Children and adolescents are thought to use oxidative metabolism to a greater extent than adults during high intensity exercise. The studies reported in this thesis examine the nature and implications of age-related differences in muscle metabolism during high intensity exercise and recovery. Chapter 4 concluded that during heavy intensity exercise, phosphocreatine (PCr) kinetics did not differ with age or sex, while Chapter 5 revealed that during very heavy intensity exercise, the fundamental τ was slower and slow component amplitude greater in men compared with adolescent boys, indicating that exercise intensity might play a role in determining age-related differences in muscle metabolism. In Chapter 6, two bouts of very heavy intensity exercise were completed, and prior exercise reduced the PCr slow component amplitude in men but not boys. Deoxyhaemoglobin (HHb) kinetics was faster in adolescents compared with adults during both heavy and very heavy intensity exercise, indicating that matching of oxygen delivery to oxygen utilisation is less precise at the onset of exercise in adolescents compared with adults. PCr recovery from high intensity exercise was faster in boys than men, but not different in girls and women, as described in Chapter 7. The speed of PCr recovery was correlated with maturity in adolescents, but was not correlated with end-exercise [PCr] or pH. Two different tests to measure mitochondrial capacity in adolescents were evaluated in Chapter 8, and a fitted curve and gated test were both used to determine PCr recovery kinetics. Finally, in Chapter 9, age-related differences in muscle metabolism and oxygenation during fatiguing exercise were examined; a strong trend for greater fatigue in adults compared with adolescents was accompanied by greater metabolic perturbation in adults. Overall, these data show that muscle metabolism and oxygenation differs between adolescents and adults during and following very high intensity exercise.

A infusão aguda de insulina promove aumento da atividade nervosa simpática e do fluxo sangüíneo muscular, sendo esses efeitos influenciados pela sensibilidade do organismo à ação da insulina no metabolismo de carboidratos. Por outro lado, a execução de uma única sessão de exercício aeróbio diminui a atividade nervosa simpática, aumenta o fluxo sanguíneo muscular e pode modificar a sensibilidade à insulina pós-exercício. Dessa forma, a execução prévia de uma única sessão de exercício físico pode modificar as respostas fisiológicas à infusão aguda de insulina, essa influência pode ser diferente em indivíduos sensíveis e resistentes à ação desse hormônio. Para investigar essa problemática, 18 homens saudáveis foram submetidos a dois clampeamentos euglicêmicos/hiperinsulinêmicos realizados, em ordem aleatória, 90 minutos após 45 minutos de: a) exercício no cicloergômetro em 50% do VO2pico (Exercício) ou b) repouso sentado (Controle). Posteriormente, os indivíduos foram divididos em dois grupos: sensíveis (n=8) e resistentes (n=10) à insulina, com base no índice de sensibilidade à insulina da amostra total. Antes e durante os clampeamentos, a glicemia, a insulina plasmática, a pressão arterial (oscilométrico), a freqüência cardíaca (EGC), a atividade nervosa simpática muscular (microneurografia) e o fluxo sanguíneo do antebraço (pletismografia) foram medidos. O exercício físico: a) reduziu a glicemia nos dois grupos, b) diminuiu a insulina plasmática durante os clampeamentos nos indivíduos resistentes e a aumentou nos sensíveis, c) não modificou a sensibilidade à insulina nos resistentes e a reduziu nos sensíveis, d) não modificou o aumento da pressão arterial sistólica promovido pela infusão de insulina, que era maior nos sensíveis, e) aumentou a elevação pressão arterial média em resposta à infusão de insulina nos indivíduos sensíveis, f) no grupo sensível, diminuiu a pressão arterial diastólica basal e aumentou essa pressão durante a infusão de insulina, g) aumentou a freqüência cardíaca, sem modificar sua resposta à infusão de insulina, h) reduziu a atividade nervosa simpática basal, sem modificar a resposta de aumento dessa atividade durante a hiperinsulinemia, I) aumentou o fluxo sanguíneo muscular basal, sem modificar a resposta desse fluxo à infusão de insulina, que aumentava apenas nos indivíduos sensíveis, j) reduziu a resistência vascular do antebraço basal, impedindo a diminuição dessa resistência com a infusão de insulina. Em conclusão: a execução prévia de uma sessão de exercício aeróbio modifica a resposta à hiperinsulinemia aguda de forma diferente em indivíduos sensíveis e resistentes à ação desse hormônio / Acute insulin infusion increases sympathetic nervous activity, and muscle blood flow. Moreover, these effects are influenced by insulin sensitivity on carbohidrate metabolism. On the other hand, a single bout of aerobic exercise decreases sympathetic activity, increases muscle blood flow, and can increase insulin sensitivity during the post-exercise period. Thus, it is possible that previous exercise can change physiological responses to acute hyperinsulinemia, and this influence might be different in insulin-resistant and sensible subjects. To test this hypotesis, eighteen healthy males underwent two euglycemic/hyperinsulinemic clamps performed, in a random order, 90 minutes after 45 minutes of: a) cycle ergometer exercise at 50% of VO2peak (Exercise), or b) sitting rest (Control). After the experiments, subjects were divided in two groups: sensibles (n=8), and resistants (n=10) to insulin action, based on insulin sensitivity index of the total sample. Before and during the clamps, glycemia, plasma insulin, blood pressure (oscilometric), heart rate (EGC), sympathetic nervous activity (microneurography), and blood flow (plethismography) were measured. Aerobic exercise: a) reduced glycemia in both groups, b) decreased plasma insulin during the clamps in the resistant group, and increased it in the sensible one, c) did not change insulin sensitivity in the resistant subjects, but decreased it in the sensible ones, d) did not change systolic blood pressure increase promoted by insulin infusion, which was greater in the sensible group, e) enhanced mean blood pressure increase to insulin infusion in sensible subjects, f) in the sensible group, reduced baseline diastolic blood pressure, and increased it during hyperinsulinemia, g) increased heart rate, without changing its increase during insulin infusion, h) decreased baseline sympathetic nervous activity, and did not change its increase during hyperinsulinemia, i) increased baseline forearm blood flow, without changing blood flow response to insulin infusion, which was characterized by an increase only in the sensible subjects, j) reduced baseline forearm vascular resistance, abolishing the reduction observed during insulin infusion. In conclusion: previous aerobic exercise modifies physiological responses to acute hyperinsulinemia in different ways in insulin-sensible and resistant subjects

