Thèses sur le sujet « VO2p kinetic »

This thesis aimed to investigate and model the vo2, response to exhaustive constant intensity running of a short duration. Study I was a Douglas bag based study that compared the vo2, response of physically active subjects to 2, 5 and 8 minute bouts of constant intensity exhaustive exercise performed in both cycling and running. Nine male subjects took part and each completed a ramp test in addition to the three constant intensity tests in both modes of exercise. In the 5 and 8minute tests the subjects achieved 97.0 ± 4.2 and 97.5 ± 2.0 % for cycling, and 98.5 ± 1.8 and 99.2 ± 2.3% for running, of the ramp test Vo,peak. In the 2 minute test, a significantly lower percentage was attained (89.9 ± 5.5% and 91.8 ± 2.5% for cycling and running respectively). In cycling VO, was still increasing over the final minute of the test, whereas in running there was no difference between the last two 30 second samples (P~0.98). It was concluded that in severe intensity exercise of a short duration VO2 may not achieve its maximum and· that in running it may plateau at this sub-maximal rate. Study 2 validated the QP9000 for the measurement of vo2, during running on a breath-by-breath basis. Six male subjects performed a ramp test and tests at rest and at moderate and severe intensities. Each test was performed twice, once using the QP9000 and once using a Douglas bag system. No difference was found for VO, between the two systems (P~0.358). The SD of the differences between the systems across exercise intensities was 97 ± 57 ml.min·1 It was concluded that the QP9000 provides a valid measure of VO, at all exercises intensities. Study 3 investigated the vo2, response of trained runners to 800 m pace running, following a track based time trial. Eight male subjects (Vo,max 68.8 ± 5.6 m1.kg·'min-') took part in the study. That vo2, reached a plateau below Vo, was confirmed by a gradient of -29 ± 275 ml.min-' during the final 30 seconds of exercise. The asymptotic vo2, was only 85.3 ± 6.6 % of the Vo,peak from a ramp test and the response was shown to be extremely fast (time constant (T) of 10.7 ± 3.4 seconds). These breath-by-breath data confirmed the response indicated in Study I. Study 4 explored the single exponential model used to describe the vo2, response and the nature and level of breath-by-breath noise in severe intensity running. Five male subjects performed a ramp test to determine the speed at anaerobic threshold (AT). Each subject then performed five 8-minute runs at a speed corresponding to 90% of the AT and five exhaustive runs at a speed that would elicit exhaustion in about 2-minutes. Analysis of the noise to signal ratio of the severe intensity data showed that the noise was Gaussian and that averaging data over repeated transitions reduced this ratio. Computer simulations of noise equivalent to the noisiest subject's data demonstrated that the use of two repeated severe intensity transitions would give 95% confidence limits of < ± 1.2 seconds for T. Study 5 examined the effect of prior supra AT exercise on the VO, response to exhaustive severe intensity running. Ten middle and long distance runners each completed a ramp test to determine AT and Vo,peak. Subjects then ran exhaustive transitions, lasting approximately 2-minutes, that were preceded by moderate (90% AT) or heavy (50% of the difference between AT and Vo,peak) intensity running. Each transition was repeated. Increased metabolic acidosis (from prior heavy intensity exercise) did not increase the asymptotic vo2, (P ~ 0.226), and this figure represented only about 90% of Vo,peak from the ramp test. The mean response time (MRT) (time to reach 63% of the overall response) was faster following heavy exercise (20.9 ± 1.9 s vs. 18.9 ± 1.0 s, P<0.05). This was however due to a reduction in the duration of the initial (cardiodynamic) phase of the response rather than a speeding of the primary (phase 2) kinetics. Study 6 analysed the differences in this response between sprint and endurance runners. Six male athletes were recruited for each group based on best times for 100 m and 10 000 m. Subjects performed repeated transitions at a speed that would elicit exhaustion in approximately 2-minutes. No difference was found in the model of the VO, response between groups. When all subjects were analysed however a strong negative relationship was demonstrated between Vo,peak (from a ramp test) and the percentage of this Vo,peak that was reached in the constant speed test (r ~ -0.811, P ~ 0.001). It was concluded that the VO, response was dependent on the aerobic capabilities of the individual. In conclusion the thesis demonstrated a vo2, response in trained subjects during exhaustive severe intensity running that was different to that which is suggested by the majority of the literature. The vo2, response tends neither to VO, required nor to Vo,max, but rather tends to a plateau that is sub-maximal. This thesis was unable to identity the mechanisms that might result in such a shortfall in the response. However there appears to be a close link with the aerobic capabilities of the individual.

Kroppens syreupptagningskinetik innebär hur snabbt syreupptagningsmekanismerna i kroppen ökar mängden upptaget syre (O2) vid ett påbörjat arbete. Detta påverkar oss dagligen genom att en snabbare reaktion leder till en mindre syreskuld efter arbetet. Syftet med studien var att jämföra VO2-kinetiken mellan ett arm- och benarbete och ett rent benarbete och försöka hitta skillnader mellan dessa. Åtta måttligt tränade försökspersoner (sex män och två kvinnor) rekryterades och fick genomgå tre tester på en specialbyggd arm- och bencykelergometer. Testerna bestod av ett VO2-maxtest (kombinerad arm- och benarbete), ett submaximalt arm- och bentest (AB) och ett submaximal bentest (B) på samma absolut arbetsintensitet (65 % av VO2max) där VO2-kinetik mättes under fyra minuters arbete. Tiden att nå 50 % av VO2-platå (tVO250) var lika mellan AB och B-test (p=0.70). Tiden till VO2-platå var 19 % kortare under arm- och benarbete (AB 82 ± 32 vs B 101 (± 24) sek; p=0.02). Förbrukat O2 under testtiden var större under AB test jämfört med B-test (AB 41 ± 4 vs B 38 ± 4 ml · kg-1; p=0.004). Enligt dessa resultat var syrekinetiken under arm- och benarbetet snabbare jämfört med bara benarbetet, vilket betydde i detta fall att syreskulden i början av arbete under kombinerat arm- och benarbete blev mindre.

When O2 uptake at the lung is used to characterise the oxidative metabolic response to increased contractile activity ( O2 kinetics) in exercising muscle, the O2 profile reflects the combined influence of all involved muscle fibres. Consequently, during high-intensity exercise that mandates activation of fibres with considerable metabolic diversity (e.g., both principal fibre types), response characteristics specific to discrete segments of the recruited pool cannot be determined. The purpose of this thesis was to identify fibre-type-specific effects of conditions that might impact O2 delivery and/or motor unit recruitment patterns on O2 kinetics by using two models that increase fibre recruitment homogeneity during exercise transitions. In four experiments, subjects initiated high-intensity exercise from a moderate baseline (i.e., performed ‘work-to-work’ transitions; M→H) to target higher-order fibres, and in two experiments, subjects cycled at extremely slow and fast pedal rates to skew recruitment toward slow- and fast-twitch fibres, respectively. At mid-range contraction frequency, O2 kinetics (as indicated by the primary time constant, τp) was slower for M→H compared to unloaded-to-high-intensity transitions (U→H) (e.g., 42 v. 33 s; Ch 4) and this slowing was ~50% greater for M→H in a supine body position (decreased oxygenation; Ch 6). Slower kinetics was also present for U→H cycling at fast compared to slow pedal rates (τp, 48 v. 31 s; Ch 8). Conversely, M→H slowing relative to U→H was absent at extreme cadences (36 v. 31 s and 53 v. 48 s for slow and fast, respectively; Ch 7). After ‘priming’ (increased oxygenation), τp was reduced for U→H after fast-cadence priming only (Ch 8) and for M→H in the supine position (Ch 6), but unaffected for upright cycle and prone knee-extension M→H, for which priming reduced the O2 slow component and delayed-onset fibre activation (as indicated by iEMG; Chs 4 and 5). These results provide evidence in exercising humans that high-order fibres possess innately slow O2 kinetics and are acutely susceptible to interventions that might alter O2 delivery to muscle.

Hipotezė: 1 tipo cukriniu diabetu sergančių merginų vegetacinių sistemų rodiklių pokyčiai krūvio metu bus didesni, nei šokėjų ir nesportuojančių. Tikslas: Įvertinti 18-22 1 tipo cukriniu diabetu sergančių merginų, greitosios adaptacijos aerobiniams ėjimo krūviams, ypatumus. Tiriamieji: 10 šokėjų, 12 nesportuojančių sveikų merginų, ir 12 sergančių 1 tipo cukriniu diabetu merginų. Tyrimo metodai: 1. Kūno kompozicija 2. dujų analizė 3. pulsometrija 4. biocheminė kraujo analizė 5. standartinis šešių minučių ėjimo krūvis bėgtakiu 6. matematinė statistika. Tyrimo organizavimas: Tyrimas atliktas 2011-2012 metais. Tyrime dalyvavo 34 merginos, kurios buvo suskirstytos į 3 grupes: I grupę sudarė 1 tipo cukriniu diabetu sergančios merginos (n=12), II grupę šokėjos (n=10), III grupę nesportuojančios sveikos merginos (n=12). Tiriamosios buvo 18-22 metų amžiaus. Tiriamosios, atvykusios į Lietuvos kūno kultūros akademijos sporto fiziologijos labaratorija, buvo supažindintos su tyrimu. Prieš tyrimą tiriamosioms buvo atlikta kūno sudėties analizė su „Tanita TBF-300-A “ svartyklėmis. “Tanita TBF-300-A” svarstyklėmis buvo nustatyta tiriamųjų: kūno masė, KMI (kūno masės indeksas), riebalų masė (%), riebalų masė (kg). Visos tyrime dalyvavusios merginos atliko 6 minučių standartinį ėjimo testą bėgtakiu VIASYS LE 200 CE (Vokietija) pagal (1 tyrimo protokolą). 6 minučių standartinio ėjimo testo metu buvo atliktas tiesioginis MDS nustatymas dujų analizatoriumi „Oxycon Mobile“ (Jaeger, Vokietija)... [toliau žr. visą tekstą]
Hypothesis: We thought that type 1 diabetic girls vegetative system parameters during exercise will be higher than the dancers and untrained. The aim of the study: To evaluate the type 1 diabetic quick adaptation of aerobic walking loads, characteristics Subjects: 10 dancers, 12 untrained healthy women, 12 patients with type 1 diabetic women. The methods of the study: 1. Body composition 2. gas analysis 3. pulsometry 4. biochemical blood analysis 5. standard 6-minute treadmill walk test 6. mathematical statistics. The organization of the study: The study was conducted from 2011 to 2012 years. The study included 34 women were divided into 3 groups: group I consisted of type 1 diabetic girls (n = 12), group II dancers (n = 10), III group of healthy untrained girls (n = 12). The participants were between 18-22 years of age. Before the study subjects was performed body composition analysis with Tanita TBF-300-A."Tanita TBF-300-A subjects were found on scales: body weight, BMI (body mass index), fat mass (%), fat mass (kg).All the girls participated in the study, carried out a standard 6-minute treadmill walk test VIASYS LE 200 CE (Germany) in accordance with (1 TABLE). Standard 6-minute walk test was carried out directly by the gas analyzer MDS "Oxycon Mobile (Jaeger, Germany). Total 6-minute walk test in a standard treadmill VIASYS LE 200 CE (Germany) and recovery time using a portable system Oxycon Mobile has been recorded in gas exchange rates of oxygen consumption (VO2)... [to full text]

This thesis developed new methods of modelling oxygen uptake in exercising humans during cycling exercise sessions to steady-state. The results will contribute to the redefinition of conventional methods of data acquisition, processing, and modelling across exercise physiology, sports science, and respiratory disease research and application. The thesis identified misconceptions within current methods of data handling, and proposed innovative methods for improved data modelling.

