate levels in trained and untrained males indicated that trained subjects performed more work and had higher heart rates and lactate levels at exhaustion untrained subjects, though heart rate and lactate levels were lower for trained subjects at a given bar mass or submaximal work load. (Author/CB)
This article reviews current literature on vocal fatigue and considers its potential relationship to vocal hyperfunction. Vocal fatigue is defined by its symptoms. Specifically, the voice user perceives an increase in phonatory effort over time that may be accompanied by decreased phonatory function. Vocal fatigue can present as a pure condition, such that no specific aetiology is apparent, or as a component of other voice disorders. The underlying bases of vocal fatigue appear to include the neurophysiological and biomechanical effects of extended periods of phonation. It can also be a function of strategies used to adapt to extended periods of phonation, such as the use of excessive muscular tension and suboptimal vocal fold posturing. Studies that have attempted to identify observable responses that are reliably associated with vocal fatigue have met with limited success, but recent advances in research methodology are promising. This review addresses current approaches to the study of vocal fatigue, especially regarding subject selection, design variables, and measurement variables. Future studies should address the relationship between vocal fatigue and other voice disorders, differences in individual responses to vocal-loading tasks, and differential evaluation and management of the neuromuscular, biomechanical, and central processes involved in vocal fatigue.
The main aim of this review is to discuss some evidence-based physiological and methodological considerations for optimal use of neuromuscular electrical stimulation (NMES) in healthy and impaired skeletal muscles. After a quick overview of the main applications, interests and limits of NMES use, the first section concentrates on two crucial aspects of NMES physiology: the differences in motor unit recruitment pattern between NMES and voluntary contractions, and the involvement of the nervous system during peripheral NMES. The second section of the article focuses on the most common NMES parameters, which entail the characteristics of both the electrical current (the input) and the evoked contraction (the output).
Voice therapies have proven to be an effective method of helping patients avoid the symptoms of vocal fatigue. This study assesses the effect of a chant-based therapy on self-perceptive symptoms of vocal fatigue. A recitational pattern was selected and a therapy regime created from important features of this chant. It was administered along with a placebo therapy to four public school teachers who were prone to vocal fatigue. A two-hour fatiguing task was administered pre- and post-therapies, during which self-evaluative measures of "vocal effort" and "voice quality" were made by the subjects. The plots of these measures were used for the purpose of determining the effects of the chant therapy. Based on changes in the subjects' responses to the fatiguing task after the delivery of the chant therapy, we concluded that this form of functional therapy has the potential to be effective in the remediation of vocal fatigue.
We quantified the recovery of voice following a 2-hour vocal loading exercise (oral reading).
Eighty-six adult participants tracked their voice recovery using short vocal tasks and perceptual ratings after an initial vocal loading exercise and for the following 2 days.
Short-term recovery was apparent, with 90% recovery within 4 to 6 hours and full recovery at 12 to 18 hours. Recovery was shown to be similar to a dermal wound healing trajectory.
The new recovery trajectory highlighted by the vocal loading exercise in the current study is called a vocal recovery trajectory. By comparing vocal fatigue to dermal wound healing, this trajectory is parallel to a chronic wound healing trajectory (as opposed to an acute wound healing trajectory). This parallel suggests that vocal fatigue from the daily use of the voice could be treated as a chronic wound, with the healing and repair mechanisms in a state of constant repair. In addition, there is likely a vocal fatigue threshold at which point the level of tissue damage would shift the chronic healing trajectory to an acute healing trajectory.
Dysphagia after stroke is associated with increased mortality, higher dependence, and longer hospitalization. Different therapeutic strategies have been introduced to improve swallowing impairment. There are no current studies that compare rehabilitation swallowing therapy (RST) and neuromuscular electrical stimulation therapy (NMES).
To compare treatment outcomes between RST and NMES intervention in stroke patients with pharyngeal dysphagia.
A randomized controlled study.