Diversos aspectos metabólicos e comportamentais possuem uma estreita relação com as condições do ambiente, havendo um compromisso entre as condições naturais e a dinâmica de modificações sobre os organismos. Devido ao grande índice de degradação ambiental proveniente da atividade humana nos últimos tempos, populações de anfíbios têm sido particularmente mais afetadas devido a sua alta sensibilidade a alterações ambientais. Em uma paisagem fragmentada, a manutenção de metapopulações viáveis é um importante fator a persistência das populações. Dentro deste contexto, este estudo propõe investigar as relações entre a fragmentação florestal e habilidade das algumas espécies de anuros para se deslocar entre os fragmentos, ou entre estes e corpos d\'água. Assim, realizamos comparações, fisiológicas e comportamentais intra e interespecífica de espécies de anuros residentes em paisagens contínuas e fragmentadas em duas localidades da Floresta Atlântica, com base em suas características morfológicas. De acordo com nossos resultados, as diferenças ambientais entre as paisagens estão relacionadas com as diferenças morfofisiológicas entre as espécies. / In the last few decades, human activity has changed environmental condition, resulting in amphibian populations decline all around the world. In this study we analyze the relationships between forest fragmentation and the ability of some frog species to move between forest fragments or between fragments and breeding sites. Our study focus relies on anuran locomotor performance and supporting physiology, and the relationship between these traits and resistance to forest fragmentation. We compare morphological, physiological and behavioral traits between populations of anurans species living in different landscapes (continuous or fragmented) of two sites in the Atlantic Forest. According to our data, differences in environmental conditions of landscape are related to morpho-physiological traits. This relationship, however, depends on the site of the Atlantic Forest and also varies between species.

The purpose of this dissertation was to examine the existence of force production and strength symmetry while concentrating on its role with performance. Specifically, in this dissertation I sought to determine if differences in symmetry exist between male and female athletes as well as between athletes of different strength levels. Various symmetry assessments were used and the amount of carryover between tests was also evaluated. Furthermore, the relationship between asymmetry magnitude and various aspects of jump performance was also assessed. The results showed that female athletes were more asymmetrical than their male counterparts for most assessments. Interestingly, weaker athletes regardless of gender were more asymmetrical than stronger athletes for all assessments. Symmetry characteristics appeared to carryover between all tests and conditions with the exception of the bilateral strength assessment. When separated by strength level, good carryover of explosive strength symmetry characteristics was noted. A trend of negative relationships was noted between jump performance and kinetic asymmetry, measured during jumps and weight distribution. Isometric mid-thigh pull force production asymmetry did not relate to jump performance as it had previously. Kinetic asymmetry was shown to influence the direction of center of mass displacement (COMd). Specifically, asymmetrical rate of force development showed the most ability to differentiate between values of COMd in the mediolateral direction. The finding that female athletes are more likely to produce force asymmetrically may indicate that they are more susceptible to the performance detriments that accompany force production asymmetry. This may also indicate that female athletes are more susceptible to injury if force asymmetry is an injury predictor. However, differences in asymmetry magnitude between the sexes may be due to differences in strength level between the sexes in the current study, as weaker athletes were shown to be more asymmetrical than their stronger counterparts. Thus, it may be inadequate strength level that is a risk factor to performance detriments and possible injury. It also appears that force production asymmetry can both alter and hinder optimal jump performance. In order to optimize performance and possibly reduce injury risk, it is recommended that weaker athletes focus on bilateral strengthening exercises.