There has been an interest in the kinetics of the V02 response during exercise at various intensities. However, most studies focus on the response of submaximal intensities whereas few studies have examined V02 kinetics at severe intensities. The purpose of this study was to evaluate the effect of exercise intensity on V02 kinetics over a range of severe intensities.

The purpose of this study was to evaluate the effect of mode and intensity on VO2 kinetics in the severe intensity domain. Seventeen participants completed 3-7 tests each on a cycle ergometer and treadmill. For each test, Tfatigue, VO2max, Tmean response, VO2GAIN, TVO2max and T@VO2max were determined. Linear regression techniques were used to describe the relationship between TVO2max and Tfatigue . VO2max values were higher in running. The VO2 response profile was faster for running than cycling and faster at higher intensities. The faster VO2 response in running may be associated with larger active muscle mass or differences in muscle activation patterns. The faster response at higher intensities may suggest that VO2 response is driven by O2 demand.

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The aim of this study was to determine the mode and the level that the physiological and performance variables influence in repeated running sprint ability. To this end, the study used 27 males participants (10 sprint runners (VEL), 8 long-distance runners (FUN) and 9 active subjects (ATI)). In a synthetic track these subjects were submitted to following tests on different days: 1) Incremental testing for determination of VO2max and maximal aerobic velocity (MAV); 2) constant velocity test at 110%MAV for determination of on- and off transition kinetics of VO2 and accumulated deficit oxygen (AOD); 3; 1 minute all-out test for determination of blood lactate concentration ([lac]s) kinetics and off-transition kinetics of VO2; and 4) repeated sprint test (10 sprints of 35 m departing every 20 s) for determine the total time of sprints, best sprint and percentage decrement score (Sdec). In every tests the [lac]s and blood pH were analyzed for observe the difference between maximal value after exercise and rest value (i.e. ∆[lac]s e ∆pH).Total time was significant different between all groups (VEL, 49,5 ± 0,9 s; FUN, 52,6 ± 3,1 s; ATI, 55,9s ± 2,6 s) and Sdec was significant lower in long distance runners compared to other groups (VEL, 8,5 ± 2,5%; FUN, 4,0 ± 2,0%; ATI, 8,3 ± 4,1%). Total time was significant correlated with best sprint (r 0,86), AOD in T110 (r = -,061) and T1min (r = -0,60), ∆[lac]s (r = -0,64) and ∆pH (r = 0,59) in RS, primary time constant (tau1) (r = -0,45) e O2 consumed in fast component after exercise in T1min (r = -0,44). Differently, Sdec was significant correlated with aerobic variables (VO2max, r = -0,59; MAV, r = -0,55; tau1 during exercise, r = 0,41), tau1 after T110 (r = 0,59) and T1min (r = 0,47), as well as, with lactate exchange ability (r 0,75). Therefore, it was concluded that repeated sprint performance is strongly influenced by anaerobic characteristics, while mechanisms related to removal of metabolites originated by anaerobic metabolism and aerobic indices influence to decrease fatigue in RS.
O objetivo deste estudo foi determinar o modo e o grau que as variáveis fisiológicas e de desempenho influenciam no desempenho em sprints repetidos. Para este fim, participaram do estudo 27 homens, sendo 10 corredores velocistas (VEL), 8 corredores fundistas (FUN) e 9 sujeitos ativos (ATI). Em uma pista sintética de atletismo estes sujeitos foram submetidos, em dias diferentes, aos seguintes testes: 1) teste incremental para determinação do VO2max e da velocidade aeróbia máxima (MAV); 2) teste de velocidade constante realizado a 110%MAV (T110) para determinar a cinética do VO2 durante e após o exercício e o déficit de oxigênio (AOD); 3) teste de um minuto máximo (T1min), para determinar a cinética da concentração de lactato sanguíneo ([lac]s) e a cinética do VO2 após o exercício; e 4) teste de sprints repetidos (RS) (10 sprints de 35m, intercalados com 20s de recuperação) para determinar o tempo total dos sprints, melhor sprint e a queda do escore em percentual (Sdec). Em todos os testes a [lac]s e o pH sanguíneo foram analisados para observar a diferença entre o valor máximo após o exercício e o valor de repouso (i.e. ∆[lac]s e ∆pH). Tempo total em RS foi significativamente diferente entre todos os grupos (VEL, 49,5 ± 0,9 s; FUN, 52,6 ± 3,1 s; ATI, 55,9s ± 2,6 s) e Sdec foi significativamente inferior em fundistas comparado aos outros grupos (VEL, 8,5 ± 2,5%; FUN, 4,0 ± 2,0%; ATI, 8,3 ± 4,1%). Tempo total foi correlacionado significativamente com o melhor sprint (r = 0,86), com o AOD no T110 (r = -0,61) e no T1min (r = -0,60), com o ∆[lac]s (r = -0,64) e ∆pH (r = 0,59) do RS, com a constante de tempo primária (tau1) (r = -0,45) e O2 consumido pelo componente rápido após o exercício no T1min (r = -0,44). Diferentemente, o Sdec foi correlacionado significativamente com variáveis aeróbias (VO2max, r = -0,59; MAV, r = -0,55; tau1 durante T110, r = 0,41), tau1 após T110 (r = 0,59) e T1min (r = 0,47), bem como, com a constante de tempo da entrada do lactato no compartimento sanguíneo no T1min (r = -0,75). Portanto, foi concluído que o desempenho em sprints repetidos é altamente influenciado por características anaeróbias, enquanto, mecanismos relacionados à remoção dos metabólitos originados pelo metabolismo anaeróbio e índices aeróbios influenciam para diminuir a fadiga em RS.

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Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)
O surgimento de equipamentos que permitem a análise do consumo de oxigênio (VO2) respiração-a- respiração, tem despertado um grande interesse nos fatores que podem influenciar sua cinética no início do exercício (resposta on). Entre os fatores mais estudados, temos a intensidade do exercício e o nível do treinamento dos sujeitos. Estes dados sugerem que a influência do exercício prévio sobre o VO2 durante o exercício incremental só ocorreria em baixas intensidades de esforço (< 60% VO2max). Os objetivos deste estudo foram: a) analisar a influência do exercício supramáximo realizado previamente, sobre os parâmetros da cinética do VO2 durante a transição repouso-exercício realizado a 50 e 70% VO2max, e b) analisar a influência do exercício supramáximo realizado previamente sobre as respostas cardiorrespiratórias e metabólicas durante o exercício de carga constante realizado a 50 e 70% VO2max. Para este estudo foram utilizados 14 ciclistas bem treinados do sexo masculino (VO2max = 63,4 + 6,5 ml.kg-1.min-1; idade = 21,4 + 3,5 anos; massa corporal = 68,1 + 6,8 kg; estatura = 174,9 + 4,6 cm) que executaram cinco testes: 1) exercício contínuo progressivo até a exaustão voluntária para a determinação do VO2max e as cargas correspondentes a 50, 70 e 120% VO2max e; 2) Quatro testes de carga constante, executados de forma aleatória e em dias separados. Nestes testes os sujeitos pedalaram durante 20 minutos em duas diferentes intensidades de exercício (50 e 70% do VO2max), realizados com e sem a execução prévia de um exercício supramáximo (120% VO2max). Foi analisada a resposta on do VO2 e também as respostas cardiorrespiratórias e metabólicas durante 20 minutos de exercício com carga constante realizados a 50 e 70% VO2max...
The appearance of an equipment that permits the oxygen consumption analysis (VO2) breath by breath has arisen a huge interest in factors which can influence its dynamics in the beginning of exercise (on response). Among the more studied factors, are the exercise intensity and training status. Meanwhile, few studies have analyzed the possible effects of previous exercise on the VO2response during exercise at moderate domain. In our lab, we have verified recently that during an incremental test performed eight minutes after a supramaximum exercise (120% VO2max), there was a significant VO2 increase in the first stage, while, at the intensities between 60% and VO2max, no alteration of VO2 was found, in accordance with the results existent in the literature. These results suggest that the influence of a previous exercise on the VO2 during the incremental exercise would just occur at low intensities (< 60% VO2 max). This model, meanwhile, does not permit to isolate a possible time effect of the exercise, once the highest intensities were always done after two or three stages, which could have favored a recovery, at least partially, of the metabolic conditions. In this way, the data until the present moment do not permit to identify if the normalization of VO2 during the incremental exercise is more dependent on the time and/or the exercise intensity. Therefore, the aims of this study were: a) to analyze the influence of the previous supramaximum exercise on the VO2 kinetics during the rest-exercise transition carried out at 50 and 70% VO2max, and b) to analyze the influence of the previous supramaximum exercise on the cardiorespiratory and metabolic responses during the constant loading exercise performed at 50 and 70% VO2max... (Complete abstract, click eletronic address below)