Twenty-three stroke patients with persistent pharyngeal dysphagia (RST 11, NMES 12) were enrolled in the present study. The subjects received 60 minutes of either RST or NMES treatment for five consecutive days, had two days off and then five more consecutive days of treatment for a four-week period or until they reached functional oral intake scale (FOIS) level 7. The outcome measures assessed were change in FOIS, complications related to the treatment and number of therapy sessions.
There were no significant differences in the stroke characteristics and the VFSS results between the two groups. At the end of treatment, the average numbers of therapy sessions per subject in the RST and NMES groups were 18.36 +/- 3.23 and 17.25 +/- 5.64, respectively, a non-significant difference. Average changes in FOIS scores were 2.46 +/- 1.04 for the RST group and 3.17 +/- 1.27 for the NMES group, statistically significant at p < 0.001. No complications were observed in either group.
While both RST and NMES therapy showed a positive effect in the treatment of persistent dysphagia in stroke patients, NMES was significantly superior.
The primary purpose of this study was to investigate the influence of personality variables and contractile forces on magnitude estimates of pain unpleasantness and pain intensity during varying levels of neuromuscular electrical stimulation (NMES). Thirty volunteers, according to their scores on a preferred coping-style questionnaire, were assigned to one of two groups, one designated "monitors" (information seekers) and the other designated "blunters" (information avoiders). All subjects were administered varying levels of two types of NMES, one causing both afferent stimulation and muscle contraction and one causing only afferent stimulation. Subjects judged the intensity and unpleasantness of each current type using magnitude estimation. Data were analyzed using a 2 x 2 x 2 x 3 (coping style x current type x pain descriptor x current level) analysis of variance. The results indicated that the rate of increase of magnitude estimates for unpleasantness and pain intensity that corresponded to increases in current were dependent on (1) the preferred coping style of the subject, (2) whether the stimulus caused a muscle contraction, and (3) whether the subject was judging the intensity or the unpleasantness of the applied stimulus. Behavioral styles appear to affect how subjects characterize the discomfort associated with NMES, and involuntary muscle contractions contribute to the discomfort felt from NMES. These results suggest that interventions tailored to a preferred coping style may increase a subject's level of tolerance to NMES and thus provide a more beneficial treatment.
To evaluate the effect of transcutaneous neuromuscular electrical stimulation (NMES) on swallowing rehabilitation.
MEDLINE, PubMed, CINAHL, NML, Cochrane Central Register of Controlled Trials, Cochrane Database of Systematic Reviews, doc online, Google, and EMBASE were searched for studies using NMES to treat dysphagia between January 1966 and August 2006.
Included were published or unpublished, English-language, clinical trials with a quantifiable dependent variable.
Two researchers independently performed data extraction. A random-effects model was used to pool study results. The Cochran Q test was used to evaluate heterogeneity, and a funnel plot and Egger test were used to evaluate publication bias. A best-research synthesis using a methodological quality analysis was conducted.
A total of 81 studies were reviewed. Seven were accepted for analysis. A significant summary effect size was identified for the application of NMES for swallowing (Hedges g, 0.66; P<.001). Heterogeneity was significant for the combined trials (P<.10). When 2 outlier trials were removed, heterogeneity was no longer significant (P<.08). Publication bias was not identified on the funnel plot or Egger test (P = .25). Best-evidence synthesis showed indicative findings in favor of NMES for swallowing.
This preliminary meta-analysis revealed a small but significant summary effect size for transcutaneous NMES for swallowing. Because of the small number of studies and low methodological grading for these studies, caution should be taken in interpreting this finding. These results support the need for more rigorous research in this area.
