O processo de instalação da fadiga implica na mudança do padrão coordenativo durante a pedalada. Desta forma a análise da contribuição de cada articulação do membro inferior para o somatório absoluto dos momentos articulares se faz necessária para o melhor entendimento dos mecanismos relacionados aos efeitos do processo de instalação da fadiga sobre o padrão coordenativo no ciclismo. O objetivo deste estudo foi comparar a contribuição das articulações do quadril, joelho e tornozelo para o somatório absoluto dos momentos articulares resultantes, assim como a força resultante e a cinemática destas articulações, ao longo do tempo, nos modelos experimentais de carga constante e de carga incremental até a exaustão. Foram avaliados onze ciclistas de estrada da categoria elite, que participam de competições regionais (Texas) e nacionais (Estados Unidos) do sexo masculino (idade 31 ± 7 anos; consumo máximo de oxigênio 62,84 ± 4,86 ml.kg-1.min-1; potência máxima 407 ± 37 W). Onze ciclistas foram avaliados no primeiro dia de avaliação, este constituindo um teste de ciclismo máximo com incrementos de carga a cada dois minutos (75, 90 e 100% da PO máxima estimada, respectivamente). No segundo dia de avaliação, dez ciclistas foram avaliados em um protocolo de ciclismo com carga entre 90 e 100% da PO máxima, definida no primeiro dia. Em ambos os testes foram mensurados o consumo de oxigênio (VO2), a força aplicada no pedal direito e a cinemática do membro inferior direito dos ciclistas. Se utilizou um modelo bidimensional dos segmentos da coxa, perna e pé, a fim de calcular as forças e momentos resultantes nas articulações do quadril, joelho e tornozelo, por meio da técnica da dinâmica inversa. Foram analisados o somatório absoluto dos momentos articulares resultantes (SMA), o percentual de contribuição de cada articulação para o SMA, a força resultante e a cinemática das articulações do quadril, joelho e tornozelo nos três estágios do teste incremental (75, 90 e 100% da PO máxima) e em quatro instantes do teste de carga constante (10, 40, 70 e 90% do tempo total do teste). No primeiro dia de avaliação (estudo 1) foi observada redução significativa da cadência de pedalada no estágio com carga a 100% da POMáx, comparado aos estágios 75% e 90% da POMáx. Observou-se ainda aumento significativo da contribuição do joelho para o SMA, no estágio a 100% da POMáx, comparado aos estágios 75% e 90% da POMáx, devido ao aumento significativo do momento resultante na articulação do joelho, no estágio a 100% da POMáx, em relação aos estágios com carga a 75 e 90% da POMáx. A força resultante nas três articulações analisadas apresentou aumento significativo ao longo do teste de carga incremental. Para as variáveis cinemáticas, foi observada redução significativa no valor médio do ângulo do tornozelo, assim como aumento significativo na sua amplitude de movimento no estágio 100% da POMáx. Para a articulação do quadril, foi observado aumento no valor médio do ângulo articular, assim como redução na sua amplitude de movimento no estágio com carga a 100% da POMáx. No segundo dia de avaliação (estudo 2) foi observada redução significativa da cadência de pedalada nos instantes 70 e 90% do tempo total de teste, comparados aos instantes 10 e 40% do tempo total. Esta foi acompanhada por redução da contribuição da articulação do tornozelo para o SMA, no instante 90% do tempo total comparado aos instantes 40 e 70% do tempo total do teste, devido ao aumento significativo do momento resultante na articulação do joelho no instante 90% comparado aos instantes 40 e 70% do tempo total e do quadril no instante 90% comparado aos instantes 10, 40 e 70% do tempo total. Se observou aumento na força resultante nas três articulações analisadas, assim como alterações na cinemática das mesmas ao longo do teste (redução do ângulo médio da articulação do tornozelo, com aumento da amplitude de movimento, aumento significativo do ângulo médio das articulações do joelho e do quadril). Os resultados observados indicaram alterações