Orientador: Benedito Sérgio Denadai
Banca: Camila Coelho Greco
Banca: Marco Tulio de Mello
Resumo: O surgimento de equipamentos que permitem a análise do consumo de oxigênio (VO2) respiração-a- respiração, tem despertado um grande interesse nos fatores que podem influenciar sua cinética no início do exercício (resposta on). Entre os fatores mais estudados, temos a intensidade do exercício e o nível do treinamento dos sujeitos. Estes dados sugerem que a influência do exercício prévio sobre o VO2 durante o exercício incremental só ocorreria em baixas intensidades de esforço (< 60% VO2max). Os objetivos deste estudo foram: a) analisar a influência do exercício supramáximo realizado previamente, sobre os parâmetros da cinética do VO2 durante a transição repouso-exercício realizado a 50 e 70% VO2max, e b) analisar a influência do exercício supramáximo realizado previamente sobre as respostas cardiorrespiratórias e metabólicas durante o exercício de carga constante realizado a 50 e 70% VO2max. Para este estudo foram utilizados 14 ciclistas bem treinados do sexo masculino (VO2max = 63,4 + 6,5 ml.kg-1.min-1; idade = 21,4 + 3,5 anos; massa corporal = 68,1 + 6,8 kg; estatura = 174,9 + 4,6 cm) que executaram cinco testes: 1) exercício contínuo progressivo até a exaustão voluntária para a determinação do VO2max e as cargas correspondentes a 50, 70 e 120% VO2max e; 2) Quatro testes de carga constante, executados de forma aleatória e em dias separados. Nestes testes os sujeitos pedalaram durante 20 minutos em duas diferentes intensidades de exercício (50 e 70% do VO2max), realizados com e sem a execução prévia de um exercício supramáximo (120% VO2max). Foi analisada a resposta on do VO2 e também as respostas cardiorrespiratórias e metabólicas durante 20 minutos de exercício com carga constante realizados a 50 e 70% VO2max... (Resumo completo, clicar acesso eletrônico abaixo)
Abstract: The appearance of an equipment that permits the oxygen consumption analysis (VO2) breath by breath has arisen a huge interest in factors which can influence its dynamics in the beginning of exercise (on response). Among the more studied factors, are the exercise intensity and training status. Meanwhile, few studies have analyzed the possible effects of previous exercise on the VO2response during exercise at moderate domain. In our lab, we have verified recently that during an incremental test performed eight minutes after a supramaximum exercise (120% VO2max), there was a significant VO2 increase in the first stage, while, at the intensities between 60% and VO2max, no alteration of VO2 was found, in accordance with the results existent in the literature. These results suggest that the influence of a previous exercise on the VO2 during the incremental exercise would just occur at low intensities (< 60% VO2 max). This model, meanwhile, does not permit to isolate a possible time effect of the exercise, once the highest intensities were always done after two or three stages, which could have favored a recovery, at least partially, of the metabolic conditions. In this way, the data until the present moment do not permit to identify if the normalization of VO2 during the incremental exercise is more dependent on the time and/or the exercise intensity. Therefore, the aims of this study were: a) to analyze the influence of the previous supramaximum exercise on the VO2 kinetics during the rest-exercise transition carried out at 50 and 70% VO2max, and b) to analyze the influence of the previous supramaximum exercise on the cardiorespiratory and metabolic responses during the constant loading exercise performed at 50 and 70% VO2max... (Complete abstract, click eletronic address below)
Mestre

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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)
O objetivo deste estudo foi analisar a influência do estado de treinamento aeróbio sobre os efeitos do exercício prévio nos parâmetros da cinética do consumo de oxigênio (VO2) durante o exercício moderado. Para isto, 14 voluntários não treinados (GNT: massa corporal, 81,2 + 10,3 kg; estatura, 1,78 + 0,07 m; idade, 21,2 + 4,0 anos) e outros 14 ciclistas treinados (GT: massa corporal, 68,2 + 6,9 kg; estatura, 1,75 + 0,05 m; idade, 21,4 + 3,5 anos) (indivíduos com no mínimo dois anos de engajamento no treinamento e competições) realizaram um teste progressivo até a exaustão voluntária para a determinação do VO2 máximo (VO2max) e do limiar de lactato (LL). Posteriormente, realizaram em diferentes dias e em ordem aleatória, duas transições repouso-exercício (seis minutos na carga correspondente a 80% do LL), sendo uma delas precedida em oito minutos pelo exercício prévio (dois tiros de um minuto na carga correspondente a 120% VO2max, com um minuto de recuperação entre eles). Durante estes testes foram coletadas amostras de sangue capilar para a determinação da concentração de lactato sanguíneo e também monitoradas as variáveis cardiopulmonares a cada incursão ventilatória. O VO2 de repouso foi aumentado (p < 0,05) pelo exercício prévio (EPS) em ambos os grupos (GNT: 0,836 + 0,061 vs. 0,506 + 0,194 L/min; GT: 0,373 + 0,055 vs. 0,577 + 0,137 L/min). O tempo da resposta média do VO2 (constante tempo da resposta geral 0-360 s) foi significantemente reduzido na condição EPS apenas para o GNT (32,9 + 7,4 vs. 28,6 + 7,7 s; p < 0,05; GT: 25,7 + 5 vs. 23,3 + 5,8 s; p > 0,05). No GT, a Assimptota (VO2 médio dos últimos dois min de exercício) mostrou-se significantemente...
The aim of this study was to analyze the influence of aerobic fitness on the effects of prior exercise on VO2 kinetics parameters during moderate-intensity exercise. Fourteen untrained subjects (UG: body mass, 81.2 + 10.3 kg; height, 1.78 + 0.07 m; age, 21.2 + 4.0 years) and fourteen well trained cyclists (TG: body mass, 68.2 + 6.9 kg; height, 1.75 + 0.05 m; age, 21.4 + 3.5 years) (more than two years of engagement in endurance training and competition) performed one incremental test to voluntary exhaustion, in order to determine the lactate threshold (LT) and maximal VO2 (VO2max). Thereafter, they performed in different days and in random order, two rest to moderate-intensity exercise transitions (six minutes at 80% of LT), preceded by either no prior exercise or prior supra-maximal exercise (two bouts of one min at 120% of VO2max, with rest of one min between them). During the tests, capillary blood samples were collected to determine lactate concentration and the pulmonary gas exchanges were monitored continuously breath-by-breath. Resting VO2 was significantly (p < 0.05) increased by prior exercise (EPS) in both groups (UG, 0.836 + 0.061 vs. 0.506 + 0.194 L/min; TG, 0.373 + 0.055 vs. 0.577 + 0.137 L/min). Mean response time (time constant of overall VO2 response - 0 - 360 s) was significantly speeded by EPS in untrained group (UG: 32.9 + 7.4 vs. 28.6 + 7.7 s, p < 0.05; TG: 25.7 + 5.0 vs. 23.3 + 5.8 s, p > 0.05). In the trained group, the Assimptota (mean last two minutes VO2 value of moderate exercise) was significantly increased by EPS (TG: 2.208 + 0.383 vs. 2.067 + 0.266 L/min, p < 0.05; UG: 1.600 + 0.269 vs. 1.600 + 0.292 L/min, p > 0.05). It can be concluded... (Complete abstract click electronic access below)

The elevated CO2 levels, elevated temperature, and lower blood pH that may occur during exercise should enhance O2 delivery to the exercising muscles. It was hypothesized that performance of prior exercise (PE) would result in a faster VO2 response, as well as a reduced slow component contribution, in subsequent exercise bouts. Five women (21 ± 1 yr) and 10 men (23 ± 2 yr) performed nine 6-min bouts of heavy intensity cycle ergometer exercise (i.e., above the ventilatory threshold, individually determined by an incremental test). Three bouts were performed without prior heavy exercise (noPE), three were performed 6 min after a 6-min bout of heavy intensity arm cranking (PEA), and three were performed 6 min after a 6-min bout of heavy intensity cycle ergometer exercise (PEL). Breath-by-breath VO2 data from each of the three sets of three tests were combined and fitted to a two-component model, which ignores the cardiodynamic phase. The primary and slow component amplitudes were truncated to reflect actual increases in VO2 in each phase. The effects of PE on the time constant of the primary component were inconsistent. As hypothesized, the amplitude of the slow component was reduced by PE (noPE vs PEA vs. PEL: 25% > 16% < 14%; p < .05). It is concluded that heavy intensity PE affects characteristics of the VO2 profile in a subsequent bout of heavy intensity leg exercise.