Blood lactate accumulation is associated with development of muscle fatigue and negatively correlated to endurance performance. No research has quantified the effects of lactate presence at moderate levels of lactate accumulation. The purpose of the present study is to test whether two moderate blood lactate concentration levels affects running economy when running at the individual lactate threshold. 7 male world class endurance athletes with an average VO2max of 80.7±2.7 ml⋅kg⋅min or 5.8±0.5 L⋅min participated in this study. After the VO2max test the subjects were resting or walking and in a random order tested for running economy at their lactate threshold velocity when the blood lactate level reached either 3 mmol⋅L or 5 mmol⋅L. After a new 5 min exercising period at maximal aerobic velocity the crossover lactate value running economy testing was performed. Running economy was significantly (p<0.05) deteriorated from 0.668±0.044 to 0.705±0.056 ml⋅kg⋅m or 5.5% (p<0.05) for blood lactate level of 3 mmol⋅L compared to 5 mmol⋅L respectively. Increased lactate level from 3 to 5 mmol mmol⋅L is thus accompanied by deteriorated running economy at lactate threshold running velocity. The deteriorated running economy at moderate levels of lactate concentration emphasizes the importance of avoiding intensities above lactate threshold in the early parts of a dominantly aerobic endurance competition. It also emphasizes the importance of a high VO2max for aerobic endurance athletes, and may partly explain the VO2 slow component as impaired running economy.
During high-intensity submaximal exercise muscle fatigue and decreased efficiency are closely intertwined, and each contributes to exercise intolerance. Fatigue and muscle inefficiency share common mechanisms, e.g. decreased "metabolic stability", muscle metabolite accumulation, decreased free energy of ATP breakdown, limited O2 or substrate availability, increased glycolysis, pH disturbance, increased muscle temperature, ROS production, and altered motor unit recruitment patterns.SUMMARYDuring high-intensity submaximal exercise muscle fatigue and a decreased efficiency of contractions are strictly intertwined, and share several common mechanisms.
The present study compared the effects of two relative intensities on heart rate and blood lactate response to resistance exercise while controlling training variables such as number of sets, number of repetitions, exercise time, and time of recovery. On two occasions 8 male subjects were asked to perform five sets of 10 repetitions (reps) in the bench press at either 50 or 70% of a one-repetition maximum (1-RM). Each set required 20 to 25 seconds to complete. Recovery time between sets was 3 minutes. Mixed factorial analysis of variance revealed an intensity and set dependent effect for heart rate (HR) and blood lactate concentrations (bLA). HR and bLA were significantly higher (p<0.05) following the 70% 1-RM trial as compared to the 50% 1-RM trial. Differences between the 50% and 70% 1-RM trials occurred following the first set of exercise. At 50% 1-RM, HR and bLA leveled off following the first two sets. However, at 70% 1-RM, significantly elevated responses were observed with increasing set number. Results from this study suggest that the bench press exercise is capable of producing significant changes in heart rate and blood lactate concentrations. These changes are affected by the exercise intensity as well as the number of sets employed and should be considered when designing a resistance exercise training program.
(C) 1993 National Strength and Conditioning Association
We tested the effect of effortful swallow combined with surface electrical stimulation used as a form of resistance training in post-stroke patients with dysphagia. Twenty post-stroke dysphagic patients were randomly divided into two groups: those who underwent effortful swallow with infrahyoid motor electrical stimulation (experimental group, n = 10) and effortful swallow with infrahyoid sensory electrical stimulation (control group, n = 10). In the experimental group, electrical stimulation was applied to the skin above the infrahyoid muscle with the current was adjusted until muscle contraction occurred and the hyoid bone was depressed. In the control group, the stimulation intensity was applied just above the sensory threshold. The patients in both groups were then asked to swallow effortfully in order to elevate their hyolaryngeal complex when the stimulation began. A total of 12 sessions of 20 min of training for 4 weeks were performed. Blinded biomechanical measurements of the extent of hyolaryngeal excursion, the maximal width of the upper esophageal sphincter (UES) opening, and the penetration-aspiration scale before and after training were performed. In the experimental group, the maximal vertical displacement of the larynx was increased significantly after the intervention (p < 0.05). The maximal vertical displacement of the hyoid bone and the maximal width of the UES opening increased but the increase was not found to be significant (p = 0.066). There was no increase in the control group. Effortful swallow training combined with electrical stimulation increased the extent of laryngeal excursion. This intervention can be used as a new treatment method in post-stroke patients with dysphagia.
The purpose of this study was to determine if measurable changes in fundamental frequency (F(0)) and relative sound level (RSL) occurred in healthy speakers after transcutaneous electrical stimulation (TES) as applied via VitalStim (Chattanooga Group, Chattanooga, TN).
