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Dystrophin is the product of the Duchenne Muscular Dystrophy gene locus, whose absence results in progressive skeletal muscle breakdown. Despite considerable work on the localisation of dystrophin and its associated complex, its role in muscle function remains unclear. In the light of the structural and mechanical instability of the dystrophic membrane, the idea was tested that dystrophin might impart membrane integrity and strength by anchoring membrane proteins and/or delineating the surface into specialised subcellular functional domains. Specifically, because dystrophin shows high sequence, structural and spatial similarities to the cytoskeletal protein spectrin; and because spectrin is proven to sterically restrict protein lateral diffusion through a subplasmalemmal network; the capacity of dystrophin to act as a 'molecular fence' to membrane diffusion was studied by comparing lateral mobility of membrane glycoproteins by fluorescence photobleach recovery in mdx and normal tissue. Secondly, as dystrophin has been proven to interact directly with proteins of the dystrophin associated glycoprotein complex in vivo, experiments addressed whether specific binding and immobilisation of the complex by dystrophin at the membrane was essential for function. Finally, given the homology of dystrophin and spectrin, the presence of dystrophin at the neuromuscular junction, and the importance of spectrins in immobilisation of voltage gated sodium channels in the nervous system, the role of dystrophin in regulating voltage gated sodium channel distribution at the neuromuscular junction was investigated. The results show that membrane glycoproteins were immobile in the presence and absence of dystrophin, suggesting dystrophin is not an essential molecular fence component. Alternatively, viability may have been the major influence on protein and lipid diffusion in these fibres and suggestions are made as to how this may be recognised and overcome for subsequent investigation. Three novel exon specific anti-dystrophin peptide antibodies were generated during the work that will be useful for studies into Duchenne muscular dystrophy in general, and dystrophin revertant fibres in particular.

Determina la recuperación de la fuerza muscular del cuádriceps y la variación del trofismo muscular del muslo en pacientes post operados de ligamento cruzado anterior en un lapso de tres meses en el programa de medicina física y rehabilitación del Centro Médico Naval Cirujano Mayor Santiago Távara. Es un estudio analítico, observacional y de tipo longitudinal. Participan 20 pacientes, entre los 20 y 50 años de edad, con diagnóstico médico de post operado de ligamento cruzado anterior. La fuerza muscular se evalúa en dos momentos, la primera evaluación se realiza al finalizar la etapa inflamatoria (tercera semana post quirúrgica) y la segunda, tres meses después. El instrumento que se utiliza para la medida de la fuerza es el test de fuerza máxima o también llamado test de resistencia máxima (1RM), cuyo índice de confiabilidad oscila entre 0.92 a 0.98. La estimación del valor de 1RM es por medio de la ecuación de Brzycki y para la categorización de la fuerza muscular, se utiliza la escala de Vivian Heyward. Encuentra que los pacientes post operados de ligamento cruzado anterior muestran un 37,5% de incremento en la fuerza muscular del cuádriceps después de tres meses de haber iniciado el programa de rehabilitación física. Al iniciar el tratamiento fisioterapéutico el 80% los pacientes presentan una fuerza muscular que los ubica dentro de una categoría mala; tres meses después de iniciado el tratamiento fisioterapéutico, el 95% de los pacientes se ubican dentro de la categoría buena. / Tesis

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Magister Artium (Sport, Recreation and Exercise Science) - MA(SRES) / Hamstrings muscle injury is the most frequent soccer-related injury in amateur and professional soccer players. Despite various interventions, the risk of hamstrings re-injury remains high. Several scientific studies examined the potential risk factors and their contribution to the occurrence of hamstrings injuries in male soccer players. The aim of the study was to investigate the relationship between selected physical characteristics, such as time-to-peak torque, hip abduction peak torque, hamstrings-to-quadriceps strength ratio, and hamstrings flexibility and the occurrence of hamstrings injuries in amateur male soccer players. A prospective, quantitative cross-sectional study design was utilized in this study. A total of 89 amateur male soccer players aged 18-35 years were recruited from the Cape Town Football District to perform functional assessments before injury occurred, which included anthropometric measurements, an evaluation of lower extremity isokinetic muscle strength (both knee and hip) and hamstrings flexibility tests. Instruments used to measure the anthropometric data were a calibrated Seca balance beam scale and stadiometer, a skinfold caliper, a sliding caliper, an anthropometer (All Harpenden, UK) and a metal tape measure. The Biodex Pro System 4 isokinetic dynamometer was used to measure lower extremity isokinetic muscle strength and a goniometer to measure hamstrings flexibility. Descriptive statistics included means and standard deviations, and inferential statistics included Pearson product-moment correlation to determine the relationship between selected physical characteristics and the occurrence of hamstrings injuries. Multivariate logistic regression via the forward stepwise method was utilised to predict potential physical characteristics (risk factors) for hamstrings injury in amateur male soccer players. Statistical significance was a p value of below 0.05. The prevalence of hamstrings injury was 4.3 %, with the multivariate logistic regression analysis indicating that time-to-peak torque was a significant predictor of the occurrence of hamstrings injury (OR = 1; p = 0.027). In conclusion, time-to-peak torque was a significant predictor of the occurrence of hamstrings injury. The players with hamstrings injuries produced a significantly slower time-to-peak torque, which has relevance for soccer players and coaches in addressing this common injury at all levels of competition.