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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior
The present study aimed to evaluate the effects of ischemic preconditioning (IPC) on the ventilatory parameters kinetics in different exercise intensities. Twelve physically active subjects (23.1±1.7 years; 176.1±4.6 cm; 77.6±8.3 kg; 46,7±5,7mL∙kg-1∙min-1) underwent in 5 different days the following tests in an electronically braked cycle ergometer: 1) incremental exercise test until maximal voluntary exhaustion in order to determine maximal oxygen uptake (VO2máx), ventilatory threshold (VT). 2) two constant work rate bouts (CWR) of 6min at moderate intensity (80%VT) interspersed with 30 min of intervention with the IPC (3x5min occlusion/3x5min reperfusion for each thigh, performed intermittently and alternately) in two different days; 3) two repetitions of 6 min CWR in severe intensity corresponding to 70%∆ (i.e., VT + 0,7 x (VO2máx VT)) interspersed by 45min passive rest followed by CPI, in two different days. IPC significantly decreased both the primary component time constant (t1) (19.2±3.3s to 14.8±3,6s) and carbohydrate oxidation (1.43±0.32g∙min-1 to 1.16±0.33g∙min-1) and increased fat oxidation (0.27±0.12g∙min-1 to 0.40±0.12g∙min-1) the for moderate intensity with the VO2 t1 (25,4±9s to 21,2±6,6s) and end VO2 (1689,1±291 para 1745,9±255,7mL∙min-1) did not differ significantly. In severe intensity IPC significantly reduced both t1 (19.2±3.3s to 14.8±3.6s; p<0.05) and end blood lactate concentration (7.48±2.58mM to 7.01±2.20mM, p<0.05), however the slow component amplitude (502,5±204,1 to 529,1±133,5mL∙min-1) and end VO2 (3406,5±474,4 to 3489,7±435,6 mL∙min-1) of VO2 kinetics remain similar. We conclude that the primary component of VO2 kinetics was accelerated by IPC during severe exercise, but not during moderate exercise, suggesting that the main effect of IPC seems to be the increase on O2 delivery induced by a higher blood flow, which corroborate with the periphery limitation hypothesis (metabolic inertia) as the main limit factor for VO2 kinetics at the onset of moderate exercise. For moderate exercise, IPC increased the CO2 retention becoming the VO2 kinetics even slower because the decrease of HCO3- content by ischemia, furthermore, the changes on substrate oxidation observed during exercise after IPC might have occurred for reperfusion-induced increases in FFA delivery and β-oxidation pre-activation
O objetivo deste estudo foi avaliar os efeitos da condição pré-isquêmica (CPI) na cinética dos parâmetros ventilatórios em diferentes intensidades de exercício. Doze indivíduos (23,1±1,7 anos; 176,1±4,6 cm; 77,6±8,3 kg; 46,7±5,7mL∙kg-1∙min-1) fisicamente ativos realizaram em 5 dias diferentes os seguintes testes em cicloergômetro de frenagem eletromagnética: 1) teste de carga incremental até exaustão voluntária para determinação das variáveis máximas (consumo máximo de oxigênio, VO2máx) e submáximas (Limiar Ventilatório, LV); 2) em dois dias diferentes duas repetições de exercício em carga constante (PCC) com 6min de duração em intensidade moderada a 80%LV intercalados com 30min de intervenção com o CPI (3x5min de oclusão/3x5 de reperfusão para cada coxa, de maneira intermitente e alternada); 3) em dois dias diferentes duas repetições de PCC de 6 min em intensidade severa correspondente a 70% do valor entre o VO2 no LV e o VO2máx (70%∆, i.e. LV + 0.7x(VO2max LV)) intercalados por 45min de repouso passivo seguidos do protocolo de CPI. Na carga moderada as variáveis que apresentaram diferença significante da condição controle para a experimental foram: a constante de tempo do componente primário (t1) do VCO2 (43,4±10,4s para 58,2±18,5s), a oxidação de carboidratos (1,43±0,32g∙min-1 para 1,16±0,33g∙min-1) e a oxidação de gordura (0,27±0,12g∙min-1 para 0,40±0,12g∙min-1). O t1 do VO2 (25,4±9s para 21,2±6,6s) e o VO2 final (1689,1±291 para 1745,9±255,7mL∙min-1) não apresentaram diferença significante no domínio moderado. No domínio severo o CPI acelerou significativamente o t1 (19,2±3,3s para 14,8±3,6s) e reduziu a concentração sanguínea final de lactato (7,48±2,58 mM para 7,01±2,20mM) não alterando a amplitude do componente lento (502,5±204,1 para 529,1±133,5mL∙min-1) e o VO2 final (3406,5±474,4 para 3489,7±435,6 mL∙min-1). Podemos concluir que a cinética do componente primário do VO2 (t1) foi acelerada após o CPI no exercício severo, sem efeitos sobre a cinética do VO2 durante o exercício moderado, sugerindo que o principal efeito do CPI parece residir sobre o aumento da oferta de O2 induzida pelas modificações no fluxo sanguíneo, corroborando com a hipótese da limitação periférica (inércia oxidativa) como principal determinante na cinética do VO2 ao início do exercício moderado. No domínio moderado, o CPI aumentou a retenção de CO2 e consequentemente tornou mais lenta a cinética do VCO2 no músculo como conseqüência da diminuição de HCO3- pela isquemia, além disso, a alteração na oxidação de substratos observada durante o exercício subseqüente o CPI provavelmente ocorreu pela maior oferta de AGL e ativação da β-oxidação induzidos pelos períodos de reperfusão

Orientador: Benedito Sérgio Denadai
Banca: Mara Patrícia Traina Chacon Mikahil
Banca: Hebert Gustavo Simões
Resumo: O objetivo deste estudo foi analisar a influência do estado de treinamento aeróbio sobre os efeitos do exercício prévio nos parâmetros da cinética do consumo de oxigênio (VO2) durante o exercício moderado. Para isto, 14 voluntários não treinados (GNT: massa corporal, 81,2 + 10,3 kg; estatura, 1,78 + 0,07 m; idade, 21,2 + 4,0 anos) e outros 14 ciclistas treinados (GT: massa corporal, 68,2 + 6,9 kg; estatura, 1,75 + 0,05 m; idade, 21,4 + 3,5 anos) (indivíduos com no mínimo dois anos de engajamento no treinamento e competições) realizaram um teste progressivo até a exaustão voluntária para a determinação do VO2 máximo (VO2max) e do limiar de lactato (LL). Posteriormente, realizaram em diferentes dias e em ordem aleatória, duas transições repouso-exercício (seis minutos na carga correspondente a 80% do LL), sendo uma delas precedida em oito minutos pelo exercício prévio (dois "tiros" de um minuto na carga correspondente a 120% VO2max, com um minuto de recuperação entre eles). Durante estes testes foram coletadas amostras de sangue capilar para a determinação da concentração de lactato sanguíneo e também monitoradas as variáveis cardiopulmonares a cada incursão ventilatória. O VO2 de repouso foi aumentado (p < 0,05) pelo exercício prévio (EPS) em ambos os grupos (GNT: 0,836 + 0,061 vs. 0,506 + 0,194 L/min; GT: 0,373 + 0,055 vs. 0,577 + 0,137 L/min). O tempo da resposta média do VO2 (constante tempo da resposta geral 0-360 s) foi significantemente reduzido na condição EPS apenas para o GNT (32,9 + 7,4 vs. 28,6 + 7,7 s; p < 0,05; GT: 25,7 + 5 vs. 23,3 + 5,8 s; p > 0,05). No GT, a Assimptota (VO2 médio dos últimos dois min de exercício) mostrou-se significantemente... (Resumo completo, clicar acesso eletrônico abaixo)
Abstract: The aim of this study was to analyze the influence of aerobic fitness on the effects of prior exercise on VO2 kinetics parameters during moderate-intensity exercise. Fourteen untrained subjects (UG: body mass, 81.2 + 10.3 kg; height, 1.78 + 0.07 m; age, 21.2 + 4.0 years) and fourteen well trained cyclists (TG: body mass, 68.2 + 6.9 kg; height, 1.75 + 0.05 m; age, 21.4 + 3.5 years) (more than two years of engagement in endurance training and competition) performed one incremental test to voluntary exhaustion, in order to determine the lactate threshold (LT) and maximal VO2 (VO2max). Thereafter, they performed in different days and in random order, two rest to moderate-intensity exercise transitions (six minutes at 80% of LT), preceded by either no prior exercise or prior supra-maximal exercise (two bouts of one min at 120% of VO2max, with rest of one min between them). During the tests, capillary blood samples were collected to determine lactate concentration and the pulmonary gas exchanges were monitored continuously breath-by-breath. Resting VO2 was significantly (p < 0.05) increased by prior exercise (EPS) in both groups (UG, 0.836 + 0.061 vs. 0.506 + 0.194 L/min; TG, 0.373 + 0.055 vs. 0.577 + 0.137 L/min). Mean response time (time constant of overall VO2 response - 0 - 360 s) was significantly speeded by EPS in untrained group (UG: 32.9 + 7.4 vs. 28.6 + 7.7 s, p < 0.05; TG: 25.7 + 5.0 vs. 23.3 + 5.8 s, p > 0.05). In the trained group, the Assimptota (mean last two minutes VO2 value of moderate exercise) was significantly increased by EPS (TG: 2.208 + 0.383 vs. 2.067 + 0.266 L/min, p < 0.05; UG: 1.600 + 0.269 vs. 1.600 + 0.292 L/min, p > 0.05). It can be concluded... (Complete abstract click electronic access below)
Mestre

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Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)
Introdução: Os pacientes com Miopatia Mitocondrial (MM) e Oftalmoplegia Externa Progressiva (OEP) apresentam disfunção na cadeia respiratória com incapacidade de aumentar a extração de oxigênio muscular e sintetizar ATP aerobicamente, levando à intolerância ao esforço e lentificação da cinética do O2. Quando a extração de oxigênio é comprometida, na tentativa de se manter o consumo de oxigênio muscular, uma hipótese é que estes pacientes poderiam aumentar compensatoriamente a oferta de oxigênio, apresentando, assim, uma resposta hipercinética cardiovascular e ventilatória. Por outro lado, alguns indícios de menor oferta de oxigênio foram encontrados em pacientes com MM, como um menor fluxo sanguíneo muscular no antebraço e uma maior capacidade de produção de ATP após a suplementação de oxigênio. A cinética do O2 na fase de recuperação (REC) nos fornece, assim, subsídios quanto ao pagamento do débito de oxigênio tecidual e ao reabastecimento do estoque de oxigênio sanguíneo após o exercício. Ao nosso conhecimento, a cinética do O2 REC nunca foi avaliada nos pacientes com MM, assim como a integração desta variável com as respostas não-invasivas cardiovasculares e de extração de oxigênio muscular. Objetivo: contrastar as dinâmicas da oferta e da utilização de oxigênio na recuperação do exercício em pacientes com MM; e identificar os principais mecanismos fisiopatológicos da intolerância ao esforço nestes indivíduos. Métodos: Foram avaliadas em 12 pacientes com MM e 12 controles saudáveis, as cinéticas de recuperação: (i) do O2 pulmonar, (ii) da variação na concentração da deoxiemoglobina ([HHb], mensurada pela espectroscopia de raios quasi infravermelhos - NIRS) no vasto lateral, (iii) do débito cardíaco (DC) por bioimpedância transtorácica, após um teste de carga constante de alta intensidade (70% da carga máxima atingida em teste incremental prévio) até o limite da tolerância em cicloergômetro. Resultados: Foram observadas cinéticas mais lentas de reoxigenação da [HHb], ([HHb] = 43,7 ± 21,2 vs 27,5 ± 6,7) e do O2 ( O2 = 58,1 ± 25,1 vs 38,8 ± 7,6) nos pacientes com MM em relação aos controles, respectivamente. Estas respostas foram associadas a uma cinética de DC mais rápida em relação ao O2, nos pacientes comparados aos controles (T½DC * 1,44 / O2 = 1,3 ± 0,4 vs 1,7 ± 0,6). Conclusão: Os pacientes com MM na forma OEP apresentam, na recuperação do exercício de alta intensidade, um pagamento elevado do débito de oxigênio contraído no exercício e reoxigenação mais lenta da [HHb]. Estas respostas, associadas à cinética mais rápida do DC em relação ao O2 são indícios de que possa haver um déficit no transporte de oxigênio microvascular, além do comprometimento mitocondrial característico desta doença.
Background: Mitochondrial Myopathy patients (MM) and Progressive External Ophthalmoplegia (PEO) present with respiratory chain dysfunction and inability to increase muscle oxygen extraction and aerobic ATP synthesis, leading to exercise intolerance and slower O2 kinetics. When oxygen extraction is impaired, in an attempt to maintain muscle oxygen uptake, these patients could increase oxygen delivery, thus exhibiting a hyperkinetic cardiovascular and ventilatory response. On the other hand, some evidence of oxygen delivery impairment was found in MM patients, such as a decrease in muscle blood flow in the forearm and a greater capacity for ATP production after oxygen supplementation. Recovery O2 kinetics provides information on tissue oxygen debt repayment and oxygen blood store replenishment after exercise. To our knowledge, recovery O2 kinetics has never been evaluated in MM patients, as well as its integration with the non-invasive cardiovascular and muscle reoxygenation responses. Objective: to contrast oxygen delivery and utilization dynamics on exercise recovery of MM patients and to identify the main pathophysiologic mechanisms of exercise intolerance in these subjects. Methods: Were evaluated in 12 MM patients and 12 healthy controls, the recovery kinetics of: (i) O2 (ii) deoxyhemoglobin variation ([HHb], measured by near-infrared spectroscopy - NIRS) in vastus lateralis, (iii) cardiac output (CO) by transthoracic bioimpedance, after a high-intensity constant work rate test (70% of maximal workload in a previous incremental test) to the limit of tolerance in a cycle ergometer. Results: We detected slower kinetics for [HHb] ([HHb] = 43.7 ± 21.2 vs. 27.5 ± 6.7) and for O2 ( O2 = 58.1 ± 25.1 vs. 38.8 ± 7.6) in MM patients compared to controls, respectively. Additionally, these responses were associated with a faster recovery CO kinetics in relation to O2 kinetics in MM patients compared to controls (T½DC*1,44 / O2 = 1,3 ± 0,4 vs. 1,7 ± 0,6). Conclusion: Patients with MM and PEO present with a higher oxygen debt and slower reoxygenation kinetics in the recovery of a high-intensity exercise test. Those responses were associated with a faster CO recovery in relation to O2 kinetics, indicating a microvascular oxygen transport deficit, besides the characteristic mitochondrial impairment observed in these patients.
TEDE
BV UNIFESP: Teses e dissertações