no padrão coordenativo dos ciclistas devido ao processo de instalação da fadiga, estes ocorrendo de forma distinta nos dois protocolos avaliados. As estratégias de controle das articulações durante a pedalada, parecem não ser características inerentes do gesto motor, sendo estas adaptáveis às demandas aumentadas nas articulações devido às alterações na cadência de pedalada e no processo de instalação da fadiga. / Fatigue process has been proposed to change the coordinative pattern; therefore, the analysis of the contribution of each joint to the average absolute joint moment should improve the understanding of the fatigue effects on the coordinative pattern during cycling. The aim of the present study was to compare the contribution of each joint to the average absolute joint moment, as the resultant force and kinematics of the hip, knee, and ankle joints, in an incremental and in a constant workload cycling test to exhaustion. Eleven male road cyclists competing at regional (Texas) and national (United States) levels (age: 31 ± 7 years; maximal oxygen uptake 62.84 ± 4.86 ml.kg-1.min-1; maximal power output 407 ± 37 W) volunteered to participate in the study. Eleven cyclists were submitted to an incremental maximal cycling test with two minutos of workload increment (75, 90 e 100% of POMax, respectively). On the second day, ten cyclists were evaluated in a constant cycling test, in which the workload was set between 90 and 100% of POMax, as defined on the first evaluation day. During both days the oxygen uptake (VO2), right pedal forces and lower limb kinematics were acquired. A bidimensional model of the thigh, leg and foot segments allowed to calculate the resultant forces and moments at the hip, knee and ankle joints by means of inverse dynamics. The average absolute joint moment (SMA), the contribution of each joint to the SMA, the resultant force and kinematics of the hip, knee and ankle joints were analyzed on three stages of incremental cycling test (75, 90 e 100% of POMax), and on four instants of constant workload cycling test (10, 40, 70 and 90% of total time). On the first evaluation day (study 1), a significant decrease of pedaling cadence was observed at the 100% of POMax stage, compared with 75% and 90% of POMax stages. There was also a significant increase of knee joint contribution to the SMA at 100% of POMax stage, compared with 75% and 90% of POMax stages, due to a significant increase of knee joint absolute moment at 100% of POMax stage, compared with 75% and 90% of POMax stages. The resultant joint force on the three joints have significantly increased, while joint kinematics has changed with the increase of workload (reduced mean ankle angle, with increased ankle range of motion) For hip joint, there was a significant increase of mean angle, with reduced range of motion at 100% of POMax. On the second evaluation day (study 2) a significant reduction of pedaling cadence was observed at the 70% and 90% of total time, compared with 10% and 40% of total time. This result was followed by a significant reduction of the ankle joint contribution to the SMA at the 90% of total time, compared with 40% and 70% of total time, due to a significant increase of knee resultant joint moment on the 90% of total time, compared with 40% and 70% of total time, and for the hip resultant joint moment at the 90% of total time, compared with 10, 40, and 70% of total time. There was also a significant increase of the resultant joint force and a change on kinematics of the three joints throught the test (reduced mean ankle angle, with increased range of motion, and a significant increase of the mean value of knee and hip angles). The results indicated that the coordinative pattern changed with fatigue, with discrete effects in each cycling test. The strategies of joint control during cycling should not be an innate robust motor behavior, but these strategies should be adaptable to higher demands on the joints, as significant changes on pedaling cadence and fatigue.

