Made available in DSpace on 2014-06-11T19:22:12Z (GMT). No. of bitstreams: 0 Previous issue date: 2009-12-15Bitstream added on 2014-06-13T19:48:21Z : No. of bitstreams: 1 ambrozin_arp_dr_botfm.pdf: 169682 bytes, checksum: e35521aad39da34ec6c55a5da6cd12ad (MD5) / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / Algumas variáveis propostas para predizer o risco de complicação pósoperatória (CPO) são a altura no teste da escada (TE) e a distância do teste de caminhada de seis minutos (TC6) e acreditamos que o tempo no teste da escada (tTE) também pode ser utilizado para este fim. Além disso, são utilizados a prova de função pulmonar e os índices pré-operatórios. Objetivo: Determinar se os índices de Torrington e Henderson, American Society of Anesthesiologists, Goldman, Detsky e Charlson, a variável VEF1 da espirometria e as variáveis obtidas nos testes de esforço (TC6 e TE) podem ser preditivos das complicações pós-toracotomia e qual deles seria o melhor preditor dessas complicações. Método: Foram avaliados pacientes com indicação de toracotomia para ressecção pulmonar ou não, maiores de 18 anos. As comorbidades foram obtidas e traçados os índices de Comorbidade de Charlson, de risco de Torrington e Henderson, de Goldman, de Detsky e o ASA. A espirometria foi realizada de acordo com a ATS, em espirômetro Medgraphics Pulmonary Function System 1070. O TC6 foi realizado segundo os critérios da ATS e a distância prevista calculada. O TE foi realizado numa escada à sombra, composta por seis lances, num total de 12,16m de altura. O tTE em segundos percorrido na subida da altura total foi obtido e a partir deste a Potência (P) foi calculada utilizando a fórmula clássica. Também foi estimado o VO2 a partir do tTE (VO2 t) e da P (VO2 P). No intra-operatório foram registradas as complicações e o tempo cirúrgico. E no pós-operatório foram registradas as CPOs. Para análise estatística os pacientes foram divididos em grupos sem e com CPO. Foi aplicado o teste de acurácia para obtenção dos valores preditivos para o TC6 e para o tTE, a curva ROC e dessa o ponto de corte. As variáveis foram testadas para uma possível associação com as CPO pelo teste t de... / Some varieties purposed to predict the postoperative complication (POC) risk are the height in the stair-climbing test (SCT) and the distance in the six minute walk test (6MWT), we also believe that the time on the stair-climbing test can also be used for this purpose. Besides, the pulmonary function test and the preoperative index are also used. Objectives: We aim to determine if the Charlson, Torrington and Henderson, Goldman, Detsky and American Society of Anesthesiologists indexes, the variable FEV1 obtained on the Spirometry and on the Cardiopulmonary Exercise Testing (6MWT, SCT) can be predictive of the complication after thoracic surgery and which one of them would be the best. Method: Patients with indication to thoracic surgery, for resection or not, and older than 18 years old were evaluated. The comorbidities were obtained and the Comorbidity Charlson, Torrington and Henderson risk, Goldman, the Detsky and ASA indexes were calculated. The spirometry was performed according to ATS in Medgraphics Pulmonary Function System 1070. The 6MWT was performed according to the ATS criteria and the predicted distance was calculated. The SCT was performed indoor, on six flights of stairs, which results as a 12,16m climb. The time on the SCT was obtained after finished the stair height total in seconds and the Power (P) was calculated using the class formula. The maximum oxygen uptake (VO2) was estimated from the time of SCT (VO2 t) and the P (VO2 P). In the intraoperative was registered the complication and the surgery time. And in the postoperative was registered the POC. In the statistics analysis, the patients were divided in groups with and without POC. It was applied the accuracy test for the distance 6MWT and for the time in the SCT. We have found the cutoff from the ROC curve. The correlation between the variables and POC were tested using the t test for independent population ... (Complete abstract click electronic access below)