The purpose of this study was to determine whether working in the field of deaf education, as opposed to general education, results in a higher level of technology integration. A secondary goal was to determine if deaf educators who are deaf integrate technology at a higher level than their hearing counterparts. The instrument chosen for this study was the LoTi Technology Use Profile, a tool used to explore the role of technology in the classroom. A total of 92 participates were included in the study of which 48 were regular educators and 44 were deaf educators. The participants were selected from a population pool whereby teachers were presumably pre-disposed to using technology based upon their attendance at a technology training session in the form of a conference or a class. Deaf educators as a whole did not perform as well as general educators on the LoTi scales. Given the fact that the technology-minded general educators who comprised the sample population of this study scored exceptionally high on the LoTi scales, further research is needed to ensure comparability between the two groups. The findings of the current study do suggest, though, that deaf educators who are deaf have the potential to integrate technology to a greater degree than deaf educators who are hearing. Thus, a primary recommendation is to conduct a national LoTi survey of typical, rather than technology-minded, deaf educators as a comparison to the 2004 national survey of typical general educators.

A corrida representa um importante segmento do triathlon, sendo precedida pela prova de ciclismo. A compreensão dos efeitos do ciclismo sobre o desempenho da corrida, portanto, se torna indispensável para a otimização dos resultados finais de uma prova. O objetivo desse estudo foi comparar as variáveis cinemáticas, eletromiográficas e o consumo de oxigênio da corrida no triathlon com àquelas de uma corrida isolada e de uma corrida prolongada. As seguintes variáveis foram avaliadas no presente estudo: (1) freqüência e amplitude de passada; (2) o valor RMS (root mean square) médio do sinal EMG dos músculos bíceps femoral, reto femoral, vasto lateral, gastrocnêmio medial e tibial anterior; e, (3) o VO2. Participaram desse estudo nove triatletas do sexo masculino. O protocolo de avaliação foi realizado em três etapas: (1) teste para obtenção do VO2 máx, realizado em esteira ergométrica; (2) teste que envolveu a sucessão ciclismo-corrida da prova de triathlon (CT), com 40 km de ciclismo, seguidos de10 km de corrida – em um contexto de prova simulada; e (3) teste de corrida prolongada (CP), em que o atleta correu o tempo correspondente aos 40 km de ciclismo somado a 10 km de corrida. Os primeiros 10 km dessa corrida prolongada constituíram a corrida isolada (CI). Os dados cinemáticos, eletromiográficos e o VO2 foram coletados e analisados a partir de três intervalos: 1°, 5° e 9° km de corrida. O nível de significância dos testes estatísticos aplicados foi de α < 0,05. Os resultados não demonstraram diferenças significativas entre as diferentes corridas. Já entre os intervalos, foi verificada uma diminuição da amplitude de passada entre os intervalos 1 e 2, e entre os intervalos 1 e 3, bem como um aumento do valor RMS do músculo vasto lateral do intervalo 1 para o intervalo 3. A partir da análise específica da corrida do triathlon, foi encontrado um aumento da freqüência e da amplitude de passada entre os intervalos. A inexistência de diferenças entre as corridas se contrapõe aos resultados de estudos encontrados na literatura. Entretanto, os presentes resultados podem ser justificados à medida que o VO2 de teste se manteve abaixo do VO2 correspondente ao segundo limiar ventilatório. A existência de diferenças significativas entre os intervalos para algumas das variáveis analisadas pode sugerir a incidência de fadiga no transcorrer da atividade.
Running represents an important segment of triathlon and is preceded by cycling. Therefore, studying the influence of cycling in running performance is essential for performance optimization. The aim of this study was to compare the kinematic and electromyographic variables and oxygen uptake of the triathlon running with a prolonged run and an isolated run. The following parameters were analyzed and compared: (1) the kinematic variables stride frequency and stride length; (2) mean value of the RMS signal of EMG of the biceps femoris, rectus femoris, vastus lateralis, gastrocnemius medialis and tibialis anterior muscles; and, (3) the VO2. Nine male triathletes performed the tests, which were performed on three stages: (1) VO2 max test, performed on a treadmill; (2) 40km of cycling followed by 10km of running time-trial (CT), with 40 km of cycling, followed by 10 km of running – simulated race; (3) prolonged run test (CP): the athletes ran the time corresponding to the 40 km of cycling and more 10 km of running after it. The first 10 km of this prolonged run test was considered the isolated run (CI). Kinematic and eletromyographic variables and VO2 variables were collected and analyzed at three distinct moments: 1°, 5° e 9° km of the run. Statistical tests were applied for an α < 0.05. No significant differences were found between the running types. Between moments, decreased on stride length between moments 1 and 2, and between moments 1 and 3, was observed. There was an increase in the EMG signal RMS of the vastus lateralis from moment 1 to moment 3. In the comparison of triathlon running moments, were found increase in stride frequency and in stride length between moments. No differences were found in literature between running types, a completely opposite result compared to our results. However, these results can be justified for the VO2 values, which remained bellow the VO2 values corresponding to ventilatory threshold. The significant differences between moments of some variables may suggest a fatigue effect in the results.

Le modèle bioénergétique de P.E. di PRAMPERO permet d'expliquer la performance dans les disciplines de locomotion (course à pied, cyclisme, natation, ...) à partir d'une puissance métabolique et d'un indice de la dépense d'énergie par unité de distance parcourue. Néanmoins, pour les épreuves de natation de haute intensité telles que le 100m crawl, le contexte environnemental rend l'estimation de la puissance métabolique d'origine aérobie techniquement difficile. L'objectif de cette thèse est alors de proposer une nouvelle approche des réponses aérobies d'un 100-m nage libre, réalisé dans des conditions les plus proches possible d'une compétition. Le travail expérimental a porté sur des nageurs entraînés. Dans un bassin de 25-m, la procédure propose que les nageurs réalisent une performance sur 100-m nage libre à allure de compétition et trois épreuves (25m, 50m, 75m) réitérant les mêmes allures intermédiaires que celles du 100-m. VO2 est mesuré avant et juste après chaque épreuve, pendant 1min, par rétro-extrapolation. Les valeurs de VO2 mesurées à la fin des épreuves de 25m, 50m, 75m et 100m permettent de reconstruire la cinétique de VO2 d'une épreuve de 100-m. Les résultats contrastent avec les estimations des cinétiques de VO2 publiées précédemment : VO2 augmente plus vite dans la première moitié de l'épreuve (à 50m, VO2 ≈ 94%VO2max), atteint 100 %VO2max au 75ème mètre de l'épreuve puis chute de 7% sur le dernier 25-m. Une estimation de la contribution relative du métabolisme aérobie montre également des valeurs plus importantes que celles publiées jusqu'à ce jour, du fait de l'atteinte précoce de VO2max en cours d'épreuve
The bioenergetic model proposed by P.E. di PRAMPERO explains performance in most human locomotions (running, cycling, swimming, ...) using indexes of metabolic power and energy cost of locomotion. Nevertheless, for 100-m front crawl events, environmental conditions make the aerobic power measurement difficult. The main purpose of this thesis is therefore to propose a new procedure to estimate aerobic responses during a 100-m front crawl event, performed in competition conditions. Trained swimmers participated to this study. In a 25-m swimming pool, the procedure includes a 100-m front crawl performance in competition conditions, and then, three tests (25-m, 50-m, 75-m) following the pacing strategy of the 100-m event. VO2 is not measured during the tests, but before and just at the end of each test with a breath-by-breath method. Each post-test VO2 (after 25m, 50m, 75m and 100m) allows to reconstruct the VO2 kinetics of the 100-m performance. The results differ from previous studies in that VO2 increases faster in the first half of the race (at 50m, VO2 ± 94%VO2max), reaches VO2max at the 75th meter; then a decrease in VO2 corresponding to 7% of VO2max appears during the last 25m. The estimation of aerobic contribution shows higher values than those previously published, because VO2max is reached very early during the race