abstract: Cardiovascular disease and diabetes are major health burdens. Diabetes is a primary risk factor of cardiovascular disease, and there is a strong link between obesity and risk of developing diabetes. With the prevalence of prediabetes highest among overweight/obese individuals, investigation into preventative strategies are needed. Aerobic exercise is a potent stimulus for both insulin and non-insulin dependent glucose uptake into the skeletal muscle. A single exercise session can improve insulin sensitivity within hours after exercise. The effects of intensity, type, and volume of exercise on glucose homeostasis have been studied extensively; however, controlling for muscle contraction frequency with a constant exercise intensity and workload has not been examined. The purpose of this study was to compare muscle contraction frequency during aerobic exercise by altering cycling cadence on insulin sensitivity and vascular health. Eleven obese males (age=28yr, BMI=35kg/m2) completed three conditions in random order: 1) control-no exercise; 2) 45-min cycling at 45 revolutions per minute (45RPM) at 65-75%VO2max; 3) 45-min cycling at 90RPM at 65-75%VO2max. Glucose control and insulin sensitivity were assessed with oral glucose tolerance tests (OGTT) 4 hours post-exercise. Vascular health was assessed via flow-mediated dilation (FMD) pre-exercise, 1-hr and 2-hr post exercise and ambulatory blood pressure was assessed pre-exercise, and continually every 15 min post-exercise. Linear mixed models were used to compare the mean differences in outcome variables. There were no significant differences found between control and both exercise conditions for all OGTT outcomes and no differences were found between control and exercise in FMD (all, p>0.05). Significant effects for exercise were found for both brachial and central blood pressure measures. Brachial systolic blood pressures were lower at 2- and 4-hr post-exercise by approximately -10 and -8mmHg, respectively (p<0.001 and p=0.004) versus control. Central systolic blood pressures were lower at 2-, 3-, and 4-hr post-exercise by approximately -8, -9 and -6mmHg, respectively (p<0.001, p=0.021 and p=0.004) versus control. In conclusion, aerobic exercise, regardless of muscle contraction frequency, were unable to effect glucose control and insulin sensitivity. Similarly, there was no effect on vascular function. However, there was a significant effect of aerobic exercise on reducing post-exercise blood pressure. / Dissertation/Thesis / Doctoral Dissertation Exercise and Nutritional Sciences 2017

O processo de instalação da fadiga implica na mudança do padrão coordenativo durante a pedalada. Desta forma a análise da contribuição de cada articulação do membro inferior para o somatório absoluto dos momentos articulares se faz necessária para o melhor entendimento dos mecanismos relacionados aos efeitos do processo de instalação da fadiga sobre o padrão coordenativo no ciclismo. O objetivo deste estudo foi comparar a contribuição das articulações do quadril, joelho e tornozelo para o somatório absoluto dos momentos articulares resultantes, assim como a força resultante e a cinemática destas articulações, ao longo do tempo, nos modelos experimentais de carga constante e de carga incremental até a exaustão. Foram avaliados onze ciclistas de estrada da categoria elite, que participam de competições regionais (Texas) e nacionais (Estados Unidos) do sexo masculino (idade 31 ± 7 anos; consumo máximo de oxigênio 62,84 ± 4,86 ml.kg-1.min-1; potência máxima 407 ± 37 W). Onze ciclistas foram avaliados no primeiro dia de avaliação, este constituindo um teste de ciclismo máximo com incrementos de carga a cada dois minutos (75, 90 e 100% da PO máxima estimada, respectivamente). No segundo dia de avaliação, dez ciclistas foram avaliados em um protocolo de ciclismo com carga entre 90 e 100% da PO máxima, definida no primeiro dia. Em ambos os testes foram mensurados o consumo de oxigênio (VO2), a força aplicada no pedal direito e a cinemática do membro inferior direito dos ciclistas. Se utilizou um modelo bidimensional dos segmentos da coxa, perna e pé, a fim de calcular as forças e momentos resultantes nas articulações do quadril, joelho e tornozelo, por meio da técnica da dinâmica inversa. Foram analisados o somatório absoluto dos momentos articulares resultantes (SMA), o percentual de contribuição de cada articulação para o SMA, a força resultante e a cinemática das articulações do quadril, joelho e tornozelo nos três estágios do teste incremental (75, 90 e 100% da PO máxima) e em quatro instantes do teste de carga constante (10, 40, 70 e 90% do tempo total do teste). No primeiro dia de avaliação (estudo 1) foi observada redução significativa da cadência de pedalada no estágio com carga a 100% da POMáx, comparado aos estágios 75% e 90% da POMáx. Observou-se ainda aumento