Theoretical mechanical benefits of biarticular muscles include reduced displacements and force potentiating shifts in linear velocities during multi-joint coupled motions. A cadaveric model was developed to compute muscle kinematics of biceps femoris (BFL and BFS) during four classes of coupled knee and hip joint motion, as well as running and walking gait (Six subjects, Vicon Motion Analysis). The examples of the classes of motion were: KEHE-jump (knee extension and hip extension), KFHF-tuck (knee flexion and hip flexion), KFHE-kick (knee flexion and hip extension), and KEHF-paw (knee extension and hip flexion). BFL peak and mean velocity shifts relative to BFS were seen in all four coupling classes (p<0.05) and the majority of the gait subclasses (p<0.05). Muscle displacements were larger in BFL for both KFHE-paw and KEHF-kick (p<0.05), smaller in KFHF-tuck (p<0.05), but not significantly different in KEHE-jump or during most of the running gait subclasses, except for during KFHE-late mid stance and KEHF-mid swing, where they were larger for BFL (p<0.05). The mechanical benefits associated with BFL velocity shift relative to BFs were identified in KFHF, KEHF motions, and certain subclasses of gait. In contrast, there were potential mechanical detriments due to velocity shift relative to BFs in the KEHE-jump, KFHE-paw, and the majority of KEHE and KFHE subclasses in both gait cycles. The possible mechanical benefits associated with displacement conservation of BFL relative to BFs would be realized in KFHF-tuck jump, but not during KEHE-jump and the gait cycle subclasses. The findings of this study reveal both mechanical benefits and detriments of biarticular muscles, and have immediate implications for neural control of biarticular muscles during movement.

Everyday movements, such as reaching for a drink of water or typing on a keyboard highlight the relative ease with which we move and interact with our surroundings. However, the success of these skilled movements depends on the motor system’s ability to consider a variety of factors, such as the goal of the behavioral task, the surrounding environment and the physical properties of the musculoskeletal system. Recent theories of voluntary motor control, namely optimal feedback control, suggest that such skilled motor behavior is achieved through sophisticated feedback control. This thesis investigates one physiological implication of this theory. Specifically, we hypothesize that rapid feedback responses following mechanical perturbations possess many of the functional attributes thought to be reserved for voluntary control because these two systems have contributions from similar neural substrates (eg. motor areas in cortex). Our studies were specifically designed to investigate rapid feedback responses during the long-latency epoch, which occurs between 50-100ms following a mechanical perturbation. Consistent with our hypothesis, we found that the sophistication of the long-latency response rivals that of voluntary control. In our first study (Chapter 2) we examined if rapid feedback responses were sensitive to features of the end target. We found that muscle activity during the long-latency epoch was modulated by the size/shape of the end. In our second study (Chapter 3) we observed flexible responses in muscle activity during the long-latency epoch that reflected rapid ‘decisions’ during online control regarding how to navigate around obstacles in the environment as well as how to select amongst multiple potential goals. In our final study (Chapter 4) we examined if rapid feedback responses in the shortened muscle parallel the sophisticated responses observed in the lengthened muscle. We found that unloading a pre-excited muscle elicited sophisticated inhibitory responses, including knowledge of limb mechanics and rapid target selection, during the long-latency epoch that are comparable to the excitatory responses observed during loading. Taken together, the studies presented in this thesis demonstrate that the responses in the long-latency epoch reflect several functional attributes typically reserved for voluntary control. / Thesis (Ph.D, Neuroscience Studies) -- Queen's University, 2014-04-29 16:54:12.489

Theoretical mechanical benefits of biarticular muscles include reduced displacements and force potentiating shifts in linear velocities during multi-joint coupled motions. A cadaveric model was developed to compute muscle kinematics of biceps femoris (BFL and BFS) during four classes of coupled knee and hip joint motion, as well as running and walking gait (Six subjects, Vicon Motion Analysis). The examples of the classes of motion were: KEHE-jump (knee extension and hip extension), KFHF-tuck (knee flexion and hip flexion), KFHE-kick (knee flexion and hip extension), and KEHF-paw (knee extension and hip flexion). BFL peak and mean velocity shifts relative to BFS were seen in all four coupling classes (p<0.05) and the majority of the gait subclasses (p<0.05). Muscle displacements were larger in BFL for both KFHE-paw and KEHF-kick (p<0.05), smaller in KFHF-tuck (p<0.05), but not significantly different in KEHE-jump or during most of the running gait subclasses, except for during KFHE-late mid stance and KEHF-mid swing, where they were larger for BFL (p<0.05). The mechanical benefits associated with BFL velocity shift relative to BFs were identified in KFHF, KEHF motions, and certain subclasses of gait. In contrast, there were potential mechanical detriments due to velocity shift relative to BFs in the KEHE-jump, KFHE-paw, and the majority of KEHE and KFHE subclasses in both gait cycles. The possible mechanical benefits associated with displacement conservation of BFL relative to BFs would be realized in KFHF-tuck jump, but not during KEHE-jump and the gait cycle subclasses. The findings of this study reveal both mechanical benefits and detriments of biarticular muscles, and have immediate implications for neural control of biarticular muscles during movement.