A prospective, repeated-measures design.
Ten healthy female and 10 healthy male speakers, 20-53 years of age, participated in the study. All participants were nonsmokers and reported negative history for voice disorders. Participants received 1 hour of TES while engaged in eating, drinking, and conversation to simulate a typical dysphagia therapy protocol. Voice recordings were obtained before and immediately after TES. The voice samples consisted of a sustained vowel task and reading of the Rainbow Passage. Measurements of F(0) and RSL were obtained using TF32 (Milenkovic, 2005, University of Wisconsin). The participants also reported any sensations 5 minutes and 24 hours after TES.
Measurable changes in F(0) and RSL were found for both tasks but were variable in direction and magnitude. These changes were not statistically significant. Subjective comments ranged from reports of a vocal warm-up feeling to delayed onset muscle soreness.
These findings demonstrate that application of TES produces measurable changes in F(0) and RSL. However, the direction and magnitude of these changes are highly variable. Further research is needed to determine factors that may affect the extent to which TES contributes to significant changes in voice.
The lack of a physiological definition of "vocal fatigue" is a central problem in prevention research that seeks to identify effects of voice effort and acoustic signs of potential vocal fold lesions. This report presents a three-part synthesis of electromyographic (EMG) and acoustic observations from a study that served to define physiological features of vocal fatigue. The study used a technique of EMG to show that, contrary to views that laryngeal tissues are largely nonfatiguable, voice effort induces spectral compression in the contraction potentials of glottal adductors typically associated with muscle fatigue. In subsequent analyses, these observable attributes served to identify, in seven subjects with widely differing profiles, consistent signs of voice tremor and effects of vocal loading on the voice apparatus. Given the novel character of this criterion-based approach, the first part (section "The Rationale of Electromyographic Observations of Fatigue") describes the EMG technique and its usefulness in observing in vivo effects of vocal loading. The second part (section "Acoustic Signs of Fatigue in Muscles Involved in Voicing") summarizes the results of a test that served to determine whether the identified signs of tremor reflect muscle fatigue induced by voice effort or by "general fatigue" associated with waking hours. The third part (section "Compensatory Stabilization of Tremor and Effects of 'Critical Fatigue'") presents the results of analyses of compensatory effects in three laryngeal muscles by reference to EMG observations of one subject in conditions of vocal loading. Taken together, the results illustrate the benefits of an approach based on objective criterion changes in muscle fatigue and show that valid tremor signs may, nonetheless, be sporadic, given the varying compensatory behavior of muscles in fatiguing conditions.
The aim of the present study was to further subdivide the type II fibers of the human thyroarytenoid and posterior cricoarytenoid muscles by means of a modified myosin ATPase reaction. In order to understand the functioning of these highly strained muscles better, it is important to know the respective percentage of fatigue-resistant type IIA fibers and fatigable type IIB fibers. The material comprised the larynges of seven laryngectomized males aged between 45 and 70 years and four laryngectomized females aged between 39 and 72 years. After having been frozen in nitrogen, 10-microns-thick sections were cut from the laryngeal muscles in a cryostat. The pH-lability of the enzyme that can be utilized in a classical myosin ATPase reaction permits a differentiation between fiber types I, IIA and IIB. Evidently, this is not possible with every human muscle. The fiber types IIA and IIB of the thyroarytenoid and the posterior cricoarytenoid muscles could be clearly distinguished by means of the inhibition reactivation myofibrillar ATPase technique. Using this method, the myosin ATPase enzyme was initially inhibited by hydroxymercuribenzoate and subsequently reactivated by cysteine. Regarding the incidence of type I and IIA fibers, there was a statistically significant difference between the thyroarytenoid and the posterior cricoarytenoid muscles. The type IIA fiber content was statistically significantly higher in the arytenoid muscle than in the posterior cricoarytenoid muscle. The percentage of type IIB fibers was low, not only in the thyroarytenoid muscle and the posterior cricoarytenoid muscle but also in the other laryngeal muscles.(ABSTRACT TRUNCATED AT 250 WORDS)