significativo da contribuição do joelho para o SMA, no estágio a 100% da POMáx, comparado aos estágios 75% e 90% da POMáx, devido ao aumento significativo do momento resultante na articulação do joelho, no estágio a 100% da POMáx, em relação aos estágios com carga a 75 e 90% da POMáx. A força resultante nas três articulações analisadas apresentou aumento significativo ao longo do teste de carga incremental. Para as variáveis cinemáticas, foi observada redução significativa no valor médio do ângulo do tornozelo, assim como aumento significativo na sua amplitude de movimento no estágio 100% da POMáx. Para a articulação do quadril, foi observado aumento no valor médio do ângulo articular, assim como redução na sua amplitude de movimento no estágio com carga a 100% da POMáx. No segundo dia de avaliação (estudo 2) foi observada redução significativa da cadência de pedalada nos instantes 70 e 90% do tempo total de teste, comparados aos instantes 10 e 40% do tempo total. Esta foi acompanhada por redução da contribuição da articulação do tornozelo para o SMA, no instante 90% do tempo total comparado aos instantes 40 e 70% do tempo total do teste, devido ao aumento significativo do momento resultante na articulação do joelho no instante 90% comparado aos instantes 40 e 70% do tempo total e do quadril no instante 90% comparado aos instantes 10, 40 e 70% do tempo total. Se observou aumento na força resultante nas três articulações analisadas, assim como alterações na cinemática das mesmas ao longo do teste (redução do ângulo médio da articulação do tornozelo, com aumento da amplitude de movimento, aumento significativo do ângulo médio das articulações do joelho e do quadril). Os resultados observados indicaram alterações no padrão coordenativo dos ciclistas devido ao processo de instalação da fadiga, estes ocorrendo de forma distinta nos dois protocolos avaliados. As estratégias de controle das articulações durante a pedalada, parecem não ser características inerentes do gesto motor, sendo estas adaptáveis às demandas aumentadas nas articulações devido às alterações na cadência de pedalada e no processo de instalação da fadiga. / Fatigue process has been proposed to change the coordinative pattern; therefore, the analysis of the contribution of each joint to the average absolute joint moment should improve the understanding of the fatigue effects on the coordinative pattern during cycling. The aim of the present study was to compare the contribution of each joint to the average absolute joint moment, as the resultant force and kinematics of the hip, knee, and ankle joints, in an incremental and in a constant workload cycling test to exhaustion. Eleven male road cyclists competing at regional (Texas) and national (United States) levels (age: 31 ± 7 years; maximal oxygen uptake 62.84 ± 4.86 ml.kg-1.min-1; maximal power output 407 ± 37 W) volunteered to participate in the study. Eleven cyclists were submitted to an incremental maximal cycling test with two minutos of workload increment (75, 90 e 100% of POMax, respectively). On the second day, ten cyclists were evaluated in a constant cycling test, in which the workload was set between 90 and 100% of POMax, as defined on the first evaluation day. During both days the oxygen uptake (VO2), right pedal forces and lower limb kinematics were acquired. A bidimensional model of the thigh, leg and foot segments allowed to calculate the resultant forces and moments at the hip, knee and ankle joints by means of inverse dynamics. The average absolute joint moment (SMA), the contribution of each joint to the SMA, the resultant force and kinematics of the hip, knee and ankle joints were analyzed on three stages of incremental cycling test (75, 90 e 100% of POMax), and on four instants of constant workload cycling test (10, 40, 70 and 90% of total time). On the first evaluation day (study 1), a significant decrease of pedaling cadence was observed at the 100% of POMax stage, compared with 75% and 90% of POMax stages. There was also a significant increase of knee joint contribution to the SMA at 100% of POMax stage, compared with 75% and 90% of POMax stages, due to a significant increase of knee joint absolute moment at 100% of POMax stage, compared with 75% and 90% of POMax stages. The resultant joint force on the three joints have significantly increased, while joint kinematics has changed with the increase of workload (reduced mean ankle angle, with increased ankle range of motion) For hip joint, there was a significant increase of mean angle, with reduced range of motion at 100% of POMax. On the second evaluation day (study 2) a significant reduction of pedaling cadence was observed at the 70% and 90% of total time, compared with 10% and 40% of total time. This result was followed by a significant reduction of the ankle joint contribution to the SMA at the 90% of total time, compared with 