Corticospinal and intracortical excitability are excitability measures of the central nervous system responsible for motor generation, and are studied for their contribution to fine motor skill execution and learning. Since the need for proper execution of fine motor skills is ever-present and necessary for everyday life, identification of physiological pathways that may disrupt or enhance corticospinal and intracortical excitability is an important research topic. This thesis investigates the effects of baroreceptor unloading on corticospinal and intracortical excitability during various motor tasks. Baroreceptor unloading is a physiological response to common hemodynamic stress (e.g. hypovolemia and orthostasis). The motor tasks investigated are complete muscular relaxation, individual isometric low-force contraction of a muscle, and an isometric co-contraction of a muscle in a joint-stabilizing task. The effects of baroreceptor unloading on corticospinal and intracortical excitability appear to be very task specific. The results are discussed in view of available pharmacological and physiological research, and potential neural pathways for the observed effects are suggested. The overall conclusion is that baroreceptor unloading increases corticospinal excitability and decreases intracortical inhibition in a resting muscle, does not produce any observable effects during individual muscle activity, and decreases corticospinal excitability during joint-stabilizing co-contraction.

No description available.

Thesis (M.S.)--University of Wisconsin--Madison, 1984. / Typescript. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves 76-79).

Recently, attentional focus studies involving force production have demonstrated that when participants focused externally motor units were recruited more efficiently and muscular communication was enhanced. When participants focused internally, however, increased "noise" was incorporated into the neuromuscular system resulting in energy waste. The present study explored the effects of an external or internal focus of attention in the isometric wall sit endurance test. Since motor unit recruitment is more efficient under an external focus, it was hypothesized that participants (n = 23) would have a higher endurance time when they focused externally (ex. I want you to focus on pretending like you are sitting in a chair through the duration of the trial) rather than internally (ex. I want you to focus on keeping your knee at 90 degrees through the duration of the trial). Results revealed when participants focused externally they had a significantly higher endurance time (68.41 ± 34.12 sec) than when they focused internally (60.22 ± 34.54 sec). Participants also adopted the correct attentional focus in a majority of the endurance trials (70% and 69% for the external and internal conditions, respectively). This was the first study to demonstrate the benefits of an external focus over an internal focus in an isometric wall sit endurance test. Future studies should use biomechanical analyses such as EMG and kinematic measures and perceived force measures such as RPE to explore the reasons why an external focus provided performance benefits.

Made available in DSpace on 2014-06-11T19:28:33Z (GMT). No. of bitstreams: 0 Previous issue date: 2012-02-06Bitstream added on 2014-06-13T19:58:07Z : No. of bitstreams: 1 silva_mg_me_guara.pdf: 891887 bytes, checksum: f0821f5c19c026a3c479d3e2370051df (MD5) / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / O chute no futebol é um gesto técnico bastante estudado, devido a sua importância dentro de uma partida, porém existem algumas lacunas importantes a serem preenchidas, principalmente quanto a sua análise no aspecto quantitativo. Este estudo teve como objetivo encontrar um sistema eficaz de análise dos fatores técnicos intervenientes na performance motora de jogadores de futebol de campo. Neste sentido tornou-se de fundamental importância avaliar parâmetros biomecânicos aplicados durante o chute com o dorso do pé em atletas de categorias de base, a fim de melhorar a performance motora e corrigir falhas não detectadas pela análise qualitativa. Desta forma foi elaborado um sistema de medidas específico, que teve como ponto central da pesquisa, a análise do movimento de chute ao gol. Utilizou-se a cinemetria bidimensional (2D), visando analisar o ângulo formado pelo joelho da perna de apoio; a força de reação do solo ou força vertical (Fv); o COP (centro de pressão) medido pelo equilíbrio do pé de apoio e deslocamento em fases determinantes do chute; e através de acelerômetro, encontrou-se o comportamento da aceleração ou desaceleração produzidas nas fases do movimento de chute. A amostra foi constituída de quatro indivíduos com idades compreendidas entre 16 e 19 anos, atletas da equipe do Resende Futebol Clube, sendo dois da categoria juniores e dois da categoria juvenil. O teste consistiu na execução de chutes com o dorso do pé cujo objetivo foi acertar o alvo posicionado a nove metros do voluntário; o chute caracterizou-se por ser funcional, mas ao mesmo tempo empregando potência. Os resultados encontrados foram coerentes para Fv e aceleração na análise inter-voluntários. Em relação à velocidade alcançada pela bola para inter-voluntários, os resultados apresentaram padrão esperado... / The kick in soccer is a technical gesture extensively studied because of its importance within a game, but there are some important gaps to be filled, specially regarding its analysis on the quantitative aspect. This study aimed to find an effective system of analysis of technical factors involved in motor control performance of soccer players in the field. In this sense has become of paramount importance to assess biomechanical parameters applied during the kick with the instep of the basic categories of athletes, to improve motor performance and to correct errors not detected by qualitative analysis. Thus was developed a system of specific measures, which had as its central point of the research, analysis of the motion of kicking the goal. Kinemetry used the two-dimensional (2D) to evaluate the angle formed by the knee of the supporting leg, the ground reaction force, especifically vertical force (Fv), the COP (center of pressure) measured by the balance of the foot support and decisive shift in phases of the kick, and by accelerometer, found the behavior of acceleration or deceleration produced in the phases of the motion of kick. The sample consisted of four individuals aged between 16 and 19 years, athletes team Resende Football Club, two juniors and two categories of the youth category. The test consisted in the execution of kicks with the instep whose goal was to hit the target positioned at nine meters of the volunteer, the kick was characterized by being functional, but at the same time employing power. The results were consistent for Fv and acceleration parameters between inter-volunteers and the ball speeds were registered according with literature. The results showed the expected pattern, however, COP parameter presented the individual pattern between inter-volunteers and showed same trend for intra- volunteers

