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Relação entre a rigidez muscular dos isquiotibiais e a taxa de produção de força dos flexores do joelho
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Objetivo: Explorar a associação entre a taxa de produção de força e a rigidez passiva e ativa dos músculos isquiotibiais. Método: Dezoito sujeitos saudáveis do sexo masculino (25,2 ± 4,8 anos; 79,1 ± 10,8 kg; 177,6 ± 6,4 cm de altura) com prática de treino superior a 2 anos (i.e. treino de força, atletismo federado e futebol amador) participaram na investigação. Os sujeitos foram posicionados em decúbito ventral com a anca em posição neutra (0º), joelho a 30º de flexão e tornozelo a 15º de flexão plantar. Os pés foram fixados a sensores de força individuais, sobre os quais foram realizadas contrações bilaterais isométricas de flexão do joelho, sendo obtidas curvas força-tempo para o dois membros, das quais foram extraídos a força máxima, a taxa de produção de força em diferentes intervalos de tempo, momento em que o força máxima é atingida e o valor do mesmo. A rigidez muscular (passiva e ativa) foi avaliada recorrendo à técnica de elastografia de ondas de cisalhamento, em regime passivo (posição estática em repouso) e em regime ativo (contração a 20% contração voluntária isométrica máxima). Foram testados, aleatoriamente, todos os músculos isquiotibiais, tendo sido avaliados, de forma randomizada, 9 membros dominantes e 9 membros não-dominantes. O software Matlab (The Mathworks Inc., Natick, Massachusetts, USA) foi utilizado para o processamento dos outputs obtidos pelo ecógrafo usado na avaliação elastográfica e a análise estatística foi realizada recorrendo ao software SPSS.
Objective: Explore the association between the knee flexors rate of force development and the (active and passive) muscular stiffness of the hamstrings Methods: Eighteen healthy male subjects (25,2 ± 4,8 years; 79,1 ± 10,8 kg; 177,6 ± 6,4 cm height) with training experience (e.g., resistance training, athletics and football) participated in the intervention. These subjects were prone positioned with neutral hip position (0º), knee flexed at 30º and ankle 15º plantarflexed. The feet were fixed to individual force sensors, on which were performed bilateral isometric knee flexion contractions, from which were obtained force-time curves for the two legs. From these force-time curves, maximum force, rate of force development at various time intervals (from force onset and between two time points in the curve), time to maximum force and the respective value were gathered. Muscular stiffness (active and passive) was measured through shear wave elastography, in passive condition (static rested position) and active condition (contraction at an intensity corresponding to 20% of the maximum voluntary isometric contraction). All hamstring muscles were randomly evaluated in 9 dominant limbs and 9 non-dominant limbs. Matlab software (The Mathworks Inc., Natick, Massachusetts, USA) was used for data processing of the outputs obtained by the ultrasound and the statistical analysis was executed using SPSS software. Results: Negative and positive moderate correlations were found, respectively, between late rate of force development (150-200ms) and passive muscle stiffness of the biceps femoris short-head (r=0,49) and between early rate of force development (50-100ms) and semimembranosus active muscle stiffness (r=0,49). Conclusion: The present results refute the initial hypothesis although the limitations related to sample size and the methodology, that were induced by the COVID-19 pandemic, should be wisely recognized. Given these limitations, future studies should explore this study’s subject with an enhanced methodology.
Objective: Explore the association between the knee flexors rate of force development and the (active and passive) muscular stiffness of the hamstrings Methods: Eighteen healthy male subjects (25,2 ± 4,8 years; 79,1 ± 10,8 kg; 177,6 ± 6,4 cm height) with training experience (e.g., resistance training, athletics and football) participated in the intervention. These subjects were prone positioned with neutral hip position (0º), knee flexed at 30º and ankle 15º plantarflexed. The feet were fixed to individual force sensors, on which were performed bilateral isometric knee flexion contractions, from which were obtained force-time curves for the two legs. From these force-time curves, maximum force, rate of force development at various time intervals (from force onset and between two time points in the curve), time to maximum force and the respective value were gathered. Muscular stiffness (active and passive) was measured through shear wave elastography, in passive condition (static rested position) and active condition (contraction at an intensity corresponding to 20% of the maximum voluntary isometric contraction). All hamstring muscles were randomly evaluated in 9 dominant limbs and 9 non-dominant limbs. Matlab software (The Mathworks Inc., Natick, Massachusetts, USA) was used for data processing of the outputs obtained by the ultrasound and the statistical analysis was executed using SPSS software. Results: Negative and positive moderate correlations were found, respectively, between late rate of force development (150-200ms) and passive muscle stiffness of the biceps femoris short-head (r=0,49) and between early rate of force development (50-100ms) and semimembranosus active muscle stiffness (r=0,49). Conclusion: The present results refute the initial hypothesis although the limitations related to sample size and the methodology, that were induced by the COVID-19 pandemic, should be wisely recognized. Given these limitations, future studies should explore this study’s subject with an enhanced methodology.
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Elastografia Flexão do joelho Força rápida Isquiotibiais Taxa de produção de força Torque Rigidez Elastography knee flexion Rapid force Hamstrings Rate of force development Torque Stiffness