40% and 70% of total time, due to a significant increase of knee resultant joint moment on the 90% of total time, compared with 40% and 70% of total time, and for the hip resultant joint moment at the 90% of total time, compared with 10, 40, and 70% of total time. There was also a significant increase of the resultant joint force and a change on kinematics of the three joints throught the test (reduced mean ankle angle, with increased range of motion, and a significant increase of the mean value of knee and hip angles). The results indicated that the coordinative pattern changed with fatigue, with discrete effects in each cycling test. The strategies of joint control during cycling should not be an innate robust motor behavior, but these strategies should be adaptable to higher demands on the joints, as significant changes on pedaling cadence and fatigue.

Humans naturally select a point at which to transition from walking to running when gradually increasing locomotor speed. This point is known as the walk-to-run transition (WRT). The WRT is traditionally expressed in terms of speed and is known to occur within a close range of 2.1 m/s, which is an accepted heuristic (i.e., empirically based, rounded) threshold value. Very little research exists defining the WRT in terms of cadence (steps/min) despite the fact that spatial temporal aspects of gait underlying the WRT include this parameter. Preliminary evidence suggests that the WRT may be associated with a cadence of 140 steps/min in adults. This overlooked approach to identifying the WRT may be better than speed because of the simplicity and accessibility of recording cadence in both lab- and free-living settings. Wearable technologies can be used to determine cadence in real-time in a variety of settings, and could be used in the future to expand our current knowledge of the WRT. In turn, this knowledge could be used to inform training practices and/or rehabilitation of gait disorders. The purposes of this secondary analysis of an existing treadmill-based data set were to: (1) identify the optimal WRT cadence threshold, and (2) compare the accuracy of the cadence cutpoint to the previous WRT indicators identified in literature (i.e., speed and Froude number). This secondary analysis focused only on the data collected from the 28 participants (20 men, 8 women) whose protocol was terminated due to selecting to run during the treadmill portion of the larger CADENCE-Adults study. The CADENCE-Adults protocol consisted of a series of five-minute bouts beginning at 0.2 m/s and increasing in 0.2 m/s increments, with each bout followed by two minutes of standing rest. Participants could choose to walk or run each bout. The cadence of the bout during which the participants chose to run was considered the WTR cadence, and ROC analyses were performed to determine the optimal cadence cutpoint. Sensitivity, specificity and overall accuracy were calculated to compare the accuracy of the speed and Froude values from literature to the calculated cadence cutpoint. In addition, these analyses were expanded post hoc to also examine the accuracy of the previously proposed cadence cutpoint from the literature and the speed and Froude cutpoint identified from the dataset. Following analyses, three cadence cutpoints (134, 139, or 141 steps/min) were identified that shared equal overall accuracy (92.9%); therefore, there was no single optimal cutpoint. This also occurred for the speed cutpoints, where both 1.9 and 2.0 m/s shared overall accuracies of 78.6%. The optimal Froude cutpoint identified was 0.46 (82.0% overall accuracy). The rank-order overall accuracy of previously identified cutpoints were: a cadence of 140 steps/min (91.1%), Froude number of 0.5 (76.8%) and speed of 2.1 m/s (66.1%). Based on the identified optimal cadence cutpoints, a heuristic range of running cutpoints was recommended anchored on specificity vs. sensitivity preferences. For researchers interested in identifying episodes more likely to be running behavior (with the preference that very few episodes of walking behavior are mistakenly identified), it would be best to use 140 steps/min. However, if they want to be as inclusive as possible in identifying episodes of running behavior (and can tolerate more mistakenly identified episodes walking behavior), they could use 135 steps/min. When applied to this dataset, 96.0% (24/25) of the individuals who were ≥140 steps/min were running, but this decreased to 92.5% (25/27) with ≥135 steps/min. In conclusion, cadence clearly performed much better in terms of overall accuracy when compared to traditionally used WRT indicators of speed and Froude numbers. The recommended heuristics cadence cutpoint range can be used by researchers who want to evaluate the locomotor patterns of individuals when analyzing free-living step-defined data collected using wearable devices.