Resumo: O chute no futebol é um gesto técnico bastante estudado, devido a sua importância dentro de uma partida, porém existem algumas lacunas importantes a serem preenchidas, principalmente quanto a sua análise no aspecto quantitativo. Este estudo teve como objetivo encontrar um sistema eficaz de análise dos fatores técnicos intervenientes na performance motora de jogadores de futebol de campo. Neste sentido tornou-se de fundamental importância avaliar parâmetros biomecânicos aplicados durante o chute com o dorso do pé em atletas de categorias de base, a fim de melhorar a performance motora e corrigir falhas não detectadas pela análise qualitativa. Desta forma foi elaborado um sistema de medidas específico, que teve como ponto central da pesquisa, a análise do movimento de chute ao gol. Utilizou-se a cinemetria bidimensional (2D), visando analisar o ângulo formado pelo joelho da perna de apoio; a força de reação do solo ou força vertical (Fv); o COP (centro de pressão) medido pelo equilíbrio do pé de apoio e deslocamento em fases determinantes do chute; e através de acelerômetro, encontrou-se o comportamento da aceleração ou desaceleração produzidas nas fases do movimento de chute. A amostra foi constituída de quatro indivíduos com idades compreendidas entre 16 e 19 anos, atletas da equipe do Resende Futebol Clube, sendo dois da categoria juniores e dois da categoria juvenil. O teste consistiu na execução de chutes com o dorso do pé cujo objetivo foi acertar o alvo posicionado a nove metros do voluntário; o chute caracterizou-se por ser funcional, mas ao mesmo tempo empregando potência. Os resultados encontrados foram coerentes para Fv e aceleração na análise inter-voluntários. Em relação à velocidade alcançada pela bola para inter-voluntários, os resultados apresentaram padrão esperado... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: The kick in soccer is a technical gesture extensively studied because of its importance within a game, but there are some important gaps to be filled, specially regarding its analysis on the quantitative aspect. This study aimed to find an effective system of analysis of technical factors involved in motor control performance of soccer players in the field. In this sense has become of paramount importance to assess biomechanical parameters applied during the kick with the instep of the basic categories of athletes, to improve motor performance and to correct errors not detected by qualitative analysis. Thus was developed a system of specific measures, which had as its central point of the research, analysis of the motion of kicking the goal. Kinemetry used the two-dimensional (2D) to evaluate the angle formed by the knee of the supporting leg, the ground reaction force, especifically vertical force (Fv), the COP (center of pressure) measured by the balance of the foot support and decisive shift in phases of the kick, and by accelerometer, found the behavior of acceleration or deceleration produced in the phases of the motion of kick. The sample consisted of four individuals aged between 16 and 19 years, athletes team Resende Football Club, two juniors and two categories of the youth category. The test consisted in the execution of kicks with the instep whose goal was to hit the target positioned at nine meters of the volunteer, the kick was characterized by being functional, but at the same time employing power. The results were consistent for Fv and acceleration parameters between inter-volunteers and the ball speeds were registered according with literature. The results showed the expected pattern, however, COP parameter presented the individual pattern between inter-volunteers and showed same trend for intra- volunteers / Orientador: Tamotsu Hirata / Coorientador: Henrique Martins Rocha / Banca: Mauro Pedro Peres / Banca: Luiz Heleno Moreira Duque / Mestre

No description available.