Cancer (CA) is the second leading cause of death in the United States preceded only by cardiovascular disease (CVD). Over the past 30 years, the 5-year survival rate for all cancers combined has increased by more than 20%. This improved survival rate is due to early diagnosis and advances in treatment involving a multimodality treatment approach that includes radiotherapy [RT] with about half of all CA patients receiving some type of RT sometime during the course of their treatment. Cardiotoxicity is one of the most important adverse reactions of RT and leads to a meaningful risk of CVD-related morbidity and mortality. Radiotherapy-related cardiotoxicity is a heterogeneous clinical syndrome characterized by symptoms related to impaired cardiac function due to radiation-injury to one or more cardiac structures. Furthermore, the relative risk of CVD increases with increasing incidental radiation dose to the heart. There is not a unified consensus on the definition of CA-related cardiotoxicity although most trials have focused on changes in resting systolic function, and/or development of cardiac symptoms.Commonly used tools to assess cardiac function are insensitive to minor injury hence subtle changes may go unnoticed for many years. Cardiotoxicity definitions should include a dynamic functional assessment of the CV system. This may allow detection of latent CV abnormalities before the precipitous decline of resting myocardial function or the development of CV symptomology that may impact quality of life. Cardiopulmonary exercise testing (CPET) including measurement of peak oxygen consumption (VO2) is the gold standard for the assessment of cardiorespiratory fitness (CRF). Cardiorespiratory fitness is a strong, independent predictor of mortality, CVD-related mortality, HF-related morbidity and mortality, CA-related mortality and may be involved in the pathophysiologic link between anti-CA related treatments and the increased risk of late CVD events. Emerging evidence indicates CRF may be reduced in CA survivors and have utility to detect subclinical cardiotoxicity, but this has not been evaluated in CA survivors treated with RT with significant heart involvement. This dissertation consists of one literature review and one comprehensive paper that will examine the ability of CPET to detect subclinical cardiotoxicity.

No description available.

In this thesis an integrated, dynamic model for cardiovascular and respiratory systems has been developed. Models of cardiopulmonary system, airway mechanics and gas exchange that preexisted in literature have been reviewed, modified and combined. Combined model composes the systemic and pulmonary circulations, left/right ventricles, tissue/lung compartments, airway/lung mechanics and gas transportation. Airway resistance is partitioned into three parts (upper, middle, small airways). A collapsible airways segment and a viscoelastic element describing lung tissue dynamics and a static chest wall compliance are included. Frank-Starling Law, Bowditch effect and variable cerebral flow are also employed in the model. The combined model predictions have been validated by laboratory data collected from two healthy, young, male subjects, by performing dynamic bicycle exercise tests, using Vmax 229 Sensormedics, Cardiopulmonary Exercise Testing Instrument. The transition from rest to exercise under a constant ergometric workload is simulated. The initial anaerobic energy supply, autoregulation and the dilatation of pulmonary vessels are considered. Mean arterial blood pressure and the blood gas concentrations are assumed to be regulated by the controllers of the central nervous system namely, the heart rate and alveolar ventilation. Cardiovascular and respiratory regulation is modeled by a linear feedback control which minimizes a quadratic cost functional.

No description available.