A análise das variáveis associadas à fadiga muscular durante protocolos de ciclismo até a exaustão (incremental e carga constante), ou mesmo simulados (contrarrelógio), e suas implicações em parâmetros cinéticos e cinemáticos, têm sido descritas na literatura em modelos experimentais. Alterações encontradas nas articulações do quadril, joelho e tornozelo, associadas a mudanças no direcionamento das forças aplicadas ao pedal (melhora da técnica de pedalada) durante testes de ciclismo incrementais e/ou constantes, parecem estar relacionados a estratégias musculares intrínsecas para manutenção do trabalho e postergar os efeitos da fadiga. Entretanto, evidências suportam que a aplicação de Laserterapia de Baixa Potência (LBP) reduz os efeitos da fadiga muscular sobre o desempenho, principalmente em modalidades esportivas com um grande componente aeróbico, tal como o ciclismo. Entretanto, ainda não está claro na literatura qual a dosagem ideal de LBP a ser utilizada nessas atividades. Portanto, o objetivo deste estudo foi investigar os efeitos de diferentes dosagens de LBP sobre o desempenho em teste de tempo de exaustão em ciclistas. Além disso, foi analisado os efeitos do LBP sobre o conteúdo de frequências dos sinais de EMG e a cinética de VO2 durante os testes de exaustão. Vinte ciclistas competitivos do sexo masculino participaram de um estudo, randomizado, duplocego e placebo-controlado. Os atletas realizaram teste incremental de ciclismo até a exaustão (dia 1) para determinar o consumo máximo de oxigênio (VO2MÁX) e a potência máxima (POMÁX), seguido de outros quatro testes até a exaustão (dias 2 a 5) na POMÁX do teste incremental. Antes de cada teste de exaustão, diferentes dosagens de LBP (3, 6 e 9 J/diodo, ou 135, 270 e 405 J/coxa, respectivamente) ou placebo. Aumento do desempenho nos testes de exaustão foi observado com a LBP-3J (~22 s; p < 0,01), LBP-6J (~13 s; p = 0,03) e LBP- 9J (~13 s; p = 0,02), comparado com o placebo (149 ± 23 s). Embora LBP-6J e LBP-9J não aumentaram a ativação muscular em comparação com o placebo, a LBP-3J, aumentou a ativação das bandas de alta frequência em comparação com o placebo no final do teste de exaustão, em ambos os membros inferiores (p ≤ 0,03). Os resultados na cinética de VO2, resultaram e redução do constante de tempo (Tau) e déficit de O2 com a aplicação de LBP comparado ao placebo (p < 0,05). Não foram encontradas diferenças (p > 0,05) entre as condições experimentais para amplitude de VO2 e tempo de atraso do VO2. Em conclusão, nosso estudo demonstrou que a fototerapia pode ser um agente ergogênico eficaz para aumentar o desempenho de ciclistas (independente da dose utilizada), e isto se deve ao aumento da ativação das bandas de alta frequência (LBP-3J), bem como da redução do Tau e déficit de O2 (LBP-3 6 e 9J), durante testes máximos de ciclismo até a exaustão.
The analysis of muscle fatigue variables during cycling protocols to exhaustion (incremental and constant load) or simulated (time trial), and its implications on kinetic and kinematic parameters, has been described in the literature for experimental models. Changes in hip, knee and ankle joints (such as increased range of motion and reduced ankle contribution to the total joint torque), associated with changes in the direction of the forces applied to the pedal (improved pedaling technique) during cycling tests, seems to be related to strategies for maintaining muscle work in order to postpone fatigue effects. However, evidences supports that application of low-level laser therapy (LLLT) minimizes fatigue effects on muscle performance. However, the ideal LLLT dosage to improve athletes’ performance during sports activities, such as cycling, is still unclear. Therefore, the goal of this study was to investigate the effects of different LLLT dosages on cyclists’ performance during a time-to-exhaustion test. In addition, we looked at the effects of LLLT on the frequency content of the EMG signals and kinetics of VO2 to assess fatigue mechanisms. Twenty male competitive cyclists participated in a crossover, randomized, double-blind and placebo controlled trial. They performed an incremental cycling test to exhaustion (day 1) determine maximal oxygen output (VO2MAX) and maximal power output (POMAX) followed by four time-to-exhaustion tests (days 2 to 5) at their individual POMAX. Before each time to exhaustion test, different LLLT dosages (3, 6 and 9 J/diode; or 135, 270 and 405 J/thigh, respectively) or placebo were applied at the quadriceps muscle bilaterally. Power output and muscle activation from both lower limbs were acquired throughout the tests. Increased performance at the exhaustion tests was observed with the LLLT-3J (~22 s; p < 0.01), LLLT-6J (~13 s; p = 0.03) and LLLT-9J (~13 s; p = 0.02) compared to placebo (149 ± 23 s). Although LLLT-6J and LLLT-9J did not show significant differences in muscle activation compared to placebo, LLLT-3J led to an increased high frequency content compared to placebo in both limbs at the end of the exhaustion test (p ≤ 0.03). The results in kinetics VO2, resulting in reduction of time constant (Tau) and deficit O2 with LLLT applications compared to the placebo condition (p < 0.05). No differences (p > 0.05) were found between the experimental conditions for VO2 amplitude and VO2 delay time. In conclusion, this study has shown that the phototherapy can be an effective ergogenic agent to increase cycling performance (regardless of the dose used), and this is due to increased activation of the high frequency bands (LLLT-3J) as well as the reduction of Tau and deficit of O2 (LLLT-3, 6 and 9J), during maximum cycling exhaustion test.

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Universidade Federal de Sao Carlos
The objective of the present study was to analyse and compare the kinetics of oxygen consumption between groups during running in severe domain. Eighteen healthy and sedentary participants were separated by sex, nine men and women (25,20 ± 2,60 years; 22,10 ± 1,80 years and, 77,30 ± 12,30 kg; 58,60 ± 9,60 kg, respectively). An incremental test was realized at treadmill to determine the associated speed to VO2max (vVO2max) and running to exhaustion (Tlim) at vVO2max to determine the VO2 kinetics, with data expressed by average and standard desviation. The VO2max (3,29 ± 0,62 vs 1,90 ± 0,39 L/min) (p≤0,0001); vVO2max (14 ± 2 vs 10 (3) km.h-1) (p<0,0108); amplitude (3 ± 0,70 vs 1,80 ± 0,40 L/min) (p<0,0003) was significantly increased to men. There was not detected a statistic difference between men and women to the constant time [35,80 (22,30) s vs 36,50 (6,60) s] (p<0,2973); Tlim [271 (118) s vs 261 (73) s] (p<0,6849); Target time to achieve VO2max [142,30 (84,50) s vs 175,80 (24,60) s] (p<0,2973); %Tlim to TAVO2max [43,70 (24,40) vs 72,50 (17,70)] (p<0,1903); time maintained at VO2max (TMVO2max) [145,10 (72,50) s vs 64,20 (65,30) s] (p<0,1359), expressed values by median and interquartil amplitude. We conclude that the VO2 kinetics is similar between young and sedentary men and women, despite the biggest VO2 value demonstrated by men. The prescription value to the aerobic intervalled training do not have make off the proposed by literature for medium and high performance athletes.
O presente estudo teve como objetivo analisar e comparar a cinética de consumo de oxigênio entre gêneros em corrida no domínio severo. Participaram do estudo nove homens e nove mulheres (25,2 ± 2,6 anos; 22,1 ± 1,8 anos e, 77,3 ± 12,3 kg; 58,6 ± 9,6 kg, respectivamente). Foi realizado teste incremental em esteira rolante para determinação da velocidade associada ao VO2max (vVO2max), e corrida até a exaustão (Tlim) na vVO2max para determinar a cinética do VO2. O VO2max (3,29 ± 0,62 vs 1,90 ± 0,39) (p≤0,0001), vVO2max (14,0 ± 2,0 vs 10,0 (3,0) km.h-1) (p<0,0108) e a amplitude (3,0 ± 0,7 vs 1,8 ± 0,4 L/min) (p<0,0003) (M±DP) foram significativamente maiores para os homens. Não foi detectada diferença estatística entre homens e mulheres para a constante tempo (τ) [35,8 (22,3) s vs 36,5 (6,6) s] (p<0,2973), Tlim [271,0 (118,0) vs 261,0 (73,0)] (p<0,6849), tempo para atingir o VO2max (TAVO2max) [142,3 (84,5) s vs 175,8 (24,6) s] (p<0,2973), %Tlim para TAVO2max [43,7 (24,4) vs 72,5 (17,7)] (p<0,1903); tempo mantido no VO2max (TMVO2max) [145,1 (72,5) s vs 64,2 (65,3) s] (p<0,1359), valores expressos pela mediana e amplitude interquartil. Concluímos que a resposta da cinética do VO2 é semelhante entre homens e mulheres jovens sedentários, apesar do maior valor de VO2max apresentado pelos homens. Palavras chave: Cinética VO2; Gênero; Domínio Severo

Les oxydes doubles lamellaires de cobalt et les oxydes de vanadium ont récemment suscité un vifintérêt suite à la découverte de leurs propriétés thermoélectriques prometteuses. Nos efforts visentà synthétiser de nouveaux composés dérivés de ces systèmes en utilisant la synthèse à l'étatsolide, l'échange d'ions et/ou les techniques hydrothermales. Afin de moduler et d'optimiser leurscaractéristiques thermoélectriques, nous avons ajusté la composition des oxydes de cobalt grâce àdes substitutions appropriées. Au sein du dioxyde de vanadium quasi-1D, nous avons considérétrois différentes structures polymorphes : M1, A et B. Nous avons exploré les différents systèmesen construisant l'ensemble des diagrammes de phases. Nous avons également étudié l'effet de lasubstitution du vanadium par le molybdène et le chrome sur la stabilité de ces structurespolymorphes et caractérisé leurs propriétés électroniques en relation avec les mécanismes detransition de phase.

