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.

Background: Performing aerobic exercise and maintaining high levels of aerobic fitness may have positive effects on both brain structure and function in older adults. Despite decades of research however, there is still a rather poor understanding of the neurocognitive mechanisms explaining the positive effects of aerobic exercise on cognition. Changes in prefrontal gray matter as well as dopaminergic neurotransmission in striatum are both candidate neurocognitive mechanisms. The main aims of this thesis are: 1. To investigate the effects of aerobic exercise and fitness on cognition and magnetic resonance imaging (MRI) derived gray matter volumes using data from a 6 month physical exercise intervention in older adults (Study I). 2. To simulate the effect of atrophy in longitudinal positron emission tomography (PET) which could pose a challenge to interpreting changes in longitudinal PET imaging (Study II). 3. To study the influence of aerobic exercise and fitness on the dopamine D2-receptor (D2R) system in striatum using [11C]raclopride PET as a potential mechanism for improved cognition (Study III). Results: In Study I, aerobic exercise was found to improve cognitive performance in a broad, rather than domain-specific sense. Moreover, aerobic fitness was related to prefrontal cortical thickness, and improved aerobic fitness over 6 months was related to increased hippocampal volume. In Study II, we identified areas in the striatum vulnerable to the effect of shrinkage, which should be considered in longitudinal PET imaging. Finally, in Study III, the effect of being aerobically fit, and improving fitness levels was found to impact dopaminergic neurotransmission in the striatum, which in turn mediated fitness-induced improvements in working memory updating performance. Conclusion: The findings in this thesis provide novel evidence regarding the neurocognitive mechanisms of aerobic exercise-induced improvements in cognition, and impacts the interpretation of longitudinal PET imaging. Performing aerobic exercise and staying aerobically fit at an older age have positive effects on cognition and brain systems important for memory and cognition. Specifically, fitness-induced changes to the dopaminergic system stands out as one novel neurocognitive mechanism explaining the positive effects of aerobic fitness on working-memory performance in healthy older adults.

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The purpose of this study was to evaluate the use of nonexercise (N-EX) data, specifically, the Perceived Functional Ability (PFA) and Physical Activity Rating (PA-R) questionnaires, with the treadmill walk-jog-run protocol to estimate VO2max in 12 to 17 year old boys and girls. Ninety-one participants (49 males and 42 females) took part in this study. Data were collected via PFA and PA-R questionnaires, a walk-jog-run submaximal treadmill test, and a maximal graded exercise test (GXT). Data collected included gender, age, height, weight, PFA and PA-R scores, heart rate (HR), treadmill speed, maximal treadmill grade, respiratory exchange ratio (RER), rating of perceived exertion (RPE), and VO2max. Regression analysis resulted in the development of two valid and reliable models to predict VO2max. Nonexercise and submaximal exercise test data were used to build the following model: VO2max (mL∙kg-¹∙min-¹) = 11.201 + (6.877 x Gender; 0 = female; 1 = male) + (3.573 x treadmill speed; mph) – (0.174 x kg) + (0.405 x PFA score) + (0.653 x PA-R score) + (1.019 x age). The model resulted in an R2 = 0.69 and a SEE = 5.16 mL∙kg-¹∙min-¹. Maximal exercise test data were used to build the following model: VO2max (mL∙kg-¹∙min-¹) = -3.264 + (3.359 x Gender; 0 = female; 1 = male) – (0.082 x kg) + (7.351 x treadmill speed; mph) + (1.750 x maximal treadmill grade). The model resulted in an R2 = 0.88 and a SEE = 3.16 mL∙ kg-¹∙min-¹. The cross-validation PRESS statistics for both models demonstrated minimal shrinkage in the accuracy of the regression model. The results of this study demonstrate, for the first time, that N-EX data can be used to accurately predict VO2max in youth. The submaximal and maximal exercise tests validated in this study can be used to assess cardiorespiratory fitness of youth having a wide range on interests and fitness levels. In addition, the use of PFA and PA-R questionnaires enforces initiatives to increase physical activity among youth. Both exercise tests use a self-selected treadmill speed that elicits a steady-state HR of 70% of the participants age-predicted maximal HR. The use of a self-selected walking, jogging, or running speed accommodates youth with different levels of physical fitness, motivation, and interests. The exercise test protocol presented in this study is practical for use in schools, athletic facilities, and community fitness centers. The equipment required to administer the exercise test presented in this study is limited to a treadmill and a HR monitor. Together with the use of PFA and PA-R questionnaires, the submaximal and maximal exercise tests are efficacious to coaches, fitness professionals, and physical educators in a variety of settings.