Apart from motor and sensory function loss, an injury to the spinal cord can cause sympathetic dysfunction, which has been shown to affect immune responses. In this thesis, data from five experimental studies have been collected to compare physiological and psychophysiological exercise responses between wheelchair athlete subgroups with different disabilities (tetraplegic, paraplegic, and non-spinal cord-injured). In two preparatory studies, physiological exercise responses to exhaustive (Chapter 4) and submaximal exercise (Chapter 5) were investigated in all three disability subgroups. Whilst reliability measures for peak oxygen uptake (VO2peak) were in a range observed previously in able-bodied athletes, the variation in tetraplegic athletes was larger when expressed relative to their VO2peak, questioning the use of this variable to track small changes in aerobic capacity in athletic populations. Submaximal physiological and psychophysiological exercise responses were found to be similar between disability subgroups when expressed as a percentage of VO2peak, justifying the protocol used in the laboratory study on mucosal immune function, which was based on the same percentages of VO2peak for all disability subgroups. The most extensive study of this thesis, detailed in Chapter 6, showed that single laboratory-controlled 60-min exercise sessions increase both salivary secretory immunoglobulin A (sIgA), a marker of mucosal immunity, and α-amylase, a marker of sympathetic activation in all three disability subgroups. However, the impaired sympathetic nervous system in tetraplegic athletes seemed to influence the fine-tuning of their sIgA response when compared with paraplegic and non-spinal cord-injured athletes, resulting in a larger exercise-induced increase of sIgA secretion rate when compared to paraplegic and non-spinal cord-injured athletes. Based on these results, the study detailed in Chapter 7 investigated sIgA responses in tetraplegic athletes during wheelchair rugby court training. Despite their disability, these athletes showed responses thought to be governed by the sympathetic nervous system, such as reductions of saliva flow rate as a result of strenuous exercise. Similarly, the responses observed in Chapter 8 imply a comparable trend of chronic sIgA exercise responses in tetraplegic athletes as found in the able-bodied population, namely a decrease in sIgA secretion rate during periods of heavy training. These are the first studies in wheelchair athlete populations to investigate mucosal immune responses. Interestingly, despite the disruption of their sympathetic nervous system, some responses in tetraplegic athletes are comparable with findings in able-bodied populations. It is possible that due to their highly trained nature, these tetraplegic individuals are able to compensate for their loss of central sympathetic innervation. This may be by way of adapted spinal reflex or parasympathetic nervous system activity, or increased sensitivity of receptors involved in autonomic pathways. Therefore, sympathetic nervous function in tetraplegic athletes may be qualitatively altered, but in parts still be functional.

Objetivo: Avaliar o condicionamento cardiorrespiratório de crianças e adolescentes com BOPI através do teste cardiopulmonar de exercício (TCPE). Métodos: Foram estudadas 20 crianças com BOPI, com idade de 8 a 16 anos, que estavam em acompanhamento ambulatorial. Os pacientes realizaram TCPE máximo em esteira, teste de caminhada de seis minutos (TC6), espirometria e pletismografia, seguindo as diretrizes ATS/ACCP, ATS e ATS/ERS, respectivamente. Para o cálculo dos percentuais esperados, foram utilizados: Armstrong (TCPE); Geiger (TC6); Kundson (espirometria), Zapletal (pletismografia). Resultados: A idade média foi de 11,4 ± 2,2 anos; 70 % meninos; peso: 36,8 ± 12,3 Kg; altura: 143,8 ± 15,2 cm; IMC: 17,6 ± 3,0. Na espirometria, os pacientes apresentavam os fluxos forçados diminuídos e, na pletismografia, os volumes estavam aumentados, quando comparados com a população de referência. No TCPE, 11 pacientes apresentaram valores do VO2 de pico inferiores (77,5 ± 37,5%) a 80% do percentual do predito e o VO 2LV foi considerado normal (40%VO2). A relação VE/VVM aumentada foi observada em 68% pacientes. A média da distância total percorrida foi de 512 ± 102 m (77,0 ± 15,7%). O VO2 de pico não se correlacionou com distância (TC6); no entanto, correlacionou-se com a CVF (L) (r=0,90/p=0,00), o VEF1 (L) (r=0,86/ p=0,00) e a VR/CPT (r=-0,71/ p=0,02) e, em percentual do predito, com a VR/CPT (-0,63/ p=0,00). Conclusões: O presente estudo demonstra que os pacientes com BOPI apresentam valores do consumo de oxigênio inferiores ao da população hígida e a reserva ventilatória diminuída, sugerindo que