Questa tesi ha studiato l'effetto dell'ipossia nella determinazione della cinetica del consumo di ossigeno polmonare (VO2p) in adulti giovani ed anziani. Il consumo di ossigeno polmonare (VO2p), la frequenza cardiaca (HR), il flusso ematico agli arti inferiori (LBF) e l’ossigenazione muscolare [HHb] sono stati esaminati durante una fase di transizione da un esercizo al cicloergoemtro senza carico, ad uno di moderata intensità ,in normossia e in ipossia. I giovani adulti e anziani hanno mostrato cinetiche del VO2p più lente in ipossia rispetto alla normossia. In condizioni di ipossia, gli adulti anziani hanno mostrato una mancanza di coordinazione tra l’apporto di ossigeno ai muscoli e l’utilizzo dell’ossigeno all'interno del muscolo. Questo è il fattore determinante del rallentamento delle cinetiche del consumo di ossigeno in anziani sottoposti ad uno stimolo ipossico . Contrariamente agli adulti anziani, i giovani adulti hanno mostrato una buona coordinzazione tra l’apporto e l’utilizzo di ossigeno nel muscolo sia in normossia che in ipossia. Così, altri fattori paiono responsabili del rallentamento della cinetica del VO2p osservato nei i giovani adulti in ipossia. Per gli adulti anziani, la risposta vasodilatatrice all'ipossia dipende dalla potenza meccanica. A potenze meccaniche molto basse gli anziani sono stati in grado di controbilanciare, con un aumento del flusso sanguigno, il calo della concentrazione arteriosa di ossigeno (CaO2) indotto dall’ ipossia, impedendo così il rallentamento della cinetica del VO2p. A potenze meccaniche maggiori tuttavia, gli adulti anziani hanno mostrato in ipossia una cinetica lenta del VO2p, una mancanza di coordinazione tra l’apporto di ossigeno ai muscoli e l’utilizzo dell’ossigeno all'interno del muscolo.
This thesis investigated the effect of hypoxia in determining the rate of adjustment in pulmonary O2 uptake (VO2p) for young and older adults. The pulmonary oxygen uptake (VO2p), heart rate (HR), limb blood flow (LBF), and muscle deoxygenation [HHb] were examined during the on-transient of moderate-intensity exercise in normoxia and hypoxia. Young and older adults exhibited slower VO2p kinetics in hypoxia compared to normoxia. Under hypoxic conditions, older adults showed a great mismatch between O2 delivery and O2 utilization within the muscle, this being responsible for the slower VO2p kinetics. On the other hand, young adults did not show significant differences in the matching of O2 delivery and O2 utilization between normoxia and hypoxia. Thus, factors other than the microvascular O2 delivery (i.e central O2 delivery and/or mithocondrial respiration) are responsible for the slower VO2p kinetics observed for young adults under hypoxic conditions. For older adults, the vasodilatory response to hypoxia was found to depend on the work rate. At very low work rate, older adults were able to counterbalance the hypoxia-induced drop in CaO2 with an increased blood flow, thus preventing the slowing of the VO2p kinetics. At higher work rate however, older adults exhibited a slow VO2p kinetics, with a great mismatch between O2 delivery and O2 utilization within the muscle.

The study of the oxygen consumption (VO2) kinetics is focused on the understanding of how human metabolism adjusts during the transition from a condition of resting/movement to another in order to satisfy the new energetic demand. As an integrated index of pulmonary, cardiovascular and muscles capacity VO2 kinetics have gained progressively increasing interests during the XX and the early XXI centuries. Thanks to the development of new technologies as well as an always increasing community of interested scientists in this subject, the knowledge in this field has been expanded considerably. However, some of the topics related to VO2 kinetics remain debated and call for further research. One of these topics is the loss of efficiency of human locomotion that occurs at the higher metabolic intensities, after the transitory period in which a new steady-state in VO2 should be achieved. This phenomenon is typically called VO2 “slow component”, as representative of a further increase in VO2 after the expected steady-state. The importance of the VO2 slow component lies in its link with exercise tolerance and on the understanding of the adaptations of the human body during physical activity. Therefore, researchers have tried to define the physiological underpinning of the slow component and to develop intervention strategies to reduce its amplitude. Nevertheless, a number of physiological uncertainties regarding the mechanistic bases of the slow component exist and require to be clarified. The purpose of this thesis was to deal with this gap and to study the origins of the VO2 slow component, and the loss of efficiency of locomotion that the slow component represents. In chapter one, a brief explanation of the VO2 response during exercise and the current explanatory theories for the VO2 slow component are provided. In chapter two, the experimental aims of the thesis are explained. Then, the results of four different studies are presented in chapters three, four, five, and six. Finally, chapter seven summarizes the main findings of this research work.

Traditionally, exercise intensity is expressed as a percentage of maximal oxygen uptake (VO2max). It is known that as exercise intensity increases in any individual, unique thresholds exist that demarcate boundaries associated with specific physiological and metabolic profiles. The concept of threshold intensities is complex and has generated a large amount of debate within the scientific community. Much of the controversy extends from differences in ideas in determining a specific intensity of exercise below which exercise is sustainable for long durations and above which is unsustainable for prolonged periods. This thesis is organized into five main chapters. The 1st study aimed at clarifying the physiological rational behind the concept of threshold-based exercise intensity. We focused on comparing the most common threshold indexes used to partitions intensity of exercise into ranges (i.e. moderate, heavy, very heavy and severe domains)). Those are: Maximal Lactate Steady State (MLSS), Critical Power (CP), Respiratory Compensation Point (RCP) and the deoxyhemoglobin breakpoint ([HHb]BP). Whether commonalities between these “thresholds” exist, the notion of “critical metabolic rate” is presented as the highest metabolic rate at which exercise is well tolerated for long durations. The 2nd and 3rd studies focused on the determination of alternative methods for exercise intensity threshold identification using novel statistical approaches and/or different measurement techniques. Identification of exercise intensity domains has important implications/applications for research interventions, however the most common indexes of threshold intensity that are nowadays used are often cumbersome, invasive, time consuming and pose a burden to participants and researchers involved. For these reasons, alternative methods that are not only valid but also time effective and non-invasive are very attractive. Finally, in the 4th and the 5th study the body response to exercise above this threshold intensity phenomenon that demarks sustainable versus unsustainable physical activity is investigated. It is nowadays recognised that the exercise intensity at which this progressive loss of metabolic stability become manifest (called “excess VO2” and “VO2 slow component” in the two exercise paradigms respectively) occurs at intensity of exercise above the “critical metabolic rate” (study #1), a landmark that demarcates the lower boundary of the “heavy” intensity domain. Attention is therefore given to the possible role of an intervention affecting this loss of efficiency in the heavy-intensity domain of exercise and therefore affects the genesis of the “excess” VO2 and/or the VO2 slow component. Collectively, the studies contained within this thesis have contributed to better understand the “threshold” phenomenon and the physiological bases behind it. Additionally, new methods of threshold determination have been developed giving practical alternative tests for its determination in different contexts and populations. Finally, this thesis has also provided useful information regarding the body metabolic response in the heavy intensity domain (i.e. above “threshold”) and the role of strength training as a possible determinant in affect such a body response to high intensity training.