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In order to address the long-term complications that arise from poor venous return, a hallmark of the Fontan physiology, we assessed the feasibility of a non-invasive, home therapy that will improve the health of the patient during the heart transplant waiting period and ameliorate the quality of life. In order to achieve this goal we tested a device that applies pressure to the lower extremities of the body (legs and abdomen) in a pulsating fashion with the goal of augmenting systemic blood flow to the pulmonary arteries. This treatment will enhance flow from the great veins and through the lungs and serve as adjunctive clinical treatment of single ventricle physiology. The specific aim of this study was to show improvements in cardiorespiratory measurements after applying external pressure as a proxy for improved health in the Fontan patient. Various studies have shown the impaired exercise capacity of post-operative Fontan patients, but very little data exists focusing on a period much later after the surgery. Our results among the two subjects completed so far have shown a moderately beneficial improvement in exercise capacity after the compression therapy. Subjects performed a treadmill exercise stress test at VCU that was followed by six days of applied external pressure treatment and finished with a final post-treatment stress test. Cardiorespiratory data was collected and analyzed for improvements from base level. Overall an improvement in exercise duration time, VO2 peak, ventilatory threshold, and OUES was observed, with only VE / VCO2 slope having mixed results. Both subjects seem to be relatively healthy Fontan patients, as indicated by their VO2 peak, VE/VCO2 slope and OUES. As a result, benefits of treatment may vary among a cohort of Fontan patients with poor health condition; a failing Fontan physiology for instance. The improvement in exercise capacity suggests that this therapy could be very beneficial to Fontan patients. These results warrants follow up studies to explore the extent of the clinical benefits of compression treatment among the Fontan population.

Thin films and coatings of oxides are used in various fields of science and technology, such as semiconductor and optoelectronic devices, gas sensors, protective and wear resistant coatings etc. Of late, there has been a tremendous interest in pure and doped vanadium dioxide as thermoelectric switch material. VO2 has been doped with hetero-atoms such as W, Mo, Nb, Ti etc. and effects of doping have been correlated with feasibility of being used as a smart window material. The oxide Al2O3 has been studied as an alternative gate dielectric. Ga2O3 is also a contender for replacing SiO2 as a dielectric material. Atomic layer deposition (ALD) is a technique for the deposition of thin films of various materials and is found to be of considerable scientific and technological importance. In particular, using β-diketonate complexes as precursors is very useful in preparing thin films of oxides, as these precursors already contain a metal-oxygen bond. In this thesis, β-diketonate complexes have been used as precursors for deposition of thin films. The thesis has been divided into two parts: First part deals with deposition and characterization of thin films of VO2 on glass and fused quartz. The second part deals with synthesis and chemical and thermal characterization of bimetallic Al-Ga acetylacetonates along with thin film deposition using the same. Chapter 1 presents a brief introduction to application of thin films of oxides in various fields of science and technology. A brief introduction to the ALD reactor used for the current work is also presented. The importance of thermal analysis of precursors for CVD is briefly reviewed. Chapter 2 deals with the instruments and methods used for the work done for this thesis. In Chapters 3 and 4 of the thesis, a detailed study of deposition of VO2 films on glass and fused quartz has been presented. The films deposited have been analyzed using a host of techniques, for their texture, microstructure and electrical properties. In spite of chemical similarities, considerable differences in structure and properties have been observed between the films deposited on the two substrates. These differences have been explained on the basis of the small chemical differences between the two substrates. Chapters 5, 6 and 7 deal with synthesis, thermal characterization and use of bimetallic Al-Ga precursors, respectively. The bimetallic acetylacetonates have been synthesized using ‘homogenization in solution’ approach. Chemical characterization of the precursors revealed that nominal percentages of Al and Ga are retained in the solid precursors. Single crystal structure confirmed the observation. Thermal analysis of the precursors showed that the precursors, which are solid solutions of Al and Ga acetylacetonates, show negative deviation from the Raoult’s Law. Films were deposited using these precursors and were found to near completely retain the composition of the precursors. Chapter 8 of the thesis presents the conclusions of the current work and proposes future directions.