o comprometimento pulmonar pode ser um dos fatores limitantes para o exercício. / Objective: To assess the physical conditioning of children and adolescents with Post Infectious Bronchiolitis Obliterans (PIBO) through cardiopulmonary exercise testing (CPET). Methods: 20 children with PIBO, in follow-up at an outpatient clinic carried out CPET, six minute walking test (6MWT) and pulmonary function tests (PFT), following ATS/ACCP e ATS guidelines, respectively. Results were expressed as percentage of predicted reference values: Armstrong’s for CPET, Geiger’s for 6MWT, Knudson’s for spirometry, and Zapletal’s for plethysmography.Results: Means ± SD were: for age, 11,4 ± 2,2 years; weight: 36,8 ± 12,3 kg; height: 143,8 ± 15,2 cm; BMI: 17,6 ± 3,0. Gender: 70% boys. When compared to reference values, PFT had lower forced flows (spirometry) and increased volumes (plethysmography). CPET had 11 patients with reduced VO2peak values (< 80% predicted) and had normal VO2LV (VO2peak40%). An increased VE/MVV ratio was observed in 68% of patients. The mean distance (6MWT) was 77,0 ± 15,7% of predicted (512 ± 102 m). VO2peak did not correlate with 6MWT; however, it did correlate with FVC(L) (r=0,90/p=0,00), with FEV1(L) (r=0,86/p=0,00) and with RV/TLC (r=-0,71/p=0,02). When in percentage of predicted, with RV/TLC (r=-0,63/ p=0,00). Conclusions: This study shows that PIOB patients have lower oxygen consumption values when compared to the reference population. They also showed a diminished pulmonary reserve which might have contributed to that exercise limitation.

Contexto: Esta tese procurou estabelecer um novo método de mensuração instantânea de fadiga central e periférica durante o exercício de corpo inteiro até a capacidade aeróbica máxima em seres humanos. Até agora, a mensuração da fadiga central e periférica tem sido limitada a tarefas musculares isoladas ou a momentos específicos após o exercício, nos quais as condições fisiológicas que levaram aos sintomas limitantes do exercício já estão abrandadas. Assim, desenvolver um método que supere estas limitações permitiria demonstrar pela primeira vez as contribuições relativas da fadiga central e periférica na limitação ao exercício, no qual haja estimulação máxima dos sistemas neuromuscular e cardiovascular. Objetivo: Desenvolver e validar um método para quantificar a fadiga muscular periférica (MF, definida como a potência produzida para uma determinada estimulação muscular), fadiga de ativação (AF, definida como a atividade muscular evocável máxima), sua soma, fadiga de desempenho (PF, definida como a perda de potência isocinética voluntária máxima em comparação com a basal) durante o exercício realizado no cicloergômetro em capacidade aeróbica máxima. Além disso, esta tese teve como objetivo determinar as taxas de recuperação nas quais MF, AF e PF retornaram à linha de base após a intolerância durante o exercício de corpo inteiro em seres humanos. Métodos: Para quantificar a fadiga durante o exercício de corpo inteiro, foi desenvolvido um método para permitir uma rápida transição do ciclismo padrão (em que a relação entre potência e cadência é hiperbólica) para o ciclismo isocinético (em que a potência é independente da cadência, e a cadência é fixa). Assim, ao pedir para o participante realizar um esforço isocinético máximo em qualquer ponto durante o exercício ou na fase de recuperação, permitiu-se quantificar o declínio velocidade-específica da potência isocinética máxima (PISO). A diferença na PISO entre a linha de base e o exercício quantifica a PF. Foi testado se a relação de base entre PISO e potência eletromiográfica em 5 músculos da perna (RMS EMG) era velocidade dependente, linear e reprodutível, de tal modo que as contribuições relativas para PF pudessem ser isoladas a partir de: 1) a diminuição da ativação muscular (AF) ; e 2) o declínio na PISO num dado grau de ativação (MF). Resultados: Participantes saudáveis (n=13, 29-72 anos, variando em capacidade aeróbica de 23,5 até 62,4 ml/min/kg) completaram tiros isocinéticos esforço-variável de curta duração (5 s) a 50, 70 e 100 rpm para caracterizar a relação basal entre EMG RMS e potência isocinética. As correlações entre EMG-Piso basais foram lineares (r2= 0,95 ± 0,04) e velocidade dependente (análise de covariância). Posteriormente, testes de exercício incrementais repetidos foram realizados em uma bicicleta ergométrica e as trocas gasosas e a ventilação foram mensuradas respiração a respiração. O exercício encerrava com um esforço isocinético máximo (5 s) a 70 rpm. Na intolerância, PISO (duas pernas, 335 ± 88 W) foi ~ de 45% menos do que na linha de base (630 ± 156 W, p <0,05). Após a intolerância, houve recuperação da PISO em 3 minutos (p <0,05). AF e MF (medido em uma perna) foram de 97 ± 55 e 60 ± 