Delayed-onset muscular soreness (DOMS), the sensation of pain and stiffness in the muscles that occurs from 1 to 5 d following unaccustomed exercise, can adversely affect muscular performance, both from voluntary reduction of effort and from inherent loss of capacity of the muscles to produce force. This reduction in performance is temporary; permanent impairment does not occur. A number of clinical correlates are associated with DOMS, including elevations in plasma enzymes, myoglobinemia, and abnormal muscle histology and ultrastructure; exertional rhabdomyolysis appears to be the extreme form of DOMS. Presently, the best treatment for DOMS appears to be muscular activity, although the sensation again returns following the exercise. Training for the specific contractile activity that causes DOMS reduces the soreness response. The etiology and cellular mechanisms of DOMS are not known, but a number of hypotheses exist to explain the phenomenon. The following model may be proposed: 1) high tensions (particularly those associated with eccentric exercise) in the contractile/elastic system of the muscle result in structural damage; 2) cell membrane damage leads to disruption of Ca++ homeostasis in the injured fibers, resulting in necrosis that peaks about 2 d post-exercise; and 3) products of macrophage activity and intracellular contents accumulate in the interstitium, which in turn stimulate free nerve endings of group-IV sensory neurons in the muscles leading to the sensation of DOMS.
In muscle tension dysphonia (MTD) excessive tension of both the internal and external laryngeal muscles is observed. In the present pilot study, 9 pairs of surface electrodes were used to determine the electromyographic (EMG) characteristics of different muscles in the perioral area and anterior neck before and during phonation. Eleven patients with MTD and 5 normal speakers were included within the study. The results show a 6-8-fold increase of EMG activity and/or an alternation of the EMG activity level in the perioral and supralaryngeal muscles before and during phonation in most of the patients with MTD. It is not clear whether these muscles are activated as compensation for excessive tension of internal laryngeal muscles, or whether they are responsible for some of the voice disorders.
The purpose of this investigation was to examine the effects of dehydration on the lactate threshold and performance time to exhaustion in women.
Seven moderately trained women (age = 23.6 +/- 1.6 yr) performed two graded exercise tests on separate occasions, once in a normally hydrated state (HY) and once in a dehydrated state (DE). Dehydration was achieved by a 45-min submaximal exercise the evening before testing, followed by a 12-h period of fluid restriction. VO2, VCO2, V(E), R-values, blood lactate, and catecholamine concentrations were measured at baseline and during each workload. Plasma volume and plasma osmolality were also determined. Body weight dropped significantly for the dehydrated trial (2.6 +/- 0.7%).
There was a corresponding decrease in plasma volume measured (3.5 +/- 2.6%). The VO2max (3.1 +/- 0.3 L x min(-1) HY; 3.0 +/- 0.1 L x min(-1) DE) obtained was not significantly different between the hydration and dehydration trial. Plasma norepinephrine, epinephrine, and lactate concentrations were not significantly different at baseline or maximum intensity although epinephrine concentrations were higher for the dehydrated trial during submaximal workloads. Lactate concentrations were highly correlated with epinephrine (r = 0.95 HY; r = 0.97 DE). The lactate threshold occurred at a significantly lower relative percent of VO2max for the dehydrated trial (72.2 +/- 1.1% HY; 65.5 +/- 1.8% DE) as well as a lower absolute power output when compared with that in the hydrated trial. There was a significant decrease in time to exhaustion for the dehydrated trial (17.3 +/- 0.7 min HY; 16.3 + 0.7 min DE). Time to exhaustion for the dehydrated trial was correlated with the % VOmax at which the lactate threshold occurred (r = 0.74).
These data indicate that low levels of dehydration induced a shift in the lactate threshold, in part because of elevated epinephrine concentrations. This shift may have been one cause for the decrease in time to exhaustion for the dehydrated trial.