Implication de l'oxygénation cérébrale dans les limitations à l'exercice musculaire des personnes non-entraînées et sportifs d'endurance. L'objectif général de ce travail était de déterminer si l'oxygénation cérébrale était un facteur de la limitation à l'exercice de type aérobie. Dans un premier temps, nous nous sommes attachés à étudier le rôle de l'oxygénation cérébrale mesurée par la Spectroscopie dans le proche Infra-Rouge (NIRS) dans la limitation de l'exercice progressif maximal en rampe. Nous avons montré l'existence d'un seuil de déclin de l'oxygénation cérébrale associé au point de compensation respiratoire (RCP). L'amélioration de la performance avec une supplémentation d'O2 était liée au décalage de ce seuil à de plus hautes intensités d'exercice chez des sujets actifs (étude 1). Dans un second temps, nous avons montré que ce seuil de déclin de l'oxygénation, retrouvé aussi chez des sportifs entraînés en endurance apparaîssait à de plus hautes intensités d'exercice que chez des sujets non-entraînés (étude 2). Enfin, nous avons déterminé l'impact de l'hypoxémie artérielle induite par l'exercice (HIE) des sportifs d'endurance sur l'oxygénation cérébrale au cours d'un exercice maximal en rampe et d'un exercice de temps limite à charge constante. Nous avons ainsi montré que l'oxygénation cérébrale était augmentée avec la HIE suggérant un effet compensatoire à l'hypoxémie artérielle au cours de l'exercice progressif maximal en rampe. Ceci, n'existait pas au cours de l'exercice de temps limite ne supportant pas l'implication de l'oxygénation cérébrale dans ce type d'exercice (étude 3). Ces travaux ont donc mis en évidence l'implication de l'oxygénation cérébrale dans la limitation de l'exercice maximal en rampe chez des sujets actifs et des sportifs entraînés en endurance présentant ou pas une HIE. Toutefois, elle ne semble pas être un facteur majeur de limitation de l'exercice de temps limite.

Abstract Aim: The purpose of the study is to show the influence of Proton Pump Inhibitors (PPI in form of esomeprazole) on the bioactivation of dietary nitrate (sodium-nitrate solution) in submaximal exercise, through affecting the gastric pH. Method: Randomized, doubled-blinded, placebo-controlled and crossover study with six subjects (mean ± SD, age 29 ± 5years, height 170 ± 5 centimeters, weight 70 ± 5 Kg, BMI 24,36 ± 1,75 Kg/m2 blood pressure 119/ 77 ± 6 mmHg, 3 male and 3 female). They were tested in two different trials. Every trial consisted of two parts. One part was cycling on 4 different submaximal stages (80W/60RPM, 80W/90RPM, 120W/60RPM, 120W/90RPM) for 5 minutes each, with 90 minutes rest in between. The same protocol was repeated. In the beginning of the resting time a sodium nitrate solution (NaNO3-, 10mg/kg body weight) was ingested. VO2, VCO2, RER, VE, Lactate, Glucose, heart rate and blood pressure were recorded. Venous blood samples were taken. Whether esomeprazole (10mg) or a placebo were taken 24h, 12h and directly before being tested in both trials. Subjects were pleased to have a nitrate poor diet starting when taking the pills. An information sheet was provided. Results: No significant differences were found between the post values and the treatment. Tendencies of a higher oxygen consumption when taking esomeprazole (2,62%) in comparison to placebo (0,11%) were observed. Systolic BP decreased by 3,91% with the placebo while it decreased just 2,04% with esomeprazole after intake. Sex-specific differences occurred in the metabolism of esomeprazole and dietary nitrate. RER showed a significant post nitrate difference between the female and male participants with t=.006 and a significance in predietary nitrate intake. VE in female (40,79 ± 7,20 L/min) and (50,03 ± 10,09 L/min) in male were as well significant (t=.017). Conclusion: Tendencies of effects of PPI are seen in the post-values of VO2 and BP after intake of dietary nitrate. Gender-differences are shown in RER and VE. More research is needed to see the impact of dietary nitrate on the human body under submaximal load.