50 W, respectivamente. As médias de viés (± limites de concordância) para a reprodutibilidade foram as seguintes: PISO na linha de base 1 ± 30 W; PISO na recuperação 0-min 3 ± 35 W; e EMG em PISO 3 ± 14%. Conclusões: A relação basal EMG-PISO foi bem modelada por uma função linear, que foi reprodutível no dia-a-dia. A variabilidade das mensurações EMG-PISO individuais entre ~ 25% e 100% de esforço, em torno do modelo linear, foi suficientemente forte de modo que a relação linear basal permitiu uma quantificação precisa de AF e MF no limite de tolerância e na recuperação do exercício aeróbico máximo. Foi também demonstrado que a relação EMG-PISO foi velocidade dependente, como esperado a partir da curva parabólica de potência-velocidade. Assim, esta tese apresenta um novo método útil para identificar as contribuições da fadiga central e periférica na limitação do exercício de corpo inteiro em seres humanos. / Background: This thesis sought to establish a new method for instantaneous measurement of central and peripheral fatigue during whole-body exercise up to maximal aerobic capacity in humans. Until now, measurement of central and peripheral fatigue has been limited to isolated muscle tasks or to time points after exercise where the physiological conditions that brought about the limiting symptoms for exercise have subsided. Thus, development of a method to overcome this would allow the first demonstration of the relative contributions of central and peripheral fatigue to limiting exercise that elicited maximal strain of the combined neuromuscular and cardiopulmonary systems. Objective: To develop and validate a method for quantifying peripheral muscle fatigue (MF, defined as the power produced for a given muscle stimulation), activation fatigue (AF, defined as the maximal evocable muscle activity), their sum, performance fatigue (PF, defined as the decline in maximal voluntary isokinetic power compared to the fresh, baseline, state) during cycling exercise at maximal aerobic capacity. In addition, this thesis aimed to determine the rate with which MF, AF and PF recovered to baseline after intolerance during whole-body exercise in humans. Methods: To quantify fatigue during whole-body exercise, a method was developed to allow a rapid switch from standard cycling (where the relationship between power and cadence is hyperbolic) to isokinetic cycling (where power is independent of cadence, and cadence is fixed) to be implemented. By asking the participant to give a maximal isokinetic effort at any point during exercise or recovery, allowed the velocity-specific decline in maximal isokinetic power (PISO) to be measured. The difference in PISO between baseline and exercise quantified PF. It was tested whether the baseline relationship between PISO and electromyographic power in 5 leg muscles (RMS EMG) was velocity dependent, linear and reproducible, such that the relative contributions to PF could be isolated from: 1) the decline in muscle activation (AF); and 2) the decline in PISO at a given activation (MF). Results: Healthy participants (n=13, 29 to 72 years old, ranging in aerobic capacity from 23.5 to 62.4 ml/min/kg) completed short (5 s) variable-effort isokinetic bouts at 50, 70, and 100 rpm to characterize the baseline relationship between RMS EMG and isokinetic power. Individual baseline EMG-PISO relationships were linear (r2 = 0.95 ± 0.04) and velocity dependent (analysis of covariance). Subsequently, repeated ramp incremental exercise tests were performed on a cycle ergometer and breath-by-breath gas exchange and ventilation was measured. Exercise was terminated with a maximal isokinetic effort (5 s) at 70 rpm. PISO at intolerance (two legs, 335 ± 88 W) was ~45% less than baseline (630 ± 156 W, p < 0.05). Following intolerance, PISO recovered within 3 minutes (p < 0.05). AF and MF (measured in one leg) were 97 ± 55 and 60 ± 50 W, respectively. Mean bias (± limits of agreement) for reproducibility were as follows: PISO at baseline 1 ± 30 W; PISO at 0-min recovery 3 ± 35 W; and EMG at PISO 3 ± 14%. Conclusions: The baseline EMG-PISO relationship was well modelled by a linear function, which was reproducible day-to-day. The variability of the individual EMG-PISO measurements between ~25% and 100% effort, around the linear model, was sufficiently tight that the baseline linear relationship allowed for a precise quantification of AF and MF at the limit of tolerance and in recovery from a maximal aerobic exercise task. It was also demonstrated that the EMG-PISO relationship was velocity dependent, as expected from the parabolic nature power-velocity curve. As such, this provides a valuable new method to identify the contributions of central and peripheral fatigue to limiting whole-body exercise in humans.