The StrongARM comparator is utilized in many analog-to-digital converters (ADCs) because of its high power efficiency and rail-to-rail outputs. The performance of the comparator directly affects the speed, power, and accuracy of an ADC. However, the StrongARM comparator performance parameters such as delay, noise, and offset measured directly from silicon prototypes are rare in literature and often consist of small sample sets. In addition, existing techniques to measure the comparator require large chip areas, making it impractical to characterize a large number of comparators to obtain stochastic parameters such as offset and noise. This work presents novel circuit techniques to measure a large number of comparators (4,000) in a compact chip area to directly obtain silicon data including delay, noise, offset, and power. The proposed techniques also relax the requirement on the test instruments to measure the small time values. Four comparators with different transistor size ratios have been designed and measured to study the performance tradeoffs. In addition, this work presents a method utilizing supercomputing resources to simulate the large design space of the StrongARM comparator to observe the performance trends. Measurements are compared to simulations showing their accuracy and, for the first time, detailed study on the performance trends with different transistor size ratios.

Space instrumentation technology is an essential tool for rocket and satellite research, and is expected to become popular in commercial and military operations in fields such as radar, imaging, and communications. These instruments are traditionally implemented on printed circuit boards using discrete general-purpose Analog-to-Digital Converter (ADC) devices and other components. A large circuit board is not convenient for use in micro-satellite deployments, where the total payload volume is limited to roughly one cubic foot. Because micro-satellites represent a fast growing trend in satellite research and development, there is motivation to explore miniaturized custom application-specific integrated circuit (ASIC) designs to reduce the volume and power consumption occupied by instrument electronics. In this thesis, a model of a new Plasma Impedance Probe (PIP) architecture, which utilizes a custom-built ADC along with other analog and digital components, is proposed. The model can be fully integrated to produce a low-power, miniaturized impedance probe.

Ce manuscrit décrit l’étude et la mise en œuvre d’une source laser ultrarapide à taux de répétition élevé dans l’infra-rouge moyen, pour des applications à la physique des champs forts et à la spectroscopie moléculaire multidimensionnelle. Cette source est basée sur le phénomène d’amplification paramétrique optique à dérive de fréquence, qui permet la génération d’impulsions de quelques cycles optiques.Tout d’abord, nous présentons les applications de ces sources, ainsi que leurs paramètres importants, débouchant sur un cahier des charges pour la source à l’étude. Un état de l’art des sources paramétriques présentées dans la littérature scientifique nous permet ensuite d’appréhender la diversité des architectures et des performances atteintes. En particulier, nous soulignons les points cruciaux que sont la nature et les performances du laser de pompe, le mécanisme de génération du signal à amplifier, ainsi que la robustesse de la synchronisation temporelle entre le signal et la pompe.Nous étudions ensuite la possibilité d’émettre un signal autour de la longueur d’onde de 1,55 µm à partir d’impulsions femtoseconde de pompe à 1,03 µm par génération de supercontinuum dans un cristal massif de YAG. Nous menons ainsi une étude détaillée des propriétés de la partie infra-rouge du supercontinuum obtenu, en termes de contenu spectral, cohérence, propriétés statistiques tir à tir et long terme, et propriétés spatiales. Cette étude nous permet de conclure sur la validité de cette approche pour générer le signal à amplifier.Nous arrivons