Running is achieved by cyclic execution of movements that ultimately allows a person to move. Each cycle is divided into two phases. The first phase is where power is absorbed as the body\'s center of mass is lowered and decelerated. The second being where power is generated and the center of mass is propelled upwards and forwards. Power absorption is primarily done by quadriceps muscles while plantar flexors generate most of the power during push-off phase. Variations in speed and slope are met by adjustments in the same direction of force produced by lower limb muscles and, due to changes in energy expenditure, of heart rate. In this context, analysis of variability offer a non-invasive way to measure how well-adjusted muscles are to cope with variations in demand. Thus, our aim was to investigate the relationship between the variability of contractions of muscles from the quadriceps and plantar flexors with changes in speed and slope and in heart rate. Secondarily, we sought to verify if the patterns observed in a restricted group of subjects could also be noted in a wider population. To answer these questions, we used electromyography to collect data of intervals between successive contractions of vasti and gastrocnemius muscles of seventeen runners across several target runs. These runs were chosen with several different speeds and slopes. Runners were divided into two experimental groups: Experiment 1 contained no restrictions regarding age and fitness level while Experiment 2 did control for these variables. Linear regressions and gradients showed that even though variability estimators correlated negatively to speed and/or slope, they could be better explained by changes in heart rate. Thus our main conclusion was that variability between contractions is inversely proportional to muscle activation, in relation to its maximum capacity. As a consequence, different combinations of speed and slope could result in the same variability despite differences in metabolic profile, as long as the power output remains constant. Due to methodological issues, we could not reach a decisive conclusion regarding the comparison between the more restricted and more heterogeneous groups of volunteers, although results suggest that the runners respond to changes of speed and slope in a similar way regardless of differences in age and fitness level / Durante a corrida, uma série de movimentos é realizada de forma cíclica que, em última análise, fazem com que o corpo se desloque. Cada ciclo é dividido em uma fase em que ocorre absorção de trabalho conforme o centro de massa é rebaixado e desacelerado e uma fase em que ocorre produção de trabalho, conforme o centro de massa é impulsionado para cima e para frente. Os músculos do quadríceps e flexores plantares são os principais responsáveis pela absorção e geração de trabalho, respectivamente. Variações na velocidade da corrida e na inclinação do terreno requerem ajustes da força muscular e, como consequência, da freqüência cardíaca. Neste contexto, análises de variabilidade oferecem uma maneira de medir a adequação do sistema muscular às variações na demanda. Assim, buscamos investigar a relação entre a variabilidade das contrações de músculos do quadríceps e flexores plantares com alterações na velocidade, inclinação e potência; bem como verificar se os padrões observados em um grupo restrito de indivíduos se aplicavam a uma amostra mais variada. Para isso, coletamos dados de intervalos entre contrações do vasto e gastrocnêmio de dezessete voluntários durante corridas realizadas em diferentes combinações de velocidade e inclinação da esteira. Os sujeitos foram divididos em dois grupos experimentais: no Experimento 1, não houve restrições quanto à idade e condicionamento, enquanto que no Experimento 2 essas variáveis foram controladas. Regressões lineares e gradientes mostraram que, embora os estimadores de variabilidade correlacionem negativamente com velocidade e inclinação, eles são melhor explicados por mudanças no consumo energético (i.e.,frequência cardíaca). Assim, concluímos que a variabilidade é inversamente proporcional à força muscular, em relação à sua capacidade máxima. Como conseqüência, diferentes combinações de velocidade e inclinação podem resultar na mesma variabilidade, apesar das diferenças no perfil metabólico. Devido a complicações metodológicas, não pudemos chegar a uma conclusão definitiva em relação a comparação entre voluntários dos Experimentos 1 e 2, embora os resultados sugiram que corredores respondam a mudanças de velocidade e inclinação de maneira semelhante, independentemente de diferenças de idade e nível de condicionamento