Objetivo: Avaliar o condicionamento cardiorrespiratório de crianças e adolescentes com BOPI através do teste cardiopulmonar de exercício (TCPE). Métodos: Foram estudadas 20 crianças com BOPI, com idade de 8 a 16 anos, que estavam em acompanhamento ambulatorial. Os pacientes realizaram TCPE máximo em esteira, teste de caminhada de seis minutos (TC6), espirometria e pletismografia, seguindo as diretrizes ATS/ACCP, ATS e ATS/ERS, respectivamente. Para o cálculo dos percentuais esperados, foram utilizados: Armstrong (TCPE); Geiger (TC6); Kundson (espirometria), Zapletal (pletismografia). Resultados: A idade média foi de 11,4 ± 2,2 anos; 70 % meninos; peso: 36,8 ± 12,3 Kg; altura: 143,8 ± 15,2 cm; IMC: 17,6 ± 3,0. Na espirometria, os pacientes apresentavam os fluxos forçados diminuídos e, na pletismografia, os volumes estavam aumentados, quando comparados com a população de referência. No TCPE, 11 pacientes apresentaram valores do VO2 de pico inferiores (77,5 ± 37,5%) a 80% do percentual do predito e o VO 2LV foi considerado normal (40%VO2). A relação VE/VVM aumentada foi observada em 68% pacientes. A média da distância total percorrida foi de 512 ± 102 m (77,0 ± 15,7%). O VO2 de pico não se correlacionou com distância (TC6); no entanto, correlacionou-se com a CVF (L) (r=0,90/p=0,00), o VEF1 (L) (r=0,86/ p=0,00) e a VR/CPT (r=-0,71/ p=0,02) e, em percentual do predito, com a VR/CPT (-0,63/ p=0,00). Conclusões: O presente estudo demonstra que os pacientes com BOPI apresentam valores do consumo de oxigênio inferiores ao da população hígida e a reserva ventilatória diminuída, sugerindo que o comprometimento pulmonar pode ser um dos fatores limitantes para o exercício. / Objective: To assess the physical conditioning of children and adolescents with Post Infectious Bronchiolitis Obliterans (PIBO) through cardiopulmonary exercise testing (CPET). Methods: 20 children with PIBO, in follow-up at an outpatient clinic carried out CPET, six minute walking test (6MWT) and pulmonary function tests (PFT), following ATS/ACCP e ATS guidelines, respectively. Results were expressed as percentage of predicted reference values: Armstrong’s for CPET, Geiger’s for 6MWT, Knudson’s for spirometry, and Zapletal’s for plethysmography.Results: Means ± SD were: for age, 11,4 ± 2,2 years; weight: 36,8 ± 12,3 kg; height: 143,8 ± 15,2 cm; BMI: 17,6 ± 3,0. Gender: 70% boys. When compared to reference values, PFT had lower forced flows (spirometry) and increased volumes (plethysmography). CPET had 11 patients with reduced VO2peak values (< 80% predicted) and had normal VO2LV (VO2peak40%). An increased VE/MVV ratio was observed in 68% of patients. The mean distance (6MWT) was 77,0 ± 15,7% of predicted (512 ± 102 m). VO2peak did not correlate with 6MWT; however, it did correlate with FVC(L) (r=0,90/p=0,00), with FEV1(L) (r=0,86/p=0,00) and with RV/TLC (r=-0,71/p=0,02). When in percentage of predicted, with RV/TLC (r=-0,63/ p=0,00). Conclusions: This study shows that PIOB patients have lower oxygen consumption values when compared to the reference population. They also showed a diminished pulmonary reserve which might have contributed to that exercise limitation.