donc à définir une architecture inédite basée sur l’utilisation d’un laser de pompe basé sur un amplificateur à fibre dopée ytterbium de forte énergie délivrant des impulsions de 300 fs 400 µJ à la cadence de 125 kHz. La durée courte rendue possible par le choix de cette technologie de pompe nous permet de bénéficier d’un certain nombre d’avantages importants : la génération efficace de supercontinuum autour de 1,55 µm, ce qui entraine une synchronisation temporelle très robuste entre pompe et signal. D’autre part le couple étireur – compresseur est constitué de simples lames de matériaux massifs, ce qui permet une grande efficacité et une gestion simplifiée de la phase spectrale. Enfin, la courte durée de pompe augmente le seuil de dommage en intensité crête, ce qui permet l’utilisation de cristaux non linéaires courts et augmente la bande spectrale d’amplification. Des expériences supplémentaires sont menées pour étudier les phénomènes limitant la puissance au sein des cristaux de MgO:PPLN. Les étages d’amplification sont tous réalisés en géométrie colinéaire, ce qui permet d’utiliser le signal et l’idler sans introduction de chirp angulaire. Toutes ces caractéristiques permettent la génération de deux faisceaux en sortie portant des impulsions de 50 fs 20 µJ à 1550 nm et 70 fs 10 µJ à 3,1 µm. / This thesis describes the design and construction of an ultrafast high repetition rate laser source in the mid-IR, for applications in strong-field physics and multidimensional molecular spectroscopy. This source is based on optical parametric chirped-pulse amplification, allowing the generation of few-cycle pulses.We first present some applications of these lasers, along with important parameters, to define specifications for the considered source. We then briefly outline the state of the art of similar ultrafast sources described in the literature, to highlight the variety of architectures and performances. In particular, several key points are identified, namely the nature and performances of the pump laser source, the method to generate a seeding signal, and the robustness of temporal synchronization between pump and signal pulses.We proceed to study the possibility of emitting a seed signal around 1.55 µm wavelength by supercontinuum generation in a bulk YAG crystal from femtosecond pump pulses at 1.03 µm. A detailed analysis of the properties of the infrared spectral content of the supercontinuum is carried out, focusing on spectral bandwidth, coherence, shot-to-shot and long term stability, and spatial properties. This work allows us to conclude that supercontinuum generation is a valid approach to generate the seed signal.This leads us to define a novel architecture built around an ytterbium-doped fiber femtosecond pump source delivering 300 fs 400 µJ pulses at a repetition rate 125 kHz. The short pump pulse duration compared to bulk Yb:YAG or Nd:YVO4 based systems results in a number of important advantages. First, it allows efficient seeding at 1550 nm using supercontinuum generation directly from the pump pulses in a bulk YAG crystal, resulting in extremely robust passive pump – signal synchronization. The short pump pulse duration also allows the use of millimeter to centimeter lengths of bulk materials to provide stretching and compression for the signal and idler, which minimizes the accumulation of higher-order spectral phase. Finally, the shorter pump pulse duration increases the damage peak intensity, permitting the use of shorter nonlinear crystals to perform the amplification, which increases the spectral bandwidth of the parametric process. Additional experiments are performed to sort out the phenomena that limit power scaling in MgO:PPLN crystals. The OPCPA stages are all operated in collinear geometry, allowing the use of both signal and idler without the introduction of angular chirp on the latter. These points result in the dual generation of 70 fs 23 µJ signal pulses at 1550 nm and 60 fs 10 µJ idler pulses at 3070 nm from a simple setup.