The main metabolic pathway involved during an exercise of duration greater than 1 minute is the oxidative metabolism. The functional evaluation of oxidative metabolism is based on the analysis of two main functional indexes: O2max and O2 kinetics. These indexes are determined by a finite ability to deliver oxygen to the working muscles (central factor) and a limited ability of the muscles to extract oxygen (peripheral factor). The relative contribution of central and peripheral factors to the overall limitation of oxidative metabolism, yet remains controversial. Near Infrared Spectroscopy (NIRS) was recently added to the classical methods of muscle oxidative metabolism functional evaluation. NIRS is a non-invasive technology that continuously monitors changes (relative or absolute) in oxygenated and deoxygenated haemoglobin (HHb). NIRS HHb signal directly depends on the ratio between the muscular O2 utilization rate and the capillary O2 delivery in the region explored by the probe, providing a non-invasive estimate of the changes in O2 extraction occurring inside the muscles. The general aim of the thesis is to elucidate the relative contribution of central and peripheral factors in limiting oxidative metabolism by the application of non invasive techniques. We have proposed to modulate oxidative metabolism with different manipulations: 1) High fat diet; 2) Heavy intensity warm up and 3) two kinds of training: Aerobic and Isotonic. In the study #1 we used a high fat diet (HFdiet) to manipulate the peripheral factor in healthy young moderate trained males. Animal and human studies suggest that fat adaptation induces structural and functional muscle adaptations that may benefit oxidative metabolism. We tested the hypothesis that a long term HFdiet enhances oxidative metabolism by augmenting the muscle’s capacity to extract oxygen. 22 young healthy moderately trained males (28±5 yrs, 53±6 ml*Kg-1*min-1) were randomly assigned to: Hdiet (HFD, 55% of calories from fat, 30% carbohydrate and 15% proteins) or control diet (C, 30, 55 and 15%) for 10 days. Before and after the diet the subjects performed an incremental cycling test to exhaustion and 3 step transitions at moderate intensity. Respiratory variables and heart rate (HR) were measured bbb. The maximal and submaximal response to exercise were evaluated ( O2, respiratory exchange ratio, R) and the kinetics of pulmonary O2 were fitted by a double exponential model. HF diet was associated with a shift in substrate selection towards a higher contribution of fat to the production of energy in the moderate intensity domain of exercise (reduced R). Furthermore, HFD increased the speed of adaptation of pulmonary O2 kinetics by the reduction of the time constant of the primary component. Our findings support the hypothesis that, in healthy young males, a 10-day high fat diet may increase the speed of adaptation of oxidative metabolism at the onset of a moderate intensity exercise by increasing the relative contribution of fats oxidation to ATP production. In the study #2 we applied heavy intensity warm-up (HWu) to manipulate O2 delivery in sedentary healthy older adults. HWu increases VO2 kinetics during successive moderate intensity transitions. We tested the hypothesis that such improvement is due to a better matching of O2 delivery to utilization within the working muscles. We tested the hypothesis that HWu improvement is due to a better matching of O2 delivery to utilization within the working muscles, rather than to an increase in O2 bulk delivery. In 21 healthy older adults (65.7 5 yrs) we measured contemporarily and non-invasively indexes of the overall speed of adaptation of the oxidative metabolism ( i.e. pulmonary O2 kinetic), of the bulk O2 delivery (i.e. ) and of the rate of muscle deoxygenation (i.e. HHb) during moderate intensity step transitions, either with (Wu) or without (nWu) prior Hwu. The local matching of O2 delivery to utilization was evaluated by the HHb/ O2 ratio index. The innovative findings of this study are: i) HWu does not modify the speed of adaptation of bulk O2 delivery (i.e. ) and TPR; ii) HWu reduces the “overshoot” of the HHb/ O2 ratio, suggesting a better matching of O2 delivery to O2 utilization. Our data are compatible with the hypothesis that, in older adults, HWu, may beneficially affect oxidative metabolism thanks to acute improvement of the local matching of O2 delivery to O2 utilization. The evidences of Study # 2 motivated us to apply a manipulation that modifies O2 delivery in an adaptive way. Thus in the study #3 we applied aerobic training (AT) to manipulate O2 delivery in sedentary healthy older adults. We tested the hypothesis that older adults may benefit from 12 weeks of AT mainly thanks to an adaptive enhancement of O2 delivery to the working muscles. 14 healthy elderly (66 ± 6 yrs) were tested before and after a 12-week training consisting of an AT or a control (remained sedentary). Subjects performed: the same test protocol described in study # 2. Cardio-respiratory variables were measured bbb and muscle oxygen extraction (HHb) was measured, at the vastus lateralis, by quantitative NIRS. We calculated the time delay and the time constant of both the primary component of the pulmonary O2 and of HHb. The main findings of this study wereAT: i) increased O2max and pulmonary O2 kinetics, preceded (Wu) or not (nWu) by HWu; ii) did not modify the speed of adaptation of muscle oxygen extraction (HHb kinetics); iii) abolished the HWu effect in pulmonary O2 kinetics; iv) attenuated HWu effect in muscle oxygen extraction kinetics; v) abolished the peak of the HHb/ O2 ratio. Our data are compatible with the hypothesis that, in older adults, AT may beneficially affect oxidative metabolism thanks to an adaptive improvement in the matching of O2 delivery to the local O2 utilization. The attenuation yet not an abolishment of the HWu effect in HHb kinetics suggested us an underlying limitation in muscle O2 extraction, unaffected by AT. Isotonic Training is known to increase strength and muscle mass in older adults. We tested the hypothesis that older adults may benefits from 12 weeks of isotonic + aerobic training (IT) thanks to an adaptive enhancement in O2 delivery and O2 utilization. 14 healthy elderly (66 ± 6 yrs) were tested before and after a 12-week training consisting of an isotonic training added to aerobic training (IT) or a control condition (remained sedentary). Subjects performed the test protocol described in study #2 and were measured the variables and analyzed data as described for study # 4 The main finding of this study was that IT produced at the lungs an attenuation of HWu effect (i.e.TD remained shorter). These results suggested that older adults can be beneficially affected by IT, however it is not enough to produce the necessary variations in muscle O2 delivery to completely avoid HWu effect. Furthermore at muscle level the variations IT supressed the HWu effect. Thus in agreement with our hypothesis isotonic training added to aerobic training was enough to eliminate completely the effect of priming exercise. Regarding nWu exercise, the effect of IT was a reduction in the HHb/ O2 ratio peak, suggestive of a better matching in O2 delivery to the O2 utilization following training. Our data are compatible with the hypothesis that in older adults oxidative metabolism may be beneficially affected by IT thanks to an adaptive improvement of the local O2 delivery and a further adaptations in the working muscle to O2 utilization. In summary, eucaloric high fat diet, priming and training (aerobic and isotonic) beneficially affect the speed of adaptation of oxidative matabolism at the onset of an exercise of moderate intensity. The observed benefits are related to a variable combination of adaptations in O2 delivery and utilization that have been non-invasively evaluated in our studies.
The main metabolic pathway involved during an exercise of duration greater than 1 minute is the oxidative metabolism. The functional evaluation of oxidative metabolism is based on the analysis of two main functional indexes: O2max and O2 kinetics. These indexes are determined by a finite ability to deliver oxygen to the working muscles (central factor) and a limited ability of the muscles to extract oxygen (peripheral factor). The relative contribution of central and peripheral factors to the overall limitation of oxidative metabolism, yet remains controversial. Near Infrared Spectroscopy (NIRS) was recently added to the classical methods of muscle oxidative metabolism functional evaluation. NIRS is a non-invasive technology that continuously monitors changes (relative or absolute) in oxygenated and deoxygenated haemoglobin (HHb). NIRS HHb signal directly depends on the ratio between the muscular O2 utilization rate and the capillary O2 delivery in the region explored by the probe, providing a non-invasive estimate of the changes in O2 extraction occurring inside the muscles. The general aim of the thesis is to elucidate the relative contribution of central and peripheral factors in limiting oxidative metabolism by the application of non invasive techniques. We have proposed to modulate oxidative metabolism with different manipulations: 1) High fat diet; 2) Heavy intensity warm up and 3) two kinds of training: Aerobic and Isotonic. In the study #1 we used a high fat diet (HFdiet) to manipulate the peripheral factor in healthy young moderate trained males. Animal and human studies suggest that fat adaptation induces structural and functional muscle adaptations that may benefit oxidative metabolism. We tested the hypothesis that a long term HFdiet enhances oxidative metabolism by augmenting the muscle’s capacity to extract oxygen. 22 young healthy moderately trained males (28±5 yrs, 53±6 ml*Kg-1*min-1) were randomly assigned to: Hdiet (HFD, 55% of calories from fat, 30% carbohydrate and 15% proteins) or control diet (C, 30, 55 and 15%) for 10 days. Before and after the diet the subjects performed an incremental cycling test to exhaustion and 3 step transitions at moderate intensity. Respiratory variables and heart rate (HR) were measured bbb. The maximal and submaximal response to exercise were evaluated ( O2, respiratory exchange ratio, R) and the kinetics of pulmonary O2 were fitted by a double exponential model. HF diet was associated with a shift in substrate selection towards a higher contribution of fat to the production of energy in the moderate intensity domain of exercise (reduced R). Furthermore, HFD increased the speed of adaptation of pulmonary O2 kinetics by the reduction of the time constant of the primary component. Our findings support the hypothesis that, in healthy young males, a 10-day high fat diet may increase the speed of adaptation of oxidative metabolism at the onset of a moderate intensity exercise by increasing the relative contribution of fats oxidation to ATP production. In the study #2 we applied heavy intensity warm-up (HWu) to manipulate O2 delivery in sedentary healthy older adults. HWu increases VO2 kinetics during successive moderate intensity transitions. We tested the hypothesis that such improvement is due to a better matching of O2 delivery to utilization within the working muscles. We tested the hypothesis that HWu improvement is due to a better matching of O2 delivery to utilization within the working muscles, rather than to an increase in O2 bulk delivery. In 21 healthy older adults (65.7 5 yrs) we measured contemporarily and non-invasively indexes of the overall speed of adaptation of the oxidative metabolism ( i.e. pulmonary O2 kinetic), of the bulk O2 delivery (i.e. ) and of the rate of muscle deoxygenation (i.e. HHb) during moderate intensity step transitions, either with (Wu) or without (nWu) prior Hwu. The local matching of O2 delivery to utilization was evaluated by the HHb/ O2 ratio index. The innovative findings of this study are: i) HWu does not modify the speed of adaptation of bulk O2 delivery (i.e. ) and TPR; ii) HWu reduces the “overshoot” of the HHb/ O2 ratio, suggesting a better matching of O2 delivery to O2 utilization. Our data are compatible with the hypothesis that, in older adults, HWu, may beneficially affect oxidative metabolism thanks to acute improvement of the local matching of O2 delivery to O2 utilization. The evidences of Study # 2 motivated us to apply a manipulation that modifies O2 delivery in an adaptive way. Thus in the study #3 we applied aerobic training (AT) to manipulate O2 delivery in sedentary healthy older adults. We tested the hypothesis that older adults may benefit from 12 weeks of AT mainly thanks to an adaptive enhancement of O2 delivery to the working muscles. 14 healthy elderly (66 ± 6 yrs) were tested before and after a 12-week training consisting of an AT or a control (remained sedentary). Subjects performed: the same test protocol described in study # 2. Cardio-respiratory variables were measured bbb and muscle oxygen extraction (HHb) was measured, at the vastus lateralis, by quantitative NIRS. We calculated the time delay and the time constant of both the primary component of the pulmonary O2 and of HHb. The main findings of this study wereAT: i) increased O2max and pulmonary O2 kinetics, preceded (Wu) or not (nWu) by HWu; ii) did not modify the speed of adaptation of muscle oxygen extraction (HHb kinetics); iii) abolished the HWu effect in pulmonary O2 kinetics; iv) attenuated HWu effect in muscle oxygen extraction kinetics; v) abolished the peak of the HHb/ O2 ratio. Our data are compatible with the hypothesis that, in older adults, AT may beneficially affect oxidative metabolism thanks to an adaptive improvement in the matching of O2 delivery to the local O2 utilization. The attenuation yet not an abolishment of the HWu effect in HHb kinetics suggested us an underlying limitation in muscle O2 extraction, unaffected by AT. Isotonic Training is known to increase strength and muscle mass in older adults. We tested the hypothesis that older adults may benefits from 12 weeks of isotonic + aerobic training (IT) thanks to an adaptive enhancement in O2 delivery and O2 utilization. 14 healthy elderly (66 ± 6 yrs) were tested before and after a 12-week training consisting of an isotonic training added to aerobic training (IT) or a control condition (remained sedentary). Subjects performed the test protocol described in study #2 and were measured the variables and analyzed data as described for study # 4 The main finding of this study was that IT produced at the lungs an attenuation of HWu effect (i.e.TD remained shorter). These results suggested that older adults can be beneficially affected by IT, however it is not enough to produce the necessary variations in muscle O2 delivery to completely avoid HWu effect. Furthermore at muscle level the variations IT supressed the HWu effect. Thus in agreement with our hypothesis isotonic training added to aerobic training was enough to eliminate completely the effect of priming exercise. Regarding nWu exercise, the effect of IT was a reduction in the HHb/ O2 ratio peak, suggestive of a better matching in O2 delivery to the O2 utilization following training. Our data are compatible with the hypothesis that in older adults oxidative metabolism may be beneficially affected by IT thanks to an adaptive improvement of the local O2 delivery and a further adaptations in the working muscle to O2 utilization. In summary, eucaloric high fat diet, priming and training (aerobic and isotonic) beneficially affect the speed of adaptation of oxidative matabolism at the onset of an exercise of moderate intensity. The observed benefits are related to a variable combination of adaptations in O2 delivery and utilization that have been non-invasively evaluated in our studies.