Contexto: Esta tese procurou estabelecer um novo método de mensuração instantânea de fadiga central e periférica durante o exercício de corpo inteiro até a capacidade aeróbica máxima em seres humanos. Até agora, a mensuração da fadiga central e periférica tem sido limitada a tarefas musculares isoladas ou a momentos específicos após o exercício, nos quais as condições fisiológicas que levaram aos sintomas limitantes do exercício já estão abrandadas. Assim, desenvolver um método que supere estas limitações permitiria demonstrar pela primeira vez as contribuições relativas da fadiga central e periférica na limitação ao exercício, no qual haja estimulação máxima dos sistemas neuromuscular e cardiovascular. Objetivo: Desenvolver e validar um método para quantificar a fadiga muscular periférica (MF, definida como a potência produzida para uma determinada estimulação muscular), fadiga de ativação (AF, definida como a atividade muscular evocável máxima), sua soma, fadiga de desempenho (PF, definida como a perda de potência isocinética voluntária máxima em comparação com a basal) durante o exercício realizado no cicloergômetro em capacidade aeróbica máxima. Além disso, esta tese teve como objetivo determinar as taxas de recuperação nas quais MF, AF e PF retornaram à linha de base após a intolerância durante o exercício de corpo inteiro em seres humanos. Métodos: Para quantificar a fadiga durante o exercício de corpo inteiro, foi desenvolvido um método para permitir uma rápida transição do ciclismo padrão (em que a relação entre potência e cadência é hiperbólica) para o ciclismo isocinético (em que a potência é independente da cadência, e a cadência é fixa). Assim, ao pedir para o participante realizar um esforço isocinético máximo em qualquer ponto durante o exercício ou na fase de recuperação, permitiu-se quantificar o declínio velocidade-específica da potência isocinética máxima (PISO). A diferença na PISO entre a linha de base e o exercício quantifica a PF. Foi testado se a relação de base entre PISO e potência eletromiográfica em 5 músculos da perna (RMS EMG) era velocidade dependente, linear e reprodutível, de tal modo que as contribuições relativas para PF pudessem ser isoladas a partir de: 1) a diminuição da ativação muscular (AF) ; e 2) o declínio na PISO num dado grau de ativação (MF). Resultados: Participantes saudáveis (n=13, 29-72 anos, variando em capacidade aeróbica de 23,5 até 62,4 ml/min/kg) completaram tiros isocinéticos esforço-variável de curta duração (5 s) a 50, 70 e 100 rpm para caracterizar a relação basal entre EMG RMS e potência isocinética. As correlações entre EMG-Piso basais foram lineares (r2= 0,95 ± 0,04) e velocidade dependente (análise de covariância). Posteriormente, testes de exercício incrementais repetidos foram realizados em uma bicicleta ergométrica e as trocas gasosas e a ventilação foram mensuradas respiração a respiração. O exercício encerrava com um esforço isocinético máximo (5 s) a 70 rpm. Na intolerância, PISO (duas pernas, 335 ± 88 W) foi ~ de 45% menos do que na linha de base (630 ± 156 W, p <0,05). Após a intolerância, houve recuperação da PISO em 3 minutos (p <0,05). AF e MF (medido em uma perna) foram de 97 ± 55 e 60 ± 50 W, respectivamente. As médias de viés (± limites de concordância) para a reprodutibilidade foram as seguintes: PISO na linha de base 1 ± 30 W; PISO na recuperação 0-min 3 ± 35 W; e EMG em PISO 3 ± 14%. Conclusões: A relação basal EMG-PISO foi bem modelada por uma função linear, que foi reprodutível no dia-a-dia. A variabilidade das mensurações EMG-PISO individuais entre ~ 25% e 100% de esforço, em torno do modelo linear, foi suficientemente forte de modo que a relação linear basal permitiu uma quantificação precisa de AF e MF no limite de tolerância e na recuperação do exercício aeróbico máximo. Foi também demonstrado que a relação EMG-PISO foi velocidade dependente, como esperado a partir da curva parabólica de potência-velocidade. Assim, esta tese apresenta um novo método