Foot strike type affects running mechanics and may influence overuse injury occurrence. Measuring the interaction between cumulative load and foot strike type may provide additional information that could eventually help with understanding injury mechanisms. The purpose of this study was to determine how foot strike type affects cumulative loading in runners, and to determine if individual metrics change throughout a 5-kilometer sub-maximal run. 30 participants ran on an instrumented treadmill for 5 km at 3.15 m/s with their preferred foot strike type (14 rearfoot strike, 16 non-rearfoot strike). Stride rate, foot strike angle, loading rate, per stride and per km (cumulative) vertical ground reaction force impulse, impact peak, absolute peak, knee negative work, and ankle negative work were calculated and compared across time and between groups. Per stride between-group main effects were seen for stance time (p=0.003), foot strike angle (p<0.001), and loading rate (p=0.040), all of which were greater for rearfoot strike runners. Per stride and cumulative ankle and knee negative work also showed significant differences, with ankle negative work being greater for non-rearfoot strike runners (p=<0.001 per stride, p=<0.001 cumulative) and knee negative work being greater for rearfoot strike runners (p=0.014 per stride, p=0.008 cumulative). Both loading rate and cumulative vertical ground reaction force impulse decreased significantly over time (p=0.035, p=<0.001 respectively). In summary, we found a few differences in per stride and cumulative metrics between foot strike groups, namely ankle and knee loading as previously observed. However, as a whole, individual variability in vertical ground reaction force loading patterns was more apparent than any group distinctions. We also found patterns in previous research suggesting that study design components, specifically self-selected speed and habituation, affect variables such as stride rate and peak vertical ground reaction force. The common perception that non-rearfoot strike runners have a higher stride rate was not supported in this study. Lastly, we determined that cumulative calculations can be different if taken at the beginning vs the end of a run. Quantifying injury risk is complicated and cumulative damage models should take into account individual load capacity and training session characteristics (e.g., warm-up time, length, intensity, and rest time).

The purpose of this study was to compare high-resistance cycle training (HRCT) with resistance training (RT), and their effects on Wingate anaerobic test watt max (Wmax) and watt average (Wave), strength (improvement in 1 repetition max [RM]), and time-trial performance. Twenty-five healthy college-age untrained male subjects were randomly assigned to the HRCT (n=10), RT (n=10), or control (n=5) group. All subjects completed pre and posttesting for the leg press (LP), 30 s Wingate anaerobic test, and 15-min time-trial. Subjects also completed familiarization tests prior to pretesting in the Wingate anaerobic test and 15-min time-trial. HRCT and RT subjects trained 2x/wk for 8 weeks with at least 48 hrs between training sessions. During each training session HRCT completed 4 x 30 sec efforts increasing resistance when >65 rotations per minute (rpm) could be maintained for the full training session. RT completed 3 x 10 repetitions of leg press with weight increasing 5 -10 lbs when all repetitions were completed during a training session. ANOVA with Tukey post-hoc was used to determine if differences existed between the groups. Within group change was analyzed using paired T-test. Effect size was computed to determine meaningfulness of differences. HRCT and RT groups both showed statistical significance (p < 0.05) pre to posttesting in LP, Wingate anaerobic test Wmax and Wave, and 15-min time-trial. Control group also showed statistical significance (p < 0.05) pre to posttesting in LP and 15-min time-trial. Significant between group differences were noted between HRCT and control in Wingate anaerobic test Wmax (p=0.03) and Wave (p = 0.007) and 15-min time-trial (p = 0.003). There was a significant difference between RT and control on the 15-min time-trial (p = 0.008). When comparing HRCT and RT no statistical difference was seen in LP, Wingate anaerobic test Wmax and Wave, and 15-min time-trial. High-resistance cycle training and RT resulted in similar strength gains. However, HRCT showed greater improvements in cycling specific activities: 30 s Wingate anaerobic test Wmax and Wave, and 15-min time-trial. Results suggested that HRCT may increase performance on bike related assessments when compared to RT.

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