The purpose of this study was to determine the acute effects of stretching and local vibration on flexibility and explosive strength in competitive female gymnasts. Flexibility was measured in the forward-split position and jump characteristics were recorded using a force plate. Analysis included flight time (FT), jump height (JH), peak force (PF), instantaneous forces, and rates of force development (RFDs). Randomly assigned and counterbalanced groups were: simultaneous vibration-stretching (VS) (n=22), stretching-only (n=7), and vibration-only (n=8). VS showed statistically greater measures of flexibility in both the right and left leg, favored and non-favored legs pre- versus post-treatment. Vibration-only group resulted in statistically greater right forward-split flexibility and non-favored leg flexibility. There were no statistical differences in JH, FT, PF, instantaneous forces, or RFDs in the VS, stretching-only, and vibration-only groups' pre- versus post-treatment tests. The conclusion was simultaneous vibration-stretching greatly increased flexibility while not altering explosive strength.

The purposes of this dissertation were three-fold. The first was to identify the approximate distances characterizing early-, mid-, and late-acceleration in a population of Division I men’s collegiate soccer players. The secondary purpose was to investigate the relationships between various strength-power variables and key sprint characteristics during early-, mid-, and late-acceleration in a population of Division I men’s soccer players. The final purpose of this dissertation was to compare the spatiotemporal characteristics of “strong” versus “weak” and “more powerful” versus “less powerful” Division I men’s soccer players during early-, mid-, and late- acceleration. The following are the major findings of this dissertation. The early-, mid-, and late-acceleration zones within this sport population coincide with distances of approximately 0-2.5, 2.5-6, and 6-12m, respectively. Peak power (PP) and rate of force development (RFD) at 90ms appear to be strongly related to shorter ground contact times in each of these zones, while PP and RFD at 200 and 250ms showed strong relationships with step frequency during mid-acceleration. Not surprisingly, athletes who were characterized as “strong” or demonstrated “higher power outputs” appeared to achieve greater sprint velocity by expressing higher step frequency, particularly during mid-acceleration, as well as abbreviated ground contact times across each sub-section of acceleration. These results support the importance of developing high levels of maximal strength, PP, and RFD to enhance sprint acceleration. Additionally, these findings may also be used to strategically integrate speed development and resistance training practices into the annual training plan. The amalgamation of these training variables may allow practitioners to better manage fatigue and elicit desired performance adaptations at the appropriate times of the training year.

The purpose of this dissertation was to determine if a there was a dose-response relationship across an NCAA Division I men’s soccer season. Specifically, this dissertation serves to: 1.) assess the validity of duration measurements that have previously been used to calculate session RPE during competitive matches, 2.) determine the degree and magnitude of change in intermittent endurance performance across a season and to observe how change in endurance relates with training load, 3.) determine the degree and magnitude of change in strength and explosiveness across a season, and to see how these strength changes relate to training load. 1.) Minutes played were found to be the most accurate duration for calculating session RPE during men’s NCAA Division I soccer matches. 2.) Endurance performance, measured using the Yo-Yo IR1, increased by an average of 14 percent from pre to post season. Furthermore, a large, negative relationship was observed between training load and change endurance performance. These relationships suggest that excessive accumulation of training load can impair endurance performance. The congested NCAA DI match schedule may make it difficult to prevent excessive training loads. 3.) When players were grouped by amount of college soccer experience (upper and underclassmen), upperclassmen jumped significantly higher than underclassmen during the preseason. Moreover, the upperclassmen maintained or increased jump height from pre to post season, while underclassmen experienced a general decrease in jump height from pre to post season. Moderate relationships indicate a positive relationship between training load from resistance training and changes in strength. Likewise, these same relationships strengthened in the players who received more playing time during matches. Taken together, the high numbers of moderate relationships indicate a high level of individual variability. Dose-response relationships with strength variables were not sufficiently established. The overall findings of this dissertation provide evidence that subjectively and objectively monitoring training load and soccer-related performance variables can assist coaches in making decisions that will promote the welfare of their team.

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