The development of acidosis during intense exercise has traditionally been explained by the increased production of lactic acid, causing the release of a proton and the formation of the acid salt sodium lactate. On the basis of this explanation, if the rate of lactate production is high enough, the cellular proton buffering capacity can be exceeded, resulting in a decrease in cellular pH. These biochemical events have been termed lactic acidosis. The lactic acidosis of exercise has been a classic explanation of the biochemistry of acidosis for more than 80 years. This belief has led to the interpretation that lactate production causes acidosis and, in turn, that increased lactate production is one of the several causes of muscle fatigue during intense exercise. This review presents clear evidence that there is no biochemical support for lactate production causing acidosis. Lactate production retards, not causes, acidosis. Similarly, there is a wealth of research evidence to show that acidosis is caused by reactions other than lactate production. Every time ATP is broken down to ADP and P(i), a proton is released. When the ATP demand of muscle contraction is met by mitochondrial respiration, there is no proton accumulation in the cell, as protons are used by the mitochondria for oxidative phosphorylation and to maintain the proton gradient in the intermembranous space. It is only when the exercise intensity increases beyond steady state that there is a need for greater reliance on ATP regeneration from glycolysis and the phosphagen system. The ATP that is supplied from these nonmitochondrial sources and is eventually used to fuel muscle contraction increases proton release and causes the acidosis of intense exercise. Lactate production increases under these cellular conditions to prevent pyruvate accumulation and supply the NAD(+) needed for phase 2 of glycolysis. Thus increased lactate production coincides with cellular acidosis and remains a good indirect marker for cell metabolic conditions that induce metabolic acidosis. If muscle did not produce lactate, acidosis and muscle fatigue would occur more quickly and exercise performance would be severely impaired.
Twenty-four females (mean age 38 years) with varying amounts of vocal training read aloud from a book for 45 min (70 dB at 40 cm distance). Symptoms of the throat and voice were ascertained with a questionnaire before, during and after the test. Fundamental frequency (F(0)) and sound pressure level (SPL) were measured. The alpha ratio describing the spectrum slope was calculated: SPL in the range 1-5 kHz minus SPL in the range 50 Hz-1 kHz. All measurements were made for the 1st, 5th, 15th, 30th and the 45th min of loading and for text reading before and after it. F(0), SPL and alpha values rose during the test, which may indicate adaptation to loading. During the first 5 min, however, these parameters showed a decreasing tendency, possibly reflecting warm-up. Subjects with more vocal training had a lower F(0) in the loading test. SPL seemed to reflect variation of symptoms during loading. Changes in acoustic parameters did not distinguish between subjects with most and fewest symptoms of fatigue in this test.
The present investigation was conducted to see the effect of subcutaneous fat on the transmission characteristics of an electrical stimulus applied to the skin and conducted to skeletal muscle. Two groups of subjects participated. In one, the subjects were three males and three females whose average age was 24.6+/-1.5 years, average weight was 74.8+/-18.2kg, and average height was 176.4+/-10.3cm. The other was a group of 30 subjects who average age was 26.2+/-1.9 years, average height 177.3+/-11.5cm, average weight 92.4+/-19.8kg. Electrical stimulation was applied above the quadriceps muscle at a current of 5mA and with sine and square wave stimulation at a frequency of 30Hz and a pulse width of 250micros. Current movement was measured on the skin and into muscle with surface and needle electrodes. The results showed that the thickness of the subcutaneous fat layer was directly related to signal loss from the skin (correlation between subcutaneous fat thickness and RC time constant was 0.96, p<0.001). Because of the subcutaneous fat layer and the resulting capacitance, an RC low pass filter is created such that square wave stimuli are not transmitted well into muscle whereas sine wave stimuli pass easily. Thus, when considering surface stimulation of nerve or muscle, any volume conductor model must take subcutaneous fat into consideration since the RC low pass filter created by fat will filter surface signals or, conversely, signals such as EMG which are generated in muscle but measured on the surface of the skin.
An investigation of fatigue, DOMS, and spectral/cepstral measurements in healthy speakers post-NMES
- Fowler
Exploring the use of laryngeal NMES on voice and its role in voice therapy
- Gorham-Rowan
Effect of transcutaneous electrical stimulation on acoustic and perceptual measures of vocal function across body types
- Harmon
Vocal fatigue: Some biomechanical considerations
- Titze