Background: In vivo study of the mechanical behavior of tendons may bring advances in evaluating the impact of intervention programs for fl exibility and strength, in clinical practice and sports. Objective: The aim of this study was to quantify the relative strain and slackness of achilles tendons during passive mobilization, for four ankle joint angles and two knee angles. Methods: The displacement of the muscle-tendon junction was quantifi ed by means of ultrasound images acquired during passive ankle mobilization, with the aid of an electrogoniometer and an electromyograph to ensure the achievement of the required angles and muscle inactivity, respectively. Results: The strain values ranged from 4.28%±2.37 to-0.94%±1.58 for the fully extended knee, and from 2.38%±1.63 to-2.32%±2.16% for the fl exed knee. Conclusions: The values found in this study confi rm those in the literature and demonstrate how the Achilles tendon participates in length changes in the muscle-tendon unit during passive movement. These results suggest that the mechanical properties of tendinous tissues affect the relationship between the length of muscle fi bers and the joint angle, even during this type of movement.
RESUMO: Estudos têm demonstrado uma redução na tensão específi ca de músculos hipertrofi ados, decorrente, em parte, da reestruturação da arquitetura muscular causada pelo treinamento de força. O índice de tensão específi ca dos fl exores de cotovelo, defi nido como a razão do torque pelo volume muscular, foi calculado em um grupo de praticantes de treinamento de força com alta carga. A ultra-sonografi a foi utilizada para estimativa do volume muscular. O torque máximo e o volume muscular foram superiores aos valores relatados para não-praticantes e ratifi cam estudos com grupo similar. O índice de tensão específi ca não apresentou redução em comparação aos descritos para outros grupos, como atletas de diversas modalidades e não-praticantes. Isso sugere a manutenção da efi ciência muscular com o treinamento de força.
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