útil para identificar as contribuições da fadiga central e periférica na limitação do exercício de corpo inteiro em seres humanos. / Background: This thesis sought to establish a new method for instantaneous measurement of central and peripheral fatigue during whole-body exercise up to maximal aerobic capacity in humans. Until now, measurement of central and peripheral fatigue has been limited to isolated muscle tasks or to time points after exercise where the physiological conditions that brought about the limiting symptoms for exercise have subsided. Thus, development of a method to overcome this would allow the first demonstration of the relative contributions of central and peripheral fatigue to limiting exercise that elicited maximal strain of the combined neuromuscular and cardiopulmonary systems. Objective: To develop and validate a method for quantifying peripheral muscle fatigue (MF, defined as the power produced for a given muscle stimulation), activation fatigue (AF, defined as the maximal evocable muscle activity), their sum, performance fatigue (PF, defined as the decline in maximal voluntary isokinetic power compared to the fresh, baseline, state) during cycling exercise at maximal aerobic capacity. In addition, this thesis aimed to determine the rate with which MF, AF and PF recovered to baseline after intolerance during whole-body exercise in humans. Methods: To quantify fatigue during whole-body exercise, a method was developed to allow a rapid switch from standard cycling (where the relationship between power and cadence is hyperbolic) to isokinetic cycling (where power is independent of cadence, and cadence is fixed) to be implemented. By asking the participant to give a maximal isokinetic effort at any point during exercise or recovery, allowed the velocity-specific decline in maximal isokinetic power (PISO) to be measured. The difference in PISO between baseline and exercise quantified PF. It was tested whether the baseline relationship between PISO and electromyographic power in 5 leg muscles (RMS EMG) was velocity dependent, linear and reproducible, such that the relative contributions to PF could be isolated from: 1) the decline in muscle activation (AF); and 2) the decline in PISO at a given activation (MF). Results: Healthy participants (n=13, 29 to 72 years old, ranging in aerobic capacity from 23.5 to 62.4 ml/min/kg) completed short (5 s) variable-effort isokinetic bouts at 50, 70, and 100 rpm to characterize the baseline relationship between RMS EMG and isokinetic power. Individual baseline EMG-PISO relationships were linear (r2 = 0.95 ± 0.04) and velocity dependent (analysis of covariance). Subsequently, repeated ramp incremental exercise tests were performed on a cycle ergometer and breath-by-breath gas exchange and ventilation was measured. Exercise was terminated with a maximal isokinetic effort (5 s) at 70 rpm. PISO at intolerance (two legs, 335 ± 88 W) was ~45% less than baseline (630 ± 156 W, p < 0.05). Following intolerance, PISO recovered within 3 minutes (p < 0.05). AF and MF (measured in one leg) were 97 ± 55 and 60 ± 50 W, respectively. Mean bias (± limits of agreement) for reproducibility were as follows: PISO at baseline 1 ± 30 W; PISO at 0-min recovery 3 ± 35 W; and EMG at PISO 3 ± 14%. Conclusions: The baseline EMG-PISO relationship was well modelled by a linear function, which was reproducible day-to-day. The variability of the individual EMG-PISO measurements between ~25% and 100% effort, around the linear model, was sufficiently tight that the baseline linear relationship allowed for a precise quantification of AF and MF at the limit of tolerance and in recovery from a maximal aerobic exercise task. It was also demonstrated that the EMG-PISO relationship was velocity dependent, as expected from the parabolic nature power-velocity curve. As such, this provides a valuable new method to identify the contributions of central and peripheral fatigue to